Mixtures (Seperation Techniques) Flashcards

1
Q

State what is meant by a mixture?

A

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

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2
Q

What is a compound?

A

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.

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3
Q

State two differences between compounds and mixtures?

A
  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
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4
Q

What is a pure substance?

A

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.

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5
Q

What is an impure substance?

A

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

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6
Q

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

A

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.

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7
Q

Are there any examples of natural mixtures?

A

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

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8
Q

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

A

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.

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9
Q

State what a solution is?

A

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.

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10
Q

What is dissolving?

A

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.

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11
Q

What is a solute?

A

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

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12
Q

What is a solvent?

A

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.

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13
Q

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

A

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

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14
Q

Describe the arrangements of particles in a solution?

A

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

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15
Q

Is water the only solvent?

A

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

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16
Q

Are some glues solutions?

A

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

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17
Q

Can gases dissolve in a solvent?

A

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

18
Q

What is a saturated solution?

A

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

19
Q

What is solubility?

A

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.

20
Q

What does insoluble mean?

A

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

21
Q

How does temperature affect solubility?

A

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.

22
Q

What is filtration?

A

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.

23
Q

How does filtering work?

A

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.

24
Q

What is the filtrate?

A

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

25
Q

What is the residue?

A

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

26
Q

List three uses of filtration?

A

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.

27
Q

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

A

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.

28
Q

Describe how salt can be separated from seawater?

A

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.

29
Q

What is evaporation?

A

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

30
Q

What is distillation?

A

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

31
Q

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

A

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.

32
Q

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

A

You can use distillation to separate water from inky water.

33
Q

State what chromatography does?

A

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.

34
Q

How does chromatography work?

A

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

35
Q

What is a chromatogram?

A

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

36
Q

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

A

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

37
Q

What are pigments?

A

Colours that make up something

38
Q

What is chromatography used for?

A

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

39
Q

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

A

Yes, this is the main purpose of chromatography.

40
Q

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

A

Chromatography and filtration.