In this module, you will learn:
- the differences between compounds and mixtures
- the process of electrolysis
Resources to help you:
Textbook: page 63 and 66
The differences between
Compounds and Mixtures
While they share the similarity of being made of more than one element, they are clear differences between compounds and mixtures. The main differences between them are as follows:
Compounds
1 - The proportion or ratio of compound's constituents (what they are made of) is fixed.
For example water is a compound that is always consists of two hydrogen and one oxygen. By changing the proportion, it becomes a different compound, e.g. hydrogen peroxide consists of two hydrogen and two oxygen.
2 - Compounds are formed by a chemical reaction.
3 - Compounds cannot be broken down by physical methods such as filtration, evaporation, distillation, chromatography, or using magnets.
Mixtures
1 - The proportion or ratio of mixture's constituents (what they are made of) is not fixed.
For example sea water from Brunei and sea water from France are mixtures but the amount of water and the other salts will not be the same.
2 - Mixtures are not formed by a chemical reaction.
3 - Mixtures can be broken down by physical methods.
A simple electrolysis of water
Source: https://www.youtube.com/watch?v=HQ9Fhd7P_HA
Electrolysis
Compounds cannot be separated by physical methods. However, they can be separated by a method called electrolysis.
Electrolysis is the process whereby an electric current is passed over a solution of the compound which causes it to separate into it's individual elements at their respective electrodes.
You should be familiar with the electrolysis of water:
In the electrolysis of water, water will break into its elements hydrogen and oxygen. Hydrogen will appear on the negative electrode (cathode) and Oxygen will appear on the positive electrode (anode).
You should also know that the volume of hydrogen produced will be 2x that of oxygen.