Thursday, September 4, 2008
Thurs-Day 1
AP Chem: we finished our discussion of acid/base safety by drawing out the net ionic equations that occur when an acid and base neutralize each other.
We then did a few problems involving unit conversion and sig figs.
Two VERY important problems arose:
one involving the squaring or cubing of a conversion factor and the other involving the conversion of the + or - uncertainty value.
Remember, when you have to square or cube a unit in order for the units to cancel, you must also square or cube, respectively, the value of the conversion factor fraction.
For example, 100 cm = 1m but 100 cm^3 does NOT equal 1 m^3 !
To do the conversion, you must cube each measurement:
(100 cm)^3 = (1m)^3 , when multiplied out shows that 1000000 cm^3 = 1 m^3.
In the case of converting the uncertainty or error built into any set of measurements,
you only need to multiply by the conversion factor WITHOUT adding or subtracting anything else; this is MUCH more easily seen by example as follows:
If you want to convert 42 C + or - 5 C to Fahrenheit, first take care of the measurement part.
That is [42 C x (9/5)] + 32 = 108 F
BUT THEN only multiply the + or - 5 part by the 9/5 conversion factor BECAUSE, for every 9 degrees F, the Celsius scale changes by 5 degrees.
so + or - 5 times 9/5 = 9 degrees F.
so the final answer is that 42 C + or - 5C is equal to 108 F + or - 9 F.
Also, as suggested in class, you can get the same answer by converting the higher and lower temperatures (with error added in) to Fahrenheit and then get the difference between the upper and lower values and then divide that difference by TWO.
e.g. 42 C + 5 C = 47 C ; [47 C x (9/5)] + 32 = 117 F
42 C - 5 C = 37 C ; [37 C x (9/5)] + 32 = 99 F
117 F - 99 F = 18 F ; 18F / 2 = 9 F , which is the same uncertainty as calculated above!
Bio 6/7- we finished our discussion on the characteristics that are common to all organisms/living things. We then focused on the 9 specific life functions that keep organisms alive: nutrition, excretion, synthesis and assimilation, transport, growth, respiration, regulation, reproduction, and immunity. All of these life processes are part of an organism's metabolism.
We then tried a group activity that will give us practice with the greatest method ever devised to show whether an explanation or claim should be supported or rejected. This method is the SCIENTIFIC METHOD.
Bio 8- We continued our discussion of the 9 specific life functions that keep organisms alive: nutrition, excretion, synthesis and assimilation, transport, growth, respiration, regulation, reproduction, and immunity. All of these life processes are part of an organism's metabolism.
We then did a few problems involving unit conversion and sig figs.
Two VERY important problems arose:
one involving the squaring or cubing of a conversion factor and the other involving the conversion of the + or - uncertainty value.
Remember, when you have to square or cube a unit in order for the units to cancel, you must also square or cube, respectively, the value of the conversion factor fraction.
For example, 100 cm = 1m but 100 cm^3 does NOT equal 1 m^3 !
To do the conversion, you must cube each measurement:
(100 cm)^3 = (1m)^3 , when multiplied out shows that 1000000 cm^3 = 1 m^3.
In the case of converting the uncertainty or error built into any set of measurements,
you only need to multiply by the conversion factor WITHOUT adding or subtracting anything else; this is MUCH more easily seen by example as follows:
If you want to convert 42 C + or - 5 C to Fahrenheit, first take care of the measurement part.
That is [42 C x (9/5)] + 32 = 108 F
BUT THEN only multiply the + or - 5 part by the 9/5 conversion factor BECAUSE, for every 9 degrees F, the Celsius scale changes by 5 degrees.
so + or - 5 times 9/5 = 9 degrees F.
so the final answer is that 42 C + or - 5C is equal to 108 F + or - 9 F.
Also, as suggested in class, you can get the same answer by converting the higher and lower temperatures (with error added in) to Fahrenheit and then get the difference between the upper and lower values and then divide that difference by TWO.
e.g. 42 C + 5 C = 47 C ; [47 C x (9/5)] + 32 = 117 F
42 C - 5 C = 37 C ; [37 C x (9/5)] + 32 = 99 F
117 F - 99 F = 18 F ; 18F / 2 = 9 F , which is the same uncertainty as calculated above!
Bio 6/7- we finished our discussion on the characteristics that are common to all organisms/living things. We then focused on the 9 specific life functions that keep organisms alive: nutrition, excretion, synthesis and assimilation, transport, growth, respiration, regulation, reproduction, and immunity. All of these life processes are part of an organism's metabolism.
We then tried a group activity that will give us practice with the greatest method ever devised to show whether an explanation or claim should be supported or rejected. This method is the SCIENTIFIC METHOD.
Bio 8- We continued our discussion of the 9 specific life functions that keep organisms alive: nutrition, excretion, synthesis and assimilation, transport, growth, respiration, regulation, reproduction, and immunity. All of these life processes are part of an organism's metabolism.
# posted by C @ 10:51 AM 
