helium

Everyday

1. A very light gas with no colour or smell that is lighter than air; it is used to fill party balloons and airships so they float. tree →
2. A chemical element (symbol He), the second lightest of all. tree →

In the lessons

In science, helium is lighter than air, so helium balloons rise; the Sun makes helium from hydrogen. It does not burn, so it is safer than hydrogen in airships. Safety: never breathe in helium from balloons or tanks — it can stop you getting oxygen and make you pass out. Phrases: «helium balloon», «filled with helium».

Examples

• The party balloons were filled with helium. tree →
• Helium balloons float up into the sky. tree →
• Helium is lighter than air. tree →
• The Sun turns hydrogen into helium. tree →
• Don't breathe in helium; it can be dangerous. tree →
• A helium balloon goes floppy after a few days. tree →
• Let balloons go only if they won't harm birds and sea animals. tree →

Note

Uncountable: «some helium». A gas, not a liquid. The funny squeaky voice trick is not safe. Released balloons come down as litter that can hurt wildlife.