Topic 3 Chemical changes

Question 1

Alkali

Answer 1

Produces hydroxide ions (OH-) in aqueous solutions with a pH range between 7 and 14.

Question 2

Indicators:

Answer 2

A chemical used in a titration reaction to identify the end point of the reaction by a clear colour change. Examples include phenolphthalein and methyl orange.

Question 3

Neutralisation:

Answer 3

The reaction in which an acid and a base react to form a salt and water.

Question 4

Oxidation:

Answer 4

A reaction involving the gain of oxygen. Oxidation is the loss of electrons.

Question 5

Ph scale

Answer 5

pH scale: A measure of the acidity or alkalinity of a solution. The scale ranges from 0-14 and can be measured using universal indicator or a pH probe.

Question 6

Reduction:

Answer 6

Reduction is the gain of electrons.

Question 7

Titration:

Answer 7

A technique used where a solution of known concentration is used to determine the concentration of an unknown solution.

Question 8

Universal indicator

Answer 8

Universal indicator: A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.

Question 9

Weak acid

Answer 9

Weak acid: An acid which is only partially ionised in an aqueous solution. This means only a small number of the H* ions are released. Examples of weak acids include ethanoic, citric and carbonic acids.