SciHawks

Bio- we discussed the mechanism of antibiotic resistance evolution in a population of bacteria. We used the tenets of the Theory of Evolution to show that overpopulation (of bacteria) leads to competition for resources which leads to the "selection" of those bacteria that have the best traits/adaptations for their particular environment. The (artificial) selecting agent in our case was PENICILLIN, which selected against (killed) those bacteria that had no natural resistance to the antibiotic (they lacked the allele that gives them the penicillin-resistant phenotype). Those bacteria that had natural resistance to penicillin (they were "born" that way whether or not they would ever be in a penicillin-containing environment!!!) were selected FOR by the penicillin-environment because these bacteria survived the antibiotic, were able to reproduce and pass on their penicillin-resistant alleles to their asexually reproduced offspring.
We then discussed the incompleteness/weakness of Darwin's Theory: he could not explain the CAUSES of variation within a species and also he did not know that environmentally "acquired traits" could not be passed on to offspring.
Darwin's Theory has been modified and continues to be developed in the Modern Synthetic Theory of Evolution. This theory retains/keeps most of Darwin's tenets but has much more explanatory power and supporting evidence. A source of variation are genetic mutations that produce new alleles that cause new phenotypes; also, sexual reproduction/genetic recombination
can result in new combinations of alleles that cause new phenotypes that may be advantageous in a given environment.
Chem 7/8: we took the Solutions unit exam and then we completed our precipitate lab.
Chem 9: we took the Solution unit exam.

Bio- we discussed two more examples of evolution of a species; in these cases, the selecting agents, pesticides and antibiotics, were "artificial"/created purposefully by humans.
We saw how a population of insects reproduce sexually, have variety via mutation and sexual reproduction, and compete for resources. However, when the new selecting agent, call it pesticide-A, is introduced, only those insects that ALREADY HAVE the alleles that code for enzymes that cause pesticide-A to break down can survive the pesticide-A spraying. These resistant insects NOW have an advantage, an ADAPTATION, to outcompete the other non-resistant insects. The surviving pesticide-A-resistant insects survive to reproduce and pass on their alleles to the offspring so that the next generations are resistant to pesticide-A . Thus, the species evolved into a pesticide-A resistant species.
We looked at a similar case for the evolution of penicillin-resistant streptococcus bacteria even though bacteria reproduce asexually; that just means that there tends to be less variety within a bacterial species though some variation occurs via mutation.
We then did a peppered-moth simulation lab in which lab partners played the birds/selecting agents.

Chem 7/8/9: We prepped for the unit exam. Check your work with the answer key and annotated review packet on Blackboard. Study hard and go all out tomorrow for a successful start to our last quarter!

Bio- welcome back! Here is an awesome link to a site that tracks the genetic history of humans (Homo sapiens) and here is a link to a recent article about the near EXTINCTION of the human species that occurred just 70,000 years ago!
Today, we discussed the mechanism of evolution via natural (or artificial) selection. We looked at two of four explicit examples of change/evolution of a species:
1. evolution of the modern-day long-neck giraffe from the ancestral shorter-neck giraffe
2. evolution of the peppered-moth population due to human-caused (artificial) environmental change (pollution)
Using the Darwinian explanation along with some modern understanding of genes/alleles, we showed how variation (via MUTATION, sexual reproduction, environmental influences) overpopulation, competition, SELECTION, and speciation/evolution can occur.
In the peppered-moth example, though a new species did not develop, there was a significant change in the percentage of moths with the light-color alleles; this is still an example of evolution within a population.

Chem 7/8- SOLUTIONS EXAM will be given on Wednesday!
we discussed colligative properties: boiling point ELEVATION, freezing point DEPRESSION, and vapor pressure lowering and noted that the greater the CONCENTRATION of DISSOLVED particles (ions OR molecules), the GREATER the colligative EFFECTS.

We then discussed how SOLUBLE ionic compounds (salts and hydroxide bases) DISSOCIATE into separate ions when dissolving occurs, leading to a greater concentration of dissolved particles. Therefore, given the same number of moles dissolved, IONIC compounds have GREATER colligative effects than do molecular substances (which do NOT break apart into atoms or ions).

