C1.3 - R* Separating mixtures

Question 1

When analytical chemists working on forensic or medical investigations are given an unknown sample to identify, what often is it?

Answer 1

When analytical chemists working on:
1. Forensic
Or,
2. Medical
investigations are given an unknown sample to identify, it is often a mixture of different substances

Question 2

Mixture

Answer 2

A mixture is made up of:
1. 2
Or,
2. More
substances (elements or compounds) that are not chemically combined together

Question 3

Compounds have a fixed composition.

What does this mean?

Answer 3

This means that the ratio of elements present is always the same in any particular compound

Question 4

Mixtures have no fixed composition.

What does this mean?

Answer 4

This means that the proportions vary depending on the amount of each substance mixed together

Question 5

What must be used, to separate the elements in a compound?

Answer 5

To separate the elements in a compound, chemical reactions must be used

Question 6

How can the different elements or compounds in a mixture be separated again?

Answer 6

The different:
1. Elements
Or,
2. Compounds
in a mixture can be separated again by physical means

Question 7

What are there between atoms of the different elements in the compound?

Answer 7

Between atoms of the different elements in the compound, there are chemical bonds

Question 8

What are there between atoms of the different substances in a mixture?

Answer 8

Between atoms of the different substances in a mixture, there are no chemical bonds

Question 9

Before the substances in a mixture are identified, what happens?

Answer 9

Before the substances in a mixture are identified, they are separated from each other by physical means

Question 10

What physical techniques are available to separate substances in a mixture?

Answer 10

To separate substances in a mixture, the physical techniques available are:

1. Filtration
2. Crystallisation
3. Simple distillation
4. Fractional distillation
5. Chromatography

Question 11

What do the physical techniques to separate substances in a mixture rely on?

Answer 11

The physical techniques to separate substances in a mixture rely on differences in the physical properties of the substances in the mixture

Question 12

What is the technique of filtration used for?

Answer 12

The technique of filtration used to separate substances that are insoluble in a particular solvent from those that are soluble in the solvent
(Insoluble solids from liquids)

Question 13

If your product is an insoluble solid that needs to be separated from a liquid reaction mixture, what can be used?

Answer 13

If your product is an insoluble solid that needs to be separated from a liquid reaction mixture, filtration can be used

Question 14

If your product is an insoluble solid that needs to be separated from a liquid reaction mixture, filtration can be used.
When else can filtration be used?

Answer 14

Filtration can also be used in purification

Question 15

What is the method of filtration?

Answer 15

The method of filtration is that filter paper is folded into a cone shape

Question 16

How can you separate a soluble salt from a solution?

Answer 16

To separate a soluble salt from a solution, there are 2 methods:

1. Evaporation
2. Crystallisation

Question 17

What is evaporation a really quick way of doing?

Answer 17

Evaporation is a really quick way of separating a soluble salt from a solution

Question 18

You can use evaporation only if what?

Answer 18

You can use evaporation only if the salt doesn’t decompose when its heated

Question 19

Decompose

Answer 19

Decompose means to break down

Question 20

If you want to make big crystals of your salt, what method should you use?

Answer 20

If you want to make big crystals of your salt, you should use the method of crystallisation

Question 21

The point of crystallisation

Answer 21

The point of crystallisation is:
1. When small crystals first appear around the edge of the solution/or you see crystals start to form
Or,
2. When crystals appear in a drop of solution extracted from the dish with a glass rod

Question 22

Rock salt

Answer 22

Rock salt is a mixture of:

1. Salt
2. Sand

Question 23

What method can be used to separate rock salt?

Answer 23

To separate rock salt, the methods of:
1. Filtration
2. Crystallisation
can be used

Question 24

Sand and salt are both what?

Answer 24

1. Sand

2. Salt are both compounds

Question 25

To separate a soluble salt from a solution, there are 2 methods: Evaporation and crystallisation. What is a gentler way of heating the evaporating dish rather than using a Bunsen burner and directly on a tripod and gauze?

Answer 25

During evaporation and crystallisation, a gentler way of heating the evaporating dish rather than: 1. Using a Bunsen burner 2. Directly on a tripod and gauze is by using a water bath

Question 26

What does simple distillation allow us to do?

Answer 26

Simple distillation allows us to collect the solvent itself

Question 27

Simple distillation is used for what?

Answer 27

Simple distillation is used for separating out a liquid from a solution

Question 28

A condenser (part of the distillation apparatus)

Answer 28

A condenser (part of the distillation apparatus) is an outer glass tube with water flowing through it that acts as a cooling 'jacket' around the inner glass tube from the flask

Question 29

Water goes what of the condenser?

Answer 29

Water goes: 1. In at the bottom 2. Out at the top of the condenser

Question 30

The problem with simple distillation

Answer 30

The problem with simple distillation is that you can only use it to separate things with very different boiling points

Question 31

What do you do to separate a mixture of liquids with similar boiling points?

Answer 31

To separate a mixture of liquids with similar boiling points, you use fractional distillation

Question 32

Filtration

Answer 32

Filtration is the technique used to separate substances that are insoluble in a particular solvent from those that are soluble

Question 33

Simple distillation

Answer 33

Simple distillation is separation of a liquid from a mixture by evaporation followed by condensation

Question 34

Fractional distillation

Answer 34

Fractional distillation is a way to separate liquids from a mixture of liquids by: 1. Boiling off the substances at different temperatures 2. Then condensing 3. Collecting the liquids

Question 35

Chromatography

Answer 35

Chromatography is the process whereby small amounts of dissolved substances are separated by running a solvent along a material such as absorbent paper

Question 36

What is air?

