The number of calories of heat required to raise the temperature of one gram of water by one degree c is

Because there are 4.184 joules in a calorie, the specific heat of water is 4.184 J/g-K. The ease with which a substance gains or loses heat can also be described in terms of its molar heat capacity, which is the heat required to raise the temperature of one mole of the substance by either 1oC or 1 K.

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle

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