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Chemistry > Topic 2 - states of matter and mixtures > Flashcards

Topic 2 - states of matter and mixtures Flashcards

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1
Q

Describe the arrangement of movement of particles in solids

A

Tightly packed together in a regular arrangement

Vibrate in fixed positions

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2
Q

Describe the arrangement and movement of particles in liquids

A

Close together but able to move past each other

Vibrate and move around each other

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3
Q

Describe the arrangement and movement of particles in gases

A

Well separated with no regular arrangement

Vibrate and move freely at high speeds

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4
Q

Compare the relative Energies of particles in solids, liquids and gases

A

Particles in a solid have the least amount of energy and particles in a gas have the most energy

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5
Q

What does interconversion of state mean?

A

When matter changes from one state to another due to changes in temperature or pressure

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6
Q

What are the names for the state changes from solid to liquid and vice versa?

A

Solid to liquid: melting

Liquid to solid: freezing

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7
Q

What are the names for the state changes from liquid to gas and vice versa?

A

Liquid to gas: evaporation

Gas to liquid: condensation

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8
Q

Describe the forces between particles in solids

A

Strong forces of attraction between particles which keeps them in their fixed positions

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9
Q

Describe the forces between particles in liquids

A

Weaker attractive forces than in solids

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10
Q

Describe the forces between particles in gases

A

Weakest intermolecular forces so particles are in random movement

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11
Q

How does a physical change differ from a chemical change?

A

A physical change involves changes in the forces between particles. The particles themselves remain the same and the chemical properties stay the same.
A chemical change is different as it affects the chemical properties of a substance

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12
Q

Are physical changes relatively easy to reverse?

A

Yes, because no new product is formed during the changes if state

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13
Q

What is the term describing when a solid changes straight Into a gas?

A

Sublimation

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14
Q

Describe what happens, in terms of particles, when a solid is heated and melts into a liquid

A

The particles absorb thermal energy which is converted into kinetic energy. The particles in the solid vibrate more. This causes the solid to expand until the structure breaks and becomes a liquid

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15
Q

Describe what happens, in terms of particles, when a liquid is heated and evaporated into a gas

A

The particles expand and some on the surface gain sufficient energy to overcome the intermolecular forces and evaporate. At the boiling point, all of the liquid particles gain enough energy to evaporate

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16
Q

What is a mixture?

A

A substance that contains 2 or more elements or compounds that are not chemically combined together.

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17
Q

What is a pure substance?

A

A single element or compound, not mixed with any other substance

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18
Q

How can you use melting point data to distinguish between pure substances and mixtures?

A

Pure substances have a sharp exact melting point whereas mixtures melt over a range of temperature since they consist of several elements/compounds

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19
Q

When is simple distillation used?

A

To separate a pure liquid from a mixture of liquids. Only works when the liquids have different boiling points

20
Q

How can ethanol be separated from water?

A

Simple distillation

21
Q

When is fractional distillation used to separate mixtures?

A

To separate all the elements/compounds in a mixture.

22
Q

What is the difference between fractional and simple distillation?

A

Simple distillation is Andy able to separate the liquid with the lowest boiling point from the mixture
Fractional distillation separates all the chemicals in a mixture, using their different boiling points

23
Q

How does fractional distillation work?

A

Oil is heated until it evaporates into the fractionating column.
Vapours rise up the fractionating column and condense at the different fractions, depending on the relative boiling point of each substance

24
Q

What sort of mixtures can filtration be used to separate?

A

An insoluble substance from a solution

25
Q

When is the process of crystallisation used to separate a mixture?

A

To separate a soluble solid from a solution if the solid decomposes when heated

26
Q

What process can be used to identify substances in a mixture?

A

Chromatography

27
Q

Describe the process of crystallisation

A

Pour the solution into an evaporating dish and heat gently
When the crystals start to form, remove the dish from the heat and leave to cool
Once cold, filter the crystals out of the solution and leave them in a warm place to dry

28
Q

Describe the process of filtration

A

Place filter paper in a funnel
Pour the solution containing an insoluble substance through the funnel into a conical flask
The insoluble substance will collect on the filter paper and the solution will collect in the conical flask

29
Q

How does paper chromatography work to separate a mixture?

A

The mobile phase (solvent) moves through the stationary phase (paper) so anything dissolved in the mobile phase will move up the paper
Compounds interact differently with each phase so will move different distances through the stationary phase meaning they will be separated.

30
Q

How can chromatography show the composition of a mixture?

A

Different coloured substances in the mixture will separate as they have different solubilities in the solvent and will travel at different rates

31
Q

Why should pencil be used to draw the line along the bottom of the chromatography paper?

A

It will not affect the experiment as it is insoluble in the solvent

32
Q

Why should the water (solvent) in the beaker for paper chromatography be no deeper then 1cm deep?

A

If it is deeper it will wash away the substances placed on the line on the chromatography paper

33
Q

Why should you use a lid when carrying out paper chromatography?

A

To prevent the solvent evaporating

34
Q

How many spots will a pure substance produce on a chromatogram?

A

Only one

35
Q

How many spots will an impure substance produce on a chromatogram?

A

As it contains more than one compound so it will produce more spots (one spot for each chemical)

36
Q

What is an Rf value?

A

The ratio between the distance travelled by the dissolved substance (the solute) and the distance travelled by the solvent

37
Q

How do you calculate arc values?

A

Distance travelled by substance/distance travelled by solvent

38
Q

When measuring the distance moved by a substance on the chromatography paper, where should you measure between

A

From the pencil baseline to the middle of the spot of the substance

39
Q

Will substances with a higher solubility in the solvent travel further up the chromatography paper? Why?

A

Yes because they will stay dissolved in the solvent for longer

40
Q

How could you separate salt from a mixture of sand and salt?

A

Add water to the mixture
Filter the solution to remove the insoluble sand
Evaporate the water to collect the salt crystals

41
Q

How can liquids be separated if they have different densities?

A

They will naturally sit on two layers so use a flask with a tap on the bottom. Open the tap to collect the bottom liquid

42
Q

What does potable mean?

A

Safe to drink

43
Q

How can waste and groundwater be made potable?

A

Sedimentation: large insoluble particles sink to the bottom after the water is left still for a while
Filtration: removes small insoluble particles by passing the water through layers of sand and filters
Chlorination: kills bacteria and microorganisms which are too small to be removed by filtration

44
Q

How can see water be made potable?

A

Distillation

45
Q

What issues surround the process of making seawater potable?

A

Extremely expensive as it requires a lot of energy to boil large volumes of water
Wastewater is toxic due to the high concentration of salt so must be disposed of carefully

46
Q

What is deionised water?

A

Water that has had metallic ions (such as copper or calcium ions removed

47
Q

Why is deionised water used in experimental analysis?

A

It is uses to prevent ions in the water interacting with the substances under analysis. If it wasn’t deionised, false positive results may be produced

Chemistry (8 decks)

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