Anonymous
Anonymous asked in Science & MathematicsPhysics · 1 decade ago

# heating-cooling curve?

What is a heating-cooling curve? What does it show and what is its signifigance? How is it useful? What is latent heat?

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• 1 decade ago

1. Many compounds and elements can be melted from a solid crystalline state to a liquid state. The heating and cooling curves for these processes have the same general features. During heating, the temperature rises steadily until the melting temperature is reached. Once melting begins, the temperature remains constant until all of the material has melted. The temperature then rises again

2/3. Most substances melt at different temperatures. Melting temperature is, therefore, a characteristic. Since there are lots of substances known, however, melting temperature alone nearly always cannot provide a unique identification of a material. Another rather unique characteristic of a substance is its ability to hold heat. (This is called the heat of fusion.) A cooling curve depends upon both the melting temperature and the heat of fusion, so it combines two characteristics and, therefore, serves as an excellent fingerprint. The amount of heat needed to bring about melting does depend upon the amount of substance. For this reason, characteristic heating curves should be based upon molar quantities. Rather than use time as the x-axis in a curve, we could use amount of heat added. This would allow a comparison of heating curves to be made between different sets of apparatus.

4. the heat given off or absorbed when a material melts or freezes, or boils or condenses. For example, when ice is heated, once the temperature reaches 0 o C, it's temperature won't increase until all the ice is melted. The ice has to absorb heat in order to melt. But even though it's absorbing heat, it's temperature stays the same until all the ice has melted. The heat required to melt the ice is called the latent heat. The water will give off the same amount of latent heat when you freeze it.

• NJGuy
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