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Edexcel Chemsitry > Topic 2: States of Matter > Flashcards

Topic 2: States of Matter Flashcards

1
Q

what are the 3 states of matter

A

solid
liquid
gas

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2
Q

how can you model the different states of matter

A

using the particle model

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3
Q

describe how to use the particle model

A

each particle is represented by a solid sphere

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4
Q

draw particle model of a solid

A
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5
Q

describe the arrangement, movement and relative energy of particles in a solid

A

Particles are touching in a fixed regular lattice structure
The particles are not moving and there is no energy.

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6
Q

why are the particles in a solid in a fixed position

A

there are strong forces of attraction between particles which hold them together

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7
Q

explain what happens to solids when they are heated

A

the particles vibrate more as the solid is heated which causes solids to expand.

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8
Q

draw particle model of a liquid

A
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9
Q

describe the arrangement, movement and relative energy of particles in a liquid

A

particles are touching but are free to move past each other, there is more energy than solid particles but less energy than gas particles.

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10
Q

why are liuid particles able to flow over each other

A

the force of attraction beteen particles are not as strong as between solid particles

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11
Q

draw a particle model of a gas

A
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12
Q

describe the arrangement, movement and relative energy of particles in a gas

A

particles are free to move in random motion so have no regular arrangement and travel in straight lines, and have a lot of energy (more energy than solid or liquid state

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13
Q

explain why a gas will escape from a container if it isn’t air-tight

A

gases dont keep a definite shape or volume

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14
Q

what is a feature of gases

A

when particles bounce off walls of a container they exert a pressure on the walls

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15
Q

what happens when gases are heated up

A

the hotter the gas gets, the faster the gas particles move.
gases either expand when heated or their pressure incrases

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16
Q

what is it called when a solid is heated to a liquid

A

melting

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17
Q

explain how melting occurs

A
  • when a solid is heated, its particles gain more energy
  • this makes the [articles vibrate more, which weakens the forces that hold th esolid together. This makes the solid expand
  • at a certain temperature the particles have enough energy to break free from their positions. This is called melting and the solid changes state into a liquid
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18
Q

what is it called when liquid changes state to a gas

A

evaporating

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19
Q

explain how evaporation takes place

A
  • when a liquid is heated, the particles gain more energy
  • this energy makes the particles move faster which weakens and breaks bond holding liquid particles together.
  • at a certain temperature the particle have enough energy to break their bonds. This is called evaporating and the liquid turns to a gas.
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20
Q

what is it called when a gas changes state to a liquid

A

condensation

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21
Q

explain how gases can condense into liquids

A
  • when a gas is cooled, the particles lose energy
  • this loss of energy makes the particles move slower which increases the strength of the bonds holding gas particles together
  • turning gas particles into liquid particles
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22
Q

what is it called when a liquid chnages state to a solid

A

freezing

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23
Q

explain how a liquid changes state into a solid

A
  • when a liquid is cooled, the particles lose energy
  • this loss of energy makes the particles move much slower to the point that they vibrate which increases the strength of the bonds holding liquid particles together
  • turning liquid particles into solid particles
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24
Q

what is it called when a solid changes state to a gas

A

sublimation

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25
Q

what is a physical change

A

when a substance canges from one state of matter to another due to heating or cooling

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26
Q

what is a chemical change

A

happens during chemical reactions where bonds between atoms break and the atoms change places.

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27
Q

how to work out what state substances will be under certain conditions

A
  • the melting point of D is 801 and boiling point is 1413
  • that means it’s a solid below 801 and a gas above 1413 and a liquid in-between.
  • 1000 is between 810 and 1413 so D is a liquid at 1000
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28
Q

what is a pure substance

A

a substance that is completely made up of a single element or compound

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29
Q

Explain the difference between the use of ‘pure’ in chemistry compared with its everyday use and the differences in chemistry between a pure substance and a mixture

A

In everyday use, pure means to be made up of only 1 thing. However, in chemistry, pure means to be made up of only 1 element or compound. A mixture is made up of different substances, mixed together but not bonded.

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30
Q

what is a feature of pure substances

A

they have specific, sharp melting and boiling points

31
Q

what is the difference in melting points between pure substances and mixtures

A
  • pure substances have a specific, sharp melting and boiling point whereas a mixture (or impure substance) will melt gradually over a range of temperatures
32
Q

how can you measure the melting point of a substance

A

use melting point apparatus
- this piece of kit allows you to heat up a small sample of a solid very slowly so you can observe and record the exact temp it melts at

33
Q

what can you do to measure melting point of a substance if there is no melting point apparatus

A

you could use a water bath and a thermometer - although it is harder to contorl temp as exactly as when using melting point apparatus

34
Q

Interpret melting point data to distinguish between pure substances and mixtures

A
  • Adil’s results show that solid B must be a mixture, because it melted over a range of temperatures (rather than melting at a specific temp, as the other 3 solids did)
35
Q

explain What types of mixtures can be separated by using:
simple distillation

A

Simple distillation can be used to separate a mixture of liquids with different boiling points, as it allows the separation of components based on their boiling points.