We also illustrated that soluble salts (e.g. NaCl, KOH, (NH4)2SO4) are STRONG electrolytes, forming concentrated saturated solutions of CHARGED ions capable of conducting electricity.
Insoluble salts (e.g. PbCl2, AgBr, BaSO4) are WEAK electrolytes, forming DILUTE saturated solutions i.e. LOW concentrations of ions, which causes little to no electrical conductivity.
Molecular substances (EXCEPT for ACIDS- compound formulas that begin with "H", e.g. HCl) are NON-electrolytes. Thus, when molecules are dissolved in water, NO IONS form because covalent bonds are not broken via dissolving. So, solutions of molecular substances (e.g. CH3OH, C6H12O6, CH4, CO2, N2, Cl2) do NOT conduct electricity and do not have as large a colligative effect as do STRONG electrolytes.
We then discussed our precipitation lab.

Chem 9- SOLUTIONS EXAM will be given on Wednesday!
we discussed colligative properties: boiling point ELEVATION, freezing point DEPRESSION, and vapor pressure lowering and noted that the greater the CONCENTRATION of DISSOLVED particles (ions OR molecules), the GREATER the colligative EFFECTS.

We then discussed how SOLUBLE ionic compounds (salts and hydroxide bases) DISSOCIATE into separate ions when dissolving occurs, leading to a greater concentration of dissolved particles. Therefore, given the same number of moles dissolved, IONIC compounds have GREATER colligative effects than do molecular substances (which do NOT break apart into atoms or ions).

We also illustrated that soluble salts (e.g. NaCl, KOH, (NH4)2SO4) are STRONG electrolytes, forming concentrated saturated solutions of CHARGED ions capable of conducting electricity.
Insoluble salts (e.g. PbCl2, AgBr, BaSO4) are WEAK electrolytes, forming DILUTE saturated solutions i.e. LOW concentrations of ions, which causes little to no electrical conductivity.
Molecular substances (EXCEPT for ACIDS- compound formulas that begin with "H", e.g. HCl) are NON-electrolytes. Thus, when molecules are dissolved in water, NO IONS form because covalent bonds are not broken via dissolving. So, solutions of molecular substances (e.g. CH3OH, C6H12O6, CH4, CO2, N2, Cl2) do NOT conduct electricity and do not have as large a colligative effect as do STRONG electrolytes.

Have a HAPPY, restful, and fun vacation!

Bio- we discussed Darwin's FIVE factors that produce the evolutionary changes within a species and cause the formation of new species.
Variation
Overpopulation
Competition
Natural Selection
Speciation
Darwin's ideas stemmed from decades of observations of the natural world. His same ideas were independently conceived and supported by Sir Alfred Wallace.
We will further explore and give specific examples of Darwinism and then modify that theory due to its limitations and inability to answer certain questions.

Chem 7- we did some solution dilution problems and then learned about the COLLIGATIVE PROPERTIES of solutions. Colligative properties are freezing point DEPRESSION, boiling point ELEVATION, and vapor pressure LOWERING and are due solely to the CONCENTRATION of solute particles in solution. Since IONIC COMPOUNDS dissociate into two or more moles of ions per mole of salt dissolved, each mole of salt dissolved has a greater colligative effect i.e. an even LOWER freezing point, an even higher boiling point than a mole of a molecular compound (with the possible exception of strong acids).

Chem 8/9-we did some solution dilution problems and then learned about the COLLIGATIVE PROPERTIES of solutions. Colligative properties are freezing point DEPRESSION, boiling point ELEVATION, and vapor pressure LOWERING and are due solely to the CONCENTRATION of solute particles in solution. Since IONIC COMPOUNDS dissociate into two or more moles of ions per mole of salt dissolved, each mole of salt dissolved has a greater colligative effect i.e. an even LOWER freezing point, an even higher boiling point than a mole of a molecular compound (with the possible exception of strong acids).

