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Chemistry > Topic 10: Qualative Analysis And Nano Particles > Flashcards

Topic 10: Qualative Analysis And Nano Particles Flashcards

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1
Q

How do you carry out a flame test?

A

1) light a Bunsen burner and open the air hole to give a hot blue flame.
2) pick a small amount of the substance using a wire loop.
3) hold the sample in the edge of the flame and observe the flame colour.

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2
Q

Why must the wire loop be placed in hydrochloric acid and what is it made of?

A

It must be cleaned in hydrochloric acid before testing each substance. It is made of platinum so is inert. It also gives no colour to the flame.

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3
Q

Why might nichrome be used instead platinum in the wire loop when flame testing?

A

It is much cheaper but produces a faint orange flame.

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4
Q

What do flame tests test for?

A

Cations produces different flame test colours. Flame tests with work with solid samples and with solutions but flame colours from solids are easier to see.

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5
Q

What flame colour does lithium produce?

A

Red

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6
Q

What flame colour does sodium produce?

A

Yellow

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7
Q

What flame colour does potassium produce?

A

Liliac

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8
Q

What flame colour does calcium produce?

A

Orange-red

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9
Q

What flame colour does copper produce?

A

Blue-green

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10
Q

Machines can also be used instead of flame tests to analyse substances. Using scientific instruments may improve:

A
  • sensitivity (they can detect much smaller amounts)
  • accuracy (they give values closer to the true values)
  • speed.
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11
Q

What is a flame photometer?

A

Measures the light intensity of the flame colours produced by metal ions. Its data is used to determine the concentration of a metal ion in a dilute solution.

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12
Q

What is calibration curve?

A

A graph used to determine the concentration of a substance in a sample.

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13
Q

Define the term standard solution:

A

A solution containing a known concentration of a substance.

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14
Q

How can a metal ion in an unknown solution be identified?

A

matching its spectrum to that of a known metal ion. (A flame photometer separates out the colours to produce a spectrum of light emitted by each metal ion.

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15
Q

Define the term emission spectra:

A

A set of wavelengths of light or electromagnetic radiation showing which wavelengths have been given out (emitted) by a substance.

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16
Q

How can water which has been contaminated from waste produced by mines be cleaned?

A

The polluting metal compounds can be removed by using hydroxide solution. This reacts with the metal ions to produce a precipitate, which settles out and can be removed.

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17
Q

What is a precipitation reaction?

A

It is a reaction in which an insoluble product is formed from 2 soluble reactants.

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18
Q

How can you test for metal ions?

A

Sodium hydroxide solution can be used to test for metal ions in a solution. A few drops of hydroxide solution are added to test the solution. Different metal ions produce different coloured hydroxide precipitates.

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19
Q

What precipitate does iron (ll) produce?

A

Green

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20
Q

What precipitate does iron (lll) produce?

A

Brown

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21
Q

What precipitate does copper produce?

A

Blue

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22
Q

What precipitate does calcium produce?

A

White

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23
Q

What precipitate does aluminium produce?

A

White

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24
Q

How can you distinguish between aluminium and calcium as they both produce a white precipitate when sodium hydroxide is added to the solution containing those ions?

A

Aluminium hydroxide disappears to form a colourless solution when excess sodium hydroxide is added to the solution containing aluminium ions. The solution containing calcium ions stays colourless.

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25
Q

How can you test for ammonium ions?

A

1) Dilute sodium hydroxide solution can also be used to detect ammonium ions.
2) ammonia gas is produced when the mixture containing ammonia warmed.
3) ammonia can be identified from its sharp smell but a confirmatory test is used to identify if ammonia is present.
4) ammonia changes damp red litmus paper to blue.

26
Q

How are carbonate ions (which are negative) tested for in solids and solutions?

A

Add dilute hydrochloric acid to the test substance and look for bubbling caused by the production of carbon dioxide. The bubbles could be another gas so to make sure it’s carbon dioxide collect the gas. Carbon dioxide turns lime water milky.

27
Q

How can you test for sulphate ions (which are negative)?

A

1) add a few drops of dilute hydrochloric acid to the solution.
2) this acidified the solution and removes carbonate ions that might also give a precipitate in the test.
3) then add a few drops of barium chloride solution.
4) a white precipitate of barium sulphate forms if the sample contains sulphate ions.

28
Q

What kind of compounds to halogens form?

A

They are non-metal elements and form halide ions.

29
Q

How can you identify halide ions in a solution?

A
  • add a few drops of dilute nitric acid.
  • this acidifies the solution and removes any carbonates that may form a precipitate in the test.
  • then add a few drops of solider nitrate solution.
  • different coloured silver halide precipitates form, depending on the halide ion present.
30
Q

What are the different silver halide precipitate colours?

A

Bromide - cream
Chloride - white
Iodide - yellow

31
Q

What are ceramics?

A

A range of durable compounds that change very little when heated.

32
Q

What are the properties of ceramics?

