PHY 111 - Chapter 14 Outline

# PHY 111 - Chapter 14 Outline - 14.1 Internal Energy The...

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14.1 – Internal Energy The internal energy of a system is the total energy of all of the molecules in the system except for the macroscopic kinetic energy (kinetic energy associated with macroscopic translation or rotation) and the external potential energy (energy due to external interactions) A system is whatever we define it to be: one object or a group of objects A change in the internal energy of a system does not always cause a temperature change 14.2 – Heat Heat is energy in transit between two objects or systems due to a temperature difference between them A calorie is defined as the heat required to change the temperature of 1 g of water by 1 o C 1 cal = 4.186 J 1 Calorie = 1 kcal = 10 3 cal A system can possess energy in various forms but it cannot possess heat or work. Heat and work both describe a particular kind of energy transfer Heat flows from a system at higher temperature to one at lower temperature An object expands when the average distance between atoms or molecules increases. Generally, liquids have larger coefficients of volume expansion than solids because the molecules are more loosely bound 14.3 – Heat Capacity and Specific Heat Q is positive for heat flow into the system and negative for heat flow out of the system For many substances, T is approximately proportional to the heat Q . The constant of proportionality is called heat capacity (C) C = _Q SI unit of heat capacity = J/K T Heat capacity is a measure of how much heat must flow into or out of the system to produce a given temperature change Specific heat capacity (c) of a substance is defined as the heat capacity per unit

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PHY 111 - Chapter 14 Outline - 14.1 Internal Energy The...

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