Answer 36

Air is a mixture of gases, mainly: 1. Nitrogen 2. Oxygen 3. Carbon dioxide 4. Argon

Question 37

Air is a mixture of gases, mainly nitrogen, oxygen, carbon dioxide and argon. These gases all can be what?

Answer 37

These gases all can be separated out fairly easily

Question 38

What is crude oil?

Answer 38

Crude oil is a mixture of different length hydrocarbon molecules

Question 39

The properties of a mixture

Answer 39

The properties of a mixture are a mixture of the properties of the separate parts

Question 40

The properties of a mixture are a mixture of the properties of the separate parts. The chemical properties of a substance aren't affected by it being part of a mixture. Example

Answer 40

For example, a mixture of iron powder and sulfur powder will show the properties of both: 1. Iron 2. Sulfur

Question 41

Simple distillation allows us to collect the solvent itself instead of just letting it evaporate off into the air. Example

Answer 41

For example, some countries with a lack of fresh water sources purify seawater to obtain usable water

Question 42

What can you use simple distillation to do?

Answer 42

You can use simple distillation to get pure water from seawater

Question 43

How can you use simple distillation to get pure water from seawater?

Answer 43

You can use simple distillation to get pure water from seawater, because the water: 1. Evaporates 2. Is condensed and collected

Question 44

The problem with simple distillation is that you can only use it to separate things with very different boiling points. If the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again. If you have a mixture of liquids with similar boiling points, what do you need?

Answer 44

If you have a mixture of liquids with similar boiling points, you need another method instead of simple distillation to separate this

Question 45

Heating ---> Evaporating --->

Answer 45

Heating ---> Evaporating ---> Cooling ---> Condensing

Question 46

The physical techniques to separate substances in a mixture rely on differences in the physical properties of the substances in the mixture. Examples

Answer 46

For example: 1. Different solubilities in a solvent Or, 2. Different boiling points

Question 47

If your product is an insoluble solid that needs to be separated from a liquid reaction mixture, filtration can be used. Filtration can also be used in purification. Example

Answer 47

For example, solid impurities in the reaction mixture can be separated out using filtration

Question 48

You can use evaporation only if the salt doesn't decompose when its heated. If it does, then what will you have to use?

Answer 48

If the salt decomposes when its heated, then you will have to use crystallisation

Question 49

Decompose means to break down. | What does thermal decomposition mean?

Answer 49

Thermal decomposition means to break down with heat

Question 50

Sand and salt are both compounds, but salt dissolves in water, whereas sand doesn't. What does this vital difference in their physical properties give?

Answer 50

This vital difference in their physical properties gives a great way to separate them

Question 51

The different elements or compounds in a mixture can be separated again by physical means, using what?

Answer 51

``` The different: 1. Elements Or, 2. Compounds in a mixture can be separated again by physical means, using the differences in properties of each substance in the mixture ```

Question 52

The method of filtration is that filter paper is folded into a cone shape. What happens to the solid?

Answer 52

The solid is left in the filter paper

Question 53

The method of filtration is that filter paper is folded into a cone shape. What happens to the solid?

Answer 53

The solid is left in the filter paper

Question 54

If you want to make big crystals of your salt, you should use the method of crystallisation, rather than what?

Answer 54

If you want to make big crystals of your salt, you should use the method of crystallisation, rather than evaporation

Question 55

Rock salt is a mixture of salt and sand. | It is what in water?

Answer 55

Rock salt is spread on the roads in winter

Question 56

Sand and salt are both compounds, but what?

Answer 56

Sand and salt are both compounds, but salt dissolves in water, whereas sand doesn't

Question 57

During evaporation and crystallisation, a gentler way of heating the evaporating dish rather than using a Bunsen burner and directly on a tripod and gauze is by using a water bath, but you could also use what?

Answer 57

During evaporation and crystallisation, a gentler way of heating the evaporating dish rather than: 1. Using a Bunsen burner 2. Directly on a tripod and gauze is by using a water bath, but you could also use an electric heater

Question 58

Simple distillation allows us to collect the solvent itself, instead of just what?

Answer 58

Simple distillation allows us to collect the solvent itself, instead of just letting it evaporate off into the air

Question 59

The problem with simple distillation is that you can only use it to separate things with very different boiling points. What happens if the temperature goes higher than the boiling point of the substance with the higher boiling point?

Answer 59

If the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again

Question 60

The properties of a mixture are a mixture of the properties of the separate parts, The chemical properties of a substance aren't affected by it what?

Answer 60

The chemical properties of a substance aren't affected by it being part of a mixture

Question 61

For example, a mixture of iron powder and sulfur powder will show the properties of both iron and sulfur. It will contain what?

Answer 61

A mixture of iron powder and sulfur powder will contain: 1. Grey magnetic bits of iron 2. Bright yellow bits of sulfur

Question 62

You can use simple distillation to get pure water from seawater, because the water evaporates and is condensed and collected. Eventually you'll end up with what?

Answer 62

Eventually you'll end up with just the salt left in the flask

Question 63

You can use simple distillation to get pure water from seawater, because the water evaporates and is condensed and collected. Eventually you'll end up with what?

Answer 63

Eventually you'll end up with just the salt left in the flask

Question 64

The problem with simple distillation is that you can only use it to separate things with very different boiling points. If the temperature goes higher than the boiling point of the substance with the higher boiling point, they will mix again. If you have a mixture of liquids with similar boiling points, you need another method instead of simple distillation to separate this, like what?

Answer 64

If you have a mixture of liquids with similar boiling points, you need another method instead of simple distillation to separate this, like fractional distillation