SciHawks

AP Chem - took the unit exam on Gases. Two additional question will be tested on Wednesday or Friday.

AP Chem - we began our Quantom Atom unit by showing the various characteristics (and their meaning) of electromagnetic waves: amplitude, wavelength, frequency, and speed.
We discussed how atomic theory evolved as better technology revealed more and more about the nature of the atom. We will continue with Rutherford, Bohr, et al on Tuesday.
Expect questions on the following:


1. Gas stoichiometry with emphasis on applying the gas laws to determine moles and masses of reactants and products. There will be a repeat of the question part involving the determination of all aqueous ion concentrations after a reaction has gone to completion.
GETTING THE CORRECT BALANCED EQUATION MAY REQUIRE THAT YOU BALANCE THE EQUATION VIA THE REDOX HALF-REACTION METHOD IN EITHER BASE OR ACID SO MAKE SURE THAT YOU REVIEW THAT METHOD. MOST OF YOU DID WELL WITH THAT ON THE SOLUTION STOICHIOMETRY TEST.

2. Descriptive chemistry/ equation writing of the four "gas-forming reactions" (see answers to equation writing assignment posted on Edline (posted this weekend)! Your grades for that assignment are also posted).

3. Explanation, in terms of (a) molecular collision frequency and (b) molecular collision force/kinetic energy,
of any permutation of the ideal gas law.

4. Graham's Law of Effusion in terms of relative rates OR times for different gases.

5. Average (rms) speed of a gaseous molecule of a substance at a given temperature.

6. Dalton's Law questions involving partial pressure, mole fraction, and total pressure. Among other things, this applies to reactions in which a gas is collected over water.

7. Van der Waal's gas equation and the explanation of the magnitude of the "a" and "b" correction factors of a given substance.

8. the postulates of kinetic-molecular theory relating to the how and why a real gas will behave ideally or will deviate from ideal behavior.


Bio - we showed with examples, the net results of mitosis and cytokinesis, with special emphasis of the fact that the daughter cells produced contain the SAME number and types of chromosomes that the original cell had; that is made possible by the DNA exact replication/doubling during the S phase of interphase, and the even separation/distribution of the chromosomes at anaphase.
We discussed the three purposes/uses of cell division - continued efficient metabolism, growth of a complex organism, and repair of damaged tissue.
In 7/8, we went on to discuss cancer/cancer cells.

AP Chem - we finished the marathon gas unit questions; two things to especially watch out for:
1.be sure to draw out what is occuring in solution so that you can SEE the aqueous ions remaining in solution (in your "after" picture) so that you can correctly calculate the concentrations of those remaining ions in the new/final solution volume. If the ion is a "spectator"/not in the net ionic equation, then you MUST use the INITIAL number of moles of that ion in solution to calculate its concentration in one step. MOST of you did not practice that before the last test even though it was done in class and in many practice problems.
2. you MUST show all unit cancellation in the average molecular speed calculation; you saw that in the reference table formula , the 8.31 Joules per mole Kelvin value of R must be broken down to its fundamental components of kilogram meters squared per second squared, and even then the "k" in kilograms must be replace by "x 1000", in order for the units to properly cancel, which must be shown, otherwise credit will not be given.
A list of possible question types will be posted for Monday's exam.

Bio - we went through, step by step, the phases of mitosis, drawing out and noting the significant events of each phase. We showed the net outcome of mitosis with cytokinesis, the production of daughter cells, smaller than the original cell, but containing the SAME number and types of chromosomes.

AP Chem - did our final and marathon problem of this unit, which incorporated most/all of the quantitative aspects of gases/stoichiometry. This question did not have the qualitative gas law explanations, so be ready to explain any of the gas laws EXACTLY as documented in class, complete with illustrations.

Bio - we drew out the structure of part of a DNA molecule (which coils around histone proteins to make up your chromosomes) both before DNA replication, and after replication, showing the enzyme-aided unzipping of the DNA molecule, and the complementary base pairing that enables two perfect replica DNA molecules to form from one DNA molecule. We noted that, even though the DNA replicates, the number of chromosomes STAYS THE SAME because the number of centromeres is still the same; the net result of the DNA replication is just that each chromosome now is made up of two chromatids instead of just one chromatid.
In 7/8 :We then viewed an animation of the entire cell cycle, and noted the important stages of interphase, and the important stages of mitosis (and the features of each stage).

