SciHawks

AP Chem - did more quantitative work in which we calculated specific quantities of conjugates that are added to form of buffer of a specific volume and concentration of each conjugate.

SPRING BREAK ASSIGNMENT is posted on Blackboard
(the AP exam Part II has now been uploaded too ).

Bio - performed a gamete formation/ meiosis simulation followed by simulated fertilization.
In this activity, we got to SEE and manipulate the real sources of variation that occur when sex cells are made and to SEE yet another source of variety in the "genetic recombination" that occurs during the fertilization of an egg cell via a sperm cell; we also kept track of the number of chromosomes, i.e. the half-haploid number of the (pair of each chromosome type) DIploid number.
We then simulated non-disjunction of a homologous pair during anaphase I and saw the effect on the gametes and potential embryos of having either ONE extra chromosome or ONE fewer chromosome - this leads to developmental problems e.g. mental retardation, organ malformation, etc.
I'll try to post even more practice quizzes later. STUDY FOR TOMORROW- then vacation!

AP Chem - we did a base-buffer problem in which we added a certain volume of strong acid and noted the changes. By now, you must immediately recognize ALL Bronsted acids and bases and know exactly how they react- one loses an H+, the other gains an H+. That's ALL that they do!
We then saw how to choose appropriate acids, bases, and salts to make a buffer of a designated pH.

AP Chem - we saw how to determine whether a given salt solution is slightly acidic or slightly basic given that BOTH of the salt's ions hydrolyze water; we simply use the Ka and Kb information given for the hydrolysis by these ions (sometimes, we must use the pKa and pKb of their CONJUGATES, which we saw in class).
We then showed how to calculate the effect on the concentrations of conjugate acids and bases in a buffer solution, when a strong acid or strong base is added; we also saw the effect of adding a strong acid to a non-buffer solution (much greater effect on the pH).
We saw the convenient bookkeeping method of using a SRFC Table, which we use whenever solution volume is changing. The most important thing to do in these problems is to DRAW OUT WHAT IS IN SOLUTION so that you can SEE what is reacting. You then set up your SRFC table based on the actual (limiting) reactant equation that you see. The results of your table either are plugged into the H-H equation (if still in the buffer 1/10 - 10/1 region) or put into an ICE table using either the hydrolysis of water by the conjugate base or by the conjugate acid, BOTH/EITHER will get you the same correct answer!

We looked at sex cell creation/ gametogenesis via meiosis in both males and females, paying particular attention to the TWO main sources of variety in DNA/allele combinations : 1. crossing over during prophase I and 2. independent assortment of chromosomes during metaphase I. We also examined how the DIPLOID number of chromosomes in the PRIMARY sex cells is HALVED as the sperm or egg is formed.
We then discussed the development of the embryo that is attached to the uterus: after fertilization, MITOSIS occurs so that the embryo forms a BALL of cells, the blastula which eventually turns into a THREE-LAYER mass of cells, the GASTRULA. We discussed how cell differentiation and specialization causes each layer to DEVELOP into particular organs/organ systems. Inner layer cells form inner organs, middle layer cells form middle layer organs, and outer layer cells form outer layer organs.
We then did worksheets on meiosis and a comparison or meiosis and mitosis.

AP Chem - we derived the Henderson-Hasselbalch equation for basic buffers and then did a problem in which a solution of a Bronsted base and a solution of the salt of the base's conjugate acid were mixed.

Bio - we reviewed the first division in meiosis (meiosis I) and saw that the number of chromosomes was HALVED such that each SECONDARY sex cell has ONE OF EACH chromosome (for a total of 23 chromosomes, in humans), i.e. the HAPLOID/MONOPLOID number of chromosomes; at this point the chromosomes are DOUBLE-chromatid chromosomes so there is yet another round of meiosis (meiosis II), the result of which is the production of gametes, each with the same haploid/monoploid number of single-chromatid chromosomes.
We saw that the division of cytoplasm is EQUAL in making 4 sperm cell gametes but UNEQUAL in making an OVUM/egg cell gamete and three polar bodies.

AP Chem - we discussed and drew the various types of Lewis acid base reactions and added to our descriptive chem base. We also showed the periodic trends of oxides i.e. metal oxides form hydroxide bases in water and nonmetal oxides for acids in water.
We then did more buffer problems, first by deriving the Henderson-Hasselbalch equation and showing the STRICT conditions under which you can use this simple equation using the INITIAL conjugate acid and base concentrations.

