Gases and Expansion

As gas molecules move farther and farther apart, the gas expands, or takes up more volume. Over time a gas will completely fill the space it is in. If the gas is in a closed container, the molecules expand until they are stopped by the walls of the container. If the gas is in an open container, the gas molecules expand out of the container and become part of the air surrounding them.

The movement of gas molecules from one area to another is called diffusion. One way we experience diffusion is with our sense of smell. If a bottle of perfume is opened at one end of a room, in time the scent will be smelled on the other side of the room. The room has become the gas’s container. The perfume molecules have mixed with the room’s air molecules and have diffused throughout the room.

Natural gas is found in the soil after living things break down under pressure. This gas is used as a fuel for such things as heating our homes and cooking food.View Larger Image

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