CC2a

Question 1

What is a pure substance?

Answer 1

A substance made up of only one type of atom or molecule
.it has a fixed composition

Question 2

What is a mixture?

Answer 2

A substance that contains more than one type of atom or molecule. not chemically bonded together

Question 3

How can you tell a substance is pure from his melting point?

Answer 3

The melting point is fixed (a flat line on a heating curve)

Question 4

How can you tell substance is a mixture from its melting point?

Answer 4

A mixture melts over a range of temperatures (a diagonal line on a heating curve)

Question 5

What happens to atoms of a pure substance as it melts?

Answer 5

All the atoms gain enough energy to overcome the weak forces of attraction between them and become liquid

Question 6

Why did the temperature not change as a pure sentence

Answer 6

All the particles have the same composition and the same force of the attraction between them so they melt at the same temperature until all the substances have changed state

Question 7

What is it meant by filtration

Answer 7

Using a filter to separate solids and liquids

Question 8

What sort of mixes can be separated by filtration

Answer 8

Filtration is used to separate insoluble solids from liquid or solutions (Can be used to separate separate solids from a gas)

Question 9

What sort of mixture is that? Can be separated by crystallisation

Answer 9

Solutions- mixture of a soulute and a solvent the saw you can be separated by a solution by crystallisation

Question 10

What apparatus is needed in a lab for filtration

Answer 10

For filtration you need an evaporation basin, beaker of water on a tripod, and Bunsen burner

Question 11

What apparatus is needed in a lab for cystillation

Answer 11

For crystilation you need an evaporating basin, beaker of water on a tripod an Bunsen burner

Question 12

Explain how to form crystals during crystallisation

Answer 12

Crystals form when the solvent is evaporated and becomes a saturated solution. Crystal starts to form as the solute leaves the solution. if the solvent evaporate slowly then the larger the crystals form as the particles have more times to arrange themselves in regular pattern.

Question 13

Explain how much is are separated by filtration

Answer 13

Solvent and so you will pass through a filter paper, but insoluble substances cannot be trapped in the paper leaving a residue

Question 14

Describe how some mixtures can be separated by chromatography

Answer 14

Some substances dissolved better than others do when a solvent move along a piece of paper it carries the substances that are dissolved at this different speed so they are separated

Question 15

Explain ways of reducing risk when separating mixtures by filtration crystallisation

Answer 15

Wearing eye protection in case of spitting and to stop heating before the solution is completely dry or to use steam from the back of water to heat the evaporation base and gently

Question 17

How can you identify pure substances in mixtures on chromatograms?

Answer 17

Pure substances with only have one spot on the chromatograms whereas impure or mixture will have two or more spots