chemical

Everyday

1. A chemical is a substance, especially one made or used in science or industry, such as bleach, salt or oxygen. tree →
2. Chemical as an adjective means to do with chemistry or with how substances change: a chemical reaction. tree →

In the lessons

In science everything is made of chemicals, including water and air; a chemical reaction makes new substances (burning, rusting, baking a cake). In safety lessons household chemicals like bleach, cleaners and weedkiller are dangerous: never mix them, drink them or keep them in drink bottles, and keep them out of reach of little children. Phrases: chemical reaction, household chemicals, harmful chemicals, chemical change.

Examples

• Bleach is a strong chemical, so don't touch it. tree →
• Never mix cleaning chemicals; they can make poisonous gas. tree →
• Rust is caused by a chemical reaction between iron, water and air. tree →
• Water is a chemical made of hydrogen and oxygen. tree →
• Keep chemicals in their own bottles with labels. tree →
• Baking a cake causes chemical changes in the mixture. tree →
• The scientist wore goggles when she used the chemicals. tree →
• Some farmers spray chemicals on crops to kill pests. tree →
• Now, one day Edmund made a new lantern out of something chemical that he sneaked from the school laboratory. tree →

Note

Countable as a noun: a chemical, chemicals. A «chemical change» makes something new and is often hard to undo; a «physical change» (like melting ice) does not make a new substance. Myth: «chemical» does not always mean harmful or unnatural; but unknown liquids should never be tasted or sniffed.