For example, a mixture of water and ethanol can be separated using simple distillation because ethanol has a lower boiling point than water.

36
Q

how to run a simple distillation experiment to get pure water from seawater

A
  1. pour your sample of seawater into the distillation flask
  2. set up the apparatus as shown in the digram. Connect the bottom end of the condeser to a cold tap using rubber tubing. Run cold water through the condenser to keep it cool
  3. gradually heat the distillation flask. The part of the solution that has the lowest boiling point will evaporate - in this case thats the water
  4. the water vapour passes into the condesner where it cools and condenses. It then flows into the beaker where it is collected.
  5. eventually you will end up with just the salt left in the flask
37
Q

what is the problem with simple distillation

A

you can only use it to separate substances with very different boiling points

38
Q

What types of mixtures can be separated by using:
fractional distillation

A

Fractional distillation is used to separate a mixture of liquids with similar boiling points. It is used when simple distillation cannot achieve complete separation.

39
Q

Show how to carry out the fractional distillation practical

A
  1. put your mixture in a flask. Attach a fractioning column and condenser above the flask as shown
  2. Gradually heat the flask. The different liquid will all have different boiling points - so they will evaporate at different temperatures
  3. the liquid with the lowest boiling point evaporates first. When the temperature on the thermometer matches the boiling point of this liquid, it will reach the top of the column .
  4. liquids with higher boiling points migth also start to evaporate. but hte column is cooler towards the tip, so they will only get part of the way up befre condensing and running back down towards the flask.
  5. when the first liquid has been collected, raise the temperature until the next one reaches the top
40
Q

What types of mixtures can be separated by using:
filtration

A

Filtration is used to separate a mixture of a solid and a liquid or a suspension. The mixture is passed through a filter paper, which traps the solid particles while allowing the liquid to pass through.

41
Q

Explain the experimental techniques for separation of mixtures by FILTRATION

A
  1. A filter funnel is lined with filter paper that has fine holes in it.
  2. The solvent and solute(s) pass through the fine holes to form the filtrate.
  3. Bits of insoluble substances cannot fit through the holes and so leave a residue in the filter paper
42
Q

What types of mixtures can be separated by using:
crystallisation

A

Crystallisation is used to separate a soluble solid from a solution.

43
Q

Explain the experimental techniques for separation of mixtures by CRYSTALISATION

A
  1. pour the solution into an evaporating dish and gently heat the solution. some of the water will evaporate and the solution will get more concentrated
  2. once some of the water has evaporated, or when you see crystals start to form (the point of crystallisation), remove the dish from the heat and leave the solution to cool
  3. the salt should start to form crystals as it becomes insoluble in the cold, high concentrated solution
  4. filter the crystals out of the solution, and leave them in a warm place to dry. You could also use a drying oven or a desiccator
44
Q

you could be asked to pick one of the separation techniques to separate a mixture

A
45
Q

what is chromatography used for

A

method used to separate a mixture of soluble substances and identify them

46
Q

what are the 2 phases of chromatography

A

a mobile phase, a stationary phase

47
Q

what is the mobile phase of chromatography

A

where the molecules can move - this is always a liquid or a gas

48
Q

what is the stationary phase of chromatography

A

where th emolecule can’t move - this can be a solid or a really thick liquid

49
Q

explain how chromatography works

A
  1. the ocmponents in the mixture separate out as the mobile phase moves over the stationary phase - they all ed up in different places in the stationary phase
  2. this happens because each of the chemucals in a miture will spend different amounts of time dissolved in the mobile phase and stick to the stationary phase
  3. how fast a chemicla moves through the stationary phase depends on how it ‘distributes’ itself between the 2 phases
50
Q

Explain the experimental techniques for separation of mixtures by PAPER CHROMATOGRAPHY

