Course 5 - Chemical reactions

Introduction

Chemical changes are the changes that involves the formation of new substances.

Also, chemical change is permanent.

In a chemical change, chemical reactions take place.

- Chemical reaction refers to the process by which new substances are formed with new properties.

For example;

Hydrogen + Oxygen => Water

Sodium + Chlorine => Table salt (sodium chloride)

Hydrogen and Oxygen are the REACTANTS and water is the PRODUCT.

Sodium and Chlorine are the REACTANTS and salt is the PRODUCT.

Jot down what you learnt 😎😎Thank you.

Chemical equations

Chemical equations that are written in words are called word equations.

Potassium + Chlorine => Potassium chloride

Magnesium + Oxygen => Magnesium oxide

Those are in words.

To convert word equations into chemical equations:

1. Use symbols

2. For elements we use atomicity

3. For compounds we use valency

Use ask now for atomicity and valency in case you forgot.

E.g.

Hydrogen + Oxygen => Water

Remember for elements we use atomicity.

H2 + O2 => H2O

We wrote H2 and O2 because as gases they don’t exist in nature as just H or O they must combine with another of itself to form a molecule.

For compounds we use valency.

Valency of H = 1

Valency of O = 1

H1 x O2

Exchange their valencies.

H2O

So, H2 + O2 => H2O //

E.g. 2

Sodium + chlorine => Sodium chloride

Na + Cl2 => Nacl