Thermal Energy and Matter

1
Thermal Energy and Matter

• 16.1

2
Work and Heat

• Heat is the transfer of thermal energy from one
  object to another because of a temperature
  difference.
• Heat flows spontaneously from hot objects to cold
  objects.

3
Temperature

• Temperature is a measure of how hot or cold an
  object is compared to a reference point.
• Temperature is related to the average kinetic
  energy of the particles in an object due to their
  random motions through space.

4
Thermal Energy

• Thermal energy is the total potential and kinetic
  energy of all the particles in an object.
• Thermal energy depends on the mass, temperature,
  and phase (solid, liquid, or gas) of an object.

5
Thermal Contraction and Expansion

• Thermal expansion is an increase in the volume of
  a material due to a temperature increase.
• Thermal expansion occurs when particles of matter
  move farther apart as temperature increases.

6
Specific Heat

• Specific heat is the amount of heat needed to
  raise the temperature of one gram of a material
  by one degree Celsius.
• EX if equal masses of iron and plastic absorb
  the same heat, the irons temperature rises more
  (car door compared to a car bumper).

7
Specific Heat

• The lower a materials specific heat, the more
  its temperature rises when a given amount of
  energy is absorbed by a given mass.
• Specific heat Q m x c x ?T
• Q heat absorbed by a material
• M mass - g
• c specific heat - Joules / g C
• ?T change in temperature - C

8
Measuring Heat Changes

• A calorimeter is an instrument used to measure
  changes in thermal energy.

9
Heat and Thermodynamics

• 16.2

10
Conduction

• Conduction is the transfer of thermal energy with
  no overall transfer of matter.
• Occurs within a material or between materials
  that are touching.
• Conduction in gases is slower than in liquids and
  solids because the particles in a gas collide
  less often.

11
Thermal Conductors and Insulators

• A thermal conductor is a material that conducts
  thermal energy well.
• EX metal
• A thermal insulator is a material that conducts
  thermal energy poorly.
• EX air

12
Convection

• Convection is the transfer of thermal energy when
  particles of a fluid move from one place to
  another.
• Air circulating in an oven is an example of a
  convection current.

13
Convection

• A convection current occurs when a fluid
  circulates in a loop as it alternately heats up
  and cools down.
• Convection currents are important in many natural
  cycles, such as ocean currents, weather systems,
  and movements of hot rock in Earths interior.

14
Radiation

• Radiation is the transfer of energy by waves
  moving through space.
• All objects radiate energy. As an objects
  temperature increases, the rate at which it
  radiates energy increases.

15
The 3 Laws of Thermodynamics

• 1st law energy is conserved
• 2nd law thermal energy can flow from colder
  objects to hotter objects only if work is done on
  the system.
• 3rd law absolute zero cannot be reached.