chemistry specification part 3

Question 1

describe the particle change during melting

Answer 1

-solids start to vibrate when heated which weakens the bonds that hold them together
-at a certain temp the particles have enough energy to break free from their positions and turn into a liquid.

Question 2

what does purity mean

Answer 2

a substance made up of a single element or compound

Question 3

what is paper chromatography?

Answer 3

separation of mixtures of soluble substances by running a solvent through the mixture on the paper, which causes the substances to move at different rates over the paper

Question 4

what is filtration in water treatments

Answer 4

a wire mesh to filter out large twigs etc. and a sand bed filter to get gravel and sand out the water

Question 5

what is sedimentation?

Answer 5

iron/aluminium sulfate is added to the water which makes particles clump up and settle at the bottom

Question 6

what is chlorination?

Answer 6

chlorine gas is bubbled through to kill harmful bacteria

Question 7

other than water treatment plants how else can you get potable water?

Answer 7

distillation however its very expensive

Question 8

what must you make sure of before water is used in the chemical analysis?

Answer 8

before mixing or dissolving something in the water, the water must be deionised. This means taking out ions like copper,iron ad calcium that is found in tap water.Using tap water could give a false result

Question 9

what do acids in solution produce?

Answer 9

hydrogen ions

Question 10

what do alkalis in solution produce?

Answer 10

hydroxide ions