SciHawks

AP Chem - discussed different types of catalysts; homogeneous vs. heterogeneous catalysts; the mechanism by which catalysts lower the activation energy required for an effective collision in the catalytic
pathway/mechanism via bond angle strain of the appropriate bonds to be broken for an effective collision.

Bio - we discussed two diseases of the excretory system: gout and kidney stones, their causes and effects.

AP Chem - took the unit exam on Kinetics.

Bio - reviewed four common disorders/diseases of the respiratory system organs, their causes and effects in interfering with homeostasis.
Unit HW is due tomorrow:
Period 8 - do questions 1-9
Period 11 - do questions 1-8 (we are one day behind the other section)

AP Chem: Kinetics exam on Monday covers all notes from and problem sets from the unit with emphasis on :

• Complete explanation of HOW each factor that can affect the rate of a reaction does so.
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• Explanation must be in terms of collision frequency, fraction of particles with proper orientation for an effective collision, fraction of molecules that meet or exceed the activation energy for an effective collision, and overall effective collision frequency. You should use made up numbers in your explanation.
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• Calculation of rate of reaction (from graphs or data) from rate of appearance or disappearance of products or reactants, respectively.
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• Determination of rate law, order of reaction overall, and for each reactant, from data table and from graphed data.
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• Assessing the plausibility of reaction mechanisms, after the rate law has been experimentally determined, and relating the rate law to the mechanism.
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• Determination and explanation of catalysts and intermediates in reaction mechanisms.
• Explanation/determination of catalysts and intermediates on energy/enthalpy diagrams.
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• Time-dependent rate law calculations (any order) from data tables, graphs, or time/concentration data.
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• Using the two versions of the Arrhenius equation to determine activation energy, frequency factor or rate constant at a second temperature, given graphs or data table of rate constant vs. inverse temperature, or given appropriate data.
• Knowledge/interpretation of any graphical representation of any order rate law.

As with all remaining topics in AP Chem, there are many discrete objectives, however, most of them are inter-related so that an understanding of one objective leads to an understanding of several other objectives. Also, even on somewhat quantitative topics such as kinetics, a qualitative understanding of the CAUSES of the formulas or phenomena is primary and ESSENTIAL.

In class today, we discussed the causes of the relationship among the variables in the Arrhenius equation.
We showed how to eliminate the frequency factor to come up with a derived Arrhenius equation in which we can predict the rate constant for a given reaction at a second temperature, given the rate constant at a different temperature.
We discussed the meaning of A, the frequency factor, and showed how to obtain the value from the ln A, y-intercept, on a graph of MANY data points showing the linear relationship between the ln of k and the INVERSE Kelvin temperature.

Bio- we finished up the human respiratory system, showing in detail how breathing is regulated via the nerve sensors in the medulla and aorta, which signal the diaphragm to contract, which causes air pressure differences between the air in the lungs and the external air.
We also discussed four diseases of the respiratory system in terms of cause and effect.

AP Chem - we applied the time dependent rate laws to 0th, 1st, and 2nd order questions involving remaining concentrations, times, and half-lives.
We then discussed collision theory in order to establish the relationship between activation energy and the rate of a reaction at a given temperature, which leads to the Arrhenius equation.

Bio - we discussed the structures and functions of each of the parts of the respiratory system; the whole purpose of this system is to EFFICIENTLY facilitate the absorption of oxygen into the blood in alveolar capillaries and the excretion/removal of the metabolic waste gas, carbon dioxide.

AP Chem - from experimental data tables showing the initial rate of reaction for given initial concentrations of reactants, we went through an informal method of trying various exponents in order to deduce the rate law of a given reaction, which we could then relate to the possible mechanisms for a given reaction.
We returned to our derived time-dependent rate law equations for first order kinetics; we applied the equation to two examples in which we got the half-life time from the rate constant or vice-versa; we also used our derived equation ( better than the reference table equation) to determine the time for a certain fraction or percentage of a reactant to be used up or to remain (careful about the fraction used!).

Bio - we detailed the causes and effects of the various diseases or disorders of the circulatory system.
We began the state lab on experimental design: Making Connections.

AP Chem - we derived the 0th and 1st order time dependent rate laws via graphical analysis and also via calculus.
We analyzed the line or curve that results from a 0th or 1st order kinetics of a given reactant, noting the meaning of the slope, y-intercept, and units.
Check out the Descriptive Chem folder on Edline for two problems sets; after reviewing thoroughly all previously studied reaction types, do each problem set within 5 minutes, strictly timing yourself.
You will have the same format quiz on these question types on Thursday and possibly also on Friday - 5 minute quiz, 3 questions, 25 points.

Bio - we discussed the "fluid" part of the circulatory system- the blood. We looked at the structure and function of each component, and then we discussed a few disorders of the circulatory system.

