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All matter contains heat.

Linear heat flow diagram Some things contain more heat than others, but everything contains heat. Heat is energy in motion; it moves through things. Heat transfer is the movement of energy from an object of higher temperature to an object of lower temperature. Another way of stating the second law of thermodynamics is that heat flows spontaneously from a warmer object to a colder one. It cannot flow from the cooler object to the warmer one. Once the two objects reach the same temperature, there is no more heat energy flowing between the objects. At this point, they are in thermal equilibrium. 

For example, if you feel cold, you can snuggle up to someone else to get warm. The heat from that other person will flow into you until you are both the same temperature. Because of this, the other person cools off also! Of course, you still have some heat in you even when you feel cold. So why doesn’t your heat flow out of you, making you even colder and the other person warmer? It doesn’t work that way, because heat always flows from the warmer object to the cooler one!

Heat Transfer

What is heat transfer?

Heat transfer is the movement of energy from an object of a higher temperature to an object of a lower temperature.

Heat Transfer

What is an example of heat transfer?

Answer may include: a cup of hot coffee cools off after being exposed to cooler air. The heat from the molecules in the coffee transfers to cooler molecules of the air.