SciHawks

Bio - we discussed the evolution of antibiotic resistant bacteria via the introduction of an antibiotic selecting agent. If a bacterial population, due to random mutations, has ONE or more bacterial cells that are ALREADY resistant to antibiotic "X", then these already adapted bacteria will survive and reproduce in this antibiotic X environment; the other non-resistant bacteria are much less likely to survive and reproduce. Thus, over time, this given bacterial population will have an increasing percentage of bacterial cells that are antibiotic X resistant- thus, this species of bacteria has evolved/changed.

AP Chem- we finished our Electrochemistry unit and moved on to our Nuclear Physics unit by discussing the various types of nuclear decay/ natural transmutation. In these equations, MASS NUMBER (total number of protons and neutrons) and ATOMIC NUMBER/CHARGE must be conserved.
We discussed the reasons for nuclear decay with respect to a certain stable ration of neutrons to protons in the nucleus.

Bio - we focused on two examples of evolution via natural or artificial selection:
the evolution of the peppered moth as its environment was changed by the soot produced during industrial development in the early 1900's. Here, the SELECTING AGENTS, the BIRDS (the ones that DIRECTLY determine whether a given type of moth was more likely or less likely to live) went from more easily seeing and eating the darker colored moths (due to the lighter lichen-rich forest background) to more easily seeing and eating the lighter colored moths when the environment changed to a darker soot-polluted forest background.
We then discussed the increase in the percentage of insecticide X resistance in a population of locusts due to the spraying of SELECTING AGENT insecticide X. If there were NO pre-existing locusts that had alleles that made them resistant to X, then the insecticide would likely eliminate ALL of the locusts- HOWEVER, due to the variety from mutations and sexual reproduction, SOME of the locusts ALREADY HAD insecticide-X RESISTANCE alleles and the proteins that the alleles coded for. These HIGH-ADAPTIVE VALUE were not killed by X, and were more likely to survive and reproduce to pass on their resistance alleles; thus the population of locusts EVOLVED into a greater percentage of insecticide-X resistant locusts!

AP Chem - we worked out several problems in which we calculated Ecell under NON-STANDARD conditions.We focused on the "other" type of electrochemical cell: the ELECTROLYTIC CELL.


We covered the setup and sign conventions for this cell in which non-spontaneous reactions are driven by an external voltage source/battery. Only one cell/container is necessary and no salt bridge is required because the connected battery insures a steady flow of electrons.

We did several quantitative problems involving masses/moles of a metal reduced at the cathode or moles/volume of a gas produced at the anode. We added one other step to these problems by accounting for the efficiency of the battery, which affects the quantity of charge delivered per second.

Bio - we began a series of explanations of evolution within particular species of giraffes, mosquitoes, bacteria, moths, and finches.



These explanations are examples of the Modern Synthetic (Darwin's successfully tested tenets mixed with the Laws and Theories of Genetics and Reproduction) Theory of Evolution applied to specific cases/species.


Practice drawing out/reasoning these mechanisms and you will be able to correctly explain the evolution of ANY species.

AP Chem - we took our unit exam on Ksp and Thermodynamics.

Bio - we discussed Lamarck's Theory of Evolution via use and disuse/inheritance of ACQUIRED traits; this theory was disproved via Weismann's experiments on "tail-less" mice. Weismann made sure that his experimental group of mice has "disuse" of their tails- he chopped the tails off. Lamarck's prediction was that the acquired trait of "tail-lessness" would be inherited by the offspring of these mice. In all of these experiments, the offspring of the tail-less mice had normal sized tails, at maturity; thus, Lamarck's theory was NOT supported and practically speaking, "disproved" in repeated experiments.

AP Chem - Ksp/Thermo exam tomorrow.
Be prepared- these questions are inherently tough but they will be straightforward (as in the notes):

There will be questions on the following:
Will a precipitate form?
Selective precipitation and the subsequent calculation of "complete" precipitation.
All thermodynamic relationships: calculations of delta G, H, and S.


