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Heat as energy Heat is energy transferred from one object to another because of a difference in temperature Heat naturally flows from high temperature to low temperature.

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Heat Joule determined that a certain amount of mechanical work resulted from a specific amount of heat input. Joule is credited with defining Heat as energy (or transfer of energy) Joule determined that a certain amount of mechanical work resulted from a specific amount of heat input. Joule is credited with defining Heat as energy (or transfer of energy) Heat is measure in calories or Joules. Heat is measure in calories or Joules. 1cal = 4.186J 1cal = 4.186J 1 cal is the amount of heat necessary to raise the temperature of 1 gram of water by 1 degree C. 1 cal is the amount of heat necessary to raise the temperature of 1 gram of water by 1 degree C.

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Heat 14-3 Specific Heat 14-3 Specific Heat –When you heat an object, the temperature rise depends on mass of the object and a property of the material called specific heat. –Q = mc(T2-T1) –Q = amount of heat, m = mass, c = specific heat, T = temp. –The higher the heat capacitance, the smaller the temp change for a given amount of heat input.

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Heat Calorimetry – solving problems Calorimetry – solving problems In a closed system, the heat is transferred from the hot object to the cold object or heat lost by one object = heat gained by another. In a closed system, the heat is transferred from the hot object to the cold object or heat lost by one object = heat gained by another.

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Heat Latent Heat Latent Heat –When a material changes phases from a solid to liquid or from liquid to gas, a certain amount of energy is involved in the phase change. This is called the latent heat. –Heat of Fusion: heat required to change from a solid to a liquid. –Heat of Vaporization: heat required when changing from liquid to gas. –Q = mL where m = mass and L = latent heat (look this up in a table) –During a phase change, the materials temperature stays constant.

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Heat Solving Calorimetry problems Solving Calorimetry problems Apply conservation of energy Apply conservation of energy –Heat gained = heat lost If no phase changes occur, each term will have the form Q(gain) = mc(Tf-Ti) or Q(lost) = mc(Ti-Tf) If no phase changes occur, each term will have the form Q(gain) = mc(Tf-Ti) or Q(lost) = mc(Ti-Tf) If phase changes occur, must account for these Q = mL If phase changes occur, must account for these Q = mL When the system reaches equilibrium, the final temperature of each substance will have the same value. When the system reaches equilibrium, the final temperature of each substance will have the same value.

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