Energy can be transferred from one object to another

1
Lesson 17

• Energy can be transferred from one object to
  another
• An ice cube melts when thermal
• energy from the air is transferred
• to the ice
• The transfer of thermal energy
• from the air to the ice is an
• example of heat

2
Thermal Energy and Temperature

• Kinetic energy is the energy of motion
• Thermal energy is the total kinetic
• energy of all the particles in a
• sample of matter

3
Thermal Energy and Temperature

• Thermal energy of a
• substance depends on two
• things
• The temperature of the
• substance
• 2. How much of the substance is present

4
Thermal Energy and Temperature

• Temperature is a measure of the
• average kinetic energy of the
• particles in a substance
• When the motion of the particles
• in a substance changes its temperature also
  changes

5
Thermal Energy and Temperature

• The more quickly the particles in a
• substance move, the higher its
• temperature
• Temperature is an average
• It does not depend on the total
• number of particles in a sample

6
Thermal Energy and Temperature

• Thermal energy is equal to the total kinetic
  energy of all particles in a substance
• The total is found by adding the
• energy of each individual particles
• The thermal energy of a sample
• changes as the number of particles
• in the sample changes

7
Heat

• Heat is the transfer of thermal
• energy between objects at
• different temperatures
• Heat always flows in the same direction
• From an object of a higher temperature to an
  object with a lower temperature

8
Heat

• Heat will continue to flow in
• this way until all materials are
• at the same temperature
• Heat can be transferred through matter in all
  three phases
• Heat can also be transferred through a vacuum
  or empty space

9
Heat

• The transfer of heat takes
• place in three main ways
• depending upon the type
• of matter present

10
Heat

• The three ways in which
• heat is transferred
• Conduction
• Convection
• Radiation

11
Conduction

• Heat is transferred
• through solids and liquids
• by conduction
• Conduction is the transfer
• of heat by direct contact
• of particles

12
Conduction

• When you heat a pan on a
• stove to cook food, the pan is
• heated by conduction as
• thermal energy moves from
• the stove burner to the pan
• The food in the pan is also heated by
  conduction as thermal energy flows from the pan
  to the food

13
Convection

• Heat is transferred in
• fluids (both liquids and
• gases) by convection
• Convection is the
• transfer of heat in fluids
• by the movement of currents that form in the
  fluids.

14
Convection

• As water at the bottom
• of the pot is heated,
• its particles spread
• apart
• As a result, the water at
• the bottom of the pot becomes less dense than
  the water at the top of the pot.

15
Convection

• Denser water at the top
• of the pot sinks
• downward, covering the
• warmer, less dense water
• to rise
• The cooler water becomes heated, the cycle
  repeats itself with cooler water replacing the
  warmer water below.

16
Convection

• This rising and falling motion
• creates convection currents
• that transfer heat from one
• area to another
• Convection currents in the
• atmosphere are responsible for the formation
  of winds

17
Convection

• Convection occurring
• in the ocean produces
• ocean currents

18
Radiation

• Conduction and convection
• require matter to transfer heat
• Radiation is the transfer of heat
• without matter
• Heat is transferred by the movement of
  electromagnetic waves

19
Radiation

• Because no matter is needed
• radiation can transfer heat
• through a vacuum or empty
• space
• The heat Earth receives from the sun results from
  radiation
• Radiation is also responsible for the warmth you
  feel from a fire