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chemistry gcse > Topic 3 - States Of Matter & Methods Of Separating And Purifying Substances > Flashcards

Topic 3 - States Of Matter & Methods Of Separating And Purifying Substances Flashcards

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1
Q

filtration

A

process used to separate a soluble substance from an insoluble substance

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2
Q

crystallisation

A

when solutes are separated from a solution by evaporating the solvents to leave the solutes behind

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3
Q

rf value

A

distance moved by the spot / distance moved by the solvent

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4
Q

distillation

A

to purify a liquid by doing evaporation followed by condensation

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5
Q

what are the 3 states of matter

A

liquid, solid, gas

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6
Q

particle model

A

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

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7
Q

what is the movement like in a gas

A

fast in all directions

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8
Q

what is the movement like in a liquid

A

move around each other

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9
Q

what is the movement like in a solid

A

vibrate in a fixed position

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10
Q

what’s the arrangement of particles in a gas

A

random and far apart

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11
Q

what’s the arrangement of particles in a liquid

A

random and close together

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12
Q

what’s the arrangement of particles in a solid

A

regular and compact

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13
Q

what is a state change

A

a physical change of matter

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14
Q

what happens to the particles in a state change

A

the particles do not change, only their arrangement, movement and amount of stored energy

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15
Q

how are particles attracted to another

A

by weak forces of attraction

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16
Q

how do you change from a solid to a liquid

A

melting

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17
Q

how do you change from a liquid to a gas

A

evaporation and boiling

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18
Q

how do you change from a gas to a liquid

A

condensing

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19
Q

how do you change from a liquid to a solid

A

freezing

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20
Q

how do you change straight from a gas to a solid without passing the liquid stage

A

deposition

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21
Q

how do you change straight from a solid to a gas without passing the liquid stage

A

sublimation

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22
Q

what needs to happen for these weak forces of attraction to be overcome (solid -> liquid)

A

energy must be transferred from the surroundings to the particles

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23
Q

what needs to happen for these weak forces of attraction to form (liquid -> solid)

A

energy must be transferred from the particles to the surroundings

24
Q

how can you predict the state of a substance

A

if you know its temperature, melting point and boiling point

25
Q

what state is the substance of its below the melting point

A

a solid

26
Q

what is the state of a substance if it’s above melting point but below boiling point

A

a liquid

27
Q

what state is the substance if it’s above boiling point

A

a gas

28
Q

pure substance

A

an element or compound made up of one type of particle

29
Q

tell me about the composition of a pure substance

A
  • cannot be changed
  • is the same in all parts of the substance
  • only contains one substance
30
Q

what does a mixture contain

A

elements and/or compounds that are not chemically joined together (doesn’t have a fixed position)

31
Q

physical property

A

how a substance responds to forces and energy (something you can see)

32
Q

solute

A

a substance that has dissolved in a liquid to make a solution

33
Q

solvent

A

the liquid in which a solute dissolves to make solution

34
Q

what sized crystals will be made of it forms slowly

A

bigger crystals

35
Q

what sized crystals will be made of it forms quickly

A

smaller crystals

36
Q

how to filter solution in the laboratory

A
  • a filter funnel is lined with filter paper that has holes in in
  • the solvent and solutes pass through the fine holes to form the filtrate
  • bits of insoluable substances cannot fit through the holes and so leave a residue
37
Q

how to crystallise a filtrate

A
  • a Bunsen burner is placed under boiling water
  • the filtrate is placed on top of the boiling water
  • this evaporates the filtrate carefully
  • leaves behind crystals which can be scraped from the container
38
Q

what’s a hazard in crystallisation and how do we reduce it?

A

the hazard is crystals spitting out
- reduce this by wearing eye protection, removing the Bunsen burner before the solution is completely dry and/or using steam to heat the evaporating basin gently

39
Q

paper chromatography

A

simply technique that finds out which compounds the mixture contains
- a solvent moved along a strip of paper and it carries substances in the mixture at different speeds so they are separated

40
Q

why do you need a condenser in a distillation apparatus

A

contains cold water that keeps the tube cool so that almost all of the vapour condenses and turns into a liquid

41
Q

what is fractional distillation used for

A

to separate mixtures of liquids

42
Q

what is simple distillation used for

A

to separate a solvent from a solution

43
Q

in distillation, why is there bung at the top of the flask

A

so that no gas can escape

44
Q

how does fractional distillation work?

A
  • a fractionating column is fixed above the distillation flask (contains little glass rods)
  • the hot vapour rises at the column
  • Hot vaporises at the column heating up - thus creates temperature gradient (hotter at the bottom, cooler at the top)
  • the fraction with the lowest boiling point (the same as or lower than the temperature) will reach the top of the column and the vapour will pass to the condenser
  • if the boiling point is higher than the temperature, then it will condense when it hits the cool glass and drips back down into the flask
  • if you keep heating, fractions with higher boiling points with them rise up the column and can be collected later
45
Q

how does simple distillation work

A
  • the solution is heated until it reaches its boiling point and the solvent evaporates
  • the solvent is then condensed, and it turns back into a liquid and its collected as a pure liquid
46
Q

solution

A

formed when a substance has dissolved in a liquid

47
Q

filtrate

A

a solution passing through a filter

48
Q

residue

A

material remaining in the filter after mixture has passed through it

49
Q

sedimentation stage in producing safe water

A

small particles are allowed to settle to the bottom

50
Q

filtration stage in producing safe water

A

particles are removed by passing the water through sand and gravel beds

51
Q

chlorination stage in producing safe water

A

chlorine is added to the water to kill bacteria and other microorganisms

52
Q

what stages are used to produce safe drinking water

A

1) sedimentation
2) filtration
3) chlorination

53
Q

reason for chlorination

A

to kill bacteria

54
Q

reason for filteration

A

to get rid of insoluble substances

55
Q

how do you know when a food colouring has the greatest number of coloured substances

A

it will have greatest number of spots

56
Q

mobile phase in chromatography

A

where molecules can move

57
Q

stationary phase in chromatography

A

where the molecules can’t move

chemistry gcse (6 decks)

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