A summary of useful word equations

(If you would like more explanation about the examples below see useful chemical reactions)

Any kind of chemical change can be represented by a word equation
eg the equation for burning hydrogen is Hydrogen + oxygen water

The chemicals that you start with and are used up are known as reactants
The chemicals that are formed during the reaction are known as products

Reactants    Products

Example: during respiration glucose and oxygen are converted into carbon dioxide and water, releasing energy

Glucose + oxygen
(Reactants)

carbon dioxide + water
(Products)

 

Reactions with oxygen

1. Heating copper
When copper is heated in air it forms a layer of black copper oxide on the surface
Word equation: Copper +oxygen →  copper oxide

2. Burning magnesium
Magnesium burns with a bright white flame leaving a white ash of magnesium oxide
Word equation: Magnesium + oxygen magnesium oxide

3. Burning hydrogen gas
When hydrogen burns then water is always formed
Word equation: Hydrogen + oxygen water
(Water is in fact hydrogen oxide)

4. Burning Methane (natural gas)
Methane burns with a smoky yellow flame to form carbon dioxide and water
Word equation: Methane + oxygen carbon dioxide and water

5. Burning wax
Wax burns to form carbon dioxide and water
Word equation:  Wax + oxygen carbon dioxide and water

 You will notice that the last two examples both produced carbon dioxide and water as the products.
Wax and methane are examples from a large group of chemicals known as hydrocarbons.
Carbon dioxide and water will be produced when any hydrocarbon burns
hydrocarbon carbon dioxide and water


Decomposition
The type of reaction where a compound splits apart into simpler chemicals

1. Heating copper sulphate
Copper sulphate decomposes to release water vapour, leaving a residue of  white anhydrous copper sulphate.
Word equation: Hydrated copper sulphate anhydrous copper sulphate + water

NOTE: This reaction is reversible. If water is added to anhydrous copper sulphate then the white powder turns blue again accompanied by a rise in temperature
Anhydrous copper sulphate + water   hydrated copper sulphate

2. Heating copper carbonate
Copper carbonate decomposes to release carbon dioxide, leaving a residue of  black copper oxide
Word equation: Copper carbonate copper oxide + carbon dioxide

3. Heating calcium carbonate
Calcium carbonate is the compound present in chalk and limestone.
It decomposes when heated to release carbon dioxide, leaving a white residue of  calcium oxide
The calcium oxide formed when limestone is heated is known as lime
Word equation: Calcium carbonate calcium oxide + carbon dioxide
or  
Limestone —–> lime + carbon dioxide

 
Oxidation and Reduction

Oxidation is when a substance reacts with (or joins up with) oxygen
Reduction is when a substance has oxygen taken away from it.

1. Heating carbon with copper oxide

The carbon REDUCES the copper oxide, forming carbon dioxide gas and leaving pink copper metal.
Word equation: Carbon + copper oxide carbon dioxide + copper

2. Heating coke (carbon) with iron oxide

This is the reaction that takes place in a blast furnace during the manufacture of iron
Word equation: Carbon + copper oxide carbon dioxide + iron

3. Placing burning magnesium in carbon dioxide
Word equation: magnesium + carbon dioxidemagnesium oxide + carbon

4. Reacting steam with hot magnesium
Word equation: magnesium + watermagnesium oxide + hydrogen


Displacement reactions
This is when a reactive metal displaces another metal from one of it’s compounds

1.   Reacting iron with copper sulphate solution
Word equation: Iron+ copper sulphate iron sulphate + copper


Reactions with an acid
: Neutralization

1. Adding dilute hydrochloric acid to dilute sodium hydroxide solution.
The hydrochloric acid will NEUTRALISE the sodium hydroxide (a strong alkali) forming water and common salt.
Word equation
Hydrochloric acid + sodium hydroxide sodium chloride + water

2.  Reaction between dilute hydrochloric acid and marble
This is how carbon dioxide gas is often prepared in the laboratory
Word equation
Hydrochloric acid + calcium carbonate calcium chloride + carbon dioxide↑

3.  Reaction between dilute sulphuric acid and zinc
This is how hydrogen gas is often prepared in the laboratory
Word equation
Sulphuric acid + zinc zinc sulphate + hydrogen↑

Reactions in Biology

Respiration
Respiration is the reaction that takes place in ALL living organisms that releases energy from sugar.
Word equation: Glucose + oxygen carbon dioxide + water (+ energy)

Photosynthesis
The reaction that takes place in green plants that converts carbon dioxide and water into glucose and starch, using energy from the sun.
Word equation  

Carbon dioxide + water
(Chlorophyll+ sunlight)
glucose + oxygen 

 For a more detailed explanation see ‘Photosynthesis‘ in the biology section

Fermentation
Fermentation is the name of the process that turns sugar into alcohol and carbon dioxide
It is carried out by a fungus called YEAST and is used a lot in the baking and brewing industries
Word equation: sugar carbon dioxide + alcohol