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Chemistry > 1 Elements, Compounds and Mixtures > Flashcards

1 Elements, Compounds and Mixtures Flashcards

1
Q

What is an element?

A

Substances that can’t be split into anything simpler by chemical means. It contains only one type of atom.

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2
Q

What is a compound?

A

When two or more elements are chemically combined and are always in fixed proportion.

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3
Q

How do we seperate the elements in a compound?

A

With a chemical reaction.

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4
Q

What is a mixture?

A

Different elements or compounds not chemically combined together.

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5
Q

How can mixtures be seperated?

A

By physical means.

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6
Q

What kind of things melt and boil at a fixed temperature?

A
  • Pure substances
  • Elements
  • Pure compounds
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7
Q

What happens to the melting and boiling point of mixtures?

A

They melt and boil over a range of temperatures.

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8
Q

How does the presence of impurities affect the melting and boiling points?

A
  • They lower the melting point
  • They raise the boiling point
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9
Q

What are physical separation techniques used for?

A

To separate mixtures.

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10
Q

What are the separation techniques used for?

A
  • Simple distillation
  • Fractional distillation
  • Filtration
  • Crystallisation
  • Paper chromatography
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11
Q

What does insoluble mean?

A

That the solid won’t dissolve in a liquid.

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12
Q

What does soluble mean?

A

That the solid will dissolve in a liquid.

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13
Q

What is an aqueous solution?

A

It means that the substance is dissolved in water.

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14
Q

What is filtration?

A

It is used to separate an insoluble solid from a liquid.

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15
Q

What is the residue?

A

The substance left in the filter paper.

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16
Q

What is the filtrate?

A

The liquid that comes through.

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17
Q

What is an example of the substances that could be used in filtration?

A

Silver chloride (AgCI) and water (H2O).

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18
Q

What are the results found from using filtration?

A

The insoluble solid will be on top of the filter paper, and the liquid will be in the beaker at the bottom.

19
Q

What is crystallisation?

A

It is used to separate a soluble liquid from a liquid.
(Solute from a solution).

20
Q

What is an example of substances that can be used in crystallisation?

A

Sodium chloride and water.

21
Q

How does crystallisation work?

A

The water evaporates and leaves behind the soluble solid in a crystal form.

22
Q

How can you make crystallisation happen faster?

A

You can gently heat the solution to make the water evaporate faster.

23
Q

What is simple distillation?

A

Used to separate a liquid from a solid when we want to keep the liquid.

24
Q

How does simple distillation work?

A

We evaporate the liquid by heating it and then the vapour turns back into the liquid by condensing it.

25
Q

What does the condenser do?

A

Turns the gas into a liquid.

26
Q

What is an example of substances that can be used in simple distillation?

A

Obtaining drinking water from sea water.

27
Q

What is fractional distillation?

A

Separates a mixture of liquids.

28
Q

What needs to be special about the liquids?

A

They need to have different boiling points.

29
Q

What does the fractionating column contain?

A

Glass beads.

30
Q

How do the glass beads help in fractional distillation?

A

Their high surface area in the column help with the separation of the vapours.

31
Q

What is chromatography?

A

It allows us to separate substances based on their different solubilities.

32
Q

How does chromatography work?

A

The solvent makes its way up the paper and brings the ink with it.

33
Q

What does the line on the chromatography paper have to be made out of and how much further up does it have to be from the bottom of the paper?

A

Pencil and 10cm up.

34
Q

Why does it have to be pencil?

A

Because if it was pen, the ink would move up the paper with the solvent.

35
Q

What does it mean if there are multiple spots?

A

It is a mixture of substances.

36
Q

What does it mean if there is only one spot?

A

The substance is pure - only made up of one colour.

37
Q

What is the solvent front?

A

The highest level of the solvent on the paper at any time.

38
Q

What is the solvent usually made from?

A

A non-aqueous solution.

39
Q

What affects the result found in chromatography?

A
  • Their affinity (stickiness to the paper)
  • How soluble they are (moves up the paper)
40
Q

What is a chromatogram?

A

The pattern you get.

41
Q

What does it mean if the dye doesn’t move?

A

It is not soluble in the solvent.

42
Q

What does it mean if the dye moves too much up the paper?

A

It is too soluble in the solvent.

43
Q

What does the retardation factor show?

A

It is a value to describe how far the spots move.

44
Q

How do you work out the retardation factor?

A

Distance moved by a spot (from the pencil line) / Distance moved by the solvent front (from the pencil line)

Chemistry (22 decks)

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