Kinetic Theory and Diffusion

Question 1

Describe the arrangement, movement and energy of the particles in each of the three states of matter: solid, liquid and gas

Answer 1

Solid: particles are closely and often regularly packed. The only movement the particles have is vibration. There are strong forces of attraction between the particles holding them in place.
Liquid: Particles are still mainly touching but some gaps have appeared. Liquids are less dense than the solid they came from. The forces between the particles are less effective and the particles can move.
Gas: The particles are much further apart and there are almost no forces of attraction between them.

Question 2

How are the interconversions of solids, liquids and gases achieved? Recall the names used for these interconversions

Answer 2

If you heat a solid, the energy makes the particles in it vibrate faster and faster, Eventually they vibrate fast enough that the forces of attraction between the particles are no longer strong enough to hold them together. The solid melts to a liquid, at it’s melting point,.
If the liquid is cooled again, the particles will move around more and more slowly. Eventually, they are moving slowly enough that the forces of attraction between them will hold them into a solid. The liquid freezes.
Boiling happens when the liquid is heated so strongly that the particles are moving fast enough to break all the forces of attraction in the liquid. Bubbles of Gaseous particles are formed and rise to the surface forming a gas.
If the gas is called, the particles slow down so the forces of attraction hold them as a liquid, it condenses.
Heat the solid until it sublimes. The particles gain kinetic energy and vibrates faster. This causes the Forces of attraction between the particles to be completely broken and are able to escape from the solid

Question 3

Describe and explain experiments to investigate the small size of particles and their movement

Answer 3

1.Place a crystal of potassium manganate(VII) in a beaker of water.
2. The color spreads through the water.
3. Over time you can see the color levels out but it is weaker than the original colour.
This is because particles leave the crystal, it dissolves. Then they mix among the water particles.

1. Place an open gas jar of air upside down on an open gas jar containing a few drops of red-brown bromine.
2. The color spreads upwards
   This is because the particles of bromine vapour mix among the particles of air.

Question 4

What is meant by the terms “atom” and “molecule”?

Answer 4

Atom - made up of a nucleus (protons and neutrons) with orbitals with electrons on. It is the smallest part of an element that can exist.
Molecule - two or more atoms held together by chemical bonds.

Question 5

What are the differences between elements, compounds and mixtures?

Answer 5

Elements - Are molecules or atoms of only one type of atom

Mixtures - Consists of several different elements that have not undergone a chemical reaction

Compounds - two or more elements that have been chemically bonded in fixed proportions.

Question 6

Describe experimental techniques for the separation of mixtures, including simple distillation, fractional distillation, filtration, crystallisation and paper chromatography

Answer 6

Simple Distillation - To obtain a solvent from a solution, the solution is heated, the liquid boils and turns into vapour, and the vapour is condensed into the pure liquid to be collected. The impurities are left behind, as they have far greater boiling points.
Fractional distillation - The mixture is evaporated and since all the substances inside have different boiling points, they’ll condense at different temperatures, which can then by tapped off. E.g. crude oil
Crystallisation - Solution is heated so the solvent can evaporate, which is then left so that the solution can cool and form crystals. E.g. copper sulfate
Chromatography: Used to analyse coloured substances.

1. Draw the origin with a pencil; pencil lines are insoluble
2. Put spots of colour across the origin
3. Add a solvent; must be below origin or the samples will wash off

Question 7

Explain how information from chromatograms can be used to identify the composition of a mixture

Answer 7

Some coloured substances are better at dissolving in liquid than bonding with paper; so they travel further up the paper
If two substances travel the same distance up the paper, they’re likely to be the same substance (e.g. same colour)