Chemical reactions and word equations
A reaction rearranges atoms into new substances, and an equation summarises it.
Back in Grade 6 you met irreversible changes β changes that make a brand-new material. This year you give them their proper name: chemical reactions.
In a chemical reaction, the atoms of the starting substances are rearranged to build one or more new substances. The starting substances are called the reactants; the new substances are the products.
Chemists summarise a reaction with a word equation. The reactants go on the left, the products go on the right, and an arrow shows the direction of change:
reactants β products
For example, when magnesium burns:
magnesium + oxygen β magnesium oxide
The arrow is read as "react to make" or "becomes". The "+" between two reactants means "and". As you saw last year, chemists can also use symbols and formulae to write a shorter symbol equation β but the word equation always tells the same story.
A word equation is a quick, clear way to record exactly what reacted and what was made.
- A chemical reaction rearranges atoms into new substances.
- Reactants are the starting substances; products are what is made.
- A word equation puts reactants on the left, products on the right.
- The arrow means 'react to make'.