Bio- we discussed Lamarck's hypothesis about how the various life forms on Earth evolved; Lamarck incorrectly thought that ACQUIRED characteristics could be passed on to offspring and also that the most prevalent and advantageous characteristics of a given species came about via frequent use of this traits by the parental generations; the characteristics that were not used would not show up in later generations.
Weissman disproved Lamarck's hypothesis by showing that mice tail disuse (which he caused by chopping off the tails of mice) did not produce offspring without tails; in other words, acquired characteristics are not passed on to offspring via heredity.
We introduced Darwin's Theory of Variation and Natural Selection as an explanation of the mechanism of evolution.

Chem 7/8- we did some more Table G solubility problems and saw that you must use the actual amounts of solute whenever there is a question involving adding more or precipitating some solute.
We also saw on Table F that all soluble salts make concentrated saturated solutions whereas all insoluble salts make DILUTE saturated solutions. It's true, even insoluble salts can be added to water and form a saturated solution THOUGH very little of the insoluble salt will be required (perhaps micrograms).
We then derived the dilution formula by relating moles to molarity and volume; then we did some solution dilution problems.

Chem 9-we did some more Table G solubility problems and saw that you must use the actual amounts of solute whenever there is a question involving adding more or precipitating some solute.
We also saw on Table F that all soluble salts make concentrated saturated solutions whereas all insoluble salts make DILUTE saturated solutions. It's true, even insoluble salts can be added to water and form a saturated solution THOUGH very little of the insoluble salt will be required (perhaps micrograms).
We then derived the dilution formula by relating moles to molarity and volume.

Bio- we began our Evolution Unit by defining evolution- the FACT, and Evolution- the modern theory that explains how and why the diversity of organisms that exist today came about.
Sadly, Evolutionary Theory is not presented accurately in the media and is often horrifyingly misunderstood. Already, we have cleared up some misconceptions about the fact of evolution and the Theory of Evolution.
We looked at the various general fields of science that provide evidence that SUPPORTS the Modern Synthetic Theory of Evolution: Geology, Cytology (the study of cells of various organisms), Anatomy, Embryology, and MOST importantly, Biochemistry (comparing DNA, RNA, proteins, sugars, and fats).
Starting with Geology, we saw how consecutive layers of sedimentary rock give you a relative time scale of when the fossils were created. Older fossils/older species are found in the older rock layers (near the bottom of the layers) and newer fossils/species are found in the upper layers. To estimate the absolute age of a fossil (more detailed than the relative age), geologists determine the radioactivity of the rocks in the layers, which reveals the ages of the rocks.
We will discuss the other fields that give supporting evidence to this all-encompassing theory in Biology.

Chem 7- we did several solubility curve problems and also looked at the factors that determine the rate of dissolving: temperature, surface area of SOLID solutes, pressure of GASEOUS solutes, and stirring/agitation/shaking. These factors all DIRECTLY can increase the number of solute to solvent COLLISIONS per second, which CAUSES the rate of dissolving.

Chem 8/9- we did several solubility curve problems and also looked at the factors that determine the rate of dissolving: temperature, surface area of SOLID solutes, pressure of GASEOUS solutes, and stirring/agitation/shaking. These factors all DIRECTLY can increase the number of solute to solvent COLLISIONS per second, which CAUSES the rate of dissolving.
We continued our Precipitate Bingo lab using a variety of aqueous solutions that you mixed together either to form a precipitate or to see no reaction. We will discuss that writeup on Friday.

Bio- we had our unit exam today; tomorrow we begin the most important unit in Biology: Evolution. The modern synthetic theory of evolution is the SINGLE unifying theory of ALL of biology. Everything that we studied this year can be explained and connected via this theory.
I look forward to discussing it with you.