AP Chem - we dissected the equation relating average speed of a molecule in a sample to the absolute temperature of that sample. We showed how the formula in the reference table is wrong, given the conventional units that we always use; we derived the workaround for that after showing that the Joule is actually a kg m^2 s^-2, so we just change the kg to 1000 x g, which is true by definition.
We then discussed the reasoning behind the Van der Waal's Gas Equation, which puts in two "correction terms", one to correct the decreased pressure due to "a" - intermolecular attractions, and the other to correct for the increased volume due to "b" - how big the actual molecule volumes are.
We discussed the reasons for the relative values of "a" and "b" for a given molecule or series of molecules.
We looked at (again) how to write a sufficient, organized, and logical explanation of a gas law, always relating the variable to the ONLY two factors that cause gas pressure.

Bio - we reviewed the reason that cells must divide, and added a second reason based on the constant quantity of DNA/chromosomes in the nucleus that must code for an increasing quantity of protein as the cell grows.
We looked at the DNA double-helix structure, and saw how DNA could perfectly replicate itself due to its chemical attraction for complementary base pairs, after the DNA double helix unzips (see animation on Edline).
We discussed the parts of INTERPHASE, the main part of a cell's life cycle, G1 (growth of the cell and its components), S (DNA synthesis), and G2 (further cell growth before the mitosis signal is triggered chemically).

AP Chem - we discussed Graham's Law of Effusion/Diffusion, which can be derived simply by considering the formula for average kinetic energy/ temperature as it relates to the average speed of a molecule.
We saw that the more massive molecules must be moving more slowly on average than less massive molecules, at the same temperature; thus more massive molecules must effuse at a slower rate, all other factors being equal.

Bio - began our new unit on DNA Replication, Mitosis, and Cytokinesis.
We discussed the reason/driving force for cell division, without which the cell would no longer be able to sufficiently carry out its metabolic processes.
We saw that, as a cell grows, even though the surface area increase to allow for more essential biochemicals to diffuse into the cell, the volume of the cell increases at an even greater rate so that these randomly moving essential molecules take too long to reach where they need to go to collide/react with other reactant molecules in the cell. Thus, the cell must divide/decrease its volume, or it will die.

AP Chem - We had a detailed discussion of what CAUSES pressure in a container of a sample of gas. By focusing on the 1. pressure causing collision frequency of the gas particles with the container wall and 2. the pressure causing kinetic energy/force of the collisions, we can explain/reason any of the gas laws.
We went through each of the gas laws, which are merely subsets of the ideal gas law by holding two variables constant, and seeing how/why the other two variables relate to each other via the above two factors.

Bio - we took the unit exam on Cells and Cell Transport.
Of course, practicing the various explanations of osmosis through cell membranes in hypertonic and hypotonic solutions was a big help in prepping for this exam, as was writing out the explanations of using indicators to detect the diffusion or lack thereof of glucose and starch, respectively.
Our three examples of cell organelles working together provided excellent prep for the homeostasis question.

AP Chem - we saw how each of the two-variable relationship gas laws are just a subset of the 4-variable gas law with two variables held constant.
We then began our explanation of each gas law by using THE two factors that CAUSE gas pressure:
1. collision frequency of the gas molecules
2. average KE/force of the gas molecule collisions.

We will write the gas law explanations out in logical and sufficient detail, with drawings, tomorrow.
For now, check out the animations on Edline, and keep working on the practice problems.

Bio - our unit exam on cells and cell transport is tomorrow.
Many of you gave poor, insufficient, or downright false explanations of  osmosis through a cell under hypo/iso/hypertonic solution conditions. Start from scratch and practice until you can prove to yourself exactly what we painstakingly did and drew step by step in the notes.
Today, we applied three different examples of showing, using indicators, the substances that can and cannot diffuse through a model cell membrane (celluloid).
Use the many review materials on Edline to get you even more ready for tomorrow's exam.

AP Chem - now posted on Edline are many review problems, worksheets, practice test questions. Get started on studying for the next unit exam - we have only three more subtopics in this unit.
we discussed the Dalton's Law of Partial Pressure/Ideal Gas Law problem involving a gas collected over water, a process that automatically introduces water vapor as one of the gases contributing to the total pressure. We looked at an animation of this process - see Edline.

