C12.1 - Pure substances and mixtures

Question 1

In advertising a product, what is pure taken to mean?

Answer 1

In advertising a product, pure is taken to mean ‘has had nothing added to it’

Question 2

In advertising a product, pure is taken to mean ‘has had nothing added to it’ and that it is in its natural state.
Example

Answer 2

For example, pure orange juice means from freshly squeezed oranges

Question 3

What does a pure substance mean to a chemist?

Answer 3

To a chemist, a pure substance is one that is made up of just one substance:
1. An element
Or,
2. A compound

Question 4

You can use what to identify pure substances?

Answer 4

You can use:
1. Boiling points
2. Melting points
to identify pure substances

Question 5

A test for water

Answer 5

A test for water is using white anhydrous copper sulfate

Question 6

A test for water is using white anhydrous copper sulfate.
If water is present, it will turn blue.
But, what does this test tell you?

Answer 6

This test tells you if water is present

Question 7

The test for pure water

Answer 7

The test for pure water is that its:

1. Melting point is exactly 0 degrees Celsius
2. Boiling point is exactly 100 degrees Celsius

Question 8

Fixed points

Answer 8

Fixed points are the:
1. Melting
2. Boiling points
of an element or a compound

Question 9

Why can you use melting points or boiling points to identify substances?

Answer 9

You can use melting points or boiling points to identify substances, because pure substances have characteristic, specific temperatures at which they:

1. Melt
2. Boil

Question 10

You can use melting points or boiling points to identify substances, because pure substances have characteristic, specific temperatures at which they melt and boil.
Where can these fixed points be looked up?

Answer 10

These fixed points can be looked up in:
1. Databooks
Or,
2. Databases stored on computers

Question 11

What will vary, depending on the composition of the mixture?

Answer 11

The:
1. Melting point
2. Boiling point
of a mixture will vary, depending on the composition of the mixture

Question 12

A mixture does not have a sharp what?

Answer 12

A mixture does not have a sharp:
1. Melting point
Or,
2. Boiling point

Question 13

Why does a mixture not have a sharp melting point or boiling point?

Answer 13

A mixture does not have a sharp:
1. Melting point
Or,
2. Boiling point
,because it changes state over a range of temperatures

Question 14

A mixture does not have a sharp melting point or boiling point, because it changes state over a range of temperatures.
What can this difference between pure substances and mixtures be used to do?

Answer 14

This difference between pure substances and mixtures can be used to distinguish if an unknown sample is a:
1. Pure substance
Or,
2. Mixture of substances

Question 15

A mixture does not have a sharp melting point or boiling point, because it changes state over a range of temperatures.
This difference between pure substances and mixtures can be used to distinguish if an unknown sample is a pure substance or a mixture of substances.
So what is a quick and easy test of a compound’s purity?

Answer 15

So a quick and easy test of a compound’s purity is doing an experiment to find a melting point

Question 16

The simple apparatus that can be used to determine the melting point of a solid in powdered or crystal form

Answer 16

The simple apparatus that can be used to determine the melting point of a solid in powdered or crystal form is:

1. The substance being tested
2. Oil or water bath
3. Rubber band
4. Capillary tube
5. Opening to allow air in and out of the apparatus
6. Thermometer
7. (Heat)

Question 17

What do impurities tend to do?

Answer 17

Impurities tend to:

1. Lower the melting point of a substance
2. Raise its boiling point

Question 18

Impurities tend to lower the melting point of a substance and raise its boiling point.
What does the size of the difference from the fixed point of a pure substance depend on?

Answer 18

The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it

Question 19

Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
What happens the purer the compound is?

Answer 19

The purer the compound is, the narrower the melting point range

Question 20

Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
The purer the compound is, the narrower the melting point range.
Example

Answer 20

For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius

Question 21

Formulation

Answer 21

A formulation is a mixture that has been designed to produce a useful product

Question 22

A formulation is a mixture that has been designed to produce a useful product.
What are many consumer products made up of?

Answer 22

Many consumer products are made up of complex mixtures

Question 23

A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
Example

Answer 23

For example, medicinal drugs are formulations

Question 24

A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
For example, medicinal drugs are formulations
Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that affects the body to relieve symptoms, or cure an illness.
If taken in tablet form, what can they also contain?

Answer 24

If taken in tablet form, formulations can also contain:

1. Colorants
2. Sweeteners
3. Smooth coatings to aid swallowing
4. Fillers
5. Other compounds to aid their dissolving at the most effective place in the digestive tract

Question 25

What do scientists have to test?

