Question

diagrammatic based question

Answer 1

When you heat up water, the watermolecules start moving around faster and faster. They bounce off each other and move farther apart. Because there's more space between the molecules, a volume of hot water has fewer molecules in it and weighs a little bit less than the same volume of cold water.Thus the cold water was comparatively tight molecules and so rapid expension of molecules takes place at that time.
Hope it helps.

Answer 2

a is the answer for the question