Topic 2 - States Of Matter And Mixtures

Question 1

What does the state of matter depend on?

Answer 1

The forces between the particles

Question 2

Give 4 properties of a solid

Answer 2

1) There are strong forces of attraction between particles, which hold them in fixed positions in a regular lattice arrangement
2) The particles don’t move from their positions, so all solids keep a definite shape and volume
3) The particles in a solid don’t have much energy
4) They hardly move at all. They can only vibrate about their fixed positions. The hotter the solid becomes, the more they vibrate, causing solids to expand slightly when heated

Question 3

Give 4 properties of a liquid

Answer 3

1) There is some force of attraction between the particles. They’re free to move past each other
2) Liquids don’t keep a definite shape and will flow to fill the container. They keep the same volume
3) For any substance in the liquid state, its particles will have more energy than in a solid state
4) The particles are constantly moving with random motion. The hotter the liquid is, the faster they move. This causes hem to expand slightly when heated

Question 4

Give 4 properties of gases

Answer 4

1) There’s next to no force of attraction between the particles. They’re free to move. They will travel in straight lines and only interact when they collide
2) Gases don’t tend to keep a definitive shape or volume and will always fill any container. When particles bounce off objects they exert pressure on the walls
3) For any substance in the gas state to particles will have more energy than in the solid or liquid state
4) The particles move constantly with random motion. The hotter the gas gets, the faster they mov. Gases either expand when heated, or heir pressure increases

Question 5

What do you call the process that turns solid to liquid and liquid to solid?

Answer 5

Solid -> liquid = melting

Liquid -> solid = freezing

Question 6

What do you call the process that turns a liquid into a gas and a gas into a liquid?

Answer 6

Liquid -> gas = evaporating

Gas -> liquid = condensing

Question 7

What do you call the process hat turns a solid into a gas and a gas into a solid

Answer 7

Both solid to gas and gas to solid is called sublimation

Question 8

What are chemical changes?

Answer 8

Chemical changes happen during chemical reactions when bonds between atoms break and the atoms change places.

The atoms from the substances you start off with (reactants) are rearranged to form different substances (products)

Chemical changes are often hard to reverse

Question 9

What are physical changes?

Answer 9

Physical changes are when the substance physically changes (changes state).

Physical changes are easily reversed as you can undo this by either heating or cooling

Question 10

What are pure substances?

Answer 10

Pure substances only contain on thing

Question 11

How do you test for purity using melting points?

Answer 11

Every pure substance has a specific melting and boiling point

You can use this to test purity by comparing the actual melting point of the sample to the expected value

If it is a mixture, it will melt gradually over a range of temperatures rather than a precise melting point

Impure substances will melt at different temperatures because the different substances all have different melting points

Question 12

What is simple distillation? What is it used for?

Answer 12

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

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

If you have a mixture of liquids with similar boiling points, you need another method - fractional distillation

Question 13

What is fractional distillation? What is it used for?

Answer 13

Fractional distillation is used when you have a mixture of liquids you can separate it using fractional distillation.

A good example is crude oil

Question 14

What is filtration used for?

Answer 14

Filtration is used to separate an insoluble solid from a liquid.

It can be used in purification as well. For example, solid impurities can be separated out from a reaction mixture using filtration

Simply use filtration and a funnel. Liquid goes into beaker and solid stays in funnel

Question 15

What is crystallisation? How does it work?

Answer 15

Crystallisation separates a soluble solid from a solution

Pour a solution into evaporating dish and gently heat. Some water will evaporate and solution becomes more concentrated

Once some water has evaporated or when crystals start to form, remove dish from heat

Salt should form crystals as it becomes insoluble in concentrated solution

Filter the crystals out of solution and leave to dry.

Question 16

What are the two phases of chromatography?

Answer 16

Mobile phase - where molecules can move. This is always a liquid or a gas

Stationary phase - where the molecules can’t move. This can be a solid or a really thick liquid

Question 17

In paper chromatography, what is the stationary and mobile phase?

Answer 17

Stationary phase - piece of filter paper

Mobile phase - the solvent that is moving up the filter paper

Question 18

How do you calculate Rf value?

Answer 18

Distance travelled by solute / distance travelled by solvent

Question 19

What is a chromatogram?

Answer 19

The piece of paper you end up with

Question 20

Give an example of a use of chromatography?

Answer 20

When a food producer claims to have “no artificial colours”. These colours are tested to see if the colours are a pure colour or a mixture (artificial) colour

Question 21

What is surface water?

Answer 21

Surface water is from lakes, rivers and reservoirs. In much of England and Wales, these start to run dry in the summer months

Question 22

What is ground water?

Answer 22

Ground water is from aquifers (rocks that trap water underground) in parts of England where surface water is very limited, as much as 70% of the domestic water comes from ground water

Question 23

What is waste water?

Answer 23

Waste water is from water that has been contaminated by by s human process, e.g. As a by-product from some industrial processes. Treating waste water to make it potable is preferred as opposed to wasting it, which can be polluting

Question 24

What are water treatment plants?

Answer 24

Water treatment plants are a way of water purification. Waste water and surface water need lots of treatment to make it safe to drink. 3 main ways:

Filtration - wire mesh screens, and then gravel and sand beds filter out any other solid bits

Sedimentation - iron sulfate or aluminium sulfate is added to the water, which makes fine particles clump together and settle

Chlorination - chlorine gas is bubbled through to kill harmful bacteria and other microbes

Question 25

How is distillation used to get potable water?

Answer 25

In some countries, sea water is distilled to produce drinking water

Distillation requires lots of energy and it is therefore very expensive, especially if you are trying to produce large quantities of fresh water

Question 26

What is deionised water?

Answer 26

Water that has had the ions (such as calcium, iron and copper ions) that are present in normal tap water removed

These ions are harmless in tap water, but can interfere with reactions. Using normal water would give your experiment a false result