AP Chem - we reviewed the likely and possible exponents/orders for molecules/particles in a rate law (0,1,2, 0.5 , etc.).
Very few of you knew how to do the simple, one-step calculation of determining the initial rate of appearance or disappearance of a product or reactant, respectively, given the initial rate of REACTION in a given experiment! NOTES MUST BE REVIEWED AND SOME REINFORCEMENT PROBLEMS SOLVED EACH DAY - SEE EDLINE AND TEXTBOOK.
We used a given experimental data line to solve for the rate constant at the given temperature, given that we know the rate law exponents already.

We then saw the "formal" way to use a data table and rate law ratios to determine the exponent of each substance in a rate law. When determining the exponent of a given substance, be careful NOT to choose two experiments that have the SAME concentration of that substance.
We then saw how to get the initial rate of reaction for yet another set of initial concentrations of reactants at the SAME TEMPERATURE as conducted in the other experimental trials - the final answer is posted in notes on Edline.

We looked at the parts of the "fluid", blood, which consists of red blood cells, white blood cells, platelets, and the liquid plasma.

AP Chem - we showed the "steady-state" approximation method i.e. when a proposed reaction mechanism does add up to the net equation but does not have a single elementary step that agrees with the experimental rate law; in this case, you can label the first step "fast", which reaches equilibrium between its forward and reverse steps (use a double arrow) and has a product or products that are used in the next "slow" or rate determining step. We saw that, by equating the forward and reverse reaction rate laws of the first step, that an algebraic "substitution" is possible for one of the "intermediate" molecules in the rate-determining step, which may yield agreement with the experimental rate law.
This may work, but does not HAVE to work. You must at least try the substitution, especially when you see a fast step followed by a slow step in a mechanism that does not obviously initially agree with the experimental rate law.
We explained why there is no substitution for a slow then fast step mechanism.
We then went on to experimental rate data table analysis in which we can determine the experimental rate law from three or more controlled experiment involving changing reactant concentrations, usually one reactant at a time.
We will do the formal method on Monday.

Bio - we focused on the heartbeat cycle, showing the flow of blood to and from the various parts of the heart and the important vessels directly leading to and from the heart. We discussed the heart valves, their names and functions.
We also discussed the meaning and cause of the systolic and diastolic blood pressure measurements.

AP Chem - we looked at how experimental data is collected and organized so that the rate law for a given reaction can be determined; this is a two-step process involving many trials in which initial reaction rate is determined for several different initial concentrations of a given reactant. Then, the rate vs. initial concentration data is plotted, showing the reaction order with respect to that particular reactant depending on whether a straight line or exponential curve appears.
We began reaction mechanisms, explaining the three requirements for a plausible/likely mechanism for a given overall reaction:
1. the sum of the elementary steps MUST add up to the net equation
2. the rate law of the SLOW/rate-determining step MUST match the EXPERIMENTALLY determined rate law.
3. Don't forget, a plausible mechanism should typically contain unimolecular or bimolecular collisions in each elementary step because a ter-molecular collision (or greater) is much less likely.

Bio - we began our new unit on transport and excretion, which focuses on the circulatory, respiratory, and excretory systems. We focused on the parts of the circulatory system, explained how complex organisms have CLOSED circulatory systems (the fluid/blood is always contained IN the tubes/vessels), for efficient direction of the nutrient/essential chemical-transporting blood.
We looked at the pump, fluid, and tubes i.e. the heart, blood, and arteries/veins/capillaries, and the structure of each part.

AP Chem - took the test on the remaining topics from semester one chem: Raoult's Law, Metal-ligand naming and writing, relative colligative effects, and some more descriptive chem

Bio - took the unit 8 exam on nutrition and regulation.

AP Chem - we discussed the "order" or "molecularty" of an elementary step in a reaction mechanism, and we related the rate law that results from the order; we saw mathematically how the number of a given molecule involved in the collision in an elementary step is necessarily the exponent of that molecule's concentration in the rate law written for that step.

Bio - we did our final unit review for the Endocrine and Digestive systems exam.

AP Chem - the single-period test on Raoult's Law, metal-ligand naming, etc. will be given during the first period of our double on Wednesday (NOT Tuesday). I have posted a practice test that will look like Wednesday's test (though there will be fewer descriptive chem reactions). I will post the answers by/on Tuesday. Practice and study - this should be a slam-dunk hundred.

We explained how catalysts worked by binding reactant molecules, straining their bonds and orienting them in such a way that the proper bonds are broken. This has an activation-energy lowering effect that increases the percent of collisions that have sufficient kinetic energy for bond breakage; ALSO, a catalyst increases the percentage of collisions that have proper orientation for an effective collision. Catalysts do NOT change the average kinetic energies of the reactants.
We then discussed how reaction rates are measured, the convention for measuring the instantaneous initial rate of reaction in terms of any reactant or product , and using that (via the balanced equation) to get the initial rate of a reaction.

Bio - we began our review for the unit test on the endocrine system/regulation and the digestive system/nutrition. Additional practice materials are now posted on Edline.

