SC3 - STATES OF MATTER, SEPARATING AND PURIFYING

Question 1

SOLIDS: arrangement and movement of particles

Answer 1

• ordered, neat rows
• vibrating about a fixed position

Question 2

LIQUIDS: arrangement and movement of particles

Answer 2

• random arrangement, some particles touch
• particles roll over each other

Question 3

GASES: arrangement and movement of particles

Answer 3

• random arrangement, spread far apart
• flying around with high energy

Question 4

state change: gas -> liquid

Answer 4

condensation

Question 5

state change: liquid -> solid

Answer 5

freezing

Question 6

state change: solid -> liquid

Answer 6

melting

Question 7

state change: liquid -> gas

Answer 7

evaporation / boiling

Question 8

state change: solid -> gas

Answer 8

sublimation

Question 9

describe state changes on a heating curve

Answer 9

• graph shows temperature + time
• state changes are shown as horizontal lines as during this time, the energy is used to change state and not temperature

Question 10

mixture definition

Answer 10

mixtures contain substances which are not chemically combined and can be separated

Question 11

pure material definition

Answer 11

pure materials contain only one substance

Question 12

impure materials definition

Answer 12

impure materials contain a mixture of substances

Question 13

melting point of pure substances

Answer 13

sharp melting point

Question 14

melting point of impure substances

Answer 14

a range of melting points

Question 15

describe filtration

Answer 15

• filtration can be used to separate an insoluble solid from a liquid or from a solution
• filtration works because the large particles of the residue cannot pass through the small gaps in the filter paper

Question 16

describe crystallisation

Answer 16

• crystallisation can be used to separate a soluble solid from a solution of that solid
• in crystallisation of a solution the SOLVENT is evaporated from a SOLUTION to leave the SOLUTE

Question 17

describe chromatography

Answer 17

• used to separate a mixture of substances eg. a mixture of different dyes in an ink
• the mixture separates because some dyes are more attracted to the solvent and some are more attracted to the paper

Question 18

chromatography: Rf value equation

Answer 18

Rf = distance substance has travelled / distance solvent has travelled

Question 19

hazard definition

Answer 19

what is dangerous eg. bunsen burner

Question 20

risk definition

Answer 20

the harm which the hazard could do eg. hair could catch fire

Question 21

control measure definition

Answer 21

how you could make it safer (minimise the risk) eg. tie your hair back

Question 22

describe simple distillation

Answer 22

• used to separate a solvent from a solution eg water from a water based ink
• the solution is evaporated and the gas condenses back into a test tube

Question 23

describe fractional distillation

Answer 23

• used to separate a solvent from a mixture of solvent
• the solution is evaporated and the gas condenses through a condenserback into a test tube

Question 24

stages of filtration (4)

Answer 24

1. course filtration
2. sedimentation
3. fine filtration
4. chlorination

Question 25

describe stage 1 of water purification - course filtration

Answer 25

the water is filtered to remove twigs etc.

Question 26

describe stage 2 of water purification - sedimentation

Answer 26

a chemical is added which makes particles sink to the bottom

Question 27

describe stage 3 of water purification - fine filtration

Answer 27

the water is filtered through sand

Question 28

describe stage 4 of water purification - chlorination

Answer 28

chlorine is added to kill bacteria

Question 29

distilled water vs sea water vs mineral water

Answer 29

DISTILLED WATER: pure water and contains NO dissolved salts. used for laboratory tests. uses a lot of energy, too expensive to be used for drinking water
SEA WATER: contains dissolved sodium chloride
MINERAL WATER: contains many dissolved salts