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Almost everyone knows what is heat, but to describe it in scientific terms is difficult. We know heat flow from a hot place to a cold place, but we have to be able to compare hot and cold. Then we have to know properties of heat (thermodynamics and kinetics).

Example 1

How much energy is required to heat 500 mL water from 288 K to 370 K to make two cups of coffee?


Heat capacity of water is 4.184 J ml-1 K-1 Thus, heat q is

q = 500 * 4.184 * (370 - 288) ml J ml-1 K-1 K
= 171544 J (or 172 kJ)


Example 2

The heat of melting for ice is 80 cal g-1 (6.02 kJ mol-1). How much ice will melt when 172 kJ is consumed?


The amount of ice melt by 172 kJ is

172 kJ
6.02 kJ mol-1
= 28.5 mol
= 513 g
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