Chem 7/8- we discussed another unit of concentration that is commonly used to measure minute quantities of pollutants dissolved in aqueous solutions or in air: parts per million (ppm).
We then looked at a table of solubility curves to determine the quantity of various solutes that can saturate (be dissolved in) 100. grams of water to make an aqueous solution at various temperatures. Frequently, proportions must be used in order to solve these problems because many solutions contain more or fewer than 100. grams of water.
We also saw how to tell whether a given solution is unsaturated, saturated, or will form a certain amount of precipitate. Occasionally, even an unstable supersaturated solution can form. ONLY saturated solutions are at equilibrium i.e. the rate of dissolving EQUALS the RATE of crystallization/undissolving.
We then tested our precipitate Bingo grids by doing a microscale mixing of pairs of aqueous solutions in order to see whether the double replacement reaction occurred.

Chem 9- we discussed another unit of concentration that is commonly used to measure minute quantities of pollutants dissolved in aqueous solutions or in air: parts per million (ppm).
We then looked at a table of solubility curves to determine the quantity of various solutes that can saturate (be dissolved in) 100. grams of water to make an aqueous solution at various temperatures. Frequently, proportions must be used in order to solve these problems because many solutions contain more or fewer than 100. grams of water.
We also saw how to tell whether a given solution is unsaturated, saturated, or will form a certain amount of precipitate. Occasionally, even an unstable supersaturated solution can form. ONLY saturated solutions are at equilibrium i.e. the rate of dissolving EQUALS the RATE of crystallization/undissolving.

Bio- tomorrow you'll take your Mendelian and Modern Genetics Exam, the first exam of our LAST quarter. I'm a big fan of "all's well that ends well", a BIG fan! So, let's get started with some great results this quarter and end with some top Regents scores, all of which will reflect well on your FINAL course grade (the ONLY grade that counts towards your record).

Today we discussed reproductive and therapeutic cloning as well as stem cell research. We also covered some of the test objectives; I'll post the rest of the explanations on Blackboard by 6PM.

Chem 7- we defined a quantitative measure of solution concentration called "MOLARITY", which has units of moles per liter and is symbolized by "M". We did several permutations of problem types involving molarity and we discussed how solutions are made.
For lab tomorrow, bring in a water bottle (Nalgene optional), which we will use to make some concentrated solutions (lemonade, etc.).

Chem 8/9- we defined a quantitative measure of solution concentration called "MOLARITY", which has units of moles per liter and is symbolized by "M". We did several permutations of problem types involving molarity and we discussed how solutions are made.
We then set up our "precipitate Bingo" lab sheets by predicting the double replacement reactions between pairs of aqueous solutions.

Bio- we began our unit review by doing a biotechnology worksheet. Do all of today's review handouts and check out Blackboard on Sunday for the answers to these worksheets.

Chem 7/8- we learned the theory behind and the practical uses of Table F. Salts are soluble when the multiple ion-dipole attraction between the ions in the salt's lattice and the water (solvent) molecules are GREATER than the force of attraction due to the ionic bonds between the cations and anions in the lattice. This usually occurs when the ions have a low charge ( +1 or -1) and a large size (many OPEL's). However, when the ionic bonds are too strong to be overcome even by multiple ion-dipole attractions, the salt is insoluble; this occurs if the ions have high charge (+2, +3, or -2, -3) and small size (few OPEL's).
We saw that you can predict that a double replacement reaction between aqueous salts goes to completion by seeing that an insoluble precipitate forms. After some practice, you can quickly judge, with or without Table F, whether a salt is soluble or insoluble.
We then did the Precipitate Bingo prep work of hypothesizing which pairs of ionic compounds would result in the formation of insoluble precipitates. We will test these hypotheses next week.

Chem 9- we learned the theory behind and the practical uses of Table F. Salts are soluble when the multiple ion-dipole attraction between the ions in the salt's lattice and the water (solvent) molecules are GREATER than the force of attraction due to the ionic bonds between the cations and anions in the lattice. This usually occurs when the ions have a low charge ( +1 or -1) and a large size (many OPEL's). However, when the ionic bonds are too strong to be overcome even by multiple ion-dipole attractions, the salt is insoluble; this occurs if the ions have high charge (+2, +3, or -2, -3) and small size (few OPEL's).
We saw that you can predict that a double replacement reaction between aqueous salts goes to completion by seeing that an insoluble precipitate forms. After some practice, you can quickly judge, with or without Table F, whether a salt is soluble or insoluble.

