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Temperature T

Definition of Temperature

Temperature is a quantity that defines the direction of thermal energy flow.

Definition of Temperature

Temperature (measured in kelvins) is a measure of average kinetic energyof the molecules in a substance.

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Thermal Energy Q

Thermal Energy

Energy that is transferred between a system and its surroundings by

non-mechanical means is called thermal energy.

Definition of Thermal Energy

Thermal energy is energy that is transferred from one system to anotherdue to difference in temperature.

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Internal Energy U

Definition of Internal Energy of a SystemInternal energy of a system is the total potential energy and random kineticenergy of the molecules comprising the system.

Internal Energy of SubstanceInternal energy of a substance is the total potential energy and randomkinetic energy of the molecules of the substance.

Potential energy refers to energy associated to intermolecular forces.In ideal gases the forces are negligible (internal potential energy iszero). In liquids and solids the internal potential energy cannot beneglected.

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3.2 Closed System

A closed system can exchange energy, but cannot exchange matterwith its surroundings.

If the system is heated, the internal energy of the system increases.The experiments have shown that for homogeneous systems, if nophase changes occur inside the system, the temperature change T ofthe system is directly proportional to the thermal energy Q transferred

to the system.

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3.2 Thermal Capacity C

Definition of Thermal Capacity

Thermal capacity is the energy required to raise the temperature of a bodyby 1K.

Equation of Thermal Capacity

The thermal capacity C of a body is

C=Q

T(1)

where Q is thermal energy transferred into the system, and T the absolutetemperature change of the body.

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3.2 Specific Heat Capacity c

Definition of Specific Heat CapacitySpecific heat capacity is the energy per unit mass required to raise thetemperature of a substance by 1K.

Equation of Specific Heat CapacityThe specific heat capacity c of a substance is

c=Q

mT(2)

where Q is thermal energy transferred into the system, m mass of theobject made of a particular substance, and T absolute temperature changeof the object.

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