Yes, the molecules of a gas or liquid do move away from each other when heated. Here's why:

* Kinetic Energy: Heat is a form of energy, and when you add heat to a substance, you increase the kinetic energy of its molecules. Kinetic energy is the energy of motion.

* Increased Motion: As the molecules gain more kinetic energy, they move faster and vibrate more intensely. This increased motion causes the molecules to spread out, increasing the average distance between them.

* Expansion: This spreading out of molecules is what causes gases and liquids to expand when heated.

Think of it this way: Imagine a group of people standing close together in a room. If you ask them to all start dancing wildly, they'll naturally move further apart to have space to move around. The same principle applies to molecules in a gas or liquid!

Let me know if you have any other questions.