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GCSE Chemistry > C2.1 - Purity And Separating Mixtures > Flashcards

C2.1 - Purity And Separating Mixtures Flashcards

1
Q

What is relative atomic mass?

A

Mean mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom

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2
Q

What is the chemical formula?

A

How many atoms of each element there are in a unit of substance

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3
Q

What is relative formula mass?

A

The mean mass of a unit of substance compared to 1/12 the mass of a carbon-12 atom

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4
Q

What is an empirical formula?

A

The simplest whole-number ratio of the atoms of each element in a substance

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5
Q

What does pure mean?

A

A substance that consists of just one type of substance

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6
Q

Are all mixtures pure or impure?

A

Impure

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7
Q

What does impure mean?

A

A substance that contains more than one element or compound

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8
Q

What is an alloy?

A

A mixture of a metal with one or more elements

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9
Q

How does melting point tell us if a substance is pure/impure?

A

Its melting point is less than that of the pure substance
Melts at a range of temperatures

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10
Q

The temperature of a substance remains … when it melts

A

Constant

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11
Q

What is a solute?

A

A substance that dissolves

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12
Q

What is a solvent?

A

A substance that a solute dissolves in

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13
Q

What is a solution?

A

The product formed when one substance dissolves in another

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14
Q

TRUE OR FALSE?
Substances can be soluble in one substance but insoluble in another substance?

A

True

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15
Q

What does filtration do?

A

Separates an insoluble substance in its solid state from substances in the liquid state

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16
Q

How does filtration work?

A

A solution is poured into filter paper
The tiny holes in the filter paper allow the liquid to pass through as the filtrate whilst leaving the solid behind as the residue

17
Q

In filtration, what is the name of the solid left behind by the filter paper?

A

Residue

18
Q

In filtration, what is the name of the liquid that passes through the filter paper?

A

Filtrate

19
Q

What does crystallisation do?

A

Separates the solute from the solvent

20
Q

How does crystallisation work?

A

When you heat the solution, the solvent evaporates, leaving the solute behind

21
Q

Why does crystallisation take a long time?

A

It needs to be gently heated until it becomes a saturated solution

22
Q

What does simple distillation do?

A

Separates the solvent from the solution

23
Q

How does simple distillation work?

A

The solution is heated, the solvent boils to escape the solution in gas state.
Cooled and condensed back into liquid state in another container by condenser

24
Q

What does simple distillation rely on?

A

The solvent having a much lower boiling point than the solute

25
Q

What does fractional distillation do?

A

Separates two or more substances from a mixture in liquid state

26
Q

How does fractional distillation work?

A

The two substances with the lowest boiling points boil into the fractionating column, where they condense and separate

27
Q

What does fractional distillation rely on?

A

The substances having very different boiling points

28
Q

What does chromatography do?

A

Separates mixtures of coloured compounds

29
Q

What are the two phases of chromatography?

A

Stationary phase - does not move
Mobile phase - does move

30
Q

What is the stationary phase in TLC Chromatography?

A

Thin layer of silica or aluminum powder

31
Q

How do you calculate Rf value in chromatography?

A

Distance travelled by substance
___________________________________
Distance travelled by solvent

32
Q

Why is an element like nitrogen used as the mobile phase in gas chromatography?

A

It is a noble gas, so it is unreactive with the sample

33
Q

In gas chromatography, how do we tell which component bonds strongest to the stationary phase?

A

How fast it travels through the column

34
Q

What are the advantages of using TLC over Paper chromatography?

A

Quicker
More sensitive, so smaller samples can be used
Larger range of stationary phases and solvents to choose from

35
Q

What separation method should you use when separating insoluble and soluble substances?

A

Filtration

36
Q

What separation method should you use when separating a solute dissolved in a solvent?

A

Crystallisation

37
Q

What separation method should you use when separating a liquid from the solution?

A

Simple distillation

38
Q

What separation method should you use when separating two or more liquid substances?

A

Fractional distillation

39
Q

What separation method should you use when separating coloured soluble substances?

A

Paper chromatography
Thin-layer chromatography

GCSE Chemistry (7 decks)

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