Friday, November 30, 2007
Fri-Day 1
Bio- we illustrated some diagrams of the cross-section of a leaf noting the structure and function of each part or layer.
Yes, the diagrams did not exactly match the illustrations that I posted BUT you must develop the skill of recognizing features contained in various drawings of a given structure. It's best to practice this in class when you are not being penalized for a wrong answer and when you can correct your mistakes by asking questions.
For those who are still unsure about today's handouts, I am posting answers to those handouts on Blackboard. Check them out this weekend.
We then finished our "Factors That Affect Photosynthesis" Lab noting the effect of increasing light intensity and increasing carbon dioxide concentration on the photosynthetic rate in Elodea (by measuring the oxygen production rate).
Next week, we will finish Cellular Respiration and then we will compare and contrast Photosynthesis and Cellular Respiration.
On Monday, the outline of text section 9.2 is due.
Chem 7- we discussed the quantum mechanical model of the atom, which takes into account the wave nature AND the particle nature of the electron as well as the electron-electron repulsion interactions. The end result is the calculation of all possible electron energies and of all possible electron transitions from any excited state to the ground state in atoms of any element. Thus, all spectral line for each element are predicted and associated with specific electron transitions (jumps) between two energy SUBLEVELS. We also learned that a given electron that has a specific sublevel of energy can be found in a specific shaped region of probability called an ORBITAL (which is NOT an orbit- electrons do not move in "orbits"; electrons are WAVES and thus do not have a specific location like a planet in orbit!). The trick is to remember that the "s" sublevel of energy only has one orbital, the "p" sublevel of energy has THREE equal-electron energy orbital regions, the "d" sublevel has FIVE equal-electron energy orbitals, and the "f" sublevel has SEVEN equal-electron energy orbitals. You must also know that the number of sublevels OF a principal energy level is EQUAL to the principal energy level number e.g. the n=3 (third) Principal Energy Level has THREE sublevels of electron-energy, the "s", the "p", and the "d", in increasing order of energy.
We also saw how to figure the relative energies of the various sublevels by drawing diagonal lines through the various horizontally-listed sublevels (see notes). These relative energies are calculated via the Schroedinger Equation (which is far too difficult for us to even look at).
We then practiced writing, for several elements:
ORBITAL DIAGRAMS (with the boxes, representing orbitals, and the arrows, representing electrons).
Quantum Mechanical ELECTRON CONFIGURATIONS, which show the number of electrons (using a superscript) in each OCCUPIED sublevel in an atom.
You MUST practice both of these notations this weekend and you are responsible for any hw question that involves these.
The homework packet is due on Monday and the only hw questions that are optional (won't be graded) are those that we did not cover yet in class, i.e. Lewis Dot Diagrams.
Our Atomic Concepts Unit Exam is on Wednesday.
Chem 8/9- we discussed the quantum mechanical model of the atom, which takes into account the wave nature AND the particle nature of the electron as well as the electron-electron repulsion interactions. In an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. The end result is the calculation of all possible electron energies and of all possible electron transitions from any excited state to the ground state in atoms of any element. Thus, all spectral line for each element are predicted and associated with specific electron transitions (jumps) between two energy SUBLEVELS. We also learned that a given electron that has a specific sublevel of energy can be found in a specific shaped region of probability called an ORBITAL (which is NOT an orbit- electrons do not move in "orbits"; electrons are WAVES and thus do not have a specific location like a planet in orbit!). The trick is to remember that the "s" sublevel of energy only has one orbital, the "p" sublevel of energy has THREE equal-electron energy orbital regions, the "d" sublevel has FIVE equal-electron energy orbitals, and the "f" sublevel has SEVEN equal-electron energy orbitals. You must also know that the number of sublevels OF a principal energy level is EQUAL to the principal energy level number e.g. the n=3 (third) Principal Energy Level has THREE sublevels of electron-energy, the "s", the "p", and the "d", in increasing order of energy.
We also saw how to figure the relative energies of the various sublevels by drawing diagonal lines through the various horizontally-listed sublevels (see notes). These relative energies are calculated via the Schroedinger Equation (which is far too difficult for us to even look at).
We then practiced writing, for several elements:
ORBITAL DIAGRAMS (with the boxes, representing orbitals, and the arrows, representing electrons).
Quantum Mechanical ELECTRON CONFIGURATIONS, which show the number of electrons (using a superscript) in each OCCUPIED sublevel in an atom.
Lewis Dot Diagrams, which show the number of VALENCE ELECTRONS (ONLY the HIGHEST number PRINCIPAL energy level electrons!) in an atom of a given element.
You MUST practice these this weekend and you are responsible for any hw question that involves today's material.
Reminder, the homework packet is due on Monday. Our Atomic Concepts unit exam is on Wednesday.
Yes, the diagrams did not exactly match the illustrations that I posted BUT you must develop the skill of recognizing features contained in various drawings of a given structure. It's best to practice this in class when you are not being penalized for a wrong answer and when you can correct your mistakes by asking questions.
For those who are still unsure about today's handouts, I am posting answers to those handouts on Blackboard. Check them out this weekend.
We then finished our "Factors That Affect Photosynthesis" Lab noting the effect of increasing light intensity and increasing carbon dioxide concentration on the photosynthetic rate in Elodea (by measuring the oxygen production rate).
Next week, we will finish Cellular Respiration and then we will compare and contrast Photosynthesis and Cellular Respiration.
On Monday, the outline of text section 9.2 is due.
Chem 7- we discussed the quantum mechanical model of the atom, which takes into account the wave nature AND the particle nature of the electron as well as the electron-electron repulsion interactions. The end result is the calculation of all possible electron energies and of all possible electron transitions from any excited state to the ground state in atoms of any element. Thus, all spectral line for each element are predicted and associated with specific electron transitions (jumps) between two energy SUBLEVELS. We also learned that a given electron that has a specific sublevel of energy can be found in a specific shaped region of probability called an ORBITAL (which is NOT an orbit- electrons do not move in "orbits"; electrons are WAVES and thus do not have a specific location like a planet in orbit!). The trick is to remember that the "s" sublevel of energy only has one orbital, the "p" sublevel of energy has THREE equal-electron energy orbital regions, the "d" sublevel has FIVE equal-electron energy orbitals, and the "f" sublevel has SEVEN equal-electron energy orbitals. You must also know that the number of sublevels OF a principal energy level is EQUAL to the principal energy level number e.g. the n=3 (third) Principal Energy Level has THREE sublevels of electron-energy, the "s", the "p", and the "d", in increasing order of energy.
We also saw how to figure the relative energies of the various sublevels by drawing diagonal lines through the various horizontally-listed sublevels (see notes). These relative energies are calculated via the Schroedinger Equation (which is far too difficult for us to even look at).
We then practiced writing, for several elements:
ORBITAL DIAGRAMS (with the boxes, representing orbitals, and the arrows, representing electrons).
Quantum Mechanical ELECTRON CONFIGURATIONS, which show the number of electrons (using a superscript) in each OCCUPIED sublevel in an atom.
You MUST practice both of these notations this weekend and you are responsible for any hw question that involves these.
The homework packet is due on Monday and the only hw questions that are optional (won't be graded) are those that we did not cover yet in class, i.e. Lewis Dot Diagrams.
Our Atomic Concepts Unit Exam is on Wednesday.
Chem 8/9- we discussed the quantum mechanical model of the atom, which takes into account the wave nature AND the particle nature of the electron as well as the electron-electron repulsion interactions. In an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. The end result is the calculation of all possible electron energies and of all possible electron transitions from any excited state to the ground state in atoms of any element. Thus, all spectral line for each element are predicted and associated with specific electron transitions (jumps) between two energy SUBLEVELS. We also learned that a given electron that has a specific sublevel of energy can be found in a specific shaped region of probability called an ORBITAL (which is NOT an orbit- electrons do not move in "orbits"; electrons are WAVES and thus do not have a specific location like a planet in orbit!). The trick is to remember that the "s" sublevel of energy only has one orbital, the "p" sublevel of energy has THREE equal-electron energy orbital regions, the "d" sublevel has FIVE equal-electron energy orbitals, and the "f" sublevel has SEVEN equal-electron energy orbitals. You must also know that the number of sublevels OF a principal energy level is EQUAL to the principal energy level number e.g. the n=3 (third) Principal Energy Level has THREE sublevels of electron-energy, the "s", the "p", and the "d", in increasing order of energy.
We also saw how to figure the relative energies of the various sublevels by drawing diagonal lines through the various horizontally-listed sublevels (see notes). These relative energies are calculated via the Schroedinger Equation (which is far too difficult for us to even look at).
We then practiced writing, for several elements:
ORBITAL DIAGRAMS (with the boxes, representing orbitals, and the arrows, representing electrons).
Quantum Mechanical ELECTRON CONFIGURATIONS, which show the number of electrons (using a superscript) in each OCCUPIED sublevel in an atom.
Lewis Dot Diagrams, which show the number of VALENCE ELECTRONS (ONLY the HIGHEST number PRINCIPAL energy level electrons!) in an atom of a given element.
You MUST practice these this weekend and you are responsible for any hw question that involves today's material.
Reminder, the homework packet is due on Monday. Our Atomic Concepts unit exam is on Wednesday.
# posted by C @ 6:58 PM 
Thursday, November 29, 2007
Thurs-Day 2
Bio- we explained the two major parts of photosynthesis:
1. the light-DEPENDENT steps that occur in each GRANUM/stack of thylakoids during which water is "split" into hydrogen and oxygen; also, ATP is formed as the light energy absorbed by the photosynthetic pigments is converted into chemical potential energy in the bonds of ATP.
The hydrogen becomes part of a "hydrogen carrying molecule" (NADPH) and eventually becomes part of the glucose molecule that is synthesized in the STROMA region of the chloroplast (outside of the granum). The ATP that is formed in this first step is then transferred to the stroma to supply the energy required for the synthesis of glucose from inorganic carbon dioxide.
2. the light-INDEPENDENT steps occur in the STROMA; the reason that these steps occur whether or not light is available is that the light energy from step 1 is already stored in the bonds of ATP. However, if there is no light energy to be incorporated into ATP in step 1, there will be no ATP to drive the glucose-producing "Calvin cycle" in step 2.
In step 2, the hydrogen (of NADPH) from step 1 and the CO2 are synthesized into glucose in an energy(ATP)-requiring cyclic process known as the Calvin cycle.
The glucose that is made in the stroma via these two steps is ultimately:
1. used as an energy source in plant cellular respiration
2. synthesized into a complex carbohydrate such as cellulose or starch
3. used as a reactant with other compounds to form fats/oils, proteins, or nucleic acids.
We then looked at plant physiology to see how plants maintain homeostasis by regulating the amount of water and carbon dioxide that is available to be used in photosynthesis. When there is adequate water available, the "guard cells" on the underside of the plant leaf will swell and form a "mouth/opening" called a STOMATE. With the stomates open, more CO2 can enter the cells that make up the plant leaf.
However, under arid/dry conditions, the guard cells shrivel (due to the lack of water) and the stomate/opening shrinks and eventually closes; this closing of the stomate/mouth PREVENTS further water loss from the leaf so that photosynthesis can continue although at a slower rate due to the reduction of CO2 that can diffuse into the leaf that has closed stomates.
The outline of text section 9.2 is due on Monday.
Chem 7/8- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various salt solutions because different metals have electrons that must undergo different energy transitions for the reasons explained yesterday.
We then looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
Also, in an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. This model accounts for all of the bright line spectra emission lines because it takes into account both the wave and particle natures of the electron as well as the electron to electron repulsions that occur in all atoms except for H. The repulsions between electrons and the wave nature of the electron causes the electron to exist in energy SUBLEVELS that are associated with an electron being in a specific region of probability/ORBITAL around the nucleus.
We will draw out the electron configurations of the first 20 elements using both the Bohr model and the quantum mechanical model.
Chem 9- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We focused on the Bohr model and drew out electron configurations of several different atoms and ions. We defined the terms "ground state", "excited state", and "valence electrons".
Valence electrons, which are typically the electrons that are gained, lost, or shared in a chemical reaction, are, BY DEFINITION, the electrons in the HIGHEST NUMBER/OUTERMOST principal energy level. ONLY THOSE ELECTRONS are considered to be valence electrons!
We looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
The other problem involved the picture that I showed at the end of class. We will discuss that tomorrow.
1. the light-DEPENDENT steps that occur in each GRANUM/stack of thylakoids during which water is "split" into hydrogen and oxygen; also, ATP is formed as the light energy absorbed by the photosynthetic pigments is converted into chemical potential energy in the bonds of ATP.
