CC2 Separating substances Flashcards

(26 cards)

1
Q

What is an insoluble substance?

A

a substance that isn’t dissolveable

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2
Q

What is a soluble substance?

A

soluble is a substance that can be dissolved

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3
Q

What is a solvent?

A

A liquid used to dissolve a solute

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4
Q

What is a solution?

A

a mixtured formed by a solute dissolving in a solvent

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5
Q

What is a solute?

A

A solid that is dissolved

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6
Q

How can chromatography show the difference between pure and impure substances?

A

Pure ones will only make one dot, impure substances will make more

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7
Q

How is the Rf value calculated?

A

distance moved by spot/distance moved by solvent

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8
Q

What does a substance’s Rf value depend on?

A

How soluble it is in the solvent

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9
Q

In chromatography, why must the substances be placed on a pencil line?

A

Pencil will not dissolve in the solvent

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10
Q

In chromatography why must the solvent height be lower than the pencil line?

A

So that the substances do not dissolve into the solvent off the paper

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11
Q

How is the melting point of a pure substance different from that of an impure substance?

A

Pure substance has one specific melting point. Impure substance has a melting range.

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12
Q

What is simple distillation used to separate?

A

A single liquid from a mixture

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13
Q

What is fractional distillation used to separate?

A

Multiple liquids of different boiling points

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14
Q

What is filtration used to separate?

A

An insoluble solid from a liquid

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15
Q

What is crystallisation?

A

Forming crystals of a soluble solid from a solution.

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16
Q

What is potable water?

A

Drinking water

17
Q

How can sea water be made potable?

A

By distillation

18
Q

What are the stages used to make water potable.

A

Sedimentation, filtration and chlorination

19
Q

What is a pure substance?

A

A substance made of one type of atom or molecule only.

20
Q

How would you separate water from salt water?

A

Simple distillation

21
Q

How would you separate salt from salt water?

A

Crystallisation

22
Q

Why must chemical analysis be done with pure water?

A

Because dissolved salts in non pure water would give false positive results.

23
Q

How is the melting point of a mixture different from a pure substance?

A

A pure substance has a single melting temperature, a mixture has a range of melting points.

24
Q

In chromatography, what would cause an ink not to produce any pattern?

A

If the ink was not soluble in water

25
In chromatography, what could you change if an ink did not produce any pattern?
change the solvent to one the ink is soluble in i.e. ethanol instead of water
26
How is water produced by sedimentation, filtration and chlorination different from pure water?
It contains small amounts of dissolved salts / ions