Question

Which description best represents heat flow and movement in Earth's mantle?
A.
When magma is heated, it becomes more dense and sinks. When magma is cooled, it becomes less dense and rises.

B.
When magma is heated, it becomes less dense and sinks. When magma is cooled, it becomes more dense and rises.

C.
When magma is heated, it becomes more dense and rises. When magma is cooled, it becomes less dense and sinks.

D.
When magma is heated, it becomes less dense and rises. When magma is cooled, it becomes more dense and sinks.

Answer 1

The right answer is "D. When magma is heated, it becomes less dense and rises. When magma is cooled, it becomes more dense and sinks."
This is because when a substance is heated, its particles move faster, causing it to be lighter. So, when the magma is heated, it becomes less dense, causing it to rise.
It is also vice-versa. When a substance cools, its particles move slower, making it heavier. When the magma is cooled, it becomes more dense, causing it to rise.

Answer 2

D.

Heated mantle rock expands and becomes less dense so it rises; as it cools it contracts, becomes denser, and sinks — driving convection currents in the mantle.