Thermal Energy and Heat Capacity

SPH 3U1December 1, 2010

Copyright © 2011 Pearson Canada Inc.

7.1 The Kinetic Molecular Theory of Matter

See pages 207-209.

Thermal energy is the total kinetic and potential energy of the particles within an object.

The temperature of a substance is the average kinetic energy of the particles.

Heat is the energy transferred from a warmer object to a cooler object.

Heat always transfers from a warmer to a cooler object.

• The kinetic molecular theory of matter states that matter is made up of particles that are in constant random motion.

Copyright © 2011 Pearson Canada Inc.

7.1 Thermal Energy Transfers

See page 210.

Conduction is the transfer of thermal energy by direct contact.

Convection is the transfer of thermal energy through bulk movement of particles from one location to another. Convection occurs in fluids where the particles are free to move.

Radiation is the transfer of energy as electromagnetic waves, such as visible light, and infrared and ultraviolet radiation.

These papers are floating above a radiator due to the convection currents in the air.

• Thermal energy can be transferred from one place to another by conduction, convection, and/or radiation.

The light seen in this forest is a form of radiant energy. Whenever light strikes objects, energy is transferred to those objects.

Copyright © 2011 Pearson Canada Inc.

7.1 The Kelvin Scale

•Absolute zero is the lowest temperature theoretically possible. •Except when a high level of precision is needed, it is adequate to use 0oC = 273 K•For more precise conversions, use 0oC = 273.15 K

See page 208-209.

T(K) T(oC)+273

-273

Image taken from: http://www.plantedtank.net/forums/lighting/65736-2x-15watt-t8-bulbs-30-watt.html

Copyright © 2011 Pearson Canada Inc.

7.1 Heat Capacity

See page 212-213.

Heat capacity is measured in joules per kelvin (J/K).

In general, solids have lower specific heat capacities than liquids and gases.

Specific heat capacity is determined by experiment and is known for thousands of substances. See the table on the right for some examples.

• Heat capacity is the amount of thermal energy needed to change the temperature of an object or system by 1 K or 1˚C.

Copyright © 2011 Pearson Canada Inc.

7.1 Specific Heat Capacity

See page 212-213.

Different substances have different specific heat capacities depending on their chemical structure and state.

The amount of thermal energy required to heat an object or system depends on three factors:• Mass - more mass requires more energy.

• Temperature change - a greater change requires more energy.

• Type of material - different materials require different amounts of thermal energy.

• Specific heat capacity (c) of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1 K, or 1˚C.

This photo shows a piece of the special silica used to make space shuttle thermal protective tiles. Having just been removed from a high-temperature oven, its temperature is 1260˚C. It is such a good insulator that this man is holding the tile with unprotected fingers.

Copyright © 2011 Pearson Canada Inc.

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