Monday, February 1, 2010

Heat Moves One Way

Heat Moves One Way

When thermal energy is transferred – conduction, convection, radiation – it is called heat. Heat is thermal energy moving from a warmer object to a cooler object.

If two substances have different temperatures, heat will flow from the warmer object to the colder one. When heat flows into a substance, the thermal energy of the substance increases. As the thermal energy increases, its temperature increases. At the same time, the temperature of the substance giving off heat decreases. Heat will flow from one substance to the other until the two substances have the same temperature.

What happens when you make something cold like ice cream? The ingredients used, such as milk and sugar, are not nearly as cold as the finished ice cream. In an ice cream maker, the ingredients are put into a metal can that is packed in ice. You might think that the ice transfers cold to the ingredients in the can. But this is not the case. There is no such thing as “coldness.” Instead, the ingredients grow colder as the thermal energy flows from them to the ice. Heat transfer occurs in only one direction – from a warmer object to a cooler object!

To help with our understanding of this concept, we went outside for a while today.  We discussed, and demonstrated, how our jackets, coats, sweatshirts, hats, gloves, scarves, etc. help keep us warm.  They don't make us warm, they help trap and keep our body heat close to us.

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