UNIT 5. HEAT AND LIGHT

1. HEAT AND LIGHT

2. Thermal energy always travels from a hotter
object to a colder one. Some materials transfer
thermal energy easily. They are good
conductors. Materials that dont`t transfer
thermal energy easily are called insulators.
CONDUCTION
When two objects
are in contact,
thermal energy is
transferred from one
object to the other
CONVECTION
Thermal energy
travels through a gas
or a liquid by
convection.
RADIATION
Thermal energy can
be transferred
through space by
electromagnetic
waves.

3. MELTING
Solid  Liquid
EXPANSION
Materials expand when
receive thermal energy
EVAPORATION
Liquid  Gas
CHEMICAL CHANGES
Thermal energy can cause
permanent changes
(example: when we cook food)
Thermal energy causes changes in the state of
some materials

4.  Light is radiation that we can see with our eyes.
Light travels in straight lines.
 Objects react to light in different ways:
Transparent
It doesn`t block
light
Translucent
It blocks some
light
Opaque
It blocks the light
completely

5. REFLECTION
Some objects, like
mirrors, change the
direction of the light.
The mirrors reflect
the light.
REFRACTION
When light pass through
some transparent
substances (water) it
changes direction
slightly.