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Thermal Energy
Chapter 14
Key Ideas What does temperature have to do with energy?
What makes things feel hot or cold?
What affects the rate that thermal energy is absorbed or emitted?
When is thermal equilibrium reached?
How does energy transfer happen?
Temperature and Energy
Temperature: a measure of the average kinetic energy of the particles in an object.
All particles have kinetic energy.• All particles in a substance are constantly moving.• As the average kinetic energy of the particles in an
object increases, the object’s temperature increases.
Why do some objects feel hot while other objects feel cold?
• The feeling associated with temperature difference results from energy transfer.
Temperature and Energy
Heat: the energy transferred between objects that are at different temperatures.
• Temperature changes indicate an energy transfer.
• The transfer of heat always moves from an area of higher temperature to an area of lower temperature.
• The greater the difference in the temperatures of the two objects, the faster heat is transferred.
Temperature and Energy
Heat energy can be transferred in three ways: • conduction• convection• radiation
Temperature and Energy
Radiation: movement of energy through space in the form of ultraviolet, visible light and infrared rays.
The sun warming your face All hot objects give off infrared radiation
Temperature and Energy
Conduction: the transfer of heat by physical contact.
Air molecules contacting a hot object.
Temperature and Energy
Convection: the cycle of warm air rising and cool air falling.
Temperature and Energy
Thermal Conductivity:• Depends on the rate at which thermal energy
is transferred from one end of the material to another.
• Thermal conductors: have a high rate of thermal energy transfer.
• Thermal insulators: have a slow rate of thermal energy transfer.
Temperature and Energy
Objects are continually absorbing and emitting thermal radiation.
The rate at which thermal radiation is absorbed or emitted depends on:
• Temperature• Color• Texture• Exposed surface area
Temperature and Energy
• If an object absorbs more thermal energy than it emits (no phase change), the temperature will increase.
• If the object emits more thermal energy than it absorbs (no phase change), the temperature will decrease.
Temperature and Energy
Thermal equilibrium: • The amount of thermal energy absorbed is
equal to the amount of thermal energy emitted.
• As a result, the temperature remains constant.
Temperature and Energy
Conduction and ConvectionTemperature and Energy