The hydrogen becomes part of a "hydrogen carrying molecule" (NADPH) and eventually becomes part of the glucose molecule that is synthesized in the STROMA region of the chloroplast (outside of the granum). The ATP that is formed in this first step is then transferred to the stroma to supply the energy required for the synthesis of glucose from inorganic carbon dioxide.
2. the light-INDEPENDENT steps occur in the STROMA; the reason that these steps occur whether or not light is available is that the light energy from step 1 is already stored in the bonds of ATP. However, if there is no light energy to be incorporated into ATP in step 1, there will be no ATP to drive the glucose-producing "Calvin cycle" in step 2.
In step 2, the hydrogen (of NADPH) from step 1 and the CO2 are synthesized into glucose in an energy(ATP)-requiring cyclic process known as the Calvin cycle.
The glucose that is made in the stroma via these two steps is ultimately:
1. used as an energy source in plant cellular respiration
2. synthesized into a complex carbohydrate such as cellulose or starch
3. used as a reactant with other compounds to form fats/oils, proteins, or nucleic acids.
We then looked at plant physiology to see how plants maintain homeostasis by regulating the amount of water and carbon dioxide that is available to be used in photosynthesis. When there is adequate water available, the "guard cells" on the underside of the plant leaf will swell and form a "mouth/opening" called a STOMATE. With the stomates open, more CO2 can enter the cells that make up the plant leaf.
However, under arid/dry conditions, the guard cells shrivel (due to the lack of water) and the stomate/opening shrinks and eventually closes; this closing of the stomate/mouth PREVENTS further water loss from the leaf so that photosynthesis can continue although at a slower rate due to the reduction of CO2 that can diffuse into the leaf that has closed stomates.
The outline of text section 9.2 is due on Monday.
Chem 7/8- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various salt solutions because different metals have electrons that must undergo different energy transitions for the reasons explained yesterday.
We then looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
Also, in an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. This model accounts for all of the bright line spectra emission lines because it takes into account both the wave and particle natures of the electron as well as the electron to electron repulsions that occur in all atoms except for H. The repulsions between electrons and the wave nature of the electron causes the electron to exist in energy SUBLEVELS that are associated with an electron being in a specific region of probability/ORBITAL around the nucleus.
We will draw out the electron configurations of the first 20 elements using both the Bohr model and the quantum mechanical model.
Chem 9- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We focused on the Bohr model and drew out electron configurations of several different atoms and ions. We defined the terms "ground state", "excited state", and "valence electrons".
Valence electrons, which are typically the electrons that are gained, lost, or shared in a chemical reaction, are, BY DEFINITION, the electrons in the HIGHEST NUMBER/OUTERMOST principal energy level. ONLY THOSE ELECTRONS are considered to be valence electrons!
We looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
The other problem involved the picture that I showed at the end of class. We will discuss that tomorrow.
# posted by C @ 2:58 PM
Wednesday, November 28, 2007
Wednes-Day 1
Bio- we investigated the effect of LIGHT INTENSITY (# of photons per second that hit the plant cells) on PHOTOSYNTHETIC RATE by measuring the rate of oxygen bubble formation. Since oxygen is a product of photosynthesis, the more oxygen bubbles counted per minute, the faster the rate of photosynthesis.
We also measured the effect of increasing CARBON DIOXIDE concentration on the photosynthetic rate.
Since photosynthesis is a process that is aided by enzymes in the chloroplasts, ANY factor that affects enzyme activity (protein shape) MUST affect the rate of photosynthesis. Recall these factors:
TEMPERATURE, pH, concentration of SUBSTRATE/REACTANT (in this case, CO2, H2O, and LIGHT), and concentration of enzyme.
A bit surprisingly, some of the lamps heated the water in the test tube that contained the Elodea (" 'elloooo-dear") to about 80 Celsius, which denatured the photosynthetic enzymes! That explained why the plant suddenly stopped producing oxygen.
The next text hw is to outline section 9.2; that hw is due on Friday.
Chem 7- we further discussed the Bohr Model of the atom; we noted that when the electrons are in the lowest available principal energy levels, the atom is in the GROUND STATE. The GROUND STATE electron configurations for each element are listed in the Reference Tables and there is ONLY one ground state electron configuration per element. If an electron in a ground state atom absorbs a certain SPECIFIC amount of energy (a QUANTUM) taking the electron farther away from the nucleus, the electron has undergone an ELECTRON TRANSITION to a higher principal energy level. The difference in energy between the electrons original principal energy level and the principal energy level that the electron went to is EXACTLY equal to the quantum of energy that was absorbed.
Then, the same electron will eventually undergo an electron transition to a lower principal energy level (due to the electron's attraction to the positive nucleus); thus the electron loses energy. This "lost energy" is transformed into a packet of light energy, a photon. The photon energy is EXACTLY equal to the energy lost by the electron. The energy lost by the electron is EXACTLY equal to the difference in energy between the two principal energy levels traversed by the electron.
Since only certain specific color/energy photons are ever emitted by excited state atoms of an element, the electrons must only have certain SPECIFIC energy levels and also, there must only be certain specific DIFFERENCES in energy between any two energy levels in any atom. That is Bohr's main contribution the atomic model and his finding that electrons can only have certain levels of energy has ALWAYS been supported by experiment.
Also, since different elements have different emission spectra, they must have different energy DIFFERENCES between their respective principal energy levels; this is so because each different element has a different number of potential energy-decreasing PROTONS (as we saw with our H vs. He example).
Chem 8/9-we further discussed the Bohr Model of the atom; we noted that when the electrons are in the lowest available principal energy levels, the atom is in the GROUND STATE. The GROUND STATE electron configurations for each element are listed in the Reference Tables and there is ONLY one ground state electron configuration per element. If an electron in a ground state atom absorbs a certain SPECIFIC amount of energy (a QUANTUM) taking the electron farther away from the nucleus, the electron has undergone an ELECTRON TRANSITION to a higher principal energy level. The difference in energy between the electrons original principal energy level and the principal energy level that the electron went to is EXACTLY equal to the quantum of energy that was absorbed.
Then, the same electron will eventually undergo an electron transition to a lower principal energy level (due to the electron's attraction to the positive nucleus); thus the electron loses energy. This "lost energy" is transformed into a packet of light energy, a photon. The photon energy is EXACTLY equal to the energy lost by the electron. The energy lost by the electron is EXACTLY equal to the difference in energy between the two principal energy levels traversed by the electron.
Since only certain specific color/energy photons are ever emitted by excited state atoms of an element, the electrons must only have certain SPECIFIC energy levels and also, there must only be certain specific DIFFERENCES in energy between any two energy levels in any atom. That is Bohr's main contribution the atomic model and his finding that electrons can only have certain levels of energy has ALWAYS been supported by experiment.
Also, since different elements have different emission spectra, they must have different energy DIFFERENCES between their respective principal energy levels; this is so because each different element has a different number of potential energy-decreasing PROTONS (as we saw with our H vs. He example).
We then did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various solutions because different metals have electrons that must undergo different energy transitions for the reasons explained above.
We also measured the effect of increasing CARBON DIOXIDE concentration on the photosynthetic rate.
Since photosynthesis is a process that is aided by enzymes in the chloroplasts, ANY factor that affects enzyme activity (protein shape) MUST affect the rate of photosynthesis. Recall these factors:
TEMPERATURE, pH, concentration of SUBSTRATE/REACTANT (in this case, CO2, H2O, and LIGHT), and concentration of enzyme.
A bit surprisingly, some of the lamps heated the water in the test tube that contained the Elodea (" 'elloooo-dear") to about 80 Celsius, which denatured the photosynthetic enzymes! That explained why the plant suddenly stopped producing oxygen.
The next text hw is to outline section 9.2; that hw is due on Friday.
Chem 7- we further discussed the Bohr Model of the atom; we noted that when the electrons are in the lowest available principal energy levels, the atom is in the GROUND STATE. The GROUND STATE electron configurations for each element are listed in the Reference Tables and there is ONLY one ground state electron configuration per element. If an electron in a ground state atom absorbs a certain SPECIFIC amount of energy (a QUANTUM) taking the electron farther away from the nucleus, the electron has undergone an ELECTRON TRANSITION to a higher principal energy level. The difference in energy between the electrons original principal energy level and the principal energy level that the electron went to is EXACTLY equal to the quantum of energy that was absorbed.
Then, the same electron will eventually undergo an electron transition to a lower principal energy level (due to the electron's attraction to the positive nucleus); thus the electron loses energy. This "lost energy" is transformed into a packet of light energy, a photon. The photon energy is EXACTLY equal to the energy lost by the electron. The energy lost by the electron is EXACTLY equal to the difference in energy between the two principal energy levels traversed by the electron.
Since only certain specific color/energy photons are ever emitted by excited state atoms of an element, the electrons must only have certain SPECIFIC energy levels and also, there must only be certain specific DIFFERENCES in energy between any two energy levels in any atom. That is Bohr's main contribution the atomic model and his finding that electrons can only have certain levels of energy has ALWAYS been supported by experiment.
Also, since different elements have different emission spectra, they must have different energy DIFFERENCES between their respective principal energy levels; this is so because each different element has a different number of potential energy-decreasing PROTONS (as we saw with our H vs. He example).
Chem 8/9-we further discussed the Bohr Model of the atom; we noted that when the electrons are in the lowest available principal energy levels, the atom is in the GROUND STATE. The GROUND STATE electron configurations for each element are listed in the Reference Tables and there is ONLY one ground state electron configuration per element. If an electron in a ground state atom absorbs a certain SPECIFIC amount of energy (a QUANTUM) taking the electron farther away from the nucleus, the electron has undergone an ELECTRON TRANSITION to a higher principal energy level. The difference in energy between the electrons original principal energy level and the principal energy level that the electron went to is EXACTLY equal to the quantum of energy that was absorbed.
Then, the same electron will eventually undergo an electron transition to a lower principal energy level (due to the electron's attraction to the positive nucleus); thus the electron loses energy. This "lost energy" is transformed into a packet of light energy, a photon. The photon energy is EXACTLY equal to the energy lost by the electron. The energy lost by the electron is EXACTLY equal to the difference in energy between the two principal energy levels traversed by the electron.
Since only certain specific color/energy photons are ever emitted by excited state atoms of an element, the electrons must only have certain SPECIFIC energy levels and also, there must only be certain specific DIFFERENCES in energy between any two energy levels in any atom. That is Bohr's main contribution the atomic model and his finding that electrons can only have certain levels of energy has ALWAYS been supported by experiment.
Also, since different elements have different emission spectra, they must have different energy DIFFERENCES between their respective principal energy levels; this is so because each different element has a different number of potential energy-decreasing PROTONS (as we saw with our H vs. He example).
We then did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various solutions because different metals have electrons that must undergo different energy transitions for the reasons explained above.
# posted by C @ 8:03 PM
Tuesday, November 27, 2007
Tues-Day 2
Bio - we introduced the life process of photosynthesis in which light energy is used to convert inorganic carbon dioxide and water into glucose and oxygen. The radiant/light energy from the sun is ultimately stored in the covalent bonds in glucose as chemical potential energy; the oxygen gas is a by-product due to the "splitting" of the water molecules via photolysis that occurs during photosynthesis.
We discussed the organelle in which photosynthesis occurs: the choroplast. Key structures of the chloroplast are the grana, which are stacks of thylakoid "pankcake-shaped" structures that contain the light/energy absorbing pigment, chlorophyll. The other key region of the chloroplast is the STROMA, which is the jelly-like material that surrounds the grana, where glucose is synthesized.
We also saw that green plants have more than one type of chlorophyll pigment in their chloroplasts as well as other light-absorbing pigments e.g. carotenes and xanthophylls. These various pigments are advantageous to plants because more and different colors of light energy can then be absorbed by the plant so that it can have the energy for photosynthesis.
Finally, we saw that chlorophyll a and chorophyll b best absorb red light and blue light but that they REFLECT/do not absorb green light, which is why plants appear green. Thus, photosynthetic rate will be greatest when blue and/or red light is used.
Chem 7/8- we discussed the Bohr Model of the Atom, which shows each electron in an orbit that corresponds to the specific energy of the electron. The farther away the orbit of the electron from the nucleus, the higher the electron's energy.
Bohr's Model explains how atoms of a given element, when excited by an energy source, will emit only specific energy photons. Here's the important thing: the specific energy of each emitted photon is EXACTLY equal to the energy lost by the electron as the electron went from a higher principal energy level to a lower principal energy level; furthermore, the energy of the emitted photon is EXACTLY equal to the DIFFERENCE in energy between these two energy levels.
