Here's why:

* Temperature and Kinetic Energy: Temperature is a measure of the average kinetic energy of the particles within a substance. Kinetic energy is the energy of motion.

* Faster Movement: Higher temperatures mean the particles have more kinetic energy, so they move faster on average.

* States of Matter: This is why water molecules move fastest as a gas (steam), then as a liquid (water), and slowest as a solid (ice).

So, if you have three containers with water at different temperatures, the container with the hottest water will have the water molecules moving the fastest.