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OCR GCSE CHEMISTRY > Paper 3 > Flashcards

Paper 3 Flashcards

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1
Q

Which state expands to fill the container it is in?

A

Gas

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2
Q

What kind of changes are physical changes?

A

When a substance changes state or shape, or breaks into new pieces

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3
Q

Compare forces of attraction between gas and solid state.

A

Gas state- no forces of attraction between particles

Solid state- strong forces of attraction between atoms, so particles are held in fixed positions in a regular lattice arrangement

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4
Q

Describe the movement of liquid particles

A

They are constantly moving with random motion. They are free to move past each other, but tend to stick closely together.

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5
Q

Limitations of the particle model to describe matter

A
  • particles are not solid spheres in reality (they’re atoms ions or molecules)
  • it does not show the forces between particles, so you cannot tell how strong the forces are
  • it doesn’t give you any idea of the size of the particles, or the space between them
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6
Q

How did John Dalton describe atoms?

A

Solid spheres, with different spheres making up different elements

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7
Q

What did the gold foil experiment show?

A

That the nucleus of an atom is tiny, and that most of the atom is empty space.

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8
Q

What was the plum pudding model of the atom?

A

It described atoms as spheres of positive charge, which contained negatively charged electrons.

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9
Q

How did alpha particles provide evidence to support the theory of the nuclear atom?

A

Alpha particles were fired at a thin sheet of gold. Most of the particles went straight through the sheet, but some were deflected more than expected and a small number were even deflected backwards.

This meant that the positive charge couldn’t be spread out evenly within atoms (as described by the plum pudding model). Instead, there must be a tiny, positively charged nucleus at the centre with electrons surrounding it.

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10
Q

What did Bohr suggest about the arrangement and movement of electrons in an atom?

A

That electrons are contained in shells/fixed orbits, and that each shell has a fixed energy. His theory stated that the electrons can only be found in these shells (and not in between them).

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11
Q

Charge and mass of neutron

A

Charge is 0
Relative mass is 1

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12
Q

Typical size of a simple molecule

A

10^-10 m

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13
Q

What does mass number tell you?

A

Total number of protons and neutrons in the atom

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14
Q

How is the modern periodic table arranged?

A

In order of increasing atomic number, in rows called periods. Elements with similar chemical properties form groups.

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15
Q

What charge ions do group 7 form?

A

1-

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16
Q

Forces in an ionic bond

A

Strong electrostatic forces of attraction.

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17
Q

Limitation of dot and cross diagram to represent ionic compounds

A

It doesn’t show the structure of an ionic compound

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18
Q

Why do ionic compounds like Magnesium Bromide have a high melting point?

A

The ions are closely packed in a lattice arrangement, with very strong electrostatic attraction between the oppositely charged ions. A lot of energy is needed to overcome this strong attraction, so magnesium bromide has a high melting point.

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19
Q

What is a covalent bond?

A

A shared pair of electrons

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20
Q

One limitation of ball and stick models to represent covalent bonds

A

They suggest there are big gaps between atoms, when in reality this is where the electron clouds interact.

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21
Q

Why don’t simple molecular substances conduct electricity?

A

They don’t have free electrons or ions

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22
Q

How many covalent bonds in graphene?

A

3

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23
Q

Describe the structure of fullerenes

A

Molecules of carbon, shaped like hollow balls or tubes. The carbon atoms are arranged in rings.

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24
Q

Why do giant covalent structures have high melting points?

A

In order to melt a giant covalent structure, you have to break the strong covalent bonds between the atoms. This requires a lot of energy, so giant covalent structures have high melting points.

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25
Q

Explain how the structure of graphite makes it soft and slippery

A

Graphite has a layered structure, with only weak forces of attraction between the layers. This means the layers can easily break away from each other and slide over each other.

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26
Q

How does the size of an atom compare to the size of a nano particle?

A

Atoms are smaller than nano particles (about 0.1-0.5nm compared to 1-100nm)

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27
Q

Why are people worried about the use of nano particles in medicine?

A

Their effect on the human body isn’t fully understood and the long term heath benefits aren’t known.

28
Q

When does a polymerisation reaction occur?

A

When a polymer is formed from its monomer

29
Q

Poly(ethene) is a polymer. Describe the structure and bonding of a polymer.

A

They are made up of long chains of covalently bonded atoms. There are intermolecular forces of attraction between the chains, which can be strong or weak.

30
Q

Explain why H2O has a much lower melting point than Li2O

A

Water- simple molecular structure, with weak intermolecular forces which are easily overcome

Lithium oxide- giant ionic lattice structure with strong electrostatic forces of attraction holding the ions in place which are difficult to overcome

31
Q

Why don’t giant covalent structures conduct electricity?

A

They don’t usually have free electrons or ions, which are needed to carry a charge.

32
Q

Pure substance

A

Only contains one element or compound

33
Q

What is brass made of?