Bio - Our unit exam on sexual reproduction, meiosis, and growth/development is on next FRIDAY, March 26th. The unit hw is due on WEDNESDAY, March 24th.
We had a presentation on Science Research, a great class in which you apply and practice scientific reasoning.
We began the other main part of our unit: how sex cells/gametes are made via meiosis and the two CAUSES of variety among gametes. We saw how, during late prophase, synapsis occurs that allows certain segments of homologous chromosome pairs to CROSS-OVER each other, thus exchanging DNA segments (containing genes) between each other. We also saw that homologous chromosome pairs line up/assort INDEPENDENTLY of each other, allowing for trillions and trillions of different possible left and right side line-ups of the chromosome pairs, causing trillions and trillions of different combinations of traits from a given parent.

AP Chem - showed FOUR ways to make a buffer solution and explained how and why these solutions are "cushioned"/buffered against drastic changes in pH (hydronum or hydroxide concentation changes).
We also did a complex equilibria calculation in which we determined the pH of a buffer solution.

AP Chem- took our unit exam on acid-base simple equilibrium (complex is coming up next).

Bio - we reviewed the female reproductive system as well as the ovulation process.
Our main focus was the complex and magnificent hormonal regulation of the female reproductive system / menstrual cycle.
I posted a great animation that shows, pretty simply, the hormonal and physical changes that occur during each of the four phases: the follicle stage, ovulation, the luteal stage, and menstruation.
We did a reinforcement lab in which we took images of the significant events of the cycle and organized them in sequence on a calendar.

AP Chem - did two review problems involving acidic and basic salts and then discussed Lewis acid-base theory to show how metal oxides form basic solutions and how non-metal oxides form acidic solutions.

For the test tomorrow, there won't be questions regarding Lewis acid base theory but you can expect questions on the following topics:
Bronsted acid base theory: conjugates, predicting and explaining whether products or reactants are favored for a given acid-base reaction, given Ka's and/or Kb's.
Strong and weak acid pH, pKa, or [HA] questions, given sufficient information.
Strong and weak base pH, pKa, or [B] questions, given sufficient information.
Polyprotic acid equilibria calculations.
Acidic, basic, or neutral salt predictions with explanations based on hydrolysis reactions.
Relative strengths of acids explained in terms of bond strength AND bond polarity.
Acidic or basic salt pH calculations.

STUDY the NOTES FIRST. Then practice doing the problems as we do them IN THE NOTES.
Thank you.

Bio - we continued with female reproductive system structures and their functions; we discussed the cervix, uterus, oviducts, and ovaries.
We described what occurs when an egg is fertilized by a sperm cell in the oviduct as well as what occurs when an egg is not fertilized (menstruation).
We briefly talked about embryonic development with respect to the placenta and umbilical cord as well as the gestation period.


AP Chem - we discussed the real reason that a given salt yields a neutral, acidic, or basic solution by noting whether a given anion or cation is "strong" enough (typically, having a high enough CHARGE DENSITY) to hydrolyze water and generate either hydronium or hydroxide.
We then did a few pH, pKa, pKb ICE table problems to determine the pH of a given molar salt solution.

Bio - we discussed the structures and functions of the male reproductive system and show how each feature is an ADAPTATION=ADVANTAGEOUS CHARACTERISTIC for sexual reproduction i.e. increasing the likelihood that a sperm cell will reach and unite with an egg cell.
We also began the same analysis of the female reproductive system and then we labelled a worksheet of the male and female reproductive systems.

AP Chem - we explained the relative strengths of OXOacids by focusing on the CENTRAL ATOM adjacent to the O-H bond OR the number of O's attached to the central atom that is adjacent to the O-H bond. As usual, these structures affect BOND POLARITY which affects acid strength; however, the O-H BOND STRENGTH is nearly identical for all O-H single bonds, therefore the bond strength factor is insignificant in determining relative acid strengths.

Bio - we introduced the unit on sexual reproduction by discussing the evolutionary advantages and disadvantages of sexual reproduction.
We concluded that sexual reproduction is advantageous to a species that lives in a significantly changing environment because the variety within the population caused by sexual reproduction increases the likelihood that some members, due to their difference, will survive a generally harmful change in the environment and thus be alive to reproduce and pass on their traits that enabled them to survive in the new environment.
Asexually producing organisms have very little variety in the population so that an environmental change that harms some of the members of the population will likely negatively affect almost all of them, potentially causing extinction.
HOWEVER, sexual reproduction requires MUCH more energy in order for the sperm of the male partner to unite with the egg of the female partner- factors such as finding a mate, recognizing the mating behavior, producing specialized sex cells, etc. all require tremendous quantities of ATP. Asexual reproduction requires only one individual, no mates, no courtship behavior, much less ATP required.

AP Chem - we finished our problems on polyprotic acid equilibria and began to explain, in detail, the factors (bond strength and bond polarity) that affect acid strength. We determined relative strengths of acids H-X down a group and, from left to right, across a period.

Bio - took the unit exam on regulation via the nervous system.

AP Chem- saw how to get the concentrations of all species in a polyprotic acid problem. Note the simplifying shortcuts for the second and third ionizations.
I'll post a tutorial on Blackboard.