Each element has a different number of protons causing the electrons in its atoms to have a different and unique potential energy levels. So, NO TWO elements have the same difference in energy between ANY two corresponding energy levels. Thus, an electron that goes from n=5 to n=2 in a Hydrogen atom will emit a DIFFERENT energy photon than an electron that goes from n=5 to n=2 in an atom of ANY OTHER element. On Blackboard, I have posted the light emission spectrum video that explains the electron energy transitions in an atom.
We then finished our weighted average atomic mass lab, with emphasis on the atomic mass definition and calculations. We also did typical lab data calculations in which we practiced sig figs
and percent error.
Chem 9- we discussed the Bohr Model of the Atom, which shows each electron in an orbit that corresponds to the specific energy of the electron. The farther away the orbit of the electron from the nucleus, the higher the electron's energy.
Bohr's Model explains how atoms of a given element, when excited by an energy source, will emit only specific energy photons. Here's the important thing: the specific energy of each emitted photon is EXACTLY equal to the energy lost by the electron as the electron went from a higher principal energy level to a lower principal energy level; furthermore, the energy of the emitted photon is EXACTLY equal to the DIFFERENCE in energy between these two energy levels.
Each element has a different number of protons causing the electrons in its atoms to have a different and unique potential energy levels. So, NO TWO elements have the same difference in energy between ANY two corresponding energy levels. Thus, an electron that goes from n=5 to n=2 in a Hydrogen atom will emit a DIFFERENT energy photon than an electron that goes from n=5 to n=2 in an atom of ANY OTHER element. On Blackboard, I have posted the light emission spectrum video that explains the electron energy transitions in an atom.
We discussed the organelle in which photosynthesis occurs: the choroplast. Key structures of the chloroplast are the grana, which are stacks of thylakoid "pankcake-shaped" structures that contain the light/energy absorbing pigment, chlorophyll. The other key region of the chloroplast is the STROMA, which is the jelly-like material that surrounds the grana, where glucose is synthesized.
We also saw that green plants have more than one type of chlorophyll pigment in their chloroplasts as well as other light-absorbing pigments e.g. carotenes and xanthophylls. These various pigments are advantageous to plants because more and different colors of light energy can then be absorbed by the plant so that it can have the energy for photosynthesis.
Finally, we saw that chlorophyll a and chorophyll b best absorb red light and blue light but that they REFLECT/do not absorb green light, which is why plants appear green. Thus, photosynthetic rate will be greatest when blue and/or red light is used.
Chem 7/8- we discussed the Bohr Model of the Atom, which shows each electron in an orbit that corresponds to the specific energy of the electron. The farther away the orbit of the electron from the nucleus, the higher the electron's energy.
Bohr's Model explains how atoms of a given element, when excited by an energy source, will emit only specific energy photons. Here's the important thing: the specific energy of each emitted photon is EXACTLY equal to the energy lost by the electron as the electron went from a higher principal energy level to a lower principal energy level; furthermore, the energy of the emitted photon is EXACTLY equal to the DIFFERENCE in energy between these two energy levels.
Each element has a different number of protons causing the electrons in its atoms to have a different and unique potential energy levels. So, NO TWO elements have the same difference in energy between ANY two corresponding energy levels. Thus, an electron that goes from n=5 to n=2 in a Hydrogen atom will emit a DIFFERENT energy photon than an electron that goes from n=5 to n=2 in an atom of ANY OTHER element. On Blackboard, I have posted the light emission spectrum video that explains the electron energy transitions in an atom.
We then finished our weighted average atomic mass lab, with emphasis on the atomic mass definition and calculations. We also did typical lab data calculations in which we practiced sig figs
and percent error.
Chem 9- we discussed the Bohr Model of the Atom, which shows each electron in an orbit that corresponds to the specific energy of the electron. The farther away the orbit of the electron from the nucleus, the higher the electron's energy.
Bohr's Model explains how atoms of a given element, when excited by an energy source, will emit only specific energy photons. Here's the important thing: the specific energy of each emitted photon is EXACTLY equal to the energy lost by the electron as the electron went from a higher principal energy level to a lower principal energy level; furthermore, the energy of the emitted photon is EXACTLY equal to the DIFFERENCE in energy between these two energy levels.
Each element has a different number of protons causing the electrons in its atoms to have a different and unique potential energy levels. So, NO TWO elements have the same difference in energy between ANY two corresponding energy levels. Thus, an electron that goes from n=5 to n=2 in a Hydrogen atom will emit a DIFFERENT energy photon than an electron that goes from n=5 to n=2 in an atom of ANY OTHER element. On Blackboard, I have posted the light emission spectrum video that explains the electron energy transitions in an atom.
# posted by C @ 11:41 AM
Monday, November 26, 2007
Mon-Day 1
Bio- for HW that is due on Wednesday:
1. Outline text section 9.1
2. Write test corrections with correct and complete EXPLANATIONS of each question/answer that you got wrong.
We introduced our new unit: Cell Respiration and Photosynthesis. We will first focus on cellular respiration and then we will cover photosynthesis; we will then analyze the differences, similarities, and inter-relationships between these two vital cellular processes.
We discussed an organism's need for energy for many of its metabolic activities: active transport, muscle contractions, nerve impulses, and dehydration synthesis reactions. This energy must be derived from nutrients such as carbohydrates, which are broken down to glucose via digestive enzymes in the saliva and intestinal juices. The energy stored in the bonds of glucose is transferred to the energy stored in the bonds of ATP via cellular respiration. Whenever a cell needs energy for any metabolic process, ATP is then hydrolyzed and energy is released from the ATP molecule and is used to drive/power the metabolic process.
We noted that if energy were derived from glucose all at once, too much energy would be released and, perhaps, enzymes would then denature. Because the energy that is stored in the bonds in glucose is GRADUALLY transferred via a large series of chemical reactions/steps to the energy stored in the bonds in ATP, there is a controlled release of energy that is sufficient to meet the energy requirements of normal metabolic processes. The energy released per molecule of ATP that is hydrolyzed is not so overwhelming as to denature any proteins or heat up the cytoplasm.
Chem 7- we revisited the earlier models of the atom, the Dalton hard-neutral-sphere model and the Thomson plum pudding model. We deduced how the Laws of Constant Composition and Multiple Proportions led Dalton to his model of indivisible atoms that combine in definite, whole-number ratios. We reviewed how Thomson proposed his model of the atom based on the beam of negatively charged particles that he forced out of silver atoms in the cathode-ray tube.
We then focused on the brilliant Rutherford Gold Foil experiment which ultimately disproved Thomson's "positive diffuse jelly" component of the atom. For 1/10000 of the positively charged alpha particle to be deflected practically straight back from the foil showed that each atom has a very tiny (1/10000 the volume of the whole atom), dense/massive, positively charged nucleus. If atoms were really made of a diffuse, positive jelly, ALL of the positively charged alpha particles would have passed through the foil of gold atoms with practically no deflection.
We will discuss the next development to a more precise and accurate (Bohr) model of the atom.
Chem 8/9- we revisited the earlier models of the atom, the Dalton hard-neutral-sphere model and the Thomson plum pudding model. We deduced how the Laws of Constant Composition and Multiple Proportions led Dalton to his model of indivisible atoms that combine in definite, whole-number ratios. We reviewed how Thomson proposed his model of the atom based on the beam of negatively charged particles that he forced out of silver atoms in the cathode-ray tube.
We then focused on the brilliant Rutherford Gold Foil experiment which ultimately disproved Thomson's "positive diffuse jelly" component of the atom. For 1/10000 of the positively charged alpha particle to be deflected practically straight back from the foil showed that each atom has a very tiny (1/10000 the volume of the whole atom), dense/massive, positively charged nucleus. If atoms were really made of a diffuse, positive jelly, ALL of the positively charged alpha particles would have passed through the foil of gold atoms with practically no deflection.
We will discuss the next development to a more precise and accurate (Bohr) model of the atom.
We finished our "Atomic Mass" lab. Some are still not applying the significant figures rules properly; though sig figs are not the most important things in the world, the rules are very brief and they are never going to change. Learn them for yourself now and you won't have a problem with them again- there are many websites for practice with sig figs and the text also has examples but nothing is going to beat the Atlantic-Pacific rule/mnemonic that we did in class; also, the examples that we did regarding the addition/subtraction vs. multiplication/division rules were thorough and perfectly representative of ANY sig figs problem. Check them out.
1. Outline text section 9.1
2. Write test corrections with correct and complete EXPLANATIONS of each question/answer that you got wrong.
We introduced our new unit: Cell Respiration and Photosynthesis. We will first focus on cellular respiration and then we will cover photosynthesis; we will then analyze the differences, similarities, and inter-relationships between these two vital cellular processes.
We discussed an organism's need for energy for many of its metabolic activities: active transport, muscle contractions, nerve impulses, and dehydration synthesis reactions. This energy must be derived from nutrients such as carbohydrates, which are broken down to glucose via digestive enzymes in the saliva and intestinal juices. The energy stored in the bonds of glucose is transferred to the energy stored in the bonds of ATP via cellular respiration. Whenever a cell needs energy for any metabolic process, ATP is then hydrolyzed and energy is released from the ATP molecule and is used to drive/power the metabolic process.
We noted that if energy were derived from glucose all at once, too much energy would be released and, perhaps, enzymes would then denature. Because the energy that is stored in the bonds in glucose is GRADUALLY transferred via a large series of chemical reactions/steps to the energy stored in the bonds in ATP, there is a controlled release of energy that is sufficient to meet the energy requirements of normal metabolic processes. The energy released per molecule of ATP that is hydrolyzed is not so overwhelming as to denature any proteins or heat up the cytoplasm.
Chem 7- we revisited the earlier models of the atom, the Dalton hard-neutral-sphere model and the Thomson plum pudding model. We deduced how the Laws of Constant Composition and Multiple Proportions led Dalton to his model of indivisible atoms that combine in definite, whole-number ratios. We reviewed how Thomson proposed his model of the atom based on the beam of negatively charged particles that he forced out of silver atoms in the cathode-ray tube.
We then focused on the brilliant Rutherford Gold Foil experiment which ultimately disproved Thomson's "positive diffuse jelly" component of the atom. For 1/10000 of the positively charged alpha particle to be deflected practically straight back from the foil showed that each atom has a very tiny (1/10000 the volume of the whole atom), dense/massive, positively charged nucleus. If atoms were really made of a diffuse, positive jelly, ALL of the positively charged alpha particles would have passed through the foil of gold atoms with practically no deflection.
We will discuss the next development to a more precise and accurate (Bohr) model of the atom.
Chem 8/9- we revisited the earlier models of the atom, the Dalton hard-neutral-sphere model and the Thomson plum pudding model. We deduced how the Laws of Constant Composition and Multiple Proportions led Dalton to his model of indivisible atoms that combine in definite, whole-number ratios. We reviewed how Thomson proposed his model of the atom based on the beam of negatively charged particles that he forced out of silver atoms in the cathode-ray tube.
We then focused on the brilliant Rutherford Gold Foil experiment which ultimately disproved Thomson's "positive diffuse jelly" component of the atom. For 1/10000 of the positively charged alpha particle to be deflected practically straight back from the foil showed that each atom has a very tiny (1/10000 the volume of the whole atom), dense/massive, positively charged nucleus. If atoms were really made of a diffuse, positive jelly, ALL of the positively charged alpha particles would have passed through the foil of gold atoms with practically no deflection.
We will discuss the next development to a more precise and accurate (Bohr) model of the atom.
We finished our "Atomic Mass" lab. Some are still not applying the significant figures rules properly; though sig figs are not the most important things in the world, the rules are very brief and they are never going to change. Learn them for yourself now and you won't have a problem with them again- there are many websites for practice with sig figs and the text also has examples but nothing is going to beat the Atlantic-Pacific rule/mnemonic that we did in class; also, the examples that we did regarding the addition/subtraction vs. multiplication/division rules were thorough and perfectly representative of ANY sig figs problem. Check them out.
# posted by C @ 7:35 AM
Tuesday, November 20, 2007
Tues-Day 2
Bio- we took our unit test on transcription, translation, and mutation. Over the break, I will post your grades.When you return, be ready to work quickly and efficiently on our next unit: Photosynthesis and Respiration.
Have an enjoyable and festive Thanksgiving!
Chem 7/8- we did a lab that provided an analogy to the relative atomic mass scale as well as a way to "see" how isotopes of an element contribute to its overall "weighted average atomic mass".
Over the break, work on the lab questions and come prepared with any questions that gave your trouble. In class, we will then make sure that you all are solid gold on the questions and then you will hand the lab in.
