C12 - Chemical analysis

Question 1

C12 - What is a pure substance?

Answer 1

Something that contains only one type of substance.

Pure substances have specific temperatures at which they melt and boil.

Melting and boiling points can be used to identify pure substances

Question 2

C12 - What is a formulation?

Answer 2

A mixture that has been designed to produce a useful product.

Paints, medicines and fertilisers are examples of formulations.

Question 3

C12 - How do you calculate an Rf value?

Answer 3

Rf = distance moved by substance/ Distance moved by solvent

Question 4

C12 - Plan an experiment to investigate the colours in an ink.

Answer 4

Draw a pencil line on a piece of chromatography paper.

Place dots of known colours and a dot of the ink on the pencil line.

Place the bottom of the paper in water, making sure that the water is below the pencil line.

Wait for the water to rise up the paper.

Leave to dry.

Calculate Rf values

Compare positions of dots from known colours against those from the ink.

Question 5

C12- Testing for gases

Answer 5

Hydrogen - a lighted splint ‘pops’

Oxygen - a glowing splint relights

Carbon Dioxide - colourless limewater turns cloudy

Chlorine - damp blue litmus paper turns white