We then looked at one and did another gas stoichiometry problem involving a conventional "two-bulb" setup in which the gases are initially separated, each with unique conditions, and then combined and (usually) reacted. The extra steps in this problem involve finding the limiting reactant, using that to determine the moles of product(s), and determining the partial pressures of all remaining gases while noting that the volume of the container is now larger (because the valve between the bulbs is open).
We began to make 0.100 M solutions of various salts for our qualitative analysis lab.

Bio - there are MANY practice worksheets and quizzes on Edline, to help you to prepare for Friday's exam! Do each of them for review, and see me at extra help if you have any difficulty.
we discussed how to use indicators to "see" evidence of particular substances.
We then applied that to a cell model example, in which we drew where substances would diffuse or not depending on the TWO main factors that determine permeability through a cell membrane:
1. the SIZE of the particles (molecules or ions)
2. the charge or polarity of a particle.
In 10/11, we began the State Lab on Diffusion/Using Indicators by looking at the effect of hypertonic and hypotonic solutions on onion cells.

AP Chem - we did a gas stoichiometry problem that also used Dalton's Law of Partial Pressures to determine the total pressure due to the gases collected over water, one of which MUST be water vapor.
We then set up another gas stoichiometry problem in which the reactants are initially in separate containers or "bulbs", then they are mixed (thus changing the volumes but NOT the initial moles of each), and then they are reacted with the introduction of some source of activation energy (a taser, etc.).

Bio - HW NOTE: we did not get to objective 18, so do not answer that . We will cover that together in lab tomorrow.
We saw animations of various examples of active and passive transport, while also reviewing some organelles and life functions.
We also went over osmosis in cells in hypotonic and hypertonic solutions.
In 7/8, we saw how chemical INDICATORS can show us the presence or absence of a given substance.
This will lead into our lab in which we will, using indicators, "see" whether a given substance diffused across a membrane.

AP Chem - Solution Stoichiometry unit exam day; as you saw, the questions were practically the same as those we had done in the notes and homework- these questions test basic professional skills that all chemists must know intuitively. If you were unsure how to do any question, you should study AGAIN tonight, so that you do not repeat such errors. We will finish up the Gas Laws unit this week.

Bio - Today, we discussed the two general types of transport of substances into or out of cells: active transport ( e.g. lower to higher concentration NET movement of a substance; also, phagocytosis, pinocytosis, endocytosis, and exocytosis - examples tomorrow) AND passive transport (e.g. higher to lower concentration NET movement of a substance; diffusion, diffusion-of-water=osmosis, and facilitated diffusion.



We also looked at three examples of osmosis in HYPOtonic (too little solute, HIGHER WATER concentration/percentage) solution, ISOtonic solution, and HYPERtonic (too much solute, LOWER WATER concentration/percentage). We showed that differences in water concentration CAUSED different RATES of water flow into the cell than out of the cell causing the cell to either swell with water (and possible lysis, for animal cells), stay the same, or shrink due to water loss.


The SOLUTE particles/salt ions are NOT generally permeable (CANNOT PASS THROUGH) to cell membranes (phospholipids) other than by ACTIVE TRANSPORT through a specialized TRANSPORT PROTEIN; this is why we had to focus ONLY on the net WATER movement.
Generally, only small molecules (CO2, O2, H2O, amino acids) can get through the pores in the phospholipid bilayer of the cell (plasma) membrane. Glucose is too big too fit through the pores, but it diffuses into or out of a cell with the HELP of a facilitator protein i.e. facilitated diffusion. Starches, proteins, and DNA are generally too big to get into or out of a cell at all, but SOME proteins are actively transported out of a cell after being surrounded by a synthesized plasma membrane made in the Golgi Bodies.

AP Chem- Most of the submitted answers had some minor errors.
Most of you are reducing the numbers to just ONE significant figure, right in the middle of a multi-step calculation! Do not do that on the test tomorrow.
For example, when your calculator gives you a result of 2 x 10^-3 mol, yet the answer requires THREE sig figs, you do NOT write .002 mol, which is just ONE sig fig; you must write, .00200 mol.
You should be paranoid of ANY one non-zero digit answer to any question - at least check to see whether the one digit is appropriate.
Anyway, for the effort to submit your answers (which should have been proofed), each student who handed in her/his answers on Friday will get +2 bonus points on Monday's test.

