Why does warm water rise above cold water in a pot on a stove?
AIt is more dense than cold water
BIt has more mass than cold water
CIt is less dense than cold water
DIt has less mass than cold water
Answer & Solution
Correct answer: C. It is less dense than cold water
1. The stove heats only the water touching the bottom of the pot.
2. Heating makes the particles in that water move faster.
3. The faster particles push further apart, so that water takes up more space.
4. The same particles now fill a larger space, so the warm water is less dense.
5. Anything less dense floats above what is denser, so the warm water rises.
6. Cooler, denser water sinks to take its place and is heated in turn.
7. This circling movement is called a convection current, and it warms the whole pot.
_Source: Siyavula Natural Sciences Grade 7 (CC BY 4.0), Convection_