Acids and alkalis

What can you remember?

What does the word ‘acid’ mean? Where does it come from?

Acid tastes

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

(also the word

acute comes from this)

What do you call a chemical that

changes colour in acids and alkalis

Indicators

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

Can you name some indicators?

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

Universal Indicator

It comes in the form of a paper

Universal Indicator

It also comes in the form of a liquid

Other indicators

Red cabbage and beetroot make excellent indicators

What do we call the scale we use the measure acidity?

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

What do you call it when an acid is added to an alkali?

Neutralisation

Neutralisation

What is produced when we add an acid to an alkali?

Neutralisation

Acid + alkali salt + water

Both neutral

Can you give examples of everyday life of neutralisation?

Examples of neutralisation

What do these symbols mean?

Chemical Hazard Symbols

• Corrosive – dissolves metals, stone and skin

• Irritant – harms eyes and skin

• Flammable – burns easily

• Toxic – poisonous