What is Gas? — Physics

Definition 14.6 Primary & Middle School Physics · Chapter 14 — Solids, Liquids, Gases

A gas is stuff that spreads out to fill all the room it is given. Air is a gas: put it in a bottle, it fills the bottle to every corner; open the bottle in a bigger room, and it spreads through that too. A gas has neither its own shape nor its own resting place — offer it more room, and it takes everything.

A gas on the loose: released in one corner, it spreads until it fills the whole room.

Most gases are invisible — but not all. This sealed glass tube holds bromine, a gas with a real brown-orange color: you can see it filling every corner of its container, right up to the glass. Photo: James St. John, CC BY 2.0 (cropped). — Most gases are invisible — but not all. This sealed glass tube holds bromine, a gas with a real brown-orange color: you can *see* it filling every corner of its container, right up to the glass. *Photo: James St. John, CC BY 2.0 (cropped).*

Examples

Example 14.7 (The traveling perfume)

Someone opens a perfume bottle at one end of the room. A moment later, noses at the other end notice it. The perfume gas did not stay politely near its bottle: released, it spread through all the air of the room, corner to corner — exactly what the gas family always does.

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Examples

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