Mixtures (Seperation Techniques)

Question 1

State what is meant by a mixture?

Answer 1

A mixture is made up of several different substances. The substances are not chemically joined together. They are just mixed up.

Question 2

What is a compound?

Answer 2

In a compound, atoms of elements are strongly joined together. You could not separate them using a magnet but instead you would need a chemical reaction to separate them.

Question 3

State two differences between compounds and mixtures?

Answer 3

1. The elements in a mixture are not joined together but in a compound they are strongly joined.
2. A mixture can be separated in a physical separation technique but a chemical separate technique is needed to separate the atoms of the elements in a compound

Question 4

What is a pure substance?

Answer 4

If a substance is pure then it means that they have a sharp melting point. This shows that it has no other substances mixed with it.

Question 5

What is an impure substance?

Answer 5

If a substance is impure it means it doesn’t have a sharp melting point and therefore different substances are mixed with it.

Question 6

Describe how to find out if a sample of a substance is pure?

Answer 6

If on a graph there is a straight line to show the melting point of a solid turning to a liquid then it means it has a sharp melting point. This means it is a pure substance.

Question 7

Are there any examples of natural mixtures?

Answer 7

Most materials are mixtures. Some exist naturally:

1) most rocks are mixtures of compounds
2) seawater is a mixture of water, sodium chloride, and other salts

Question 8

Are there any examples of mixtures that are used in everyday life?

Answer 8

Chemists make mixtures that are suitable for their purpose. They work out the best amounts of each substance to add to the mixture. For example toothpaste is a mixture that we use everyday.

Question 9

State what a solution is?

Answer 9

A solution is a mixture of a liquid with a solid or gas. All parts of the solution are the same. You cannot see the separate substances.

Question 10

What is dissolving?

Answer 10

A solution is made when one substance called the solute “dissolves” into another substance called the solvent. Dissolving is when something, like a solute, goes and mixes in with the solvent, but can not see it as a solid anymore.

Question 11

What is a solute?

Answer 11

the minor component in a solution, dissolved in the solvent.

Question 12

What is a solvent?

Answer 12

A solvent is able to dissolve other substances. Another way to put it is the liquid in which a solute is dissolved to form a solution.

Question 13

How can you use mass to find out whether something is a solution?

Answer 13

If something, like a liquid, ways more after adding something to it
E.g: The mass of 1Litre of pure water is 1000g.
The mass of a solution made by dissolving 20g of sugar in 1000g of water (1000g+20g)=1020g

Question 14

Describe the arrangements of particles in a solution?

Answer 14

When sugar dissolves,water particles surround each sugar particle. Sugar particles can mix with the liquid. They are arranged randomly, and move around.

Question 15

Is water the only solvent?

Answer 15

No, an example of another solvent is propanone(also called acetone) which is a chemical. Ethanol is another example.

Question 16

Are some glues solutions?

Answer 16

Yes, they contain a sticky substance dissolved in a solvent. As the solvent evaporates, the glue dries.

Question 17

Can gases dissolve in a solvent?

Answer 17

Yes, many gases can dissolve in solvents. For example carbon dioxide gas makes drinks fizzy.

Question 18

What is a saturated solution?

Answer 18

A saturated solution contains the maximum mass of a substance that will dissolve.

Question 19

What is solubility?

Answer 19

The mass of solute that dissolves in 100g of water to make a saturated solution is called the solubility of the solute. Every substance has its own solubility.

Question 20

What does insoluble mean?

Answer 20

Some substances cannot dissolve in water. They are insoluble. Chalk (calcium carbonate) and sand (silicon dioxide) and insoluble in water.

Question 21

How does temperature affect solubility?

Answer 21

The higher the temperature, the greater the mass of a solute that dissolves. Most substances get more soluble as temperature increases, although the amount it increases differs from substance to substance.

Question 22

What is filtration?

Answer 22

Filtration, or filtering, separates a liquid from an insoluble solid. Filtration also separates a solution from a solid that is mixed with it, but not dissolved, like how a sieve separates food.

Question 23

How does filtering work?

Answer 23

You use a filter paper which has tiny holes in it. Water particles are smaller than the tiny holes. In the liquid state, water passes through the holes. This is called the filtrate. The insoluble solid is bigger than the holes and and stay in the filter paper. This is called the residue.

Question 24

What is the filtrate?

Answer 24

The filtrate is the liquid that passes through the holes of the filter paper in filtration.

Question 25

What is the residue?

Answer 25

The residue is the insoluble solid that is left on the filter paper in filtration.

Question 26

List three uses of filtration?

Answer 26

1) it separates coffee solution from ground-up coffee beans
2) oil filters in cars trap solid bits of dirt while the liquid oil passes through as the dirt would damage the engine.
3) sand filters help make water safe to drink.

Question 27

If you have a mixture of sand and salt, how can you separate the sand?

Answer 27

Add water to the mixture. Stir. The salt dissolves. The sand does not. Pour the mixture into a filter paper funnel. Salt solution passes through the paper. The residue left is the sand.

Question 28

Describe how salt can be separated from seawater?

Answer 28

Evaporation separates salt fro seawater. The sun transfers energy to the water molecules and they leave the surface of the solution. When all the water has evaporated, solid salt remains.

Question 29

What is evaporation?

Answer 29

the process of turning from liquid into a gas by being heated up.

Question 30

What is distillation?

Answer 30

Distillation is a process that uses evaporation and condensation to obtain a solvent from a solution.

Question 31

How can you separate salt solution into salt and water using distillation?

Answer 31

Water in the salt solution boils. Steam leaves the solution. Steam travels through the condenser and cools down. The steam condenses to form liquid water. Liquid water drips into the beaker.

Question 32

What can you also use distillation to separate other than sea water?

Answer 32

You can use distillation to separate water from inky water.

Question 33

State what chromatography does?

Answer 33

You can use chromatography to find out which dyes are in which colours. Chromatography separates substances in a mixture. It works when the substances in a mixture are soluble in the same solvent.

Question 34

How does chromatography work?

Answer 34

To find put which dyes are in a green felt tip pen, you can set up apparatus using a beaker with water, a piece of paper being held so that it touches the water and has a mark from the green felt tip pen on. As the water passes the green ink, the dyes in the ink dissolve. Some dyes move faster than others so they separate leaving different colours which make up the green dye- blue and yellow

Question 35

What is a chromatogram?

Answer 35

It is the piece of paper which show the separated colours that a dye is made of.

Question 36

In a chromatogram, the blue dye has moved further up the chromatogram than the yellow other. Why is this?

Answer 36

The blue dye is more soluble or the yellow dye may stick more strongly to the paper.

Question 37

What are pigments?

Answer 37

Colours that make up something

Question 38

What is chromatography used for?

Answer 38

Scientists have used a different sort of chromatography to identify food nutrients. This is because it shows the different colours in food substances.

Question 39

Can you separate substances in a mixture using chromatography if all the substances are soluble in the same solvent?

Answer 39

Yes, this is the main purpose of chromatography.

Question 40

What separation techniques could the police use when trying to figure out a case?

Answer 40

Chromatography and filtration.