SCIENCE Year 5 Heat

INTRODUCTIONS INTRODUCTIONS

Heat is a form of energy that is CONTRACTION
transferred due to the difference in
temperature. A material will become • As materials cool down the particle
hotter when gaining heat and model of matter says that their
become colder when losing heat. particles move slower and move
Temperature is the degree of hotness closer together.
or coldness of a material. • This causes the material to contract
Temperature can be measured by • Contract: To shrink or decrease in
using a thermometer. The standard volume.
unit for measuring temperature is
degree Celcius. Meniscus level is the EXPANSION
curved level is the curved level of the
liquid in the glass tube of a • Materials warm up, their particles
thermometer. move faster and spread apart.

• This causes the material to expand.
• Expand: To increase in volume.

WHAT IS THERMAL Thermal expansion
EXPANSION? results in an increase
in length, breadth,
Thermal expansion is a process where and thickness of a
a body expands in either area, volume substance.
or shape when heated.
Most of the substances solids, liquid, and
gases expand on heating and contract on
cooling. Their thermal expansions and
contractions are usually small and are
not noticeable. However, these expansions
and contractions are important in our
daily life. The kinetic energy of the
molecules of an object depends on its
temperature. The molecules of a solid
vibrate with larger amplitude at a high
temperature than at low temperatures.
Thus, on heating, the amplitude of
vibration of the atoms or molecules of an
object increases..

POURING HOT WATER INTO A
DRINKING BOTTLE

What causes the bottle
cap to pop off?

The air in the drinking bottle expanded
when it gained heat from the hot water.
This causes the bottle cap to pop off.

Overlapping glasses Metal ball

https://www.youtube.com/watch?v=ne8oPFTM_AU
https://www.youtube.com/watch?v=GgrnhHMqZDY

How can the overlapping glasses After being heated by the bunsen burner
be separated? for a few minutes, the metal ball gained
heat and expand . So, it is unable to pass
When the ice cubes are put into the through the ring but if we put it under
glasses, the glasses will contract because Cold water for a few minutes or immerse
they lose heat . Thus, the overlapping it, the metal ball can pass through again.
glasses can be separated

Gaps between connectors on Gaps between connectors on
a metal bridge a railway tracks

The gaps between the connectors on a The gaps between the connectors on a
bridge allow the bridge to expand when
the temperature of the surrounding railway track allow the track to expand
Increases to avoid them from cracking. when the temperature of surrounding
increases to avoid
them from
bending

Electric cables are hung Gaps between concrete pieces
loosely

The electric cables are hung loosely To allow expansion
between the electric poles to allow the of the concrete pieces
The wires to contract when the during hot weather
temperature decreases and to avoid the to avoid them from
cables from snapping in cold weather.
cracking.

Hot air baloon Dented ball

Hot-air balloons are able to rise due to Place the ball into a receptacle of hot
thermal expansion of air. The air in the water. The water’s heat is transferred
balloon is heated, causing the distance to the air within the ball, which will
between the particles in the air to expand causing the dent to pop out,
increase. Because the density of the air returning the ball to its proper spherical
in the hot-air balloon is lower than the shape.
density of the cooler air outside, the

balloon will rise.

Tight jar lid Unshelling hard-boiled eggs

When the lid on the jar is Leave the newly boiled egg in a
too tight and hard to receptacle of cold water for a few
open, immerse the minutes. The cold is tranferred from
mouth of the jar in hot the water to the egg, shrinking it,
water. The lid undergoes
thermal expansion and making the shell come off much easier
becomes slightly loose.
Now we can open the lid

easily.

Thermostat
control

Thermometer Thermostat
Fire alarm

Hot air baloon