Suppose you have cold feet when you go to bed, and you want something to warm your feet throughout the night. Would you prefer to have a bottle filled with hot water, or one filled with an equal mass of nails at the same temperature as the water? Explain

I prefer to have a bottle filled with hot water

Explanation:

I would prefer to have a bottle filled with hot water instead of an equal mass of nails at the same temperature, since water has higher specific heat than iron (nails). The higher the specific heat of a substance, the more heat it will emit when cooling down and it will take longer to cool. Therefore, water is the best option.