Knowing the difference between delta G, H, or S of FORMATION vs. delta G, H, or S of reaction and when it is appropriate to use each or any of these quantities.
Application of Hess's Law.
Know how to predict whether a reaction is spontaneous or not and how a temperature change will affect K or delta G standard (you must explain via Le Chatelier's Principle!).
Know how to find the temperature at which a reaction or process is at equilibrium at STANDARD pressure i.e. delta G standard = 0  therefore T = delta H standard / delta S standard assuming that delta H standard  and delta S standard are constant over a large temperature range.

AP Chemistry - we finished up Thermodynamics by showing the major calculation error of assuming that the equilibrium temperature for a process at standard conditions could be calculated from the equation that has dGo and K. We MUST use the dGo = dHo -TdSo equation because ONLY dHo and dSo remain almost the same values over a large temperature range. Any problem that asked for the value of dG at 1 atm pressure i.e. standard conditions is asking for dGo, no matter what the temperature.
We then began our final unit: Electrochemistry.

Bio - began our new unit on Evolution/Change ; we discussed "evolution/change", the FACT that has been observed over time AND ALSO "Evolution", the SCIENTIFIC THEORY that explains the change in species numbers and characteristics over time, how and why species change over time, and also accounts for the similarities and differences among species.
We looked at the five main lines of evidence that support the Modern Synthetic Theory of Evolution:
1. the Geologic/fossil record
2. comparitive anatomy
3. comparitive embryology
4. comparitive cytology/cell structure
5. biochemical evidence (DNA, protein comparisons)

AP Chem - our thermodynamics/Ksp exam is now RESCHEDULED to Wednesday, April 28.

VERY IMPORTANT!!! I made a MAJOR error in class today on the first question that we discussed, #3c. Recall that I said that something seemed strange; 298K seemed redundant and incorrect.
The error was the one that I forewarned us about!
You CANNOT use the dG = dGo + RTlnK equation to determine the T at which a process becomes spontaneous!!!
Reason: there are ALWAYS two unknowns in that equation because dGo IS NOT CONSTANT when T changes!!! As we did previously, to find the temperature at which a process just becomes spontaneous i.e. is at equilibrium under STANDARD , 1 atm, conditions, just set dGo = 0, therefore dHo= TdSo
and T = dHo/dSo
When you do this for question 3c, you get the correct and logical answer.
The corrected answer will be posted in the notes on Blackboard.
More files and practice answers will be posted this weekend.

Bio - took the unit exam on Modern Genetics

AP Chem - discussed the second law of thermodynamics and the Gibbs Free Energy equation derivation.
We then did a couple of practice test problems; answers to these questions will be posted on Blackboard.

AP Chem - we reviewed enthalpy and explained entropy in finishing up our Thermodynamics unit.

AP Chem - we finished the Ksp equilibria unit by quantitatively solving separation of ion problems via selective precipitation; we did so for both anions and for cations.
We finished up by showing which salts could become more soluble in increasingly acidic solutions: ALL salts EXCEPT for chlorides, bromides, iodides, nitrates, and perchlorates become more soluble at lower pH's due to the hydronium ion in solution reacting with the Bronsted base anion of the salt, causing an equilibrium shift in the dissolving direction.

Bio - The following objectives can be omitted from the hw; we will cover them on Tuesday and Wednesday:
#'s: 19,29,31,33,34 
The answer to objective 30 is directly in the notes handed out today (use the three examples e.g. a plant without sunlight doesn't have its chlorophyll gene turned ON.)

AP Chem - took the extensive Buffer/Titration/Ksp equilibria exam.
On Monday, you will be given a 20 minute extension to the exam.

AP Chem - we completed a Ksp precipitation problem in which we predicted the formation of precipitate by comparing Ksp toQsp; we determined the percent precipitation, and then we determined the number of grams of precipitate that formed.