Bio- HW: Outlines 13.2 and 13.3 are due by TUESDAY, due to the change in the exam date (which is now on next TUESDAY.)
we discussed some more methods involving BIOTECHNOLOGY. Specifically, we saw how gel electrophoresis is used to separate various sized fragments of DNA that were cut by various restriction enzymes. Because all humans have at least some differences in their base sequences that make up the genes of their chromosomes, restriction enzymes, which cut the DNA at specific base sequence sites, will cut the DNA from different people into different sized fragments. These fragments are loaded/injected into a gel that is hooked up to a battery. The negatively charged DNA fragments travel from the negative electrode of the battery through the gel towards the positive electrode of the battery. The larger fragments travel slowly while the smaller fragments travel more rapidly. When the bands have clearly separated, the resulting banding pattern is like a DNA fingerprint that is used to identify or to rule out individuals as the source of the DNA sample.

Chem 7- we discussed the mechanism for the rule, "LIKE DISSOLVES LIKE". That is, POLAR molecules can dissolve other polar molecules but polar molecules do NOT significantly dissolve NONPOLAR molecules because the polar molecules are more attracted to themselves than they are attracted to the nonpolar molecules. This phenomenon is all caused by the ATTRACTION of the partially charged regions (poles) of the polar molecules to the oppositely charged polar regions of other molecules (or to FULLY oppositely charged ions).
We went through each possible type of homogeneous mixture/solution and we discussed the "Tyndall test" to see whether an aqueous mixture is a TRUE (CLEAR) solution.

Chem 8/9- we discussed the mechanism for the rule, "LIKE DISSOLVES LIKE". That is, POLAR molecules can dissolve other polar molecules but polar molecules do NOT significantly dissolve NONPOLAR molecules because the polar molecules are more attracted to themselves than they are attracted to the nonpolar molecules. This phenomenon is all caused by the ATTRACTION of the partially charged regions (poles) of the polar molecules to the oppositely charged polar regions of other molecules (or to FULLY oppositely charged ions).
We went through each possible type of homogeneous mixture/solution and we discussed the "Tyndall test" to see whether an aqueous mixture is a TRUE (CLEAR) solution.

We then deciphered Table F, which lists the ions of soluble salts and or insoluble (precipitate forming) salts. This Table is useful in predicting whether a double replacement ionic reaction will occur and go to "completion".

Bio- HW: Outline Chapter 13.1 due Thursday;
Outlines 13.2 and 13.3 are due on Monday before the exam.
We discussed the purpose and mechanism of RECOMBINANT DNA.This process involves the use of RESTRICTION ENZYMES to cut two DNA molecules (usually a bacterial chromosome/plasmid and a eukaryotic chromosome) at specific sites/sequences of nucleotides. The cutting of the double stranded DNA leaves identical "sticky ends" to two DNA segments, which then hydrogen-bond/join together a.k.a "recombine" to form a single chromosome containing genes from both the plasmid and the eukaryotic chromosome. The recombinant DNA plasmid is then re-inserted, via some vector/virus, into another bacterium, which then replicates asexually and produces identical copies of the recombinant DNA plasmid. This technology can be used to insert virtually any human gene into a bacterium so that the bacteria can produce the human protein/enzyme that is coded for by that gene. This technology has revolutionized biology and medicine.

Chem 7/8- we took the multiple choice part of the exam and then we began our new unit on Solutions.
Chem 9- we took the multiple choice part of the exam.

Bio- we discussed ARTIFICIAL SELECTION, the process by which plants or animals with specific desirable traits are SELECTIVELY BRED to each other so that the alleles that code for those traits are passed on to their offspring. After many generations, most of the offspring and parents will typically have those desired traits.
INBREEDING is a type of artificial selection by which "pure-bred" organisms/ homozygous for a given trait can be created by just breeding, for many generations, the offspring that have the same traits. The goal is to have pure-bred organisms that have particular desirable traits. Occasionally, inbreeding leads to the expression of harmful traits, which occurs when heterozygotes mate and form offspring that are homozygous for a harmful recessive allele.
HYBRIDIZATION is the mating of different purebred plants or animals to form heterozygotes that can typically have BOTH of the best traits of their parents, particularly when the alleles that combine are CODOMINANT or incompletely dominant.

