Tuesday, January 6, 2009
Tues-Day 1
AP Chem- we did two colligative property problems, one involving freezing point depression and the other involving osmotic pressure. If you have forgotten how to get empirical formulas from percent composition (this is a BASIC AP chem skill that you must know intuitively by now), make sure that you review the process (and units involved) and the reasoning behind it (ALL formulas show the MOLE RATIOS (NEVER the MASS ratios) of the atoms or ions in the compound).
IMPORTANT NOTES:
even if you are given a POSITIVE freezing point depression constant on the AP exam (which is illogical), make sure that you change its sign to NEGATIVE (as in DEPRESSION).
Reminder, delta T is ALWAYS final Temp minus initial Temp, in that order!
You will ALWAYS get a NEGATIVE delta T value for freezing point DEPRESSION problems; if you do not, you did something wrong and you will lose points ESPECIALLY if you make the double error of using a positive freezing point depression constant to get the "right" answer.
To get the proper "i", van t' Hoff factor values, you must know whether a compound is an electrolyte or a nonelectroyte (or weak electrolyte). ALL molecules EXCEPT for STRONG ACIDS do not ionize significantly or at all so they have an i = 1 value; for other compounds, you must count the number of ions per formula unit of the salt or hydroxide base or you will use an
i = 2 value for any strong acid.
We then reviewed the Born-Haber cycle in order to determine the heat of formation of a salt or its lattice energy. We saw that for cations that have a charge greater than +1, you will need or be given multiple ionization energy values; we also saw that for ANIONS that have a charge more NEGATIVE than -1, you will need or be given multiple ELECTRON AFFINITY values, which typically get progressively more POSITIVE (endothermic) because you are trying to add an (negative) electron to an already created (negative) ANION.
I put up a practice worksheet for more exercise with these problems.
Bio 6/7- we covered five different ailments/diseases of parts of the digestive system, their causes and symptoms.
We then discussed the two different types of nutrition and the special advantageous adaptations that certain organisms have for their particular type of nutrition e.g. green algae have chloroplasts in order to perform photosynthesis/autotrophic nutrition.
We then reviewed the function of the major nutrients.
We did a lab using indicators to show the effect of salivary amylase on the starch contained in pretzels.
Bio 8- we covered five different ailments/diseases of parts of the digestive system, their causes and symptoms.
We then discussed the two different types of nutrition and the special advantageous adaptations that certain organisms have for their particular type of nutrition e.g. green algae have chloroplasts in order to perform photosynthesis/autotrophic nutrition.
IMPORTANT NOTES:
even if you are given a POSITIVE freezing point depression constant on the AP exam (which is illogical), make sure that you change its sign to NEGATIVE (as in DEPRESSION).
Reminder, delta T is ALWAYS final Temp minus initial Temp, in that order!
You will ALWAYS get a NEGATIVE delta T value for freezing point DEPRESSION problems; if you do not, you did something wrong and you will lose points ESPECIALLY if you make the double error of using a positive freezing point depression constant to get the "right" answer.
To get the proper "i", van t' Hoff factor values, you must know whether a compound is an electrolyte or a nonelectroyte (or weak electrolyte). ALL molecules EXCEPT for STRONG ACIDS do not ionize significantly or at all so they have an i = 1 value; for other compounds, you must count the number of ions per formula unit of the salt or hydroxide base or you will use an
i = 2 value for any strong acid.
We then reviewed the Born-Haber cycle in order to determine the heat of formation of a salt or its lattice energy. We saw that for cations that have a charge greater than +1, you will need or be given multiple ionization energy values; we also saw that for ANIONS that have a charge more NEGATIVE than -1, you will need or be given multiple ELECTRON AFFINITY values, which typically get progressively more POSITIVE (endothermic) because you are trying to add an (negative) electron to an already created (negative) ANION.
I put up a practice worksheet for more exercise with these problems.
Bio 6/7- we covered five different ailments/diseases of parts of the digestive system, their causes and symptoms.
We then discussed the two different types of nutrition and the special advantageous adaptations that certain organisms have for their particular type of nutrition e.g. green algae have chloroplasts in order to perform photosynthesis/autotrophic nutrition.
We then reviewed the function of the major nutrients.
We did a lab using indicators to show the effect of salivary amylase on the starch contained in pretzels.
Bio 8- we covered five different ailments/diseases of parts of the digestive system, their causes and symptoms.
We then discussed the two different types of nutrition and the special advantageous adaptations that certain organisms have for their particular type of nutrition e.g. green algae have chloroplasts in order to perform photosynthesis/autotrophic nutrition.
# posted by C @ 7:04 PM 
