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Science Concept: Gas Moves Fast

A gas is a substance whose molecules are in constant, rapid, random motion. As a result, a gas will spread out and take on the shape and volume of whatever container it is in—whether a jar, a room, or the atmosphere! This is very different from a liquid or a solid. The molecules in a liquid do not move as fast as those in a gas. A liquid can take on the shape of its container but will keep the same volume, no matter what container it is in. The molecules in a solid just vibrate in place. That is why a solid will retain both its shape and its volume.