We then began our discussion of the various atomic models that changed over time due to increasingly more sophisticated experiments and lab equipment. We discussed the Dalton Model of the atom and his conclusions/inferences from the experiments of Lavoisier and Proust. We then discussed Thomson's Cathode Ray (Crooke's) Tube experiment that showed that negative particles (which he called electrons) are part of an atom. We then began to discuss the Rutherford Gold Foil Experiment, which was a test of the Thomson model of the atom. We will continue our discussion on Monday. Both the Thomson and Rutherford videos are posted on Blackboard.
Also, work on the "webquest" on the atomic models. That will NOT be due on Monday but rather on Wednesday.
Reminder, for the rest of the year, I will collect and grade the unit hw packets that are given out at the beginning of each unit. The Atomic Structure (Topic #5) hw packet is due Friday, November 30th.
Have an enjoyable and festive Thanksgiving!
Chem 9- We did one of the atomic mass problems from yesterday's lab. Over the break, work on the lab questions and, if you have questions about the lab, we will finish that on Monday in class during which I will collect the lab.
We then began our discussion of the various atomic models that changed over time due to increasingly more sophisticated experiments and lab equipment. We discussed the Dalton Model of the atom and his conclusions/inferences from the experiments of Lavoisier and Proust. We then began to discuss the Thomson's Cathode Ray (Crooke's) Tube experiment that showed that negative particles (which he called electrons) are part of an atom. Over the break, view this video that is posted on Blackboard.
For homework over the break, on Blackboard, I posted a "webquest" assignment on the atomic models. That will NOT be due on Monday but rather on Wednesday.
Reminder, for the rest of the year, I will collect and grade the unit hw packets that are given out at the beginning of each unit. The Atomic Structure (Topic #5) hw packet is due Friday, November 30th.
Have an enjoyable and festive Thanksgiving!
# posted by C @ 11:11 AM
Monday, November 19, 2007
Mon-Day 1
Bio- we reviewed for tomorrow's important first test of the second quarter! For your test tomorrow, I have just posted an additional practice worksheet (with answer key) on the DNA mutation that codes for a different-shaped hemoglobin protein that causes red blood cells to have a sickle shape. I also posted a flow chart showing the central dogma of biology, which shows the two distinct/different uses for DNA.
Make sure that you fully write out and DRAW answers to each of the unit objective questions from today. If you do not, then you are not adequately prepared for tomorrow's test. You will be writing these SAME answers and drawing these SAME drawings to help you answer the applied knowledge questions on tomorrow's test.
More than anything, when you read a question tomorrow, DRAW OUT AND PREDICT your answer FIRST. DO NOT look at the answer choices until you have an answer that is AT LEAST related to the question asked. (Oftentimes, just coming up with an example or a synonym of a keyword in the question will put you on the right track.)
Then and ONLY then should you look for an answer that matches or nearly matches your prediction.
Those who do not follow this test-taking advice (and you have NO reason not to follow this advice since it WILL definitely help you) are going to spend a lot of time reading wrong answers that may be true and tempting but will be irrelevant; you will not easily see the relevance of an answer UNLESS you have a predicted answer based on your study of the unit objectives questions.
Chem 7- we reviewed how to calculate the "atomic mass" of an element by taking the WEIGHTED AVERAGE of the element's naturally occurring isotopes. A weighted average takes into account that the more abundant isotopes of an element contribute more to its average mass than do the less abundant isotopes.
We then began a discussion of atomic theory starting with ancient philosophical arguments that posited that matter was made up of indivisible, separate particles called "atomos".
We then began our discussion of how SCIENCE, with its requirement of consistently repeatable physical evidence, unraveled the mystery of the atom, a particle that is too small to ever be seen directly. We will take a tour of the models of the atom that developed, over the past 300 years, in response to new and more detailed, accurate evidence.
On Blackboard tonight, I posted some good review practice worksheets on subatomic particle calculations and definitions. Do them this week and get instant feedback on your answers.
Chem 8/9- we did several problems that involved calculating the number of each type of subatomic particle in a given atom, cation, or anion. We revisited the definitions of isotope, "mass number" ( p + n number, really), atomic number, and nucleon. You should be practicing the tutorials and worksheets that I posted on Blackboard until you can do these calculations quickly and accurately.
We then looked at the calculation of a weighted average (which is how your grades are calculated). We used this fair and logical way to get the average of a sample of particles in order to calculate the "atomic mass" of an element. We take the WEIGHTED AVERAGE of the masses of an element's naturally occurring isotopes. A weighted average takes into account that the more abundant isotopes of an element contribute more to its average mass than do the less abundant isotopes.
We then did a lab that reflects the fact that the atomic mass scale is a relative mass scale that uses the pure C-12 atom as its standard of mass. We will discuss this lab at the beginning of class tomorrow and then you will hand in the lab.
On Blackboard tonight, I posted some good review practice worksheets on subatomic particle calculations and definitions. Do them this week and get instant feedback on your answers.
Make sure that you fully write out and DRAW answers to each of the unit objective questions from today. If you do not, then you are not adequately prepared for tomorrow's test. You will be writing these SAME answers and drawing these SAME drawings to help you answer the applied knowledge questions on tomorrow's test.
More than anything, when you read a question tomorrow, DRAW OUT AND PREDICT your answer FIRST. DO NOT look at the answer choices until you have an answer that is AT LEAST related to the question asked. (Oftentimes, just coming up with an example or a synonym of a keyword in the question will put you on the right track.)
Then and ONLY then should you look for an answer that matches or nearly matches your prediction.
Those who do not follow this test-taking advice (and you have NO reason not to follow this advice since it WILL definitely help you) are going to spend a lot of time reading wrong answers that may be true and tempting but will be irrelevant; you will not easily see the relevance of an answer UNLESS you have a predicted answer based on your study of the unit objectives questions.
Chem 7- we reviewed how to calculate the "atomic mass" of an element by taking the WEIGHTED AVERAGE of the element's naturally occurring isotopes. A weighted average takes into account that the more abundant isotopes of an element contribute more to its average mass than do the less abundant isotopes.
We then began a discussion of atomic theory starting with ancient philosophical arguments that posited that matter was made up of indivisible, separate particles called "atomos".
We then began our discussion of how SCIENCE, with its requirement of consistently repeatable physical evidence, unraveled the mystery of the atom, a particle that is too small to ever be seen directly. We will take a tour of the models of the atom that developed, over the past 300 years, in response to new and more detailed, accurate evidence.
On Blackboard tonight, I posted some good review practice worksheets on subatomic particle calculations and definitions. Do them this week and get instant feedback on your answers.
Chem 8/9- we did several problems that involved calculating the number of each type of subatomic particle in a given atom, cation, or anion. We revisited the definitions of isotope, "mass number" ( p + n number, really), atomic number, and nucleon. You should be practicing the tutorials and worksheets that I posted on Blackboard until you can do these calculations quickly and accurately.
We then looked at the calculation of a weighted average (which is how your grades are calculated). We used this fair and logical way to get the average of a sample of particles in order to calculate the "atomic mass" of an element. We take the WEIGHTED AVERAGE of the masses of an element's naturally occurring isotopes. A weighted average takes into account that the more abundant isotopes of an element contribute more to its average mass than do the less abundant isotopes.
We then did a lab that reflects the fact that the atomic mass scale is a relative mass scale that uses the pure C-12 atom as its standard of mass. We will discuss this lab at the beginning of class tomorrow and then you will hand in the lab.
On Blackboard tonight, I posted some good review practice worksheets on subatomic particle calculations and definitions. Do them this week and get instant feedback on your answers.
# posted by C @ 1:08 PM
Sunday, November 18, 2007
Bio Extra Help Questions
I wasn't able to log onto Blackboard this weekend so I'll link the supplementary Unit 5 Test Objective Questions here for now.
# posted by C @ 6:15 PM
Saturday, November 17, 2007
Fri-Day 2
Bio- we discussed the Transcription and Translation Lab, reviewing the definitions. We also reviewed the order of events in those processes and then we reviewed the types of mutations.
Work on your review sheets this weekend. I will post an additional list of review questions on Blackboard.
Chem 7/8- we reviewed the similarities and differences among isotopes of an element. We completed the hw packet chart on isotopes. We further discussed ions noting that METALS tend to LOSE electrons to become positive cations BUT NON-METALS tend to gain electrons and to become negative ANIONS (not "onions"). We noted the convention for writing the symbol of an ion: value of the charge first, THEN the positive or negative SIGN to the right of the value (the opposite order signifies "oxidation state" instead of true electrostatic charge).
We then demonstrated how to calculate a WEIGHTED AVERAGE and applied this method to getting the ATOMIC MASS of an element. The atomic mass of an element is just the weighted average of the masses of the elements naturally occurring isotopes (based on their percent "abundances" as found in any natural sample of that element).
It is important to practice the setup and calculation of atomic mass.
I gave out a classwork packet. Continue to work on that for hw this weekend.
Chem 9- we reviewed the similarities and differences among isotopes of an element. We completed the hw packet chart on isotopes. We further discussed ions noting that METALS tend to LOSE electrons to become positive cations BUT NON-METALS tend to gain electrons and to become negative ANIONS (not "onions"). We noted the convention for writing the symbol of an ion: value of the charge first, THEN the positive or negative SIGN to the right of the value (the opposite order signifies "oxidation state" instead of true electrostatic charge).
I gave out a classwork packet. Continue to work on that for hw this weekend.
Work on your review sheets this weekend. I will post an additional list of review questions on Blackboard.
Chem 7/8- we reviewed the similarities and differences among isotopes of an element. We completed the hw packet chart on isotopes. We further discussed ions noting that METALS tend to LOSE electrons to become positive cations BUT NON-METALS tend to gain electrons and to become negative ANIONS (not "onions"). We noted the convention for writing the symbol of an ion: value of the charge first, THEN the positive or negative SIGN to the right of the value (the opposite order signifies "oxidation state" instead of true electrostatic charge).
We then demonstrated how to calculate a WEIGHTED AVERAGE and applied this method to getting the ATOMIC MASS of an element. The atomic mass of an element is just the weighted average of the masses of the elements naturally occurring isotopes (based on their percent "abundances" as found in any natural sample of that element).
It is important to practice the setup and calculation of atomic mass.
I gave out a classwork packet. Continue to work on that for hw this weekend.
Chem 9- we reviewed the similarities and differences among isotopes of an element. We completed the hw packet chart on isotopes. We further discussed ions noting that METALS tend to LOSE electrons to become positive cations BUT NON-METALS tend to gain electrons and to become negative ANIONS (not "onions"). We noted the convention for writing the symbol of an ion: value of the charge first, THEN the positive or negative SIGN to the right of the value (the opposite order signifies "oxidation state" instead of true electrostatic charge).
I gave out a classwork packet. Continue to work on that for hw this weekend.
# posted by C @ 10:10 AM
Thursday, November 15, 2007
Thurs-Day 1
Bio- our classroom became a cell in which we acted out the trait-expressing activities of transcription and translation. We looked at a chromosome, specifically a section of DNA that coded for a trait (curly eye lashes, for example); this section is called a gene or an allele.
We transcribed the gene's DNA to mRNA in the nucleus (at my desk) and then the mRNA travelled from the nucleus (my desk) to the ribosome (your desk) where the tRNA (your lab partner), with the matching tRNA anticodons to the mRNA codons, brought along the amino acids (from the cytoplasm) that were coded for.
If you did the translation correctly, you had the appropriate kinds and sequence of amino acids to form the functional polypeptide/protein (due to its appropriate shape). This protein expressed a trait that transported you to a monetary prize!
We then discussed the point mutations of substitution, addition/insertion, and deletion. Addition and deletion mutations cause frameshift mutations that can drastically alter the amino acid sequence that is coded for; thus, a faulty or lethal protein is made, which kills the cell.
Chem 7-we discussed isotopes of a given element noting that they have the same number of PROTONS (making them atoms of the same element) BUT a different number of NEUtrons. This difference gives the isotopes the same atomic number (# of protons) BUT different mass numbers (which are REALLY the "proton-plus-neutron" numbers!).
Thus, a S-32 atom has 16 protons and 16 neutrons but a S-34 atom has 16 protons and 18 neutrons.
We then discussed the difference between an atom and an ion of a given element. Ions have either more electrons than protons (net negative charge ions, called "anions") or fewer electrons than protons (net positive charge ions, called "cations").
We then did a chart that called for the deduction of various quantities for a given atom bases on the number of each subatomic particles that comprise the atom.
Chem 8/9- We introduced our new unit: Atomic Structure.
We reviewed our past knowledge of what particles comprise an atom, the relative masses and charges of those particles, and the locations of those particles in an atom.
We discussed the terms atom, ion, isotope, atomic number, and mass number. Regular use and application of these terms will help you remember them correctly.
We focused on isotopes of a given element noting that they have the same number of PROTONS (making them atoms of the same element) BUT a different number of NEUtrons. This difference gives the isotopes the same atomic number (# of protons) BUT different mass numbers (which are REALLY the "proton-plus-neutron" numbers!).
