Monday, February 13, 2006
AP Stats
Finished grading the first of our ultra-important series of equilibrium exams. The chasm within the class continues and widens due to, among other factors, a significant disparity in the amount of preparation for exams and, even more importantly (!), the ability to follow direction/answer the question that is asked/ basic test-taking skills/ careLESSness. For example, when you write a number SO SMALL that even YOU can't read it or use it consistently, you are throwing points away! Another example, when you say that a substance increases in concentration and then go on to explain how that same substance DECREASES in concentration, you are throwing points out the window. Another, when you indiscriminately use numbers without units or with the wrong units (a crucial bookkeeping skill in this unit) you cannot get the correct answer. When you randomly abbreviate terms without a key, as if you are writing in a CHATROOM as opposed to taking an IMPORTANT EXAM, you are throwing points away. When you write an answer, correct value or not, but you provide no clue as to how you arrived at the answer (especially when this and ALL tests and the ACTUAL AP exam only give points for work/reasoning shown), you are throwing points away. If losing countless points due to careless errors does not change your behavior, I do not know what will. I can only state that almost nothing has changed. Do NOT repeat these careless errors. Critically read your exam before you hand it in. The aforementioned factors are within the ken and control of ANY student and should always be exercised.
5 Female students score range: 130 to 150 (mostly in the 140's)...kudos! keep up the great work!
5 Male students score range: 91 to 114.
Says it all.
No such disparity has occurred in any of my previous classes at ANY level.
One basic Regents-level question that MOST of you missed:
A (solid) --> B (gas) + C (gas)
when total pressure on the system at equilibrium increases, the concentration of B will...
Le Chatelier's Principle tells us that the system will shift towards making more reactant (A) to relieve the added pressure stress by decreasing the number of moles of gaseous substances ( B and C, which CAUSE the pressure in the container/system) in the system. Fewer moles of gas in the system leads to a decrease in pressure because solids do not contribute (practically at all) to the pressure of the system and fewer moles of gas causes a lower collision frequency between the gas particles and the container walls (thus lowering the pressure). THUS, the concentration of B will DECREASE (assuming constant volume conditions) as the reaction proceeds towards equilibrium.
Think of it this way, for simplicity: when you put enough pressure on any gas, it will solidify.
5 Female students score range: 130 to 150 (mostly in the 140's)...kudos! keep up the great work!
5 Male students score range: 91 to 114.
Says it all.
No such disparity has occurred in any of my previous classes at ANY level.
One basic Regents-level question that MOST of you missed:
A (solid) --> B (gas) + C (gas)
when total pressure on the system at equilibrium increases, the concentration of B will...
Le Chatelier's Principle tells us that the system will shift towards making more reactant (A) to relieve the added pressure stress by decreasing the number of moles of gaseous substances ( B and C, which CAUSE the pressure in the container/system) in the system. Fewer moles of gas in the system leads to a decrease in pressure because solids do not contribute (practically at all) to the pressure of the system and fewer moles of gas causes a lower collision frequency between the gas particles and the container walls (thus lowering the pressure). THUS, the concentration of B will DECREASE (assuming constant volume conditions) as the reaction proceeds towards equilibrium.
Think of it this way, for simplicity: when you put enough pressure on any gas, it will solidify.
# posted by C @ 4:32 PM 
