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Chemistry > Unit 1 & 2- States Of Matter/ Methods Of Separating And Purifying Substances > Flashcards

Unit 1 & 2- States Of Matter/ Methods Of Separating And Purifying Substances Flashcards

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1
Q

What are the three states of matter?

A

Solid, liquid and gas

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2
Q

What is the arrangement of particles in gas?

A

Random and far apart

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3
Q

Describe the movement of particles in a gas

A

Fast in all directions

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4
Q

Describe the arrangement of particles in a liquid

A

Random and close together

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5
Q

Describe the movement of particles in a liquid

A

Move around each other

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6
Q

Describe the arrangement of particles in a solid

A

Regular and close together

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7
Q

Describe the movement of particles in a solid

A

Vibrate about fixed position

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8
Q

What type of changes of state changes?

A

Physical changes

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9
Q

What does not change during state changes

A

The chemical properties

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10
Q

What changes during a state change?

A

The arrangement and movement of the particles

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11
Q

How are particles held together in a solid?

A

Through many weak forces of attraction

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12
Q

How does a substance melt

A

Energy is used to overcome the forces

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13
Q

What happens during evaporation

A

The remaining attractive forces are overcome by more heat

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14
Q

Where does energy for melting and evaporation come from

A

The surroundings

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15
Q

What happens to the energy in particles during condensing and freezing

A

It is transferred from the particles to the surroundings

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16
Q

When is the temperature of a substance constant?

A

During state changes

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17
Q

The composition of a pure substance…

A

Cannot be changed and is the same in all parts of a piece of the substance

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18
Q

What types of substances are pure

A

Compounds and elements

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19
Q

Can pure substances be separated using physical methods?

A

No

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20
Q

What is a mixture?

A

A substance that contains elements and/or compounds that are not chemically bonded together

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21
Q

How can you separate mixtures into different substances?

A

Using physical processes

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22
Q

What does a fixed composition mean?

A

Any piece of the substances will have the same amount of elements in it

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23
Q

What are the forces holding the particles together in a solid?

A

Weak forces of attraction

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24
Q

At what point does a substance changes from a solid to a liquid?

A

At the melting point

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25
Q

Why does a pure substance have a precise melting point?

A

Because it has the same composition in every part of it so it’s physical properties of this same

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26
Q

Why do mixtures not have a precise melting point?

A

Because there a different compositions within the substance

27
Q

How do filters separate some mixers

A

They let smaller pieces or liquids through but trap bigger pieces or insoluble substances

28
Q

The three examples of every day filters

A

Cars, vacuum cleaners and air-conditioning systems

29
Q

What is a solution

A

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

30
Q

How can solutes be separated from a solution

A

By evaporating the solvent and leave the solute behind

31
Q

What is crystallisation

A

When the solvent of a solution is evaporated leaving solute separated from the solvent.

32
Q

How do you sizes of crystals fairy

A

If the crystal form slowly the particles have longer to form an ordered pattern

33
Q

What is solution mining

A

Water is pumped into layers of salt underground dissolving the salt in the water. The solution is then heated which evaporates leaving only the salt.

34
Q

What is a saturated solution

A

A solution that contains the maximum amount of solvent in the amount of solute at that temperature

35
Q

How can you filter solutions in a laboratory

A

Using a filter funnel lined with filter paper

36
Q

What is the residue

A

Bits of insoluble substances left on the filter paper

37
Q

How can crystallisation be used in the laboratory

A

A Bunsen burner is used to evaporate the filtrate carefully. It must not be overheated as the hot crystals spit out and can cause crystals to change chemically.

38
Q

What is a hazard

A

Something that could cause harm

39
Q

Give a hazard and solution of crystallisation

A

There is a risk of the solution spitting which can burn. People should wear eye protection and use a low flame to gently heat the solution

40
Q

What is paper chromatography

A

A simple technique that is used to find out which coloured compounds the mixtures contain

41
Q

Explain paper chromatography

A

A solvent moves along a strip of paper and carries the different substances in the mixture at different speeds so they are separated

42
Q

In paper chromatography what is the mobile phase and what is the stationary phase

A

The mobile phase is this solute and the stationary phase is the paper

43
Q

What is a chromatogram

A

The paper with the separate components.

44
Q

What is the RF value

A

The distance the compound has risen divided by the distance the solvent has risen

45
Q

What is the Rf value always below

A

1

46
Q

What can paper chromatography be used for

A

Distinguishing pure and impure substances
Identifying substances by comparing the pattern on the chromatogram with the patterns formed by known substances
Identifying substances by calculating their Rf values.

47
Q

How do you separate pure water from the dissolved solids

A

Distillation

48
Q

Describe how distillation works

A

Water is evaporated which leaves the solid minerals behind. If the water vapour is then condensed it turns back into water which is now pure.

49
Q

What are the two physical processes in distillation

A

Evaporation and condensation

50
Q

Why is a condenser more efficient during distillation

A

It means that almost all the water vapour is condensed into water

51
Q

What distillation is used to separate two or more liquids

A

Fractional distillation

52
Q

How does fractional distillation work

A

The liquid mixture is heated. Different liquids will evaporate faster than others. The first fraction of collected condensated vapour has the lowest boiling point

53
Q

How can fractional distillation separate to gases

A

The gases of cold down until they are liquid and then they are heated up slowly again

54
Q

Give three uses of fractional distillation

A

To separate the different products in crude oil
To make alcoholic drinks such as whiskey and vodka
To separate the gases in the air

55
Q

What happens in the fractional column

A

The hot water vapour rises but at first when is hits the cool glass it drips back down into the flask. As the column heats up there will be a temperature gradient. It will be hotter at the bottom and colour at the top. The faction with the lowest boiling point reach the top of the column first and the vapour will then pass into the condenser. If you keep heating factions with higher boiling points will then rise up the column and can be collected later.

56
Q

Core practical: describe the stages of simple distillation for investigating inks

A

Put the ink in the flask and vapours can be led away to be condensed.
Heat the flask of ink using a Bunsen burner.
Continue heating until you have collected a few centimetres of distillate.
Note the maximum temperature obtained.

57
Q

Core practical: describe the stages of paper chromatography for investigating inks

A

Draw a pencil line on a piece of chromatography paper about 2 cm from the bottom.
Add a small spot of ink to the pencil line
Add water to a container about 1 cm
Placed the paper into the container so the paper is supported
Take the paper out before it has reached the top and immediately mark where the solvent travelled
Calculate the Rf value

58
Q

What is the process of producing pure water from the sea

A

Desalination

59
Q

How is water separated from dissolve salts

A

Using simple distillation

60
Q

Why is simple distillation not usually a suitable method for producing large volumes of drinking water

A

Because a lot of energy must be transferred to the sea

61
Q

Where might they use simple distillation for desalination of large volumes

A

When energy resources are plentiful and cheap

62
Q

Why should pure water be used for chemical experiments

A

Because any salts dissolved in the water can affect the results of the experiment

63
Q

What does freshwater from reservoirs contain

A

Objects such as leaves and twigs, small and soluble particles such as grit and silt, soluble substances including salts, pesticides and fertilisers, bacteria and other organisms that may be harmful ro health.

64
Q

What are the main stages of purifying drinking water

A

Coarse filtration, sedimentation, fine filtration, chlorination

Chemistry (12 decks)

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