Thus, a S-32 atom has 16 protons and 16 neutrons but a S-34 atom has 16 protons and 18 neutrons.
We then discussed the difference between an atom and an ion of a given element. Ions have either more electrons than protons (net negative charge ions, called "anions") or fewer electrons than protons (net positive charge ions, called "cations").
We then did a chart that called for the deduction of various quantities for a given atom bases on the number of each subatomic particles that comprise the atom.
# posted by C @ 6:18 PM
Wednesday, November 14, 2007
Wednes-Day 2
Bio- we elucidated the sequence of events in translation beginning with the binding of mRNA to the ribosome. We then drew the tRNA approaching the mRNA followed by the hydrogen bonding attraction between the codon of the mRNA and the anticodon of the tRNA. A second tRNA molecule then joins its complementary mRNA codon at the adjacent site of the mRNA molecule. The two amino acids then form a peptide bond via dehydration synthesis, which begins the formation of the polypeptide/protein. The first tRNA is then released and then the ribosome moves along the mRNA molecule to continue translating the rest of the molecule into a polypeptide chain. When the stop codon of the mRNA is reached by the ribosome, there is no complementary anticodon for a stop codon so the amino acid (polypeptide) chain is then complete and is released from the ribosome to quickly become a functional protein (enzyme, hormone, etc.).
We then discussed different types of mutations. The simplest mutation is a point mutation of a single base. In "substitution", ene base can substitute for another, thus changing the DNA codon, which will cause a corresponding change in the mRNA codon that is transcribed, which MIGHT change the amino acid that is coded for.
There are other, single-base mutations: deletion and addition.
These point mutations are known as "frameshift mutations" because the addition or removal of a single base will alter the reading of the codon "triplets" drastically, as we demonstrated in class.
Tomorrow, we will discuss larger, chromosomal mutations.
Mutations are a source of the variety that we see within a species and between different organisms.
Chem 7/8- we did our part 1 multiple-choice quarterly today.
Grades should be posted by tomorrow.
We then introduced our new unit: Atomic Structure.
We reviewed our past knowledge of what particles comprise an atom, the relative masses and charges of those particles, and the locations of those particles in an atom.
We discussed the terms atom, ion, isotope, atomic number, and mass number. Regular use and application of these terms will help you remember them correctly.
Chem 9- we did our part 1 multiple-choice quarterly today.
Grades should be posted by tomorrow.
We then discussed different types of mutations. The simplest mutation is a point mutation of a single base. In "substitution", ene base can substitute for another, thus changing the DNA codon, which will cause a corresponding change in the mRNA codon that is transcribed, which MIGHT change the amino acid that is coded for.
There are other, single-base mutations: deletion and addition.
These point mutations are known as "frameshift mutations" because the addition or removal of a single base will alter the reading of the codon "triplets" drastically, as we demonstrated in class.
Tomorrow, we will discuss larger, chromosomal mutations.
Mutations are a source of the variety that we see within a species and between different organisms.
Chem 7/8- we did our part 1 multiple-choice quarterly today.
Grades should be posted by tomorrow.
We then introduced our new unit: Atomic Structure.
We reviewed our past knowledge of what particles comprise an atom, the relative masses and charges of those particles, and the locations of those particles in an atom.
We discussed the terms atom, ion, isotope, atomic number, and mass number. Regular use and application of these terms will help you remember them correctly.
Chem 9- we did our part 1 multiple-choice quarterly today.
Grades should be posted by tomorrow.
# posted by C @ 7:43 PM
Quarterly Grades
Due to the Quarterly Chem exam today, I am able to finish entering my grades later tonight; so, if your grades are not yet updated, then I am still entering them.
I am looking forward to a very successful second quarter with you all. That can be easier to accomplish since we know each other more than we did for a lot of the first quarter and we can then use that knowledge to learn more effectively from each other.
The pace of the Bio and Chem courses and the amount of material covered does increase during the second quarter; also, there are several breaks/vacations that can cause learning retention problems unless you are diligent in studying over your vacations. So, resolve to meet the challenges that this quarter will bring because a science class of any value is quite demanding, yet rewarding (sooner or later- haha).
I am looking forward to a very successful second quarter with you all. That can be easier to accomplish since we know each other more than we did for a lot of the first quarter and we can then use that knowledge to learn more effectively from each other.
The pace of the Bio and Chem courses and the amount of material covered does increase during the second quarter; also, there are several breaks/vacations that can cause learning retention problems unless you are diligent in studying over your vacations. So, resolve to meet the challenges that this quarter will bring because a science class of any value is quite demanding, yet rewarding (sooner or later- haha).
# posted by C @ 2:19 PM
Tuesday, November 13, 2007
Tues-Day 1
Bio- we practiced transcription and translation. We then began to discuss genetic mutations and mutagens (agents that cause mutations such as x-rays, chemical carcinogens, etc.). We then took a gene on a DNA molecule and saw how a point mutation caused the transcription of a different mRNA molecule (base sequence). HOWEVER, even though the mRNA molecule was slightly different, it STILL coded for the same protein, in this case. That happens sometimes and is caused by the fact that SEVERAL DIFFERENT mRNA codons can code for the SAME amino acid. You saw that on your mRNA codon chart during the activity today.
Tomorrow, we will look at the mutation that causes the disease "sickle cell anemia".
You will see that a SINGLE point mutation in the gene that codes for the oxygen-carrying pigment/protein, hemoglobin, causes the amino acid sequence to alter by ONE amino acid, which is enough to give the protein a VERY different shape, which causes the red blood cells to have a "sickle" shape.
So, as you will see, mutations can cause DNA to code for drastically different, harmful, fatal, or nonfunctional proteins!
CHEM Classes 7/8/9: we had our Quarterly Part II today. Part I multiple-choice section of the Quarterly exam is tomorrow.
Take HEED of this: I am grading the exam and students who are not identifying what each question is asking are losing points AND wasting time on the test answering questions that are not there. Please stop doing this to yourselves.
For example, when a question directs you to use a reference table and you do not use said table, you cannot get the question right.
Those who are employing the care of using the test-taking skills of highlighting/underlining/circling ONLY the key terms and data, drawing out and LABELING their pictures, and using the reference tables are avoiding careless errors and are doing very well.
Focus on the various multiple-choice sections and multiple-choice review packets for your last minute practice, tonight.
Tomorrow, we will look at the mutation that causes the disease "sickle cell anemia".
You will see that a SINGLE point mutation in the gene that codes for the oxygen-carrying pigment/protein, hemoglobin, causes the amino acid sequence to alter by ONE amino acid, which is enough to give the protein a VERY different shape, which causes the red blood cells to have a "sickle" shape.
So, as you will see, mutations can cause DNA to code for drastically different, harmful, fatal, or nonfunctional proteins!
CHEM Classes 7/8/9: we had our Quarterly Part II today. Part I multiple-choice section of the Quarterly exam is tomorrow.
Take HEED of this: I am grading the exam and students who are not identifying what each question is asking are losing points AND wasting time on the test answering questions that are not there. Please stop doing this to yourselves.
For example, when a question directs you to use a reference table and you do not use said table, you cannot get the question right.
Those who are employing the care of using the test-taking skills of highlighting/underlining/circling ONLY the key terms and data, drawing out and LABELING their pictures, and using the reference tables are avoiding careless errors and are doing very well.
Focus on the various multiple-choice sections and multiple-choice review packets for your last minute practice, tonight.
# posted by C @ 2:41 PM
Friday, November 9, 2007
Fri-Day 2
Bio- Reminder: HW for this weekend is to outline text section 11.3; I'll collect that on Tuesday; I will return your 11.2 outlines (grades on Blackboard) and your test corrections on Tuesday, also.
Murphy's Law struck us again today and, to add insult to injury, the projector/laptop worked fine just after the period ended (aaarghh! - haha?). Anyway, I was going to start with the "translation" video that is posted on Blackboard- view that repeatedly, this weekend.
The second important point is that, after considering our very complex and detailed drawing that showed not only transcription and translation (considered from the curly eyelash protein and working backwards -you all did very well with that!), but also the sites and organelles involved (nucleus and ribosomes), I have made one alteration to our class notes:
It is easier for us to process the information from "left to right" so I re-drew our notes with that orientation. This way, the codons are aligned in the correct order both individually and consecutively. The codons written in class were correct individually, but there consecutive base sequence was INCORRECT (my mistake).
So, just download the notes from Blackboard to replace your notes from today.
Thank you.
We will do more transcription and translation; then, we will show how mutations in the chromosomal DNA can lead to the production of "mutant" proteins (enzymes, etc.) which may lead to different traits.
Chem 7/8- HW for this weekend: as part of your review for the Quarterly Exam, do corrections on both the Gas Law test and the Kinetics/Entropy test. I will count your corrections as a hw grade, which can further boost your quarterly average.
Remember, that your corrections MUST explain HOW and WHY a given answer is correct. Often (almost always) a drawing, diagram, or sample calculation in NECESSARY for a sufficient correction.
If the corrections are done thoroughly, you will see that they naturally prepare you for the upcoming exam. If a question is unanswerable to you after you check the notes and text, email me so I can give you direction or see me at extra help in Room 301 on Tuesday morning.
We reviewed the Gas Laws exam and then we began our quarterly exam review. Revisit your past exams, homework packets, and worksheets; there, you will find examples of every single question type that can be asked on the Quarterly. Do something each day and go all out on Monday night.
Chem 9- HW for this weekend: as part of your review for the Quarterly Exam, do corrections on both the Gas Law test and the Kinetics/Entropy test. I will count your corrections as a hw grade, which can further boost your quarterly average.
Remember, that your corrections MUST explain HOW and WHY a given answer is correct. Often (almost always) a drawing, diagram, or sample calculation in NECESSARY for a sufficient correction.
If the corrections are done thoroughly, you will see that they naturally prepare you for the upcoming exam. If a question is unanswerable to you after you check the notes and text, email me so I can give you direction or see me at extra help in Room 301 on Tuesday morning.
We reviewed the Gas Laws exam and then we began our quarterly exam review. Revisit your past exams, homework packets, and worksheets; there, you will find examples of every single question type that can be asked on the Quarterly. Do something each day and go all out on Monday night.
Murphy's Law struck us again today and, to add insult to injury, the projector/laptop worked fine just after the period ended (aaarghh! - haha?). Anyway, I was going to start with the "translation" video that is posted on Blackboard- view that repeatedly, this weekend.
The second important point is that, after considering our very complex and detailed drawing that showed not only transcription and translation (considered from the curly eyelash protein and working backwards -you all did very well with that!), but also the sites and organelles involved (nucleus and ribosomes), I have made one alteration to our class notes:
It is easier for us to process the information from "left to right" so I re-drew our notes with that orientation. This way, the codons are aligned in the correct order both individually and consecutively. The codons written in class were correct individually, but there consecutive base sequence was INCORRECT (my mistake).
So, just download the notes from Blackboard to replace your notes from today.
Thank you.
We will do more transcription and translation; then, we will show how mutations in the chromosomal DNA can lead to the production of "mutant" proteins (enzymes, etc.) which may lead to different traits.
Chem 7/8- HW for this weekend: as part of your review for the Quarterly Exam, do corrections on both the Gas Law test and the Kinetics/Entropy test. I will count your corrections as a hw grade, which can further boost your quarterly average.
Remember, that your corrections MUST explain HOW and WHY a given answer is correct. Often (almost always) a drawing, diagram, or sample calculation in NECESSARY for a sufficient correction.
If the corrections are done thoroughly, you will see that they naturally prepare you for the upcoming exam. If a question is unanswerable to you after you check the notes and text, email me so I can give you direction or see me at extra help in Room 301 on Tuesday morning.
We reviewed the Gas Laws exam and then we began our quarterly exam review. Revisit your past exams, homework packets, and worksheets; there, you will find examples of every single question type that can be asked on the Quarterly. Do something each day and go all out on Monday night.
Chem 9- HW for this weekend: as part of your review for the Quarterly Exam, do corrections on both the Gas Law test and the Kinetics/Entropy test. I will count your corrections as a hw grade, which can further boost your quarterly average.
Remember, that your corrections MUST explain HOW and WHY a given answer is correct. Often (almost always) a drawing, diagram, or sample calculation in NECESSARY for a sufficient correction.
If the corrections are done thoroughly, you will see that they naturally prepare you for the upcoming exam. If a question is unanswerable to you after you check the notes and text, email me so I can give you direction or see me at extra help in Room 301 on Tuesday morning.