We also reviewed, for ASEXUALLY reproducing plants/organisms, a way to amplify the frequency of traits/offspring that are desirable via vegetative propagation: grafting, cutting, or layering. Seedless oranges first formed as a result of a random genetic mutation in the gametes of an orange tree. All seedless oranges since then were formed via grafting branches from that original tree.

Chem 7-9: we took the written-response portion of the 3rd quarterly exam; tomorrow, we take the multiple choice portion of the lab.

Bio- HW: Outline 12.1 is due tomorrow.
Today we discussed four common genetic diseases: PKU, Tay-Sachs, Sickle-Cell Anemia, and Huntington's disease.

Chem 7-9: check out Blackboard for the annotated Jan. 2008 Regents review questions/answers from the past two days of class. I'll be in Room 301 tomorrow morning if you have any last minute questions.
Also, use the past unit review packets and worksheets to study for this comprehensive quarterly exam. These resources are still ALL on Blackboard for your perusal.
As usual, a higher 3rd quarterly exam grade will REPLACE the lowest unit test grade from this quarter so study hard.

Bio- HW: text 12.1 outline is due on TUESDAY.
we discussed polygenic inheritance: a trait that is controlled/determine by more than one gene; these genes can even be on different (nonhomologous) chromosomes. The resulting trait typically has a wider/more varied range of phenotypes as is the case with eye color. So, instead of just having a dominant brown allele and a recessive blue allele, there can be more combinations among several different genes, which causes the various possible eye color shades.
We also discussed several examples of ENVIRONMENTAL effect (nurture) on GENE EXPRESSION (an organism's nature): people with the genes for melanin production do not have very dark skin unless they are exposed to sunlight, which turns the gene ON so that transcription and translation of that gene occur.

Chem 7-9: we prepped for the quarterly; over the weekend, work on the Regents exam to see what you need to work on.

Bio- we illustrated and described four types of chromosomal mutations/alterations: large segments of DNA are sometimes transferred from one chromosome to another nonhomologous chromosome; sometimes a segment of a chromosome is duplicated, inverted, or deleted. Because SEVERAL genes are usually transferred during these chromosomal alterations, the phenotype changes can be extreme or lethal.
We also reviewed common point genetic mutations such as substitution, addition, or deletion of a single nucleotide in the DNA molecule/chromosome. An addition or deletion causes a serious phenotype change because there are THREE nucleotides per codon; so, adding or deleting a SINGLE nucleotide can cause a whole frameshift in how the triplets are transcribed.

Chem 7/8- we took our Equilibrium unit exam and then we began preparation for next Tuesday and Wednesday's quarterly exam.

Chem 9- we took our Equilibrium unit exam.

Bio- HW: Outline of Section 10.2 is due on Thursday.
we drew out and discussed karyotypes, which are pictures of the homologous pairs of chromosomes found in the nucleus of a somatic/body cell. We saw how to determine the sex of a person from the karyotypes by focusing on the sex chromosomes: females have matching X chromosomes whereas males have an X and a much smaller Y sex chromosome.
We discussed the difference between a small genetic point mutation and a much larger scale chromosomal mutation.
We focused on the change in chromosome number caused by NONDISJUNCTION during either meiosis I or meiosis II. The resulting gametes, if viable, can unite with the opposite sex cell and for offspring with greater or fewer than the diploid number of chromosomes.

Chem 7/8/9 - we prepped for the upcoming Equilibrium exam by going over each problem type and reviewing some common errors/traps.

Bio- HW- the outline of text Section 10.2 is due on Thursday.
we illustrated how to draw out a pedigree chart; pedigree charts are useful for tracking and/or inferring the genotypes that exist in members of a family tree. The charts are also used to predict the probability that a given offspring will inherit a given trait from her/his parents based on the parents' and grandparents' phenotypes.
Be careful, some of these charts show the genotype of the family members but others merely show the phenotypes from which the genotypes must be inferred. It may take some trial and error to deduce/infer the genotypes of the family tree members!

