Gases

📖 In short

Gas is one of the three states of matter: solid, liquid and gas. A rock is solid with a fixed shape, water is liquid and takes the shape of its container, and a gas has no fixed shape or size but spreads out to fill whatever space it's in.

🤩 Did you know?

Most gases have no color and we can't see them.
A special smell is added to cooking gas so we can tell if it leaks.
The scientist Faraday discovered that some gases can be turned into liquids by squeezing and cooling them.
Helium is lighter than air, so a balloon filled with it floats up.

🔎 Find out more

🌟 Gases around us

The air we breathe is a mix of gases, mainly oxygen and nitrogen. Other gases include water vapor, carbon dioxide in fizzy drinks and helium in balloons.

🔍 It spreads everywhere

When someone sprays perfume in one corner of a room, you smell it soon after in the other corner, because gas molecules move fast and spread through the whole room.

💡 It can be squeezed

Gas molecules are far apart, so gas can be squeezed into a small space, like compressed air in a bike tire and compressed gas in cooking and diving cylinders.

🎯 Heat makes it expand

When a gas heats up it expands, and when it cools it shrinks. Put a blown-up balloon in the fridge for a while and you'll see it get smaller, then bigger again as it warms up!

🧩 Test yourself

1 Which of these is a gas?

2 Why can we smell perfume all over the room?

3 Which picture shows “Gases”?

🧪 Discover more

📷 Picture sources: Wikimedia Commons

Macluskie · Public domain