A

Copper and zinc

34
Q

In fractional distillation, where is the hottest point of the fractionating column?

A

At the bottom

35
Q

How to safely heat flammable compounds?

A

Using an electric heater or a water bath, rather than a Bunsen burner, to reduce the risk of the mixture catching fire.

36
Q

When can filtration be used to separate a mixture?

A

When you have a mixture of an insoluble solid and a liquid

37
Q

When can crystallisation be used to separate a mixture?

A

To separate a soluble solid from a solution

38
Q

Equipment for crystallisation

A
  • evaporating dish and a heat source
  • beaker or flask
  • funnel
  • filter paper
39
Q

Why should you put a lid on the container during a thin-layer chromatography experiment?

A

To stop the solvent from evaporating

40
Q

Why do different dyes move up different distances of the paper in paper chromatography?

A

Because each dye has a different solubility in the solvent and a different attraction to the stationary phase. The higher the solubility of the dye the less attracted it is to the paper, the more time it spent in the mobile phase, and so the further it was carried up the paper.

41
Q

What will an insoluble substance do in paper chromatography?

A

It will stay on the baseline because it can’t move up the stationary phase if it doesn’t dissolve in the solvent.

42
Q

What is the retention time of a substance?

A

The time taken for a chemical to pass through the tubing in gas chromatography apparatus

43
Q

What ion is produced by all alkalis in aqueous solutions?

A

OH-

44
Q

What ions do acids form in water?

A

H+

45
Q

Weak acid

A

Partially ionises in solution. Only a small proportion of acid particles dissociate to release H+ ions.

46
Q

Precipitation reactions

A

Occur between two soluble salts, to form an insoluble salt

47
Q

Imagine you are making a soluble salt by adding an insoluble base to an acid. How will you know when all the acid has been neutralised?

A

The excess solid will sink to the bottom of the flask and start to build up there

48
Q

Describe a method that can be used to make a pure, dry sample of an insoluble salt.

A

Choose two appropriate soluble salts and add one spatula of each to separate test tubes. Add deionised water to each test tube and shake thoroughly to dissolve each salt. Tip the two solutions into a beaker and stir well- the salt should precipitate out.

Use deionised water to remove any left over precipitate from the beaker and to rinse any remaining solution off the filter paper. Scrape the salt onto fresh filter paper and leave to dry.

49
Q

4 ions in copper Sulfate solution

A

Cu2+, SO4 2-, H+, OH-

50
Q

Solid magnesium cannot flow, but liquid magnesium can flow.

Explain why.

A

Particles in a solid are in fixed positions. Particles in a solid vibrate. Particles in a liquid can move past each other as forces between particles in a liquid are less than in a solid.

51
Q

Solid magnesium cannot be compressed. Why?

A

Particles are already tightly packed

52
Q

Why do gases fill any container three are in?

A

Particles are moving quickly in all directions as there are weak forces of attraction between the particles.

53
Q

How make a pure, dry sample of sodium chloride from a solution HCl and a solution of NaOH.

A

You use titration. Put the acid in a burette then use a Pipette to put a known volume of sodium hydroxide into the flask.

Use a (named) indicator and add acid to sodium hydroxide until the colour of the indicator changes.

Repeat to get an accurate value and repeat again with no indicator. Evaporate off the water/crystallise.

54
Q

What makes an acid dilute?

A

Small amount of acid per unit of volume

55
Q

Why do simple molecules have low boiling points?

A

Simple molecules have weak intermolecular forces between molecules.

56
Q

Explain why metals are malleable

A

They have layers of particles which slide over each other.

57
Q

Suggest a possible risk of using nano particles in sun cream

A

They could be breathed in/absorbed by skin

58
Q

Size of nano particle

A

1-100nm

59
Q

A scientist wants to improve the separation of the mixture of alcohols
Suggest a piece of equipment he could use

A

A fractionating column as it has a larger SA

60
Q

Explain why combustion is an exothermic reaction

A

More energy is released when making the bonds than taken in during bond breaking

61
Q

Element C burns in oxygen to make white clouds of its oxide
Describe how you could test the oxide to find out if the element is a metal

A

Dissolve the gas or oxide in water (make a solution). Add universal indicator. pH of over 7 is a metal, it would turn blue.

62
Q

Metallic bonding

A

Metallic bonding is the electrostatic attraction between positive metal ions and delocalised electrons.

63
Q

Why are alloys harder than metals?

A

They have different size atoms which makes it more difficult for them to slide over each other.

64
Q

What is the purpose of repeating a titration?

A

To obtain concordant results, allow a mean titre to be calculated, reduce the effect of random error

65
Q

Describe how to set up a titration

A

Use a Pipette to add a known volume of alkali to a conical flask. Add a few drops of indicator. Fill the burette with acid slowly whilst swirling.

66
Q

How do you know the end of the titration has been reached?

A

First permanent colour change

OCR GCSE CHEMISTRY (6 decks)

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