1. Summary

A chemical reaction involves a change in the physical and chemical properties, the composition and the physical state of a substance. A chemical equation is a symbolic representation of the reactants and the products using their chemical formulae.

A chemical equation contains:

-Reactants

-Products

-An arrow separates  the reactants and products  

Symbols for physical state of reactants and products:

- Solid(s)

- Liquid(l)

- Gas (g)

- Aqueous solution (aq)

- Gas produced  ((↑))

- Precipitate formed  ((↓))

- Direction of reaction ((→))

The law of conservation of mass states that the total mass of the reactants and the products should be equal.

The process of balancing chemical equation involves four steps:

1. Determining the reactants and products in a reaction.

2. Counting the number of atoms of each on both sides.

3. Selecting the elements that occur for the least number of times in the equation.

4. Changing the coefficient of the molecules of reactants or products as required.

Represents an unbalanced equation for the formation of water

Represents balanced equation for the formation of water

Represents an unbalanced chemical equation for the combustion of ethyl alcohol.

Represents balanced chemical equation for the combustion of ethyl alcohol.

Represents an unbalanced chemical equation for the decomposition of potassium chlorate.

Represents balanced chemical equation for the decomposition of potassium chlorate.

Represents an unbalanced chemical equation for the reaction of sulphuric acid with copper to form copper sulphate, water and sulphur dioxide.

Represents a balanced chemical equation for the reaction of sulphuric aicd with copper to form copper sulphate, water and sulphur dioxide.

Represents an unbalanced chemical equation for the decomposition of sodium thiosulphate with hydrochloric acid to give sodium chloride, sulphur dioxide, sulphur and water

Represents a balanced chemical equation for the decomposition of sodium thiosulphate with hydrochloric acid to give sodium chloride, sulphur dioxide, sulphur and water.

2. Videos
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3. Activities & Simulations
4. Teacher Solved Exercises
5. Questions & Answers
1 . Deliquescence
1 Answer
90 Views
2 . balance the equations
1 Answer
111 Views
3 . electrons
3 Answers
146 Views
4 . why metals have shining appearence?
1 Answer
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5 . Roasting and Calcination
1 Answer
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