AP Chem - we finished the ideal gas law problem relating gas density to its molar mass.
We then explained in detail, both of Dalton's Laws of gas pressures.
We saw that the sole factor in determining collision frequency of any ideally behaving gas at a given temperature and volume is the number of gas molecules/ moles of gas in the container.
We also saw that different gaseous substances, behaving ideally, act completely INDEPENDENTLY of each other (even though their molecules are colliding together), so they do not at all affect each others NET collision frequencies or partial pressures.
There are more solution stoichiometry practice files on Edline.
There is extra help on Monday morning, as always.
Here is a list of potential question types on Monday's solution stoichiometry exam:
1. the four gas-forming reactions, as well as the two types of previously tested double replacement reactions.
2. redox balancing via the half-reaction method including identification (with reason/definition) of oxidizing agent and reducing agent; you also should be able to recognize common oxidizers such as permanganates, chromates, and dichromates.
3. stoichiometry (from mass) with limiting reactant, and percent yield (still must know past stoichiometry units)
4. molarity calculations
5. making solutions, dilution calculations, concentrations of evaporating saturated solutions.
6. solution stoichiometry/titration (acid/base or redox) to determine the percent composition of a given element or compound in a mixture/ore or to determine the empirical formula of an unknown acid or to determine the molar mass of an acid of known general empirical formula e.g. H2X.
7. solution stoichiometry with limiting reactant, and FINAL concentrations of all non-spectator ions in solution.

Bio - we did one more example of organelles working together to maintain cell homeostasis.
We then discussed and explained the animations of the passive transport (diffusion, osmosis/diffusion of water, facilitated diffusion) and active transport (e.g. the sodium potassium pump in nerve cells).
In 7/8, we finished up the plant vs. animal cell lab, by observing the plant cells of the aquatic plant, Elodea.

AP Chem - continued to discuss the basis of the "ideally behaving" gas laws in terms of 1) kinetic energy/force of collisions of the gas molecules and 2) frequency of these molecular collisions (the more collisions per second, the greater the net force transmitted per unit area i.e. the greater the gas's pressure).
We then did a solution and gas stoichiometry problem.
We manipulated the ideal gas law into four different forms, one of which is most easily used for a given type of problem depending on whether mass, GFM, or density is given at a given T,P, and V.
We discussed ways of measuring whether a given sample of gas is indeed behaving ideally or not, and the degree to which the sample is exhibiting ideal behavior (PV/nRT ratio = 1).
The following Chapter 4 Brown-LeMay text questions are worth one bonus point each given that the submitted answer meets EACH of the following requirements:
1. legibility and clarity of writing!
2. detail with respect to units, cancellation, formulas; each step is explicitly shown.
3. accuracy (and precision/sig figs in final answer) of course.
4. description of the problem solving process via formulas, words, logic/reason.
Answers that meet the above requirements sufficiently may be rewarded one point each; an answer of inferior quality that is submitted before an answer (to the same question) of better quality will result in the point being awarded to the higher quality answer (as judged by the above criteria); in other words, you don't have to rush to submit your answer first.


The questions: (one point for answering all of 68,72,74,78 - these are simple questions, so several need to be done to earn the point) ,(100 and 103 for one point), 90, 104, 107, 109, 110, 113, 114.
There are also two non-text bonus questions posted in a file in the Unit 4 folder on Edline.
Looking forward to seeing your top-quality responses, which will then be posted on Edline. You may use your initials at the end of your answer, if you want all-time fame :)

Bio - discussed the levels of cellular organization in complex organizations; these various levels are required to carry out all of the life processes in complex organisms because these organisms have so many different chemical environments within and around each organism, so there must be whole systems of organs that can interact and aid each other in these different biochemical environments e.g. there is no atmospheric oxygen surround the bone marrow cells inside your body, so you need circulatory and respiratory organ systems to get the oxygen to these cells for aerobic respiration so that these cells can make ATP for energy for survival.
We also went through two important examples of how organelles work together to maintain cellular homeostasis.
In 10/11, we started our plant/animal cell labs.

