Teachers’ Club Science – Student worksheets
Form/Class
Teachers’ Club Science
Physics
Name
SELECTED ANSWERS AND GUIDANCE
1. When a liquid is heated the hot liquid becomes less _dense_ and rises.
Cooler liquid is drawn in to take the place of the hot liquid as it rises.
The hot liquid then cools. It becomes denser and sinks.
This process is called convection.
We say that a convection current has been set up.
Convection only occurs in liquids and _gases.
The Sun can cause very large convection currents in the atmosphere, which we call _wind.
2. a) FALSE: Conduction is how heat travels through metals
b) FALSE: Hot gases become less dense and rise
c) TRUE
d) TRUE
e) FALSE When gas cools it contacts and becomes more dense
f) FALSE only the top part of the soup would be heated. Hot liquid rises. It doesn’t sink.
3. SEA BREEZE: In the daytime the land heats up quicker than the sea. The hot air above the land becomes
less dense and rises and cooler, more dense air from above the sea is drawn into replace it. We feel this
moving air as a breeze.
LAND BREEZE: At night the land cools down quicker than the sea. This means the hotter air above the
sea expands, becomes less dense and rises. Cold, denser air from the land is drawn in to replace it.
4. Explanantions: Do not allow “HEAT RISES!”
a) Hot liquid rises when it becomes less dense when heated. The heating element must be at the bottom
otherwise the liquid below it would remain cold.
b) The radiator causes the air near it to become less dense and rise. New, colder air is drawn in to
replace it. The hot air cools, becomes denser and then sinks. A convection current is set up and all the
air in the room is heated.
c) Hot, toxic smoke from the fire becomes less dense and rises. Cooler, cleaner air is closer to the
ground. It is easier to breathe!
d) Hot, less dense air rises up chimney. New, fresh colder air is drawn into room to replace it through
cracks, windows and doorways. Ventilation!
e) Hot air rises etc….loft insulation.
f)
Hot air rises and comes into contact with the cold freezer unit, which cools it, causes it to become
denser, sink and keep the contents of the refrigerator cold. It is more efficient.
g) The fan causes the heat in the oven to be spread out evenly to avoid uneven cooking. Otherwise the
top of the oven is much warmer than the bottom due to hot air rising etc.
h) Thermals in the atmosphere are columns of hot air rising up over hot areas of terrain. These updrafts
lift the glider up and increase flight times.
BOFFIN TASKS
Students can research the answers to all these questions online. Enjoy!
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http://smart-learning.co.uk/teachers-club/teachers-club-science/
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