Name ______________________________ Period ___________ Date ________________________________
Chapter 5: Thermal Energy
Lesson 1: Thermal Energy, Temperature, and Heat
Thermal energy – The sum of kinetic and potential energy of the particles that
make up a material
 Thermal energy causes a phase change.
 Thermal energy describes the energy of the particles that make up a solid,
liquid, or gas.
Thermal Energy – Kinetic
 Every solid, liquid, gas contains trillions of tiny particles that are in motion.
 Because these particles are in motion they all have kinetic energy.
 The faster the particles move, the more kinetic energy they have.
o Solids – particles vibrate in place
o Liquids – particles move a little more freely
o Gases – particles move most freely and quickly
Thermal Energy – Potential
 Particles that make up solids, liquids, and gases also have potential energy
which is the distance between particles.
 The greater the distance between particles the greater the potential energy
of the particles.
o Solids – Particles are held close together by attractive forces
o Liquids – Particles are slightly farther apart
o Gases – Particles are much more spread out than in those in a solid
Heat – The movement of thermal energy from a warmer object to a cooler object
Why do your hands get warm when you hold a cup of coffee? The thermal energy
from the warm cup is moving to and heating up your cool hands.
 All objects contain thermal energy.
 When you heat something thermal energy transfers from one object to
another.
 The rate at which heating an object occurs depends on: The temperature
difference between the two objects
Specific Heat
 Every material has a specific heat
 Specific Heat – The amount of thermal energy it takes to increase the
temperature of 1 kg of a material by 1 degree Celsius
 Objects with a low specific heat do not take much energy to change.
 Objects with a high specific heat take a greater amount of energy to change
(example: water)
 Why does it take longer for your soup to cool off rather than a piece of
chicken? Liquids take longer to heat up and cool down because they have a
higher specific heat.

Why does the cement around an in ground pool get hot in the summer, but
the pool stays much cooler? Large amounts of water have a very high specific
heat, whereas the cement around the pool has a low specific heat.
Lesson 2: Thermal Energy Transfer
3 ways Thermal Energy can transfer:
1. Conduction
2. Convection
Think about it: Why does the ice
you put in your soda melt?
The heat from our soda moves
from the soda to the ice.
3. Radiation
 In general heat moves from warmer objects to cooler objects.
 Conduction – The transfer of thermal energy between materials by collisions
of particles
 Heat is transferred from one particle of matter to another without the
movement of the particles of matter.
 Conduction occurs best in solids because the molecules that make up the
objects are in direct contact with one another. (they always touch one
another)
 Example: A pan on a stove – the fast moving, hot particles from the fire
transfer to the cool, slow moving particles from the pan
Conductor vs. Insulator
Conductor – material through which thermal energy flows easily
 Examples – iron, aluminum, silver, copper, lead, brass
Insulator – A material through which thermal energy does not flow easily
 Slows the transfer of heat
 Examples: glass, wood, plastic, rubber, air, wool, cork, straw, paper
I.
Convection – heat is transferred by the movement of currents within a fluid
Convection Current - a circular motion that causes hot fluids to rise and
cold fluids to sink
This happens because hot molecules
are less dense and rise whereas cold
molecules are denser and sink.
II.
Radiation – The transfer of thermal energy from one material to another by
electromagnetic waves
 All matter (in example: Sun, fire, you and even ice) transfers thermal
energy by radiation.
 Warm objects emit more radiation than cool objects.
 For example: you feel the transfer of thermal energy by radiation
more near a fire than you would a block of ice.
 Radiation is the only way thermal energy can travel from the Sun to
Earth, because space is a vacuum.
 Radiation also transfers thermal energy through solids, liquids, and
gases.
 The sun heats your car through radiation.