AP Chem - after the most brutal traffic delay in the history of Long Island...
we spent our half-period introducing the physical structure of particles in the gas phase, and the relationships/quantitative Laws that exist between pairs of variables.
We discussed the reasons for these laws, and how there are no simple liquid laws or solid laws due to the variety of differences among substances in those phases.
However, to a large degree, all collections of gas particles/molecules of any substance "look" and behave very similarly, quantitative relationships/Laws can be measured and verified.

Bio - we finished up the various cell organelles and their respective life functions; we then compared and contrasted prokaryotes (no nucleus cellular organisms, mostly bacteria) and eukaryotes (true nucleus cells/organisms).
We then compared and contrasted plant and animal cells.
In 7/8, we began our plant cell vs. animal cell lab.

AP Chem - saw how acid-base titration/solution stoichiometry can be used to determine whether an acid is mono, di , or tri- protic. The other permutation is to take an acid of known empirical formula (but unknown elements other than H, of course) and use the titration data to determine its molar mass.


We then did one final assay/redox titration to determine the percent of a given element in a mixture/ore.


Bio - we reviewed the Biochem unit exam; significant improvement was shown on the scientific method answers! Keep up the good, detailed, and accurate work - those drawings definitely helped to structure your answers.
We still need to work on "relationship" between variables questions (as________ increases, the__________ increases/decreases/remains constant), AND on using the question KEYWORDS directly and appropriately in your answers.

AP Chem - we finished the marathon redox balancing stoichiometry problem that covered the common practical questions involved in these problems.
We discussed the identification of the oxidizing agent/oxidizer (the reactant that gains electrons, and is thus reduced) and the reducing agent/reducer (the reactant that loses electrons, and is thus oxidized).

In 7/8, we finished the catalase lab.

AP Chem - we learned the "half-reaction" method for balancing redox reactions in either acidic or basic solution; the base solution process requires two more steps (to neutralize the H+ ions with OH- ions) than the acid solution process.
We then used this required method to balance a redox reaction, and then do a solution stoichiometry problem.
We went through the common question types for solution stoichiometry including the determination of the concentrations of all ions in solution at the end of the reaction.

Bio - we began our unit on cells by discussing the unity of all living things: all organisms, large or small, simple or complex, consist of one or more basic living units called cells.



We discussed the relationship between advances in technology, especially in microscopy techniques and equipment, that enabled discoveries of cells and organelles within cells.

AP Chem - did a few more volumetric analysis problems, showing that titrations are often used to assay the quantity or concentration of a given substance or ion in a solution.
We began to walk through the all-important "HALF-REACTION METHOD" of redox (or any equation) balancing.
Your stoichiometry tests were returned. Well done to those who heeded my advice, which has not changed ever since our first meeting last spring before you signed up for this very challenging course.
It really should not take an epic failure for you to follow such advice; however, every year, I do see students who initially balk at any kind helpful suggestions, and then who abjectly fail, yet eventually progress tremendously, and make a significant transformation, once they treat this class with the gravity and attention that it demands. One of the ultimate long-term benefits of this course for those who successfully complete it is their development and expansion of so many essential academic skills, their exploitation of their full academic potential, and their growth in emotional toughness.

7/8 finished up the catalase lab by seeing the effect of increasing acid concentration (lowering pH) on the catalase enzyme activity.

AP Chem - we continued stoichiometry in our new unit that focuses on solutions. In order to calculate the number of moles of reactants or products in solutions, we typically will have to use the concentration and volume data about the solutions.
We saw how to properly prepare and/or dilute a solution in a "volumetric flask".
We looked at the "trick" question (really just a question that requires some thought i.e. a good question)
involving a saturated solution of a salt, and noting that the CONCENTRATION of dissolved solute does not change as solvent evaporates from the open solution container; naturally, the quantity of dissolved solute proportionally decreases via precipitation as the quantity of solvent decreases via vaporization.
Basically, the molarity of a saturated solution does not change as solvent evaporates because some solute precipitates out at the same time; otherwise the solution would become "beyond saturated", which does not normally happen in any stable solution.

We will be balancing equations by mass AND charge in this unit that contains many REDOX reactions that occur in solution.

Study hard; good luck tomorrow!