Motivation is the biggest predictor of exam success. This App will keep you at your best by ensuring your motivation stays high during this critical time.
Different Types of Chemical Reactions
When a reactant breaks down to give two or more products, we call this type of reaction decomposition.
calcium carbonate → calcium oxide + carbon dioxide
Decomposition caused by heat is called thermal decomposition.
Decomposition can also be caused by light.
silver chloride → silver + chlorine
The reverse to decomposition - combination involves often two reactants reacting to form just one product.
sodium + chlorine gas → sodium chloride
When acids react with bases, they neutralise each other the products of a neutralisation reaction are neither acids nor bases.
sodium hydroxide + hydrocholoric acid → sodium chloride + water
The products of neutralisation are a salt and water.
This reaction involves the decomposition of a compound by electricity.
lead bromide → lead + bromine gas
Natural organisms, such as yeast can cause decomposition to occur. Yeast breaks down glucose, a sugar, into alcohol.
glucose → ethanol + carbon dioxide
This reaction is important to the yeast cells since it produces the energy they require to multiply. This reaction is used in the making of beer and wines.
This reaction is also used in breadmaking.
When a reaction involving two solutions produces an insoluble product. The product appears as a precipitate. This reaction is known as precipitation.
barium nitrate + copper sulphate → barium sulphate + copper nitrate
In this reaction it is the barium sulphate that appears as the precipitate.
This reaction involves the reaction of a substance with oxygen in the air. Sometimes the word burning is used instead of combustion.
The substance that reacts with oxygen is said to be oxidised. The result is a product called an oxide.
This is an example of an exothermic reaction, one that gives out heat energy.
carbon + oxygen → carbon dioxide
iron + oxygen → iron oxide
Oxidation and reduction:
If a substance loses oxygen during a reaction it is reduced.
If a substance gains oxygen during a reaction it is oxidised.
Reduction and oxidation always take place at the same time.
For example: the reaction between black copper (II) oxide and hydrogen gas,
In the reaction above, copper (II) oxide is reduced as hydrogen takes oxygen away to form water. So the hydrogen gaining oxygen is oxidised. The copper (II) oxide is reduced to red/brown copper.