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Heat and Specific Heat. Heat can be thought of as a flow of energy due to a difference in temperatures. Heat always flows from a region of higher temperature to region of lower temperature. The joule (J) is the SI unit of energy (heat).
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Heat and Specific Heat Heatcan be thought of as a flow of energy due to a difference in temperatures. Heat always flows from a region of higher temperature to region of lower temperature. The joule (J) is the SI unit of energy (heat). Another common unit is the calorie (cal) 1 cal = 4.184 J
Heat Capacity and Specific Heat • Three things determine the quantity of heat gained or lost during a temperature. • the nature of the matter • the mass of the matter • the size of the temperature • Heat capacity is the amount of heat energy needed to raise the temperature of a given sample of matter by 1°C. • Heat capacity is an extensive property.
The specific heatof a substance is the amount of energy required to raise the temperature of one gram by one Celsius degree (1°C). Like densities, each substance has its own unique specific heat that can be used to identify it.
Specific heat is calculated according to the equation given below. q cp = ------------ m x DT • cpis the specific heat, q is the heat lost or gained, m is the mass of the sample, and ∆T is the difference between temperatures. • The above equation can be rearranged to give an equation that can be used to find the quantity of heat gained or lost with a change of temperature. q = s x m x DT
Sample Problem When a 4.0 g sample of glass was heated from 20°C to 60°C, the glass was found to have absorbed 32 J of heat. a.) What is the specific heat of this type of glass? b.) How much heat will the same glass sample gain when it is heated from 50°C to 80°C?