1b) Atoms

Diffusion is the gradual movement of particles from a high concentration to a lower concentration.

Dilution of coloured solution:

example- Potassium Manganate(VII) and Water:

1. Take a beaker of water and place some potassium manganate(VII) at the bottom, the purple colour will slowly spread out to fill the beaker
2. The particles of the potassium manganate(VII) are diffusing out among the particles of water
3. This is evidence of random motion of particles in a liquid that causes the purple colour to eventually be evenly spread out throughout the water

Diffusion Experiments:

Ammonia and Hydrogen Chlorine-

1. Aqueous ammonia gives off ammonia gas and hydrochloric acid gives off hydrogen chloride gas
2. When you set up the experiment a white ring will form of ammonium chloride in the glass tube
3. The NH3 gas diffuses from one end of the tube and the HCl gas diffuses from the other. When they meet they form Ammonium chloride.
4. The ring forms nearest to where the HCl gas was
5. This is because the particles of ammonia are smaller and lighter than the particles of hydrogen chloride and so diffuse through the air quicker

Bromine gas and air-

1. Bromine gas to brown and has a strong smell
2. Fill half a gas jar full of bromine gas and the other half full of air- separate the gases with a glass plate
3. When the glass plate is removed you'll see the brown bromine gas slowly diffuse through the air
4. The random motion of the particles means that the bromine will eventually diffuse right through the air

Atoms are made up of the nucleus (which contains protons and neutrons) and electrons which move around the nucleus

Molecules are groups of atoms

Elements consist of only one atom

Compounds are chemically bonded atoms

Mixtures are easily separated compounds as there is no chemical bond between them

Separating of mixtures:

• Filtration- used to separate an insoluble solid from a liquid
• Crystallisation- used to separate a soluble solid from a solution
• Chromatography- separate out mixtures, usually dyes. It works because different dyes move up the paper at different rates
• Simple distillation is used to separate out solutions using heat
• Fractional distillation is used to separate a mixture of liquids, for example crude oil