Separating and purifying substances

Question 1

What are the three states of matter?

Answer 1

Solid, liquid, gas

Question 2

What is the particle model?

Answer 2

It explains state changes in a substance in terms of the arrangement, movement and energy stored in its particles

Question 3

what is the arrangement of particles in a gas?

Answer 3

Random and far apart

Question 4

what is the arrangement of particles in a liquid?

Answer 4

random and close together

Question 5

what is the arrangement of particles in a solid?

Answer 5

regular and close togther

Question 6

what is the movement of particles in gas?

Answer 6

fast in all directions

Question 7

what is the movement of particles in a liquid?

Answer 7

particles move around each other

Question 8

what is the movement of a solid?

Answer 8

vibrate about fixed positions

Question 9

are state changes physical or chemical, why?

Answer 9

physical because they can reversed and the chemical properties of the substance do not change only their arrangement, movement and amount of energy

Question 10

what is deposition?

Answer 10

the direct change from gas to solid

Question 11

what is sublimation?

Answer 11

the direct change from solid to gas

Question 12

what is the change from gas to liquid called?

Answer 12

condensing

Question 13

what is the change from liquid to solid called?

Answer 13

freezing

Question 14

what is the change from solid to liquid callled?

Answer 14

melting

Question 15

what is the change from liquid to gas called?

Answer 15

evaporation and boiling

Question 16

why does the temperature stay the same at the melting and boiling point?

Answer 16

the substance is still being heated but the added energy is making the particles break away from their fixed arrangement

Question 17

what would the state be below the melting point?

Answer 17

solid

Question 18

what would the state be between the melting and boiling point?

Answer 18

liquid

Question 19

what would the state be above the boiling point?

Answer 19

gas

Question 20

what is the make-up of a pure substance?

Answer 20

cannot be changed

is the same in all parts of a piece of the substance

Question 21

why can’t we separate a pure substance into other substances?

Answer 21

it has the same fixed composition in all its parts.

Question 22

what is a mixture?

Answer 22

a mixture contains elements and/or compounds that are not chemically joined together

Question 23

True or False?
A mixture does not have a fixed composition, so you can use physical processes to separate mixtures into different substances

Answer 23

True

Question 24

What happens when a solid melts?

Answer 24

Its particles gain enough energy to overcome the weak forces of attraction between them and move away from each other at the melting point.

Question 25

True or False? | Not all of a pure substance will melt at the same temperature

Answer 25

False | All of a pure substance will ,elt at the same temperature until all of the substance has changed state.

Question 26

Do mixtures have a fixed, sharp melting point?

Answer 26

No

Question 27

What are filters used for?

Answer 27

Filters can be used to separate some mixtures, to let smaller pieces or liquids through but trap bigger ones or insoluble substances.

Question 28

What is a solution?

Answer 28

A solution is a mixture made of solutes (dissolved substances) in a liquid called a solvent.

Question 29

What is crystallisation?

Answer 29

It is used to produce solid crystals from a solution. Separating solutes from a solution by heating the solution and evaporating the solvent to leave the solutes behind. When what's left cools crystals form.

Question 30

What is the process for filtration?

Answer 30

1) Funnel is lined with filter paper 2) The solvent and solute(s) pass through to form the filtrate 3) Insoluble substances can't pass so leave a residue

Question 31

What can chromatography be used for?

Answer 31

It can be used to find out which coloured compounds the mixture contains.

Question 32

What is the mobile phase?

Answer 32

The solvent

Question 33

What is the stationary phase?

Answer 33

The paper

Question 34

What happens during paper chromatography?

Answer 34

A solvent (e.g. water) moves along a strip of paper, it carries the mixture (e.g. ink) at different speeds, so they are separated.

Question 35

What is a chromatogram?

Answer 35

The paper with the separated components on it

Question 36

True or False? | More soluble compounds are carried up faster

Answer 36

True

Question 37

How do you calculate the Rf value?

Answer 37

Rf = distance moved by the spot / distance moved by the solvent

Question 38

What is distillation used for?

Answer 38

To make pure substances by separating it from the dissolved solids

Question 39

What happens during distillation, using the example of water

Answer 39

Mineral water evaporates, only the water turns to gas (vapour). The solid minerals which have much higher boiling points are left behind. The water vapour is pure, it is then condensed and turned back to liquid.

Question 40

What is the apparatus used in distillation called?

Answer 40

A still

Question 41

What can fractional distillation be used for?

Answer 41

To separate the different products of crude oil To make alcoholic drinks such as whisky and vodka To separate out the gases in the air, after the air has been cooled and turned into liquid at -200°C

Question 42

What is producing pure water from sea water called?

Answer 42

Desalination

Question 43

Why is simple distillation not usually suitable for producing large amounts of drinking water?

Answer 43

A lot of energy must be transferred to seawater

Question 44

What does chemical analysis involve?

Answer 44

It involves using chemical reactions or sensitive machines to identify and measure the substances in a sample.

Question 45

During chemical analysis why can't the water contain dissolved salts?

Answer 45

Incorrect results will be obtained

Question 46

What does fresh water from sources like rivers, lakes and aquifers contain?

Answer 46

Objects such as leaves and twigs Small insoluble particles such as grit and silt Soluble substances including salts, pesticides and fertilisers Bacteria and other microorganisms that may be harmful to health

Question 47

What steps are needed to deal with the impurities from fresh water?

Answer 47

Screening using a sieve Sedimentation ( in which small particles are allowed to settle) Filtration using tanks containing beds of sand and gravel Chlorine is added to kill microorganisms in a process called chlorination