We reviewed the Gas Laws exam and then we began our quarterly exam review. Revisit your past exams, homework packets, and worksheets; there, you will find examples of every single question type that can be asked on the Quarterly. Do something each day and go all out on Monday night.
# posted by C @ 8:32 AM
Thursday, November 8, 2007
Thurs-Day 1
Bio- we reviewed the process of transcription of DNA to mRNA and then we proceeded to the next natural step in getting the information that is contained in DNA to be expressed as a physical trait: that step involves the TRANSLATION of the information coded in the mRNA to the synthesis of a specific sequence and number of amino acids, which is forms a specific protein (enzyme, receptor protein, recognition protein, transport protein, microfilament, etc.).
We saw that TRANSLATION takes place on a ribosome outside of the nucleus (from where the mRNA traveled) and involves the connection of mRNA with TRANSFER RNA (tRNA). We calculated that the 20 possible amino acids that can be needed for a given protein can be coded for by mRNA IF the mRNA code is taken THREE base pairs at a time. Every three base pairs makes up a TRIPLET, which is called a CODON because the triplet "calls for or codes for" ONE particular amino acid. That particular amino acid is brought to the mRNA at the ribosome by a particular tRNA that has the matching/complementary ANTICODON for the mRNA codon.
It's easier to see this by example (as in the notes and handout from today):
If the DNA coding strand is GCATTC, then the mRNA strand formed from that via transcription is CGUAAG, which contains two codons. The mRNA is transported from the nucleus to the ribosomes where it "hooks up with/associates with" the complementary tRNA anticodons. In this case the two tRNA anticodons are GCA and UUC. Thus, two amino acids, arginine and lysine (according to the codon chart!), will be bonded together (a peptide bond) and will make up a small part of the whole protein (polypeptide) that is coded for by the DNA molecule/gene.
We then did an activity in which you practiced transcription and then translation of part of a DNA molecule/gene.
CHECK OUT the video of this on Blackboard.
Tomorrow, we will look for patterns and methods that will make this process easier to see.
Chem 7- took the Gas Laws test today. Will get those back to you, tomorrow.
Beware that the Quarterly Exam is upon us and will require copious review and study. Your quarterly exam grade, if it is higher than your lowest grade, will replace that lowest grade. So, there is hope especially when things end well! Know that the time that you put into studying this weekend can pay off both in terms of increasing and/or enhancing your chemistry knowledge and in terms of your grade for the first quarter. Use the quarterly review packet from class today as a starting point in your study.
We will do a lot of quarterly review, tomorrow. Come prepared with questions from all previous units.
Chem 8/9 - took the Gas Laws test today. Will get those back to you, tomorrow.
Some people had questions about the Charles's Law lab so we went over some of those today.
Beware that the Quarterly Exam is upon us and will require copious review and study. Your quarterly exam grade, if it is higher than your lowest grade, will replace that lowest grade. So, there is hope especially when things end well! Know that the time that you put into studying this weekend can pay off both in terms of increasing and/or enhancing your chemistry knowledge and in terms of your grade for the first quarter. Use the quarterly review packet from class today as a starting point in your study.
We will do as much quarterly review as possible, tomorrow. Come prepared with questions from all previous units.
We saw that TRANSLATION takes place on a ribosome outside of the nucleus (from where the mRNA traveled) and involves the connection of mRNA with TRANSFER RNA (tRNA). We calculated that the 20 possible amino acids that can be needed for a given protein can be coded for by mRNA IF the mRNA code is taken THREE base pairs at a time. Every three base pairs makes up a TRIPLET, which is called a CODON because the triplet "calls for or codes for" ONE particular amino acid. That particular amino acid is brought to the mRNA at the ribosome by a particular tRNA that has the matching/complementary ANTICODON for the mRNA codon.
It's easier to see this by example (as in the notes and handout from today):
If the DNA coding strand is GCATTC, then the mRNA strand formed from that via transcription is CGUAAG, which contains two codons. The mRNA is transported from the nucleus to the ribosomes where it "hooks up with/associates with" the complementary tRNA anticodons. In this case the two tRNA anticodons are GCA and UUC. Thus, two amino acids, arginine and lysine (according to the codon chart!), will be bonded together (a peptide bond) and will make up a small part of the whole protein (polypeptide) that is coded for by the DNA molecule/gene.
We then did an activity in which you practiced transcription and then translation of part of a DNA molecule/gene.
CHECK OUT the video of this on Blackboard.
Tomorrow, we will look for patterns and methods that will make this process easier to see.
Chem 7- took the Gas Laws test today. Will get those back to you, tomorrow.
Beware that the Quarterly Exam is upon us and will require copious review and study. Your quarterly exam grade, if it is higher than your lowest grade, will replace that lowest grade. So, there is hope especially when things end well! Know that the time that you put into studying this weekend can pay off both in terms of increasing and/or enhancing your chemistry knowledge and in terms of your grade for the first quarter. Use the quarterly review packet from class today as a starting point in your study.
We will do a lot of quarterly review, tomorrow. Come prepared with questions from all previous units.
Chem 8/9 - took the Gas Laws test today. Will get those back to you, tomorrow.
Some people had questions about the Charles's Law lab so we went over some of those today.
Beware that the Quarterly Exam is upon us and will require copious review and study. Your quarterly exam grade, if it is higher than your lowest grade, will replace that lowest grade. So, there is hope especially when things end well! Know that the time that you put into studying this weekend can pay off both in terms of increasing and/or enhancing your chemistry knowledge and in terms of your grade for the first quarter. Use the quarterly review packet from class today as a starting point in your study.
We will do as much quarterly review as possible, tomorrow. Come prepared with questions from all previous units.
# posted by C @ 1:57 PM
Wednesday, November 7, 2007
Wednes-Day 2
Bio- we went to the Rachel's Challenge assembly from which, I hope, you all gained some valuable information that you can apply to your daily routines.
Today, in finer detail, we compared the molecular structures of DNA and RNA. We noted the differences between their nucleotides:
DNA contains DEOXYribose sugar, which has one less oxygen attached to the 5-atom ring than does RIBOSE, the sugar in an RNA nucleotide. There is a picture of the two different sugars, posted in the notes.
DNA always has THYMINE as the complementary base pair to ADENINE.
RNA forms by temporarily forming complementary base pairs with the DNA coding strand. A pairs with U (uracil) and G pairs with C.
RNA NEVER has THYMINE in it; instead it contains the very similar molecule, URACIL, anywhere that thymine would have been placed during transcription.
RNA is single-stranded helix-shaped molecule but DNA is a double-stranded helix-shaped molecule due to the complementary base pairs (A-T and G-C) that are held together via hydrogen bonding attractions.
In eukaryotes, the chromosomes, thus the DNA stays inside the nucleus whereas, after transcription, RNA goes outside the nucleus (through the pores in the nuclear membrane) to the ribosomes so that translation can begin.
Chem 7/8- tomorrow is test day. Study your notes (first), worksheets, etc.
I'll be in Room 301 at about 8AM for extra help tomorrow. Come prepared with specific questions that are giving you difficulty.
We reviewed for tomorrow's exam by explaining the causes of each gas law according to K-M theory and tenets. We also displayed each law graphically and went over some practice questions and test-taking techniques and mnemonics (don't forget to draw a PTV card on your test paper!!!)
We briefly discussed the Charles's Law lab, which will be due on Friday.
I will hand out review questions for the quarterly exam, tomorrow after the test.
Chem 9- tomorrow is test day. Study your notes (first), worksheets, etc.
I'll be in Room 301 at about 8AM for extra help tomorrow. Come prepared with specific questions that are giving you difficulty.
We reviewed for tomorrow's exam by explaining the causes of each gas law according to K-M theory and tenets. We also displayed each law graphically and went over some practice questions and test-taking techniques and mnemonics (don't forget to draw a PTV card on your test paper!!!).
I didn't collect your Charles Law lab today so hand that in tomorrow. Thanks!
I will hand out review questions for the quarterly exam, tomorrow after the test.
Today, in finer detail, we compared the molecular structures of DNA and RNA. We noted the differences between their nucleotides:
DNA contains DEOXYribose sugar, which has one less oxygen attached to the 5-atom ring than does RIBOSE, the sugar in an RNA nucleotide. There is a picture of the two different sugars, posted in the notes.
DNA always has THYMINE as the complementary base pair to ADENINE.
RNA forms by temporarily forming complementary base pairs with the DNA coding strand. A pairs with U (uracil) and G pairs with C.
RNA NEVER has THYMINE in it; instead it contains the very similar molecule, URACIL, anywhere that thymine would have been placed during transcription.
RNA is single-stranded helix-shaped molecule but DNA is a double-stranded helix-shaped molecule due to the complementary base pairs (A-T and G-C) that are held together via hydrogen bonding attractions.
In eukaryotes, the chromosomes, thus the DNA stays inside the nucleus whereas, after transcription, RNA goes outside the nucleus (through the pores in the nuclear membrane) to the ribosomes so that translation can begin.
Chem 7/8- tomorrow is test day. Study your notes (first), worksheets, etc.
I'll be in Room 301 at about 8AM for extra help tomorrow. Come prepared with specific questions that are giving you difficulty.
We reviewed for tomorrow's exam by explaining the causes of each gas law according to K-M theory and tenets. We also displayed each law graphically and went over some practice questions and test-taking techniques and mnemonics (don't forget to draw a PTV card on your test paper!!!)
We briefly discussed the Charles's Law lab, which will be due on Friday.
I will hand out review questions for the quarterly exam, tomorrow after the test.
Chem 9- tomorrow is test day. Study your notes (first), worksheets, etc.
I'll be in Room 301 at about 8AM for extra help tomorrow. Come prepared with specific questions that are giving you difficulty.
We reviewed for tomorrow's exam by explaining the causes of each gas law according to K-M theory and tenets. We also displayed each law graphically and went over some practice questions and test-taking techniques and mnemonics (don't forget to draw a PTV card on your test paper!!!).
I didn't collect your Charles Law lab today so hand that in tomorrow. Thanks!
I will hand out review questions for the quarterly exam, tomorrow after the test.
# posted by C @ 12:18 PM
Tuesday, November 6, 2007
For Wednesday...
Bio- reminder that the text section 11.2 outline is due on Wednesday.
Chem 7- On Wednesday, we will discuss the Charles's Law lab, which will then be due on Friday. We will also review for Thursday's test. Make sure that you have done ALL of the questions from the various worksheets and review packets (on Blackboard) so that I can tailor our review to your needs based on any problems that were difficult to you.
Gas Laws test is on Thursday.
Chem 9- On Wednesday, your past two labs are due.
We will review for Thursday's test. Make sure that you have done ALL of the questions from the various worksheets and review packets (on Blackboard) so that I can tailor our review to your needs based on any problems that were difficult to you.
The Gas Laws test is on Thursday.
Chem 7- On Wednesday, we will discuss the Charles's Law lab, which will then be due on Friday. We will also review for Thursday's test. Make sure that you have done ALL of the questions from the various worksheets and review packets (on Blackboard) so that I can tailor our review to your needs based on any problems that were difficult to you.
Gas Laws test is on Thursday.
Chem 9- On Wednesday, your past two labs are due.
We will review for Thursday's test. Make sure that you have done ALL of the questions from the various worksheets and review packets (on Blackboard) so that I can tailor our review to your needs based on any problems that were difficult to you.
The Gas Laws test is on Thursday.
# posted by C @ 11:39 AM
Monday, November 5, 2007
Mon-Day 1
Bio- we began our new unit, which shows the OTHER main function of DNA:
its coded information, in the form of nucleotide base sequences, is used to direct the synthesis of particular proteins that give an organism its specific characteristics/traits/features.
The coded information of the DNA molecules, which make up the chromosomes, cannot leave the nucleus; instead, the DNA sequence of bases is used as a template for the synthesis of RNA molecules, which CAN leave the nucleus without changing the number of chromosomes in the nucleus. This synthesis of RNA from DNA is called TRANSCRIPTION, which preserves the code and sequence of the DNA in a slightly different molecule, RNA. We saw how this process occurs.
There are several main differences between DNA and RNA. Today, we saw three of those differences: DNA is a double-helix of nucleotides whereas RNA is a single-helix of nucleotides;
DNA has Deoxyribose sugar as part of each nucleotide and RNA has Ribose as part of each nucleotide; DNA pairs A with T or G with C whereas RNA pairs A with U or G with C (U= uracil, which is VERY similar in shape and structure to thymine); there is NEVER NEVER NEVER any thymine in ANY RNA molecule!!!
There are three types of RNA that are transcribed from the DNA: we will see that these three types of RNA molecules work together (at the ribosomes outside of the nucleus) in the synthesis of each particular protein (a chain of amino acids) in a process called TRANSLATION.
