Chapt 11 - Heat Chapter 11 Heat Heat is energy that is...

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1 Heat Chapter 11 Heat c Heat is energy that is transferred between a system and its environment because of a temperature difference between them. c Q is used to represent the amount of energy transferred by heat between a system and its environment Units of Heat c Kilocalorie (kcal) c A kcal is the amount of energy necessary to raise the temperature of 1 kg of water by 1 o C, from 14.5° C to 15.5° C. c This is the “food calorie” c British Thermal Unit (BTU) c A BTU is the amount of energy necessary to raise the temperature of 1 lb of water by 1 o F, from 63° F to 64° F c 1 BTU = 252 cal
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2 Joules Method of Measuring the Mechanical Equivalent of Heat c 1 kcal = 4186 J c This is called the Mechanical Equivalent of Heat Specific Heats c The amount of heat (Q) per unit mass required to change the temperature of a substance by 1°C is called the specific heat (c) of that substance c Every substance has a unique specific heat. c Units are: J/(kg·C o ) c Thus, for a temperature change of T we can write Q = m·c· T Heat Flow Q = m·c· T c When the temperature increases, ΔT and ΔQ are positive and energy flows into the system c When the temperature decreases, ΔT and ΔQ are negative and energy flows out of the system
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3 Table 11-1 Specific Heats of Various Substances (Solids and Liquids) at 20°C and 1 atm Calorimetry c Isolated system b Q = 0 c But if two parts of an isolated system are at different temperatures, but in thermal contact
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Chapt 11 - Heat Chapter 11 Heat Heat is energy that is...

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