Solutlon (400g milk) (37Ttemperature increase)
1 calorie absorbed 1.5 X 10' calories. ( I T temp incr in I g milk) =
On the other hand, a bowl of hot oatmeal and a hot cup of coffee or cocoa is already a t or above body temperature and rewires no body energy as it sits there in your stomach. Being warmer than ybur body temperature, it provides your body with calories as it cools down to body temperature, and then it provides still more calories as your body digests it. Many Nigerian babies'only food is breast milk from their mothers. T h e babies are healthv and erowine normallv even though the mother's milk has ion few caloGes. The babies should be starving. However, they are not starving because the mother's body heat takes the place of food calories that a baby would ordinarily need to keep up its own body temperature. This frees calories to be used hy the babies' bodies for normal growth and development. Whether they are walking, standing. sitting, or lying down, Nigerian mothers always seem to be holding their young babies close to their bodies, and this is keeping many infants from being undernourished or even from starving to death. Reference Sricnm World. 13. IOaoIxr 30. 1972).
' What a nulritionist calls a calorie is actually a kilocalorie.
The antifreeze that the insects produce is 1.23-trihydroxypropane. (This insect antifreeze is also called glycerol and glycerin; it is a by-product of the soap industry and is used to make suppositories.) Example Problem 1 Bug X has produced an intracellular (within the cells) solution that is 3.0 rn glycerol. What is the coldest temperature helshe can survive? Solution (3.0mold glycerol solution) 1.86'C freezing point depression 1 mold glycerol solution = 5.6T freezing point depression Bug X can survive winter temperatures of a t least -5.6'C with an intracellular solution that is 3.0m elvcerol. (There areother chemicals present within the i n t r a c e k a r fluid that lower the fluid freezing point even further.) Example Problem 2 Bug Y must survive winter temperatures of -lO.O°C. How many grams of glycerol per mL of intracellular body fluid must hisher body produce? (For simplicity, assume that the intracellular fluid is just water.) Solutlon (lO.O°Cip depression)
Freeze-Proof Bugs = 495 g glycerol in 1Kg fluid
Ronald DeLorenzo
When presenting colligative properties to your classes, rather than using imaginary numbers to determine freezing point depressions of nonexistent solutions, why not use actual data t o determine information about real items of interest? Here are two examoles. Scientists have r&ntly discovered ten different insects that produce an antifreeze which helps them survive the winter.
788
Journal of Chemical Education
495 g glycerol
(
Kg fluid
I Kg fluid
) (1000
0.495g glycerol
mLnuid Bug Y must produce 0.495 g of glycerol per mL of intracellular body fluid to survive winter temperatures of -lO.O°C. It is interesting to speculate on the mechanism by which insects determine the results of these calculations. Perhaps this explains why some calculators have bugs in them. Reference Sriquerl.IMwch 19811.
ml.f l d ) =
