In general, a substance that cools off quickly has a low specific heat capacity. Specific heat capacity is the amount of heat needed to change the temperature of a unit mass of a substance by one degree Celsius.
A substance with a low specific heat capacity can release its heat energy quickly, which leads to a rapid decrease in temperature when it cools. Conversely, substances with a high specific heat capacity can retain heat for longer periods, resulting in a slower cooling rate.
For example, metals like copper have a low specific heat capacity, which is why they heat up and cool down quickly compared to water, which has a high specific heat capacity and therefore cools down slowly. So, if you observe a substance cooling off rapidly, it indicates that it does not require much heat energy to change its temperature, confirming that it has a low specific heat capacity.