Answer 25

Scientists have to test the effects that the other compounds in a formulation will have on the active drug in medicines

Question 26

What are paints, like medicinal drugs?

Answer 26

Paints, like medicinal drugs, are also common formulations

Question 27

Paints are also common formulations, like medicinal drugs. | In general, what will paints contain?

Answer 27

In general, paints will contain a: 1. Pigment 2. Binder 3. Solvent

Question 28

Paints are also common formulations, like medicinal drugs. In general, paints will contain a pigment, a binder and a solvent. Why do paints contain a pigment?

Answer 28

Paints contain a pigment to provide colour

Question 29

Paints are also common formulations, like medicinal drugs. In general, paints will contain a pigment, a binder and a solvent. Why do paints contain a binder?

Answer 29

Paints contain a binder to help the paint: 1. Attach itself to an object 2. To form a protective film when dry

Question 30

Paints are also common formulations, like medicinal drugs. In general, paints will contain a pigment, a binder and a solvent. Why do paints contain a solvent?

Answer 30

Paints contain a solvent to help the: 1. Pigment 2. Binder spread well during painting by thinning them out

Question 31

Paints are also common formulations, like medicinal drugs. | Where are other formulations found?

Answer 31

Other formulations are found in the range of cleaning agents used in the home

Question 32

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. Example

Answer 32

For example, washing-up liquids

Question 33

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. What do washing-up liquids generally contain?

Answer 33

Washing-up liquids generally contain: 1. A surfactant 2. Water 3. Colouring and fragrance additives 4. Rinse agent

Question 34

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent. Why do washing-up liquids generally contain a surfactant?

Answer 34

Washing-up liquids generally contain a surfactant, because it is the actual detergent that removes the grease

Question 35

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent. Why do washing-up liquids generally contain water?

Answer 35

Washing-up liquids generally contain water to thin out the mixture

Question 36

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent. Why do washing-up liquids generally contain colouring and fragrance additives?

Answer 36

Washing-up liquids generally contain: 1. Colouring 2. Fragrance additives to improve the appeal of the product to potential customers

Question 37

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent. Why do washing-up liquids generally contain a rinse agent?

Answer 37

Washing-up liquids generally contain a rinse agent to help water drain off crockery

Question 38

Examples of formulations

Answer 38

Examples of formulations are: 1. Medicinal drugs 2. Paints 3. Washing-up liquids 4. Fuels 5. Alloys 6. Fertilisers 7. Pesticides 8. Cosmetics 9. Food products

Question 39

In advertising a product, pure is taken to mean 'has had nothing added to it' and that it is in its what?

Answer 39

In advertising a product, pure is taken to mean 'has had nothing added to it' and that it is in its natural state

Question 40

A test for water is using white anhydrous copper sulfate | If water is present, it will turn what?

Answer 40

A test for water is using white anhydrous copper sulfate. | If water is present, it will turn blue

Question 41

A test for water is using white anhydrous copper sulfate. If water is present, it will turn blue. This test tells you if water is present. It does not tell you if what?

Answer 41

It does not tell you if the water is: 1. Pure Or, 2. Not

Question 42

Impurities tend to lower the melting point of a substance and raise its boiling point. The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it. The purer the compound is, the narrower the melting point range. For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius. However, crude caffeine extracted from tea melts in what?

Answer 42

Crude caffeine extracted from tea melts in the range 180-220 degrees Celsius

Question 43

Impurities tend to lower the melting point of a substance and raise its boiling point. The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it. The purer the compound is, the narrower the melting point range. For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius. However, crude caffeine extracted from tea melts in the range 180-220 degrees Celsius, showing what?

Answer 43

Crude caffeine extracted from tea melts in the range 180-220 degrees Celsius, showing it is an impure sample

Question 44

A formulation is a mixture that has been designed to produce a useful product. Many consumer products are made up of complex mixtures. For example, medicinal drugs are formulations. They will often only contain what?

Answer 44

Formulations will often only contain between 5% and 10% of the active drug

Question 45

A formulation is a mixture that has been designed to produce a useful product. Many consumer products are made up of complex mixtures. For example, medicinal drugs are formulations. Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that does what?

Answer 45

Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that affects the body to: 1. Relieve symptoms Or, 2. Cure an illness

Question 46

Paints are also common formulations, like medicinal drugs. Other formulations are found in the range of cleaning agents used in the home. For example, washing-up liquids. Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent. Washing-up liquids generally contain water to thin out the mixture, so it can do what?

Answer 46

Washing-up liquids generally contain water to thin out the mixture, so it can squirt more easily from the bottle