A
  • chemically inert
  • hard
  • stiff
  • brittle
  • poor electrical and thermal conductors
  • high melting points
33
Q

What kind of structures make up ceramics and how does this give them their properties?

A

Ceramic materials consist of giant structures with many strong bonds (covalent or ionic), giving them their typical properties.

E.g strong covalent and ionic bonds = high melting point

34
Q

Give 3 examples of clay ceramics:

A
  • china
  • brick
  • porcelain
35
Q

How are clay ceramics formed?

A

Made from clay moulded into the desired shape. When heated to a very high temperature tiny crystals form and join together. Sometimes china and porcelain are glazed and heated gain to form a hard, waterproof surface to be used as tiles (etc).

36
Q

How is glass made?

A

Glass is made by melting sand and then allowing it to cool and solidify.

37
Q

What similar properties to glass and clay ceramics share and how are they different.

A

Both have giant structures.

However, the atoms in glass are not arranged in regular way so glass is transparent instead of opaque like clay.

38
Q

What are polymers?

A

These are substances with high average relative masses. They are made from monomers. Smaller molecules that join together to form repeating units.

39
Q

What do properties of a polymer depend on?

A

Polymers can be moulded into complex shapes. Its properties depend on its structure and chemical composition.

40
Q

What are some of the usual properties of a polymer?

A
  • strong
  • chemically inert
  • poor electrical and thermal conductors
41
Q

What are some of the properties of a metal?

A
  • strong
  • hard
  • shiny solids
  • high melting points
  • good electrical and thermal conductors
  • malleable
42
Q

What are alloys and why can they be more useful than metal elements?

A

Alloys are a mixture of different elements. They are often stronger than individual metals.

43
Q

Why might some metals be electroplated?

A

They can be electroplated with an inert metals to improve their appearance or their resistance to corrosion.

44
Q

What is a composite material?

A

A mixture of 2 or more materials, combined to produce material with improved properties.

The individual materials often have contrasting properties. They are also usually visible in the composite material and can be separated out by physical separation methods.

45
Q

How is concrete made?

A

1) mix cement, sand, aggregate (small stone and gravel) and water together.
2) as it sets hard chemical reactions happen that bond the solid components together.
3) the sand and aggregate form the reinforcement of the concrete.
4) the reinforcement is bonded together by cement with forms the matrix.

46
Q

Define the term reinforcement:

A

In a composite material, the substance that is bound together by the matrix material.

47
Q

Define the term matrix:

A

In a composite material, it is the substance that binds the reinforcement material together.

48
Q

What are some of the properties of glass fibres?

A
  • brittle
  • have a low density
  • have a high tensile strength (resist being stretched).
49
Q

What is meant by compressive strength?

A

A measure of how well a material resists being squashed.

50
Q

What is the compressive strength of concrete and what does this mean concrete can be used for?

A

Sting in compression but weak in tension. Therefore it is suitable for road surfaces and for foundations where it will be squashed.

However, concrete beams tend to crack along their lower surfaces, which is stretched when a beam carries a load.

51
Q

Why are steel and concrete often used together?

A

Steel is dense than concrete but has a higher tensile strength - can withstand high tensions. Still reinforced concrete consists of a framework of steel bars with concrete lured in and around it. The material together is cheaper than steel still alone and less dense, and has a high tensile and compressive strength. It can also withstand high tension.

52
Q

Is wood a natural composite material?

A

Yes.

53
Q

What does wood consist of?

A

Consists of cellulose fibres in a matrix of a polymer called lignin. It is stringer along this grains than across its grain.

54
Q

What is a nanoparticle?

A

A piece of material consisting of a few hundred atoms and between 1nm to 100nm in size.

55
Q

What size are nanoparticles relative to other products?

A

Nanoparticles are bigger than atoms but smaller than cells.

56
Q

How do nanoparticles occur?

A

Naturally but can be manufactured.

57
Q

How are substances that consist of nanoparticles described?

A

As being nano-particulate.

58
Q

How to calculate surface area to volume ratio?

A

SA / Volume

59
Q

Uses of nanoparticles:

A
  • they have a large SA:V ratio which makes them useful as catalysts. E.g they can break down dirt to keep it of materials like satin resistant cloth.
  • nano-particulate titanium dioxide is transparent because it’s particles are very small, but it absorbs ultraviolet radiation. This makes it useful for almost invisible sun cream. Ultraviolet radiation can cause skin cancer.
60
Q

What are some of the risks of nanoparticles?

A

-scientists worry they may pose a risk to the environment and human health.

61
Q

How may nanoparticles pose a threat to human health?

A
  • They are small so can be breathed in.
  • they can pass through cell surface membranes due to their size.
  • their large SA:V ratio alloys them to catalyse human reactions or to carry toxic substances bound to their surfaces.
62
Q

Why are the risks of nanoparticles hard to determine?

A

They have not been used for long so scientists do not know their long term effects on the environment or the health of humans and animals.

Chemistry (14 decks)

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