Tomorrow, we have a challenging test on buffers, titrations, and some Ksp up to molar solubility in a solution with a common ion (i.e. NOT the material from today or the second period on Wednesday) .
Do as many problems as possible; the test will be a mix of problems from the notes and two practice tests.

AP Chem - we discussed the "common ion effect" for sparingly soluble salts, showing the kinetic and Le Chatelier effect of adding a soluble salt that has an ion that is the SAME/COMMON TO an ion that is in solution from the sparingly soluble salt. The net effect is to DECREASE the solubility even further of the sparingly soluble salt.
We then began a more quantitative example of this effect , seeing whether a precipitate would form when two solutions form a potential double replacement with precipitation reaction.

We finished up the menstrual cycle and meiosis/reproduction labs and then began our current unit lab on inheritance and pedigree charts.

AP Chem - we did problems in which we went forwards and backwards between solubility to molar solubility to concentrations of aqueous ions at equilibrium to the Ksp. We discussed the "master chart" showing the relationship between solution (forming) stoichiometry, molar solubility "s", the concentrations of the aqueous ions at equilibrium, and the calculation of "s" from Ksp and vice-versa.
Today's after school test is posted on Blackboard. There will be another one on Wednesday.

Bio - we went through a full example of a trait involving a dominant and recessive allele combination of the gene for pea seed shape (round or wrinkled); we determined the dominant allele and then did a "test cross" to show whether the dominant phenotype (round) parent was homozygous dominant or a heterozygote. We did so by drawing out the possible Punnet squares for each of the two cases and comparing the predicted results to the actual results.
We then began to discuss other possible relationships of allele/gene expression: COdominance in which BOTH alleles are expressed in the individual or INCOMPLETE DOMINANCE in which a NEW, BLENDED combination of the two allele traits gives a new "averaged" trait e.g. red and white alleles cause a "pink" color when the alleles are expressed together via incomplete dominance.


AP Chem - CHECK OUT Blackboard to quickly get up to speed on Ksp, slightly soluble salt equilibria: there are great tutorials/sample solved problems, and a study guide.

We finished up polyprotic acid titration and segued that right into a buffer calculation problem involving the choice of various salts of given pKa or pKb of its ions.

We then started the most complex unit of this course: sparingly soluble salt equilibria. We started with some strict definitions and some step-by-step conversions so that we can then launch into more complex and practical problems.

AP Chem - we discussed indicators and showed how and why they are useful within a narrow pH range that should include the pH at the equivalence point of a titration.
We then analyzed the titration curve for a diprotic acid. The titration curve for a triprotic acid is posted on Blackboard. Print that out and ask related questions, if any, on Monday.

Bio - we discussed how Mendel discovered the Law of Segregation/Separation of  "heredity factors" (which were really alleles on homologous chromosomes) by crossing/mating F1 generation plants with each other. The hidden or recessive hereditary factor was SEEN again in about 1 out of every 4 F2 offspring plants. Mendel correctly concluded that the hereditary factors must SEPARATE as sex cells are made. The recessive "short" hereditary factor could be "recombined" with a short hereditary factor in the opposite sex cell and then be expressed in the F2 offspring!

AP Chem - Check out Blackboard for dozens of buffer and titration questions with annotated answers as well as a titration tutorial!
We completed the quantitative titration of a weak acid by a strong base; we then reinforced the titration problem solving by showing the opposite titration, a weak base by a strong acid; here we saw similar stages of pH change but from higher to lower.
We began to discuss pH indicators, and showed that they change color based on the concentration of hydronium ion in solution (the pH of the solution).

Bio - we began our new unit on Genetics by discussing the aspects of the scientific method that Mendel used, which helped him to discover some of the laws of genetics.
We discussed Mendel's experiments and the conclusion that he inferred from the experimental data such as the Law of Dominance, which he saw by crossing two pure-bred contrasting pea plant varieties for a single trait- tall vs. short.

AP Chem - we quantitatively analyzed the steps of a titration, showing the reactions that occur and the pH changes that ensue as a result of the neutralization reaction.