What is a chemical reaction?
A chemical reaction is the reaction between substances resulting in a chemical change.
Chemical reactions are generally difficult to reverse. eg. Cooking an egg, burning paper or the rusting of iron.
Chemical reactions result in the production one or more new products with unique properites.
eg. When water is broken down by electrolysis (electricity) hydrogen and oxygen gas are produced. Each of these susbstances have completely different properties compared to water.
All chemical reactions take the form of
Reactants → Products
The chemicals that react in a reaction are called the reactants. In the reaction below water is the reactant.
The chemicals that are produced are called the products. In the reaction below hydrogen and oxygen gas are the products.
Word equations are the simpliest way to represent chemical reactions.
The reactants are written on the left hand side and the products on the right hand side.
The arrow(→) means 'gives' or 'produces'.
Examples of word equations are
- Hydrogen + Oxygen → Water
- Sodium + Chlorine → Sodium chloride
- Zinc + Hydrochloric acid → Zinc chloride + hydrogen gas
In all chemical reactions mass is conserved as reactants are transformed into products by the rearrangement of atoms.