Question

Why rate of cooling is not equal to the rate of heating?

Answer 1

How quickly a matter gets hotter or cooler depends on its specific heat capacity(if you want to keep mass out of the dependence). The greater the specific heat capacity of a substance, more is the amount of energy required to bring about a desired change in temperature. Now the rate of heat flow depends on the temperature gradient. Greater the difference between the temperature of two bodies, greater will be rate of heat flow from hotter body to colder body. 

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