Atoms (Section 1b)

Movement of Particles

1.4 describe and explain experiments to investigate the small size of particles and
their movement including: i) dilution of coloured solutions, ii) diffusion experiments

i) Dilution

Dilution is the process of a substance being put into a solvent in order to reduce it's concentration. 

The dilution of Potassium Manganate (VII) solution

1) Potassium Manganate (VII) is a bright purple substance. It is a good example of dilution because the process itself is very easy to see. 
2) If you add water to the purple solution, the potassium managanate (VII) particles will spread further apart.
3) You will see the solvent becoming less and less purple once you've added water.
4) The more water you add, the more the solvent will dilute, and the less and less purple it will become. 

Showing the colour change of Potassium Manganate (VII) before, during, and after dilution. 

ii) Diffusion

Diffusion is the gradual movement of particles from an area of high concentration to an area of low concentration. 

The diffusion of bromine gas and air 

1) Bromine gas is a brown, strong smelling gas. It is a good example of demonstrating diffusion in gases.
 2) Fill half a gas jar full of bromine gas, and fill the other half with air. Separate the two gases with a glass plate between them.
 3) When you remove the glass plate, you will be able to see the bromine gas slowing diffusing through the air.
 4) Because of the random motion of particles in a gas, the bromine will eventually diffuse completely through the air. 

1.5 understand the terms atom and molecule

Atom = A unit of matter made up of a nucleus, protons, and orbiting electrons. 

Molecule = A group of two or more atoms held together by covalent bonds. 

1.6 understand the differences between elements, compounds and mixtures

Elements = Consist of one type of atom only. They cannot be broken down into a simpler type of matter by any means, either physical or chemical. They can exist as either atoms or molecules. Examples include; nitrogen, copper, and oxygen.

Compounds = A substance made up of two or more different elements which are chemically joined together. They can be broken down into a simpler type of matter (elements), but only by chemical means, not physical means. They are often very different from the properties of the original elements. Examples include; carbon dioxide and iron sulfide. 

Mixtures = Mixtures consist of two or more different elements or compounds that are physically joined. Because of this, they can be separated by physical means, not chemical means. Unlike compounds, mixtures often retain many of the properties of it's components. The properties of a mixture are therefore a mixture of the properties of it's separate parts. Examples include; the air and crude oil.