The shape of the protein will cause the particular FUNCTION of the protein (which determines a particular trait); the shape of the protein is dictated by the particular SEQUENCE of amino acids that make up the protein; the particular sequence of amino acids of the protein are determined by the sequence of nitrogenous bases in the messenger RNA molecule; finally, the sequence of nitrogenous bases in the messenger RNA are determined by the sequence of nitrogenous bases in the DNA.
So, overall, we have the central dogma of molecular biology:
DNA codes for RNA via transcription. RNA codes for protein via translation. Proteins cause an organism to have particular traits/features.
We went over part of the DNA, mitosis, and asexual reproduction test; I was glad to see that many of you worked closer to your potential though, as we saw from test-skill review, almost all of you can do even better. As we progress and improve, this class can and should achieve a 90 or higher average on all future tests, as you have proven on this recent exam. Let's continue to improve our efforts and learn from our first quarter experiences so that we earn and produce excellent results in the next quarter.
Chem 7- we calculated and compared the densities of several different gases at STP. We saw that, given the same temperature and pressure conditions, the gas molecules with the greatest masses are the densest; this is related to the fact that, in a given volume, say 22.4 L, at the same T and P, there are the SAME number of each different type of gas molecules. So given the same number of molecules, naturally, the heaviest molecules will have the most mass in that same volume and, thus, be the densest.
We reviewed how to calculate the MOLAR MASS of a substance (the mass, in grams, of one mole of molecules of a substance) by adding up the gram atomic masses of the elements in the
We then finished our comparison and contrast of real gases vs. theoretical ideal gases and showed the conditions that would cause a real gas to behave ideally (high T and low P, KEEPING THE GAS IN THE GAS PHASE by heating and NOT squishing!) due to the overcoming of intermolecular attractions at high T and the insignificant molecular volumes at low P. We also showed, by contrast, that real gases can LIQUEFY or SOLIDIFY when they DEVIATE from ideal gas behavior at low T and high P (freeze and squish into a SOLID!).
Wednesday is our final review day for the unit exam on Thursday. We will also discuss both the can lab and the Charles lab, so bring those labs to class.
Chem 8/9- we calculated and compared the densities of several different gases at STP. We saw that, given the same temperature and pressure conditions, the gas molecules with the greatest masses are the densest; this is related to the fact that, in a given volume, say 22.4 L, at the same T and P, there are the SAME number of each different type of gas molecules. So given the same number of molecules, naturally, the heaviest molecules will have the most mass in that same volume and, thus, be the densest. We reviewed how to calculate the MOLAR MASS of a substance (the mass, in grams, of one mole of molecules of a substance) by adding up the gram atomic masses of the elements in the molecule, multiplied by each element's subscript within the molecular formula.
We then finished our comparison and contrast of real gases vs. theoretical ideal gases and showed the conditions that would cause a real gas to behave ideally (high T and low P, KEEPING THE GAS IN THE GAS PHASE by heating and NOT squishing!) due to the overcoming of intermolecular attractions at high T and the insignificant molecular volumes at low P. We also showed, by contrast, that real gases can LIQUEFY or SOLIDIFY when they DEVIATE from ideal gas behavior at low T and high P (freeze and squish into a SOLID!).
We discussed the Gay-Lussac lab (crush the can) and the Charles Law lab; the data for Table B of your lab will be posted on Blackboard tonight (Monday). Notice what happens to the RATIO of length (really volume) to Temperature when you use the Celsius data vs. when you use the converted Kelvin (absolute T) data! Can you see why the gas laws only "work" when the Kelvin temperatures are used because only Kelvin temperatures are DIRECT measures of average KE of the gas molecules (part of K-M Theory).
Those two labs are due on Wednesday. Email me if you have further questions about those labs.
its coded information, in the form of nucleotide base sequences, is used to direct the synthesis of particular proteins that give an organism its specific characteristics/traits/features.
The coded information of the DNA molecules, which make up the chromosomes, cannot leave the nucleus; instead, the DNA sequence of bases is used as a template for the synthesis of RNA molecules, which CAN leave the nucleus without changing the number of chromosomes in the nucleus. This synthesis of RNA from DNA is called TRANSCRIPTION, which preserves the code and sequence of the DNA in a slightly different molecule, RNA. We saw how this process occurs.
There are several main differences between DNA and RNA. Today, we saw three of those differences: DNA is a double-helix of nucleotides whereas RNA is a single-helix of nucleotides;
DNA has Deoxyribose sugar as part of each nucleotide and RNA has Ribose as part of each nucleotide; DNA pairs A with T or G with C whereas RNA pairs A with U or G with C (U= uracil, which is VERY similar in shape and structure to thymine); there is NEVER NEVER NEVER any thymine in ANY RNA molecule!!!
There are three types of RNA that are transcribed from the DNA: we will see that these three types of RNA molecules work together (at the ribosomes outside of the nucleus) in the synthesis of each particular protein (a chain of amino acids) in a process called TRANSLATION.
The shape of the protein will cause the particular FUNCTION of the protein (which determines a particular trait); the shape of the protein is dictated by the particular SEQUENCE of amino acids that make up the protein; the particular sequence of amino acids of the protein are determined by the sequence of nitrogenous bases in the messenger RNA molecule; finally, the sequence of nitrogenous bases in the messenger RNA are determined by the sequence of nitrogenous bases in the DNA.
So, overall, we have the central dogma of molecular biology:
DNA codes for RNA via transcription. RNA codes for protein via translation. Proteins cause an organism to have particular traits/features.
We went over part of the DNA, mitosis, and asexual reproduction test; I was glad to see that many of you worked closer to your potential though, as we saw from test-skill review, almost all of you can do even better. As we progress and improve, this class can and should achieve a 90 or higher average on all future tests, as you have proven on this recent exam. Let's continue to improve our efforts and learn from our first quarter experiences so that we earn and produce excellent results in the next quarter.
Chem 7- we calculated and compared the densities of several different gases at STP. We saw that, given the same temperature and pressure conditions, the gas molecules with the greatest masses are the densest; this is related to the fact that, in a given volume, say 22.4 L, at the same T and P, there are the SAME number of each different type of gas molecules. So given the same number of molecules, naturally, the heaviest molecules will have the most mass in that same volume and, thus, be the densest.
We reviewed how to calculate the MOLAR MASS of a substance (the mass, in grams, of one mole of molecules of a substance) by adding up the gram atomic masses of the elements in the
We then finished our comparison and contrast of real gases vs. theoretical ideal gases and showed the conditions that would cause a real gas to behave ideally (high T and low P, KEEPING THE GAS IN THE GAS PHASE by heating and NOT squishing!) due to the overcoming of intermolecular attractions at high T and the insignificant molecular volumes at low P. We also showed, by contrast, that real gases can LIQUEFY or SOLIDIFY when they DEVIATE from ideal gas behavior at low T and high P (freeze and squish into a SOLID!).
Wednesday is our final review day for the unit exam on Thursday. We will also discuss both the can lab and the Charles lab, so bring those labs to class.
Chem 8/9- we calculated and compared the densities of several different gases at STP. We saw that, given the same temperature and pressure conditions, the gas molecules with the greatest masses are the densest; this is related to the fact that, in a given volume, say 22.4 L, at the same T and P, there are the SAME number of each different type of gas molecules. So given the same number of molecules, naturally, the heaviest molecules will have the most mass in that same volume and, thus, be the densest. We reviewed how to calculate the MOLAR MASS of a substance (the mass, in grams, of one mole of molecules of a substance) by adding up the gram atomic masses of the elements in the molecule, multiplied by each element's subscript within the molecular formula.
We then finished our comparison and contrast of real gases vs. theoretical ideal gases and showed the conditions that would cause a real gas to behave ideally (high T and low P, KEEPING THE GAS IN THE GAS PHASE by heating and NOT squishing!) due to the overcoming of intermolecular attractions at high T and the insignificant molecular volumes at low P. We also showed, by contrast, that real gases can LIQUEFY or SOLIDIFY when they DEVIATE from ideal gas behavior at low T and high P (freeze and squish into a SOLID!).
We discussed the Gay-Lussac lab (crush the can) and the Charles Law lab; the data for Table B of your lab will be posted on Blackboard tonight (Monday). Notice what happens to the RATIO of length (really volume) to Temperature when you use the Celsius data vs. when you use the converted Kelvin (absolute T) data! Can you see why the gas laws only "work" when the Kelvin temperatures are used because only Kelvin temperatures are DIRECT measures of average KE of the gas molecules (part of K-M Theory).
Those two labs are due on Wednesday. Email me if you have further questions about those labs.
# posted by C @ 12:35 PM
Friday, November 2, 2007
Fri-Day 2
Reminder for Chem Classes!
The Gas Law Unit Exam has been moved to next THURSDAY (11/08), due to the shortened periods on Wednesday. Furthermore, the first quarterly exam will be given the following Tuesday and Wednesday (11/13 and 11/14, we are off for Veterans Day that Monday).
Bio- we had our unit test today. On Monday, we begin our new unit, which focuses on the other MAJOR feature of DNA: its ability to also act as a TEMPLATE for the synthesis of RNA ( "transcription", which is then used as a template for the production of proteins ("translation") which give an organism its specific traits! Basically, we'll see how particular DNA sequences (genes or "alleles") eventually get translated into specific traits such as eye color, hair color, metabolic rate, etc.
This is the MOST important unit in understanding Biology/Life at the molecular level.
If you have time, you can get a head start on the upcoming outline homework:
on Monday, you'll be assigned text section 11.2; on Wednesday, you'll be assigned section 11.3.
Chem 7/8- we did another gas density at STP problem; the key to these problems is getting the mass and volume of the particular substance. That is why we take ONE MOLE of the gas because one mole of ANY gas at STP (only!) occupies 22.4 liters of space. Then we just have to get the mass of one mole of the substance (the MOLAR MASS), which we get by adding up the atomic masses (in grams) of each atom in the formula (e.g. N2O5 has a molar mass of :
[(2 x 14. g) + (5 x 16. g)] = 108 grams; therefore, its density at STP is 108 grams divided by 22.4 liters, which is 4.82 grams per liter.
We then did our Charles's Law lab as we saw that, at constant pressure and moles of gas (a mixture of nitrogen and oxygen, in this case), as temperature decreases, the volume of the gases decreases.
We will discuss that lab and it will be due next Wednesday. Also, I found the graded Kinetics Labs in our classroom today; they were in my ditto drawer; I'll return them to you on Monday.
We then finished by explaining that real gases become more "ideal" (i.e. follow the gas laws more accurately) when they are under conditions that make the gas match the tenets of Kinetic-Molecular Theory: that their individual volumes become negligible AND that the molecules have totally overcome their attractions for each other. Thus, real gases follow the gas laws quite well when the gases are at HIGH TEMPERATURE (so the molecules can easily overcome their attractions by flying by each other so fast) and LOW PRESSURE (so there is lots of "space between" the molecules thus making each molecule's volume insignificant).
Just remember, a real gas STAYS in the GAS phase at HIGH temperatures and LOW pressures!
Chem 9- we didn't get to discuss any questions that you may have about the crushed can lab, today, so I will discuss BOTH the crushed can lab and the Charles's law lab on Monday; bring both labs in and we will go over them completely. Those labs will be due on Wednesday.
We did discuss an implication of Avogadro's Law: equal volumes of any gas at the same temperature and pressure MUST contain an equal number of molecules in that volume (it does NOT matter that one type of molecule is bigger/larger than another!!!).
One thing that has been experimentally determined and related to Avogadro's Law is that ONE MOLE of any ("ideal" - follows the gas laws and tenets of K-M Theory) gas at STP takes up 22.4 L of space. So if you have, 22.4 L of oxygen or ozone or nitrogen or carbon monoxide or carbon dioxide gas at STP, there ARE 6.02 x 10^23 molecules of any of those gases in that 22.4 L volume container.
Using our reference tables, we are fortunate that we can just look at the "atomic mass" of ANY element and know that the number seen is the MASS of that element IN GRAMS for one mole of atoms of that element, e.g. one mole of Argon atoms has a mass of 39.948 grams, whereas one mole of Neon atoms has a mass of 20.179 grams. Thus each Neon atom weighs about half as much as each Argon atom.
From this, we began to do some gas density calculations ONLY for gases at STP (1 mol of ANY gas at STP has a volume of 22.4 L)!!!
The Gas Law Unit Exam has been moved to next THURSDAY (11/08), due to the shortened periods on Wednesday. Furthermore, the first quarterly exam will be given the following Tuesday and Wednesday (11/13 and 11/14, we are off for Veterans Day that Monday).
