Vapor facts for kids

Vapor (sometimes spelled vapour in British English) is like an invisible cloud made of tiny, tiny drops of a liquid that are floating in the air. This often happens when a liquid gets hot enough to turn into a gas. Think of the steam you see above a boiling pot of water – that's water vapor!

The temperature at which a material turns into vapor depends on the air pressure around it. For example, water boils and turns into vapor at a lower temperature high up in the mountains where the air pressure is less.

What is Vapor?

Vapor is a substance that is a gas, but it's usually a liquid or a solid at normal room temperature. When you heat a liquid, its particles move faster and faster. Eventually, they gain enough energy to break away from the liquid and float freely in the air as a gas. This gas is what we call vapor.

How Does Vapor Form?

Vapor forms when a liquid gets enough energy, usually from heat, to change its state. This process is called evaporation or boiling.

• Evaporation: This happens slowly, even at cool temperatures. Think of a puddle drying up on a sunny day. The water slowly turns into vapor and disappears into the air.
• Boiling: This happens quickly when a liquid reaches a specific temperature called its boiling point. At this point, bubbles of vapor form inside the liquid and rise to the surface.

The amount of pressure around a liquid also affects when it turns into vapor. If the pressure is lower, a liquid can turn into vapor at a lower temperature. This is why water boils faster on top of a tall mountain than it does at sea level.

Where Do We See Vapor?

Vapor is all around us, even if we can't always see it!

• Water Vapor: This is the most common vapor we encounter. It's what makes the air feel humid. When water vapor cools down, it can turn back into tiny liquid drops, forming clouds, fog, or even dew on grass.
• Steam: When water boils, the visible "steam" you see is actually tiny liquid water droplets that have condensed from the hot water vapor as it mixes with cooler air. The actual water vapor itself is invisible.
• Other Vapors: Many other liquids can turn into vapor. For example, when you use perfume or nail polish remover, you can smell them because tiny amounts of the liquid are turning into vapor and floating into the air.

Images for kids

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  An ampule containing brown nitrogen dioxide vapor.

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  Water vapor in the air can cause humidity and sometimes makes light rays visible.

See also

In Spanish: Vapor (estado) para niños