Do now!Whilst you are

waiting can you answer some of the

questions on the sheet?

Last lesson

• Know how to tell if a chemical reaction has taken place

• Know what neutralisation is

• Know the general equation for the reaction between an acid and a base

• Know how to write a word equation for the reaction between an acid and a metal oxide

Chemical reactions – What to look for

Chemical reactions – What to look for

• There may be a change of colour

Chemical reactions – What to look for

• There may be a gas given off (bubbles)

Chemical reactions – What to look for

• There may be an energy change (gets hotter or colder)

Chemical reactions – What to look for

• New substances are formed, and the change is usually difficult to reverse

Physical changes

Acids and alkalis

What do you remember from

year 7?

Acid tastes

Acid tastes

Acid comes from the latin word acer, which means sharp. Acids are sharp tasting! (“Tangy”)

Indicators

Indicators are chemicals (coloured dyes) which change colour in acids and alkalis.

Litmus

Turns red in acid

Turns blue in alkali

Litmus

Turns red in acid

Turns blue in alkali

Litmus can tell us if something is an acid or an alkali, but it cannot tell us how strong the

acid or alkali is

Other indicators

Red cabbage and beetroot make excellent indicators

The pH scale

The strength of an acid is measured on the pH scale

pH stands for the “potential of hydrogen”

Universal Indicator

To measure pH, we need an indicator that has a different colour for each value of pH

Universal Indicator

Universal Indicator

It comes in the form of a paper

Universal Indicator

It also comes in the form of a liquid

Neutralisation

Neutralisation

What happens when we add an acid to an alkali?

Making a “salt” by neutralisation

• Can you stick the sheet in and read carefully?

Hydrochloric acid + potassium hydroxide (alkali)

• Makes potassium chlorid (a “salt” + water

Acid + Base “salt” + water

Hydrochloric acid + sodium hydoxide sodium chloride + water

Sulphuric acid + Potassium hydroxide Potassium sulphate + water

Nitric acid + ammonia ammonium nitrate + water

In general, hydrochloric acid makes a chloride, nitric acid makes a nitrate, and sulphuric acid makes a sulphate.

Today’s lesson

• Writing word equations for making salts by neutralisation

• Making Copper sulphate

Examples of neutralisation

Word equations for making salts

• Can you stick the sheet in and answer the questions?

Making Copper sulphate