A
  1. draw a line near th ebototm of the paper - this is the baseline. Use a pencil (pencil marks are insoluble and won’t move with the solvent as ink might). Put a spot of the micture to be separated on the line
  2. put some of the oslvent into a beaker. Dip the bottom of the paper (but not the spot) into the solvemt.
  3. put a watchglass on the top of the beaker to stop any solvent from escaping away.
  4. the solvent will start to move up the paper. When the chemicals in the mixture dissolve in the solvent, they will move up the paper too.
  5. you will see the different chemicals in the sample separate out, forming spots at different places on the paper
  6. remove the paper from the beaker before the solvent reaches the top. Mark the distance the solvent has moved (the solvent front) in pencil
51
Q

what does the amount of tiime the molecule spend in each phase depend on

A
  • how soluble they are in the solvent (molecules with a higher solublity in the solvent will spend more time in the mobile phase than the stationary phase so they end uo further up the paper)
  • how attracted they are to the stationary phase (molecules that are more attracted to the paper will spend more time in the stationary phase than the mobile phase so end up not being carried as far up the paper)
52
Q

how do you calculate the Rf valuve for each chemical

A
53
Q

what is the rf value

A

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

54
Q

what happens when there are chemicals in your mixture that are colourless

A

you can spray the chromatogram with a chemical called a locating agent to show where the spots are

55
Q

how do you find the distance travelled by the solute

A

measure distance from the baseline to the centre of the spot

56
Q

how can you Distinguish between pure and impure substances on a paper chromatogram

A

Pure substance produces one spot
Impure substance produces two or more spots

57
Q

how can you Identify substances by comparison with known substances

A
  • Paper chromatogram can be used to identify substances
    Two substances are likely to be the same if:
  • Same number + colour of spots
  • Same Rf value of spots
58
Q

You could use a mixture of simple distillation and chromatography t analyse the composition of an ink

A
  1. ink is a mixture of different dyes dissolved in a solvent
  2. to work out what solvent the ink contains, you could tyr doing simple distillation which allows you to evaporate off the solvent and collect it - assuming that the solvent has the lowest boiling point of all the substances in the ink it will evaporate first.
  3. the thermometer in the distillation set-up will read the boiling point of the solvent when it’s evaporating. You can use th eboiling point of the solvent to try and determine what it is e.g. if the solvent in a certain ink evaporated at 100°C, it would be wuite likely to be water
  4. you could carry out paper chromatorgraphy on a sample of the ink - this will separate out the different dyes in the ink, so that you can see how many there are.
  5. you can compare the rf values of the different spots on the chromatogram produced with reference values to work out what dyes are in the ink.
59
Q

what is potable water

A

water that is fit to drink

60
Q

where can we get our water form

A
  • surface water
  • ground water
  • waste water
61
Q

what is surface water

A

water from lakes, rivers and reservoirs.
In much of England and Wales these sources start to run dry during the summer months

62
Q

what is ground water

A

from aquifiers (rocks that rtrap water underground).
In parts of south-east England, where the surface water is very limited, as much as 70% of the domestic water supply comes from ground water.

63
Q

what is waste water

A

from water that’s been contaminated by a human process, e.g. as a by product from some industrial processes. Treating waste water to make it potable is preferable to disposing of the water, which can be polluting.

64
Q

Why might water not be potable?

A
  • Insoluble impurities
  • Soluble impurities
  • Bacteria
65
Q

Describe how waste and ground water can be made potable

A
  1. filtration - a wire mesh screens out large twigs etc. and then gravel and sand beds filter out any other solid bits
  2. sedimentation - iron sulfate or aluminium sulfate is added to the water, which makes fine particles clump together and settle at the bottom.
  3. Chlorination - chlorine gas is bubbled through to kill harmful bacteris and other microbes
66
Q

how else can water be made potable

A

sea water can be distilled to produce drinking water in hot countries

however, distillation need lots of energy so its very expensive especially if you’re producing large quantities

67
Q

What is chemical analysis?

A

Using chemical reactions to identify and measure substances in a sample

68
Q

Describe how water used in analysis must not contain any dissolved salts

A
  • Tap water contains small amounts of dissolved salts which may react to form unexpected cloudy precipitates causing false positives
  • This is why distilled (pure) water should always be used
69
Q

Describe an appropriate experimental technique to separate a mixture, knowing the properties of the components of the mixture

A

any of these:
Simple distillation
Fractional distillation
Filtration
Crystallisation
Paper Chromatography

70
Q

What can be used to make an Rf value more accurate?

A
  • Longer paper
  • Different medium

NOT more accurate ruler/repeat experiment

71
Q

What can be used to increase the effectiveness of distillation?

A

Use a Liebig condenser to increase effectiveness of cooling

72
Q

Why does the solvent in chromatography have to be under the pigments to start with?

A

So the solvent runs through the spots
Otherwise spots transfer onto solvent

73
Q

Why might a pigment not move in chromatography?

A

Insoluble in the solvent used

74
Q

What can be used instead of a bunsen burner to heat?

A

Electric heater
Heating mantle

Edexcel Chemsitry (9 decks)

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