Bio- we had our unit test today. On Monday, we begin our new unit, which focuses on the other MAJOR feature of DNA: its ability to also act as a TEMPLATE for the synthesis of RNA ( "transcription", which is then used as a template for the production of proteins ("translation") which give an organism its specific traits! Basically, we'll see how particular DNA sequences (genes or "alleles") eventually get translated into specific traits such as eye color, hair color, metabolic rate, etc.
This is the MOST important unit in understanding Biology/Life at the molecular level.
If you have time, you can get a head start on the upcoming outline homework:
on Monday, you'll be assigned text section 11.2; on Wednesday, you'll be assigned section 11.3.
Chem 7/8- we did another gas density at STP problem; the key to these problems is getting the mass and volume of the particular substance. That is why we take ONE MOLE of the gas because one mole of ANY gas at STP (only!) occupies 22.4 liters of space. Then we just have to get the mass of one mole of the substance (the MOLAR MASS), which we get by adding up the atomic masses (in grams) of each atom in the formula (e.g. N2O5 has a molar mass of :
[(2 x 14. g) + (5 x 16. g)] = 108 grams; therefore, its density at STP is 108 grams divided by 22.4 liters, which is 4.82 grams per liter.
We then did our Charles's Law lab as we saw that, at constant pressure and moles of gas (a mixture of nitrogen and oxygen, in this case), as temperature decreases, the volume of the gases decreases.
We will discuss that lab and it will be due next Wednesday. Also, I found the graded Kinetics Labs in our classroom today; they were in my ditto drawer; I'll return them to you on Monday.
We then finished by explaining that real gases become more "ideal" (i.e. follow the gas laws more accurately) when they are under conditions that make the gas match the tenets of Kinetic-Molecular Theory: that their individual volumes become negligible AND that the molecules have totally overcome their attractions for each other. Thus, real gases follow the gas laws quite well when the gases are at HIGH TEMPERATURE (so the molecules can easily overcome their attractions by flying by each other so fast) and LOW PRESSURE (so there is lots of "space between" the molecules thus making each molecule's volume insignificant).
Just remember, a real gas STAYS in the GAS phase at HIGH temperatures and LOW pressures!
Chem 9- we didn't get to discuss any questions that you may have about the crushed can lab, today, so I will discuss BOTH the crushed can lab and the Charles's law lab on Monday; bring both labs in and we will go over them completely. Those labs will be due on Wednesday.
We did discuss an implication of Avogadro's Law: equal volumes of any gas at the same temperature and pressure MUST contain an equal number of molecules in that volume (it does NOT matter that one type of molecule is bigger/larger than another!!!).
One thing that has been experimentally determined and related to Avogadro's Law is that ONE MOLE of any ("ideal" - follows the gas laws and tenets of K-M Theory) gas at STP takes up 22.4 L of space. So if you have, 22.4 L of oxygen or ozone or nitrogen or carbon monoxide or carbon dioxide gas at STP, there ARE 6.02 x 10^23 molecules of any of those gases in that 22.4 L volume container.
Using our reference tables, we are fortunate that we can just look at the "atomic mass" of ANY element and know that the number seen is the MASS of that element IN GRAMS for one mole of atoms of that element, e.g. one mole of Argon atoms has a mass of 39.948 grams, whereas one mole of Neon atoms has a mass of 20.179 grams. Thus each Neon atom weighs about half as much as each Argon atom.
From this, we began to do some gas density calculations ONLY for gases at STP (1 mol of ANY gas at STP has a volume of 22.4 L)!!!
# posted by C @ 11:41 AM
Thursday, November 1, 2007
Good news: Chem-Think Tutorial Website!
I am so impressed with this tutorial website; I KNOW that using this site will help you to better understand chemistry and will help you to prepare properly for tests. There is a one-time sign-up (free!) that takes about two minutes but follow-up visits to the site will be much faster because you don't have to keep entering all of your registration info.
Go to http://chemthink.com/chemthink.htm
Then, towards the center-top of the page, see "Signup";
click on that and choose "Student" for your signup option.
Click on "Student" and then enter this code on the new page where it says "Register":
8927-8193-1185 and click on Register.
Then choose your own username and password;
then select either period 7 or period 9 (whichever class you are in) and click "Register Now".
Once you're registered, log in and click on the "Preview" link at the top right of the page.
Then click on the "Gases" unit; then click on "Behavior of Gases"
There, you will go through a tutorial that will LOCK IN your understanding of chem at the most fundamental molecular (collision theory) level! Good times.
Go to http://chemthink.com/chemthink.htm
Then, towards the center-top of the page, see "Signup";
click on that and choose "Student" for your signup option.
Click on "Student" and then enter this code on the new page where it says "Register":
8927-8193-1185 and click on Register.
Then choose your own username and password;
then select either period 7 or period 9 (whichever class you are in) and click "Register Now".
Once you're registered, log in and click on the "Preview" link at the top right of the page.
Then click on the "Gases" unit; then click on "Behavior of Gases"
There, you will go through a tutorial that will LOCK IN your understanding of chem at the most fundamental molecular (collision theory) level! Good times.
# posted by C @ 12:05 PM
Thurs-Day 1
Bio- we reviewed our unit on Mitosis, Cytokinesis, DNA, and Types of Asexual Reproduction.
We also practiced TEST-TAKING skills, which are to be employed as you practice for tomorrow's test and as you take tomorrow's test so that you MAXIMIZE your score and take pride in your effort; you will also have the satisfaction of knowing that you could not try any harder when you properly employ all of the techniques together: as soon as the test BEGINS, no sooner, drawing out things that you KNOW will be tested, jotting down any information that you might forget, UNDERLINING/circling key terms in the question and ASSOCIATING those terms with your predicted answer, which you then write down.
In short answer questions, make SURE that your answer includes the KEY TERMS from the questions but does not MERELY repeat those terms; your answers will have to use those terms in a detailed description or explanation. Remember, DRAWINGS help explanations and labeled drawings are a large part of any good explanation.
The answers to the DNA tutorial handout will be posted on Blackboard this afternoon. Check your work.
Nobody came to extra help this morning. That means that everybody is very confident with the material in this unit or that you are not getting help that is available when you require it.
Chem 7- we reviewed our Graham's Law of diffusion/effusion explanation and then went on to a very important mathematical concept in Chemistry: the "MOLE" is a term used to indicate Avogadro's number of particles = 6.02 x 10^23 particles.
One thing that has been experimentally determined and related to Avogadro's Law is that ONE MOLE of any ("ideal" - follows the gas laws and tenets of K-M Theory) gas at STP takes up 22.4 L of space. So if you have, 22.4 L of oxygen or ozone or nitrogen or carbon monoxide or carbon dioxide gas at STP, there ARE 6.02 x 10^23 molecules of any of those gases in that 22.4 L volume container.
Using our reference tables, we are fortunate that we can just look at the "atomic mass" of ANY element and know that the number seen is the MASS of that element IN GRAMS for one mole of atoms of that element, e.g. one mole of Argon atoms has a mass of 39.948 grams, whereas one mole of Neon atoms has a mass of 20.179 grams. Thus each Neon atom weighs about half as much as each Argon atom.
From this, we began to do some gas density calculations ONLY for gases at STP (1 mol of any gas at STP has a volume of 22.4 L)!!!
Chem 8/9- we delved into Graham's (like the crackers) Law, which state the relationship between the relative masses of gas molecules and their respective rates of diffusion and effusion. Graham found that, at the same temperature and pressure, the heavier the gas, the slower its rate of effusion/diffusion and the lighter the gas, the faster its rate of effusion/diffusion.
We explained this phenomenon by looking at the Kelvin Temperature - average kinetic energy connection of Kinetic Molecular Theory. At the same temperature, any two samples of gas molecules will have the SAME average kinetic energy BUT, there are TWO factors that contribute to kinetic energy: velocity AND mass. So, if two molecules have the same KE, the heavier one MUST be going slower (thus diffusing slower) and the lighter one must be going faster (thus diffusing faster). This accounts for Graham's "empirical" (EXPERIMENTALLY found, not just theoretically predicted!) discovery.
We saw how to calculate the relative masses of molecules by using the "atomic mass" numbers listed in the Periodic Table. For example, N= 14.3 atomic mass units and H= 1.0 atomic mass units so, ammonia, NH3 has an atomic mass of 17.3 (one N and three H's). Carbon dioxide, CO2, has an atomic mass of 44.0 atomic mass units
( one C = 12.0 amu and two O's = 2 x 16.0 amu) = 44.0 amu ; so, under the same conditions (T and P), ammonia will diffuse/effuse faster than carbon dioxide!
We did a lab showing the effect of varying temperature on the volume of a gas that is at constant pressure and a constant number of molecules or "moles". We saw that, as the little sample of air in a capillary tube is cooled at constant external pressure, the volume of that sample of air decreases. We will discuss our data from that Charles's Law lab on Monday.
The lab write-up for the "crush the can" (Gay-Lussac's Law) lab is due Monday, after we discuss some of the questions from that lab, tomorrow.
We also practiced TEST-TAKING skills, which are to be employed as you practice for tomorrow's test and as you take tomorrow's test so that you MAXIMIZE your score and take pride in your effort; you will also have the satisfaction of knowing that you could not try any harder when you properly employ all of the techniques together: as soon as the test BEGINS, no sooner, drawing out things that you KNOW will be tested, jotting down any information that you might forget, UNDERLINING/circling key terms in the question and ASSOCIATING those terms with your predicted answer, which you then write down.
In short answer questions, make SURE that your answer includes the KEY TERMS from the questions but does not MERELY repeat those terms; your answers will have to use those terms in a detailed description or explanation. Remember, DRAWINGS help explanations and labeled drawings are a large part of any good explanation.
The answers to the DNA tutorial handout will be posted on Blackboard this afternoon. Check your work.
Nobody came to extra help this morning. That means that everybody is very confident with the material in this unit or that you are not getting help that is available when you require it.
Chem 7- we reviewed our Graham's Law of diffusion/effusion explanation and then went on to a very important mathematical concept in Chemistry: the "MOLE" is a term used to indicate Avogadro's number of particles = 6.02 x 10^23 particles.
One thing that has been experimentally determined and related to Avogadro's Law is that ONE MOLE of any ("ideal" - follows the gas laws and tenets of K-M Theory) gas at STP takes up 22.4 L of space. So if you have, 22.4 L of oxygen or ozone or nitrogen or carbon monoxide or carbon dioxide gas at STP, there ARE 6.02 x 10^23 molecules of any of those gases in that 22.4 L volume container.
Using our reference tables, we are fortunate that we can just look at the "atomic mass" of ANY element and know that the number seen is the MASS of that element IN GRAMS for one mole of atoms of that element, e.g. one mole of Argon atoms has a mass of 39.948 grams, whereas one mole of Neon atoms has a mass of 20.179 grams. Thus each Neon atom weighs about half as much as each Argon atom.
From this, we began to do some gas density calculations ONLY for gases at STP (1 mol of any gas at STP has a volume of 22.4 L)!!!
Chem 8/9- we delved into Graham's (like the crackers) Law, which state the relationship between the relative masses of gas molecules and their respective rates of diffusion and effusion. Graham found that, at the same temperature and pressure, the heavier the gas, the slower its rate of effusion/diffusion and the lighter the gas, the faster its rate of effusion/diffusion.
We explained this phenomenon by looking at the Kelvin Temperature - average kinetic energy connection of Kinetic Molecular Theory. At the same temperature, any two samples of gas molecules will have the SAME average kinetic energy BUT, there are TWO factors that contribute to kinetic energy: velocity AND mass. So, if two molecules have the same KE, the heavier one MUST be going slower (thus diffusing slower) and the lighter one must be going faster (thus diffusing faster). This accounts for Graham's "empirical" (EXPERIMENTALLY found, not just theoretically predicted!) discovery.
We saw how to calculate the relative masses of molecules by using the "atomic mass" numbers listed in the Periodic Table. For example, N= 14.3 atomic mass units and H= 1.0 atomic mass units so, ammonia, NH3 has an atomic mass of 17.3 (one N and three H's). Carbon dioxide, CO2, has an atomic mass of 44.0 atomic mass units
( one C = 12.0 amu and two O's = 2 x 16.0 amu) = 44.0 amu ; so, under the same conditions (T and P), ammonia will diffuse/effuse faster than carbon dioxide!
We did a lab showing the effect of varying temperature on the volume of a gas that is at constant pressure and a constant number of molecules or "moles". We saw that, as the little sample of air in a capillary tube is cooled at constant external pressure, the volume of that sample of air decreases. We will discuss our data from that Charles's Law lab on Monday.
The lab write-up for the "crush the can" (Gay-Lussac's Law) lab is due Monday, after we discuss some of the questions from that lab, tomorrow.
# posted by C @ 11:33 AM
