Page 149 - York Global Science 6 - Physical Science

Physical Science

Let’s Learn

Heat energy can be transferred between objects, but it only moves in one
direction: from hot to cold.

Heat energy can be transferred in three different ways and always causes a
temperature change.

Conduction

Conduction occurs when objects are in contact with each other. When
particles in a solid gain heat energy, they vibrate more quickly and collide
with other particles. A faster moving particle transfers some of its energy

to a slower moving particle when they collide. In this way, heat energy is
transferred.

Metals are very good at transferring heat energy by conduction. Not only do
the particles transfer energy when they collide, they also have free electrons
which can move to different particles. These electrons transfer heat energy
in the same way as they transfer electrical energy.

Think!
How can you reduce heat transfer by conduction?

When might you need to do this?

Convection
Convection is the transfer of heat energy
in liquids and gases, such as water and

air. The variations in temperature of liquid
or gas particles cause natural movement
of particles. Particles that have more heat

energy start to rise because they have a
lower density.

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