Bio -we covered drugs,  how drugs affect the nervous system, and various terms related to drug addiction.
Be sure to study all of your notes and THEN take the practice quizzes on Blackboard.
I'll post another worksheet on drugs, later tonight.

AP Chem- we did every permutation of weak acid and base equilibria involving individual weak acids and bases in aqueous solutions.
We also covered pKa and pKb values, qualitatively and quantitatively; there are a ton of problems on Blackboard- do them and come to extra help with any questions.
Also, you MUST be doing the daily AP exam questions, timed. You will be quizzed on these soon.
Thank you.

AP Chem - we did problems involving weak acids; given a concentration and a Ka, we determined the equilibrium concentration of hydronium ions and thus, the pH of the solution.

Bio - The nervous system unit hw objectives are due tomorrow, Tuesday; our unit exam is on Thursday.
You do not have to do unit objectives 18 through 23 ( BUT you must do #24 ) (we will cover 18-23 on Tuesday and Wednesday in class, as usual).
There was a typographical error on #10 that has been corrected (see Blackboard). Some students at extra help had questions about #10- to write the correct answer, you should draw/describe what happens at individual RECEPTOR neurons as a given stimulus/change in the environment (molecule or photon) BINDS to complementary shaped proteins on the DENDRITES - then describe the typical nerve impulse that is generated and travels from neuron to neuron.

Today, we discussed the various classifications of the nervous system by LOCATION and by TYPE OF RESPONSE. We discussed the central vs. peripheral, (and for the peripheral) the somatic (effectors are the skeletal muscles) vs. the autonomic (the effectors are glands or smooth and cardiac muscle), and (for the autonomic system) the sympathetic vs. the parasympathetic nervous systems.

We also listed 4 disorders of the nervous system: cerebral palsy, stroke, polio, and meningitis.


AP Chem - we did some pH calculations for strong acids and strong (solid mono and di-hydroxide) bases.
We also qualitatively and quantitatively discussed Bronsted-Lowry conjugate acids and bases and predicted the relative favored direction of a given reaction as equilibrium is approached. From this we could also qualitatively estimate K for the reaction as greater than or less than 1.0  .

We then began quantitative weak acid equilibrium calculations; in these problems, you MUST know when and why you can make simplifying assumptions in your equilibrium constant expression with respect to the concentration of ions formed via ionization RELATIVE to the INITIAL concentration of acid, HA. Generally, if the Ka is about 1000 times LESS than the INITIAL acid concentration (before ionization is considered), then it is safe to neglect the SUBTRACTED concentration of ionized acid in the DENOMINATOR of the K expression. You can always check that the % ionization is less than 5%; if that is the case, your assumption is/was allowed.
Check the Blackboard tutorial on this topic!

Bio - we looked at the three main sections of the human brain (the cerebrum, cerebellum, and medulla oblongata) and described their respective specialized functions.
We then finished up our Making Connections discussion and then collected data on reflexes with and without distraction of a reflex arc pathway.

AP Chem - we discussed aqueous solutions, the autoionization of water, and the pH scale. We saw how to quickly estimate pH from [H+] and vice versa.

Bio - we covered reflex arcs from receptors to sensory neurons to interneurons to motor neurons to effector muscles or glands.

AP Chem - had our first of three unit exams on Equilibrium.

Bio - we discussed the functional unit of the nervous system: the neuron. We saw how the electrochemical impulse is generated and distinguished the electrical (moving ions along the axon) part of the impulse from the chemical (neurotransmitter) part of the impulse.


AP Chem - did a few review problems for our upcoming equilibrium exam; then we discussed Bronsted-Lowry acid-base theory and applied the theory to acid-base conjugates and their concentrations at equilibrium.

AP Chem - we EXPLAINED the reason for equilibrium shifts due to system "stresses" in terms of kinetics/collision theory thus rendering Le Chatelier superfluous and insufficient. Of course, Le Chat's rule tells us WHAT the chemical shift will be BUT kinetics tells us HOW/WHY the shift really occurs.
We explained the effect of various stresses on the number of effective collisions per second in the forward and reverse reactions; thus we quantitatively explained the direction of any shift due to the stress.

We moved on to the Acid-Base unit by discussing characteristics of acids as well as the definition of Bronsted acids and bases as well as Bronsted conjugate acid base pairs.

Tomorrow, we will do two more equilibrium review problems for Thursday's test.

Bio - took our long-awaited Immune System exam. We continued to discuss the "Making Connections" lab.

AP Chem - we practiced the THREE STEP Le Chatelier Principle with which we can predict the shift in a reacting system as the result of a "stress" placed on the system originally at equilibrium.
You MUST label your exo-hot and endo-cool arrows as well as the number of moles of GASES on the reactant and products side of the balanced equation; this way you can quickly apply the three steps of Le Chat.