Temperature and Heat

Temperature

Temperature is a measure of the average kinetic energy of the particles in an object.

(how fast or slow the particles are moving)

The more kinetic energy the particles of an object have, the higher the temperature of the object is.

Average Kinetic Energy of ParticlesWhen you measure an object’s temperature, you are measuring the average kinetic energy of all the particles in the object.

The temperature of a substance doesn’t depend on how much of the substance you have.

Ex. A teapot has more tea in it than the cup does, but the temperature of the teapot and the cup are the same

Measuring Temperature

Thermometers are used to measure temperature.

Thermometers are usually filled with a liquid (mercury or alcohol) that expands due to increases in temperature.

Temperature ScalesThere are 3 common scales for measuring temperatures: Fahrenheit, Celsius, and Kelvin

Fahrenheit Scale The Fahrenheit scale is used in the U.S.

Water boils at 212 degrees

Water freezes at 32 degrees

Absolute zero at -460 degrees

Celsius ScaleUsed in most of the world

Water boils at 100 degrees

Water freezes at 0 degrees

Absolute zero at -273 degrees

Kelvin ScaleCommonly used in physical science

Water boils at 373 kelvins (k)

Water freezes at 273 k

Absolute zero at 0 k

Any temperature on the Kelvin scalecan be changed to Celsius by subtracting 273 from the number

What’s the Difference Between Temperature and Thermal Energy?

Temperature=

Thermal Energy=

What is Heat?

Heat is thermal energy moving from a warmer object to a cooler object

Energy is ALWAYS transferred from the object that has the higher temperature to the object that has the lower temperature.

Ex. Ice cubes in a drink

Thermal Energy

Thermal energy is the total kinetic energy of the particles of a substance

The amount of thermal energy depends on the temperature of a substance and how much of the substance there is.

How Do Objects Reach the Same Temperature As Each Other?

When objects that have different temperatures come into contact, energy will pass from the warmer object to the cooler object until they reach the same temperature.

Heat Transfers

Heat is transferred by

1. Conduction

2. Convection

3. Radiation

Conduction

Conduction is the transfer of thermal energy from one substance to another through direct contact.

When objects touch each other, their particles collide. The particles with higher kinetic energy transfer energy to those with lower kinetic energy.

This transfer makes some particles slow down and other particles speed up until all particles have the same average kinetic energy.

Conductors and Insulators

Substances that conduct thermal energy very well are called thermal conductors.

Ex. Metals

Substances that do not conduct thermal energy very well are called thermal insulators.

Ex. Wood, paper, clothes, and blankets (slow the transfer of heat out of your body)

Convection

Convection is the transfer of thermal energy by the movement of a liquid or a gas.

Ex. Convection currents move

heat throughout the liquid in a pot,

transfer heated air throughout a

building

Radiation

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

Radiation does not require matter to transfer thermal energy (bonfire, heat lamp).

Conduction, Convection, or Radiation?

Cooking Can Use All Three