Chemistry || C1 - C7

Question 1

Solids?

Answer 1

Strong forces of attraction between particles,

Lattice arrangement,

Fixed positions,

Don’t have a lot of energy,

Vibrate,

Hotter is gets, the more it vibrates.

Question 2

Liquids?

Answer 2

Some forces of attraction but not much,

Free to move past each other,

Stick together,

Fill shape of container,

Liquid state will have more energy than the solid state but less energy than gas,

Particles are constantly moving and as it gets hotter it gets, the faster they move. Liquids expand when they get hot.

Question 3

Gases?

Answer 3

No force of attraction,

Free to move,

Travel in straight lines and only interact when they collide,

Don’t keep a shape or volume and always fill a container,

When particles bounce off walls, they exert a pressure and bounce other way,

Gases have more energy than liquids and solids,

Constantly moving at random motion and as it gets hotter, they move faster,

Gases can expand when they’re heated or their pressure can increase.

Question 4

How Can A Substance Change State?

Answer 4

Heating or cooling,

Particles get more energy from heating,
This makes them vibrate more which weakens the bonds,
This makes the particles expand,
At a certain temperature, the particles will break free from their positions (melting or boiling).

Question 5

Chemical Reactions Changing State Of Atoms?

Answer 5

Chemical reactions are where the bonds break and the atoms change places,

This is the reactants breaking bonds and rearranging with other atoms to make products,

Chemical changes are harder to reverse compared to physical changes.

Question 6

Pure Substances?

Answer 6

When something is completely made up of a single element or compound, it is pure,

More than one element or compound is a mixture.

Question 7

How To Know If Something Is Pure,

Answer 7

Melting points show us if something is pure,

If a melting point is spread out
e.g. “70-90 degrees”, it is impure,

If it is sharp
e.g. “70 degrees”, it is pure,

You can use of a melting point apparatus to measure the melting point of a substance,

If you don’t have a melting point apparatus, use a water bath and a thermometer. This is harder to control.

Question 8

Simple Distillation?

Answer 8

Separates a liquid from a solution,

Uses heat to evaporate the substance (water) and then a condenser to turn it back into a liquid,

This can be done with seawater, to separate salt from water.

Question 9

Fractional Distillation?

Answer 9

Used to separate a mixture with similar boiling points,

Heat the liquid and use a fractioning column (filled with glass rods) to separate them,

Liquid with the lowest boiling point will evaporate first and reach the condenser,

The liquids are put into separate tubes as the temperature decreases.

Question 10

Filtration?

Answer 10

Separated an insoluble solid from a liquid,

Filter paper is folded and placed into filter.

Question 11

Crystallisation?

Answer 11

Separated a soluble solid from a solution,

Out the solution into an evaporating dish,

Heat the solution,

A lot of the water will evaporate and the solution will become more concentrated,

Water evaporates, crystals start to form. Remove the dish from heat when crystals appear,

Leave the solution to cool,

The salt becomes insoluble in the cold air and highly concentrated which forms crystals,

Filter the crystals out the solution and leave them to dry,

Or, use a drying oven or a desiccator (contains chemicals that remove water from surrounding.

Question 12

Rf Value Formula?

Answer 12

Distance travelled by solute
—————————————-
Distance travelled by solvent

Question 13

Chromatography Is?

Answer 13

Chromatography is a method used to superstar a mixture of soluble substances,

Two types of chromatography are:
Mobile Phase,
Stationary Phase.

Question 14

Mobile Phase?

Answer 14

When the molecules move,

This is always a liquid or a gas.

Question 15

Stationary Phase?

Answer 15

Where the molecules can’t move,

This can be a solids or a really thick liquid.

Question 16

Phases Effecting Chromatogram?

Answer 16

The mixture separates as the mobile phase happens,

The different substances end up in different places in the stationary Phase,

This happens because each of the chemicals will have spent a different time dissolved in the mobile phases and stuck to the stationary phase,

How fast a chemical moves through the stationary phases depends on how it distributed itself between two phases.

Question 17

Paper Chromatography?

Answer 17

The stationary phase of paper chromatography is a piece of filter paper and the mobile phase is the solvent,

Draw a line with pencil so ink doesn’t separate. Pencil marks are insoluble,

Put solvent in beaker and place bottom of water in the solvent,

Place the substance mark on the pencil line but don’t get it wet,

The solvent will move up the paper,

When the chemicals in the solvent dissolve, they will separate and move up the paper too.

Question 18

Time Spent In Each Phase Depends On?

Answer 18

How soluble they are in the solvent,

How attracted they are to the stationary phase,

Molecules with a higher solubility in the solvent (and are less attracted to the paper) will spend more time in the mobile Phase than the stationary phase. This also means they will be carried further up the paper.

Question 19

What Is The Paper Called After Chromatography Takes Place On It?

Answer 19

Chromatograms.

Question 20

Chemicals On Chromatogram Is Colourless, What Do I Do?

Answer 20

Spray a locating agent on it so they show up on the paper.

Question 21

What Is The Rf Value?

Answer 21

Is the ratio between the distance travelled by the dissolved substance at the distance travelled by the solvent,

E.g. the distance between the highest point of the paper that is actually wet and the baseline divided by the distance from baseline to chemical.

Question 22

How Cab Chromatography Be Uses As A Purity Test?

Answer 22

A pure substance will not deprecate by chromatography, it will move as one blob,

A mixture will have multiple blobs.

Question 23

Water Treatment Process?

Answer 23

Through water treatment plants, it goes through filtration, sedimentation and chlorination.

Question 24

Filtration?

Answer 24

A wire mesh screens out large twigs and drummer and then gravel and sand is filtered out.

Question 25

Sedimentation?

Answer 25

Iron sulphate or aluminium sulfate is added to water, which makes fine particles clump together and settle at the bottom.

Question 26

Chlorination?

Answer 26

Chlorine gas is bubbled through to kill harmful bacteria or any other microbes.

Question 27

What Causes Water Hardness?

Answer 27

Soluble impurities that are dissolved in water,

They are not removed as they can’t be filtered out,

These impurities included minerals.

Question 28

We Get Water From?

Answer 28

Surface water,
From lakes and reservoirs,
They can run dry sometimes,

Ground water,
From aquifers (rocks that trap water underground),

Waste water,
Water that has been contaminated by human processes,
This water can be treated to make it potable instead of polluting other areas with it.

Question 29

Distilling Sea Water?

Answer 29

This allows us to get potable water,

Distillation needs loads of energy so it is really expensive,

We don’t tend to use this method.

Question 30

Chemistry Experiments Use What Water?

Answer 30

When we do chemistry experiments (chemical analysis), we have to use pure water,

This is because chemicals might react with other elements in impure water if it is used,

Deionised Water is used when experiments involve mixing or dissolving something in water.

Question 31

Deionised Water?

Answer 31

When experiments involve mixing or dissolving something in water, this type of water is used,

This water is water that had had the ions (such as iron and copper ions in tap water) remover,

These ions can interfere with reactions which might give us a false result in an experiment.