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 
