- Volume = 200ml
Specific Gravity = 0.8
Specific Heat = 1.5 cal/g/degC
a) The Thermal Capacity of a sample is the amount of heat energy required to raise the specific sample by one degree celcius. This can calculate from the given data as follows:
- Weight of Sample = Specific Gravity * Weight of Same Volume of Water
Weight of Sample = 0.8 * 200 g
Weight of Sample = 160g
Thermal Capacity = Weight of Sample * Specific Heat
Thermal Capacity = 1.5 cal/g/degC * 160g
Thermal Capacity = 240 cal/degC
It is reassuring to see that the final result has the correct units to be a thermal capacity - an amount of energy per unit of temperature!
b) The thermal capacity we just calculated is the energy required to raise this samples temperature by one degree celcius. Now, we want to go from 22 to 37 degC, so we need to multiply the thermal capacity by 15 degC to get the number of calories required.
Energy = Thermal Capacity * Temperature Change
Energy = 240 cal/degC * 15 degC
Energy = 3600 cal
/ul] Again, we are reassured by the fact that the units work out correctly.In fact, it should be noted that this entire problem can be done with very little physics knowledge - pure application of dimensional analysis to the quantities given and wanted (and their units) can quickly solve this problem!