CHEMICAL CHANGE

PHYSICAL CHANGES

Substance looks diff erent, but chemically still the same.

Eg. Melting, breaking.Most physical changes are reversible.

PHYSICAL CHANGES

CHEMICAL CHANGE

New substances are formed. Identified by:

Colour change Light or heat produced Precipitate formed

CHEMICAL CHANGE

To save time, we can describe a chemical reaction using equations.

Hydrochloric acid reacts with magnesium metal to produce hydrogen gas and magnesium chloride.

hydrochloric acid + magnesium hydrogen gas + magnesium chloride

WORD EQUATIONS

When writing chemical equations we start with the reactants and end with products.

hydrochloric acid + magnesium hydrogen gas + magnesium chloride

What are the reactants and products in the above word equation?

CHEMICAL EQUATIONS

CHEMICAL REACTIONS

C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy

2900kJ

When a chemical reaction occurs, the particles of the substance rearrange themselves.

Another way to say this is that they change their chemical bonds.

The previous reaction is called ‘respiration’ and is happening in the cells of your body right now.

CHEMICAL REACTIONS

Write the word equation for respiration.

CHEMICAL REACTIONS

THE WORK OF CHEMISTS

Chemists use chemical reactions to create new substances, for example: Materials such as fabrics, plastics and rubber. Medicines Food products

Or extract particular substances from others for example: Petrol from crude oil Metals from mineral ore

THE WORK OF CHEMISTS

You don’t have to be a chemist to make use of chemical reactions.

Some of the ways that chemistry aff ects our everyday lives are: Cooking Medicines Air bags in cars Special effects for movies Fireworks …and many, many more!

USING CHEMICAL REACTIONS