Page 46 - Science Course 1 (Book 2)

Mo8-L2a: How is Thermal Energy Transferred?

Let’s Begin

Kinetic Molecular Theory The measure of the average kinetic energy of the
particles in a material is temperature.
The kinetic molecular theory explains how particles
move and has three major points: When the particles that make up a material move
slowly, they occupy less volume than they do at a
1. All matter is made of particles. higher temperature.
2. Particles are in constant, random motion.
3. Particles constantly collide with each Thermal expansion is the increase in volume of a
other and with the walls of their container. material due to a temperature increase.

Particles that make up all matter are in constant
motion.
When water is cooled to near its freezing point,
On average, solid particles move slowest, liquid interactions between water molecules push the
particles move faster, and gas particles move the molecules apart.
fastest.

Particles of Particles of Particles of
a solid a liquid a gas
Key Concept
As the kinetic energy As the kinetic energy
How is Thermal Energy Transferred?
of the particles that of the particles that
make up a material make up a material
What are the three points of the kinetic molecular
theory? increases, the thermal decreases, the thermal
energy of the particles energy of the particles
increases. decreases.

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