Earth and atmosphere, Year 7: more practice

The mantle

HintIt is a thick layer of hot rock.

The whyBeneath the crust is the mantle, a thick layer of hot rock that moves very slowly.

The core

HintIt is the hottest part of the Earth.

The whyThe Earth's core is mostly iron and nickel. The outer part is liquid and the inner part is solid.

It is too deep and too hot

HintThink about what happens to temperature the further down you go.

The whyThe deeper you go the hotter it gets. Drills and equipment cannot cope with the temperature and pressure.

The crust

HintCompare it to the skin of an apple.

The whyThe crust is only a few kilometres thick under the oceans and a few tens of kilometres thick under the continents.

Ice takes up more space than water, so it expands and forces the crack wider

HintWhat happens to the volume when liquid turns solid?

The whyThis is freeze–thaw weathering. It repeats night after night until pieces of rock break off.

Chemical weathering

HintIs the rock changed by a reaction, a living thing or just a force?

The whyWeak acid in rain reacts with limestone and eats it away. A chemical reaction is involved, so it is chemical weathering.

Biological weathering

HintA living thing is doing the work.

The whyBiological weathering is caused by plants and animals, such as roots growing in cracks.

Physical weathering

HintIs the rock changing into a new substance or just breaking up?

The whyRepeated expanding and contracting stresses the rock until it breaks. No new substance forms.

Argon

HintIt is an unreactive noble gas.

The whyArgon makes up a little under 1% of the air. It is a noble gas, so it does not react.

Its gases are not chemically joined and can be in different amounts

HintThink about whether the parts are bonded to each other.

The whyThe gases in air are just mixed. The amounts can vary from place to place and the gases keep their own properties.