Chemistry

Question 1

Solids

Answer 1

Solid: strong forces of attraction between particles, fixed lattice shape, particles are in fixed positions and cannot move, definite shape and volume, the particles vibrate and if heated will vibrate even more

Question 2

Liquid

Answer 2

Liquid: Weak forces of attraction between the particles, particles are randomly arranged and can slide or flow over each other randomly, volume is definite and constant but shape is not and liquid will flow to fill the bottom of container. Particles are constantly moving with random motion Particles expand if heated

Question 3

Gas

Answer 3

Gas: Almost no forces of attraction between particles, particles are free to move and are far apart, particles travel in straight lines in random directions, volume and shape are both not fixed, they vary according to the container they’re in, particles expand or pressure is increased when heated.

Question 4

Change of states

Answer 4

Solid - liquid: melting
liquid - solid: freezing
More energy - particles vibrate more and weakness the forces of attraction until a point where the particles have enough energy to break free from their positions
solid - gas: sublimation
liquid - gas: evaporation
gas - liquid: condensation
Even more energy - particles move faster and weaken and break the bonds holding liquid together.

Question 5

Test for diffusion: ammonia and hydrogen chloride gas

Answer 5

Ammonia and Hydrogen chloride gas test
Soak one cotton with aqueous ammonia and another piece of cotton with hydrochloric acid
Put both on either sides of a beaker the aqueous ammonia will release ammonia gas and the hydrochloric acid will release hydrogen chloride gas. Both gases will try and diffuse across the test tube to the opposite side, and will react together to form ammonium chloride. Their reaction forms a ring. The ring however will not be formed half way but will be formed closer to the cotton with the hydrochloric acid as particles of ammonia are smaller and lighter meaning they can travel across faster with less collisions.

Question 6

Test for diffusion: Potassium Manganate

Answer 6

Add concentration of potassium Manganate (VII) at bottom of beaker of water, the potassium manganate will spread across the water via diffusion becoming more dilute and less concentrated in the process
Potassium manganate is bright purple and the change is very apparent
If you were to add more water, the particles would spread even further and would become even more dilute

Question 7

Test for diffusion: Bromine gas and air

Answer 7

Bromine gas and air
Bromine gas is brown and strong smelling
Put Bromine gas in one half of the gas jar and air in the other. Split the 2 jars with a glass plate initially.
Remove the glass plate and the Bromine gas will diffuse through the air

Question 8

Solvent:

Answer 8

the liquid that a solute(solid) is dissolving into

Question 9

Solute

Answer 9

Solute: a substance that dissolves in a solvent (liquid)

Question 10

Solution

Answer 10

Solution: mixture of a solute and a solvent that does not separate out

Question 11

Saturated solution

Answer 11

when the maximum amount of solute is dissolved in a solvent, so no more solute will dissolve in the solution

Question 12

Solubility

Answer 12

Solubility: the ability of a solute to dissolve in a solvent

Solubility increases with temperature:

Question 13

What is solublity measured in

Answer 13

Measured in grams of solute per 100 grams of solvent.

Question 14

To investigate how temperature affects solubility

Answer 14

Mix excess ammonium chloride with 10cm^3 of water in a boiling tube to make a saturated solution, heat it in a water bath.
Stir the solution
Heat at a temperature of 25 degrees,
After 5 minutes, use thermometer to check that the temperature is 25 degrees and that all the excess ammonium chloride is sunk to the bottom
Weigh an empty evaporating basin and pour some of the solution into the evaporating basin
Reweigh the evaporating basin with the solution
Heat the evaporating basin with the solution using a Bunsen burner gently. Evaporating basin should be heated gently so only the water is evaporated and not the ammonium chloride itself (Evaporating the ammonium chloride will cause the mass of solid in the basin to decrease which will make the solubility value inaccurate.
Once all the water has been evaporated, you’re left with pure ammonium chloride. Reweigh the evaporating basin (with the ammonium chloride)
Repeat experiment but heat the saturated in water bath at different temperatures, keep everything else the same. Heat at 25 35 45 etc.
Calculate the solubility each time using the equation (solubility = mass of solid/mass of water removed x 100)

Question 15

What are elements, compounds and mixtures

Answer 15

Elements: only containing one type of atom
Compounds: a substance made of two or more different elements that are chemically bonded together
Mixture: A substance that is made of different elements that Can be separated by physical means.

Question 16

What is a pure substance

Answer 16

Pure substance: a substance that contains only one element or compound, a pure substance has a sharp and specific melting point. A mixture isn’t pure as its melting or boiling points are over a range of temperatures

Question 17

What isfiltration used for

Answer 17

Method used to separate an insoluble solid from a liquid
Pour the substance into a conical flask through filter paper (made into a funnel), the liquid will go through the filter paper whereas the insoluble solid (solid residue) will remain above the filter paper and not go through to the conical flask

Question 18

What is crystallisation used for

Answer 18

Method used to separate a soluble solid from a solution
Pour solution into evaporating basin
Heat the solution (with Bunsen burner etc.) The water will evaporate and the solution will become more concentrated
Heat until crystals begin to form or until some of the water has evaporated stop heating the solution
Leave solution to cool
Salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution.
Filter crystals out of the solution, and leave them in warm place to dry.
Heat again

Question 19

What is simple distillation

Answer 19

Simple distillation is used to separate out solutions
Separates out different liquids from a solution
Liquids in a solution have different boiling points.
Heat the flask from the bottom and the liquids with a lower boiling point will evaporate first up the flask and through the condenser that is connected to the flask, the gas condenses back into a liquid and will go through the condenser into the conical flask.
Problem with simple distillation: only works when the substances you’re trying to separate have very different boiling points.

Question 20

What is fractional distillation

Answer 20

Liquids are heated and enter a fractioning column, they are now evaporated into gases (after heated), the gases of the mixture of liquid each have different melting points. The fractioning column is hot at the bottom and cool at the top, so liquids with higher boiling points will condense towards the bottom and liquids with lower boiling points will condense nearer the top in their respective columns.