hydrogen

Everyday

The lightest of all chemical elements; a gas with no colour, smell or taste that burns easily. Its chemical symbol is H. tree →

In the lessons

In science: hydrogen is number 1 in the periodic table; it is the most common element in the universe; stars like the Sun get energy by turning hydrogen into helium. Water is H2O: two atoms of hydrogen and one of oxygen. Hydrogen is used as a clean fuel for some buses and rockets. Phrases: «hydrogen gas», «hydrogen fuel», «hydrogen and oxygen».

Examples

• Water is made of hydrogen and oxygen. tree →
• Hydrogen is the lightest gas there is. tree →
• The Sun is mostly hydrogen. tree →
• Some buses run on hydrogen fuel. tree →
• Hydrogen burns with a squeaky pop in a test tube. tree →
• Hydrogen's symbol is H. tree →
• Old airships were filled with hydrogen, which is dangerous because it burns. tree →

Note

Uncountable. Symbol H, atomic number 1. Safety: hydrogen catches fire very easily — party balloons use helium instead, which does not burn. Hydrogen is a gas at room temperature.