AP Chem - TOMORROW, after school in Room 308, we will have the initial Chemistry Olympiad informational meeting and review session. We will also go over the 2011 Chemistry Olympiad exam. Please spread the word to all interested peers.

we started the Kinetics by explaining the causes of chemical reactions - proper orientation of the colliding molecules (for bonds that must be broken to form the designated products) and sufficient kinetic energy of collision for bond breakage ; both of these factors contribute to an "effective collision".
We also discussed the influence of collision frequency on reaction rate.
The reaction rate itself is strictly the number of effective collisions per second.
We then looked at how the covalent or ionic "nature" of the reactants determines the activation energy required for effective collisions, which thus determines the reaction rate.
We looked at the FOUR possible factors that can be altered to influence the effective collision rate i.e. the rate of a reaction:
concentration, temperature, solid or liquid surface area, and (tomorrow) catalyst addition.

Bio- we did our third example of hormonal regulation - the thermoregulation of body temperature via the interaction of the hypothalamus, the pituitary, and the thyroid. We showed the negative feedback nature of this mechanism that maintains relatively constant body temperature even in temporarily cold surroundings.

AP Chem - we finished up the final Raoult's Law problems, including the "bonus" problem in which the law is used to determine the molar mass of unknown solutes. We also showed how Raoult's Law is the basis of the process of distillation/refinement of alcohol or petroleum/fossil fuels.

Bio - We did a graphical analysis of blood glucose levels, showing the cause of each of the changes on the graph.
We looked at samples of live paramecia, which digest their nutrients intracellularly.

AP Chem - we finished up the lengthy IMFA exam, and then we focused on the cause of vapor pressure.
We looked at the reason for vapor pressure depression when a solute interacts with a solvent.
We explained Raoult's Law, which holds for ideal solutions.

Bio - we gave another example of endocrine gland hormonal regulation of blood glucose - in this case, low blood glucose, caused by fasting or consuming insufficient carbohydrates, can be corrected via the action of the pancreatic hormone, glucagon. We went through the entire mechanism, emphasizing the negative feedback component that once normal blood glucose level is restored, the glucagon gene in the pancreas alpha cells is turned OFF, thus glucagon secretion STOPS.

AP Chem - took most of our unit exam on IMFA, solids, coligative properties, etc.
There really is so much to apply from our bonding unit, that the test ran somewhat long.
So, you will have ten minutes at the beginning of tomorrow's class to complete your exam.
You already know the questions, but you had to know what was going to be asked anyway.
I will address one question tomorrow, involving an unfortunate use of the term "initial"; I will explain before giving the tests to you tomorrow.
Don't be late. We will be doing Raoult's Law problems tomorrow. We must start Kinetics on Wednesday.

Bio - we reviewed the various endocrine system glands, and then we gave a detailed negative feedback mechanism by which the pancreas regulates blood glucose levels.

AP Chem - test info:

AP - we analyzed phase diagrams for two general types of substances - a substance that has a solid phase that is denser than its liquid phase (true for most substances), and a substance that has a liquid phase that is denser than its solid phase (e.g. water, not many other substances).
We looked at the important parts of the phase diagrams, and saw how to construct one from raw data of normal boiling point, normal freezing point, and the triple point (and critical point, if given).
We then began to look at the colligative property formulas.
Our unit(s) exam is on Monday. There are many practice and tutorial files on Edline.
I will likely leave out Raoult's Law on the next exam because we have enough to do with all of the other question types.

Bio - we reviewed the digestive system worksheet, and then we discussed the causes and symptoms of major diseases/disorders of the digestive system. In 10/11, we did the amylase hydrolysis of starch (in a pretzel) lab.

AP Chem - we looked at covalent network bonding in C(diamond) and C(graphite), relating the bonding to physical properties such as electrical conductivity in graphite due to the delocalized pi electrons.
We then showed and discussed metallic bonding and the IMFA's that cause molecules to be solids at sufficiently low temperatures.
Tomorrow, we will understand phase diagrams, and what can be inferred about a substance from a phase diagram.

Bio - we gave a detailed account of each digestive organ with respect to its role in mechanical and/or chemical digestion; we discussed some diseases of the digestive system.


Here is a link to a "scientific study" about diet and weight gain. Using your powerful knowledge of the scientific reasoning, judge/assess the validity/reliability of this study:
http://healthland.time.com/2012/01/04/low-protein-diets-lower-weight-but-dont-cut-fat/

AP Chem - welcome back, and Happy New Year 2012!
We reviewed coordinate covalent bonds, defined their formation via Lewis acids and bases, and saw that polyatomic ions usually have some "coordinate" covalent bonds from the central atom.
We then discussed the ionic "character" of polar covalent bonds,
and then the covalent "character" of ionic compounds of small highly charged cations and large polarizable anions.
We discussed "covalent network solids", consisting of a LATTICE of covalently bonded C or Si atoms (sometimes O is in the lattice too).

Bio - we began our unit on nutrition (especially digestion) and regulation (the endocrine controlled part).
We reviewed autotrophic and heterotrophic nutrition, ingestion, digestion, and egestion (not excretion!), and intracellular (simple organisms) digestion vs. extracellular (in "tubes" of complex organisms) digestion.
We saw two videos that give an overview of the digestive system.