Good Science Victorian Curriculum Year 7

CHEMICAL SCIENCES
4.3
ADDING OR
REMOVING HEAT
LEARNING INTENTION
At the end of this lesson I will
be able to outline the effect of
adding or removing heat on
different states of matter.
KEY TERMS
contract
to get smaller; shrink
expand
to get bigger; increase in size
thermal
relating to heat
1
You now know that the speed of the particles in a substance
depends on the substance’s temperature. Particles in a
hot substance will move quickly, while particles in a cold
substance will move slowly.
Some other changes happen when an object is heated
or cooled.
Solids expand when they are heated
If you add heat energy to a substance, the particles move faster.
Because the particles have more energy and are moving faster, they will
move further away from each other, so the substance will expand. This
is called thermal expansion.
When a solid is heated, it will expand. Different solid substances
expand at different speeds and by different amounts. Most solids do
not noticeably change their size. Metals are one type of substance that
expand noticeably when heated. When metals cool down again, the
particles lose energy and move closer together again. This is called
thermal contraction.
What is thermal expansion?
LITERACY LINK
READING
Write three questions for
a classmate based on the
information from this section.
Swap with your classmate and
answer their questions.
Figure 4.8 The expansion
of metal in very hot
weather can cause fixed
metal structures such as
train tracks and fences to
buckle or bend.
NUMERACY LINK
MEASUREMENT
To one decimal place, what is the
temperature measured by the
thermometer in Figure 4.10?
Figure 4.9 The spaces between the
joints in a bridge allow the metal
to expand in hot weather without
causing the bridge to buckle.
58 GOOD SCIENCE VICTORIAN CURRICULUM 7