In this module, you will learn:
- about mixtures
- the differences between compounds and mixtures
Resources to help you:
- Textbook: page 64, 65 and 66
- Notebook: page 29
Mixtures
A mixture consists of two or more substances, elements or compounds, that are not chemically combined.
- A mixture can be of two or more types of elements
- A mixture of two or more types of compounds
- A mixture of two or more elements and compounds
A mixture can be easily separated
Credit: @akedynamic via Twenty20
Different types of mixtures
A mixture of elements
Examples:
Bronze - a metal alloy made of a mixture of copper and tin
Steel - a metal allow made of a mixture of iron and carbon
A mixture of compounds
Examples:
Sea water - a mixture of water and salt
Milk - a mixture of water, fat, sugar, protein and vitamins
A mixture of elements and compounds
Examples:
Air - a mixture of nitrogen (element), oxygen (element) and carbon dioxide (compound), water (compound) and noble gases (elements)
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 but can be broken down using electrolysis.
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 such as filtration, evaporation, distillation, chromatography, or using magnets.
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.