Chem 7/8- we discussed the brute force memorize-able fact that ONLY TEMPERATURE can affect the value of Keq. NO OTHER FACTOR, no matter how extreme the equilibrium shift, can ever in the slightest way cause a change in the value of Keq.
For endothermic reactions/processes, increasing Temp. will cause an increase in the value of K (more products) and for exothermic reactions/processes, increasing Temp. will cause a DECREASE in the value of Keq (more REACTANTS).
We then did several "higher-level" Le Chat problems in which you had to figure out a stress that would cause a particular shift.
We saw two demonstrations of equilibrium systems:
1. the chromate-dichromate equilibrium
we showed that increasing the concentration of a product (acid) caused a shift (as seen by the color change) towards the reactants

2. the nitrogen dioxide - dinitrogen tetroxide equilibrium - from the shift as a result of temperature change, we were able to determine that the forward reaction 2 NO2 --> N2O4 was exothermic.

Chem 9-we discussed the brute force memorize-able fact that ONLY TEMPERATURE can affect the value of Keq. NO OTHER FACTOR, no matter how extreme the equilibrium shift, can ever in the slightest way cause a change in the value of Keq.
For endothermic reactions/processes, increasing Temp. will cause an increase in the value of K (more products) and for exothermic reactions/processes, increasing Temp. will cause a DECREASE in the value of Keq (more REACTANTS).
We then did several "higher-level" Le Chat problems in which you had to figure out a stress that would cause a particular shift.
Check out this link from yesterday's demo: the chromate-dichromate equilibrium

Bio- we discussed "sex-linked" traits, which are determined by the genes that are located on the "sex chromosomes". Each human body cell has one PAIR of sex chromosomes; males have non-identical sex chromosomes, one X and one Y but females have an identical pair of X "sex" chromosomes.
We saw how the percentages of offspring that show a RECESSIVE trait CAN BE different when that trait is determined by a gene on a sex chromosome. The reason for that is that a male cannot mask/hide the phenotype from a recessive allele on its X sex chromosome because the Y chromosome has, practically speaking, no alleles to dominate over the recessive allele. Thus, sex-linked traits can be determined by the fact that NEITHER parents displays a recessive trait but ONLY the MALE offspring then display the recessive trait; this is because the recessive allele was "carried" by the mother but not phenotypically expressed (because she also had a dominant allele on the other X chromosome) and passed on to the son; the son also inherited a Y sex chromosome (from his father) that had no alleles to mask/hide the recessive allele.

Chem 7- we did some Keq expression and Keq value problems while stressing that ONLY the aq. and gaseous reactants and products go into these expressions. We noted that the BALANCED equation coefficients are used as exponents of the concentrations of their respective reactants and products.
We also learned that, "practically", there are two types of reactions that go to "completion"/about 100% products. These are:
1. reactions of two aqueous solutions that form an insoluble precipitate (which then does not appreciably dissolve to cause the reverse reaction).
2. reactions of aqueous solutions and/or liquids and/or solids that form gases (which are likely insoluble and therefore do not return to the solution for a reverse reaction).

Chem 8/9- we did some Keq expression and Keq value problems while stressing that ONLY the aq. and gaseous reactants and products go into these expressions. We noted that the BALANCED equation coefficients are used as exponents of the concentrations of their respective reactants and products. We also learned that, "practically", there are two types of reactions that go to "completion"/about 100% products. These are:
1. reactions of two aqueous solutions that form an insoluble precipitate (which then does not appreciably dissolve to cause the reverse reaction).
2. reactions of aqueous solutions and/or liquids and/or solids that form gases (which are likely insoluble and therefore do not return to the solution for a reverse reaction).
We then saw two demonstrations, one that showed a double replacement reaction going to completion and the other showing an equilibrium shift in the chromate-dichromate equilibrium mixture by increasing the concentration of a product- acid.