Section 12 - Chemical Changes

Question 1

Acids and Bases - What pH value would a neutral substance have?

Answer 1

pH 7

Question 2

Acids and Bases - What is an alkali?

Answer 2

Alkali = a base that is soluble in water (pH value of more than 7) [form OH- ions in water]

Question 3

Acids and Bases - State what colours litmus indicator is in solutions

Answer 3

Red in acidic solutions
Purple in neutral solutions
Blue in alkaline solutions

Question 4

Acids and Bases - State what colours methyl orange indicator is in water

Answer 4

Red in acidic solutions

Yellow in neutral AND alkaline solutions

Question 5

Making Salts - Describe how you could make a pure sample of soluble salt from an acid and an alkali

Answer 5

React an acid with an alkali

The indicator will change colour when all the acid has been neutralised

Question 6

Electrolysis - What is electrolysis?

Answer 6

Electrolysis = the breaking down of a substance using electricity

Question 7

Electrolysis - Towards which electrode do the anions in an electrolyte move?

Answer 7

The negative ions (anions) will move towards the anode (positive electrode) and are oxidised (lose electrons)