Mixtures & Compounds

A mixture occurs when you combine matter in such a way where the components can be separated again.

 A compound results from a chemical reaction between components, forming a new substance.

For example, you can combine iron filings with sulfur to make a mixture. 

All it takes is a magnet to separate the iron from the sulfur.

 

On the other hand, if you heat the  iron and sulfur you form iron sulfide which is a compound.

Here is How 

First form a mixture - Stir some iron filings and sulfur to form a powder. You have just taken two elements and combined them to form a mixture. You can separate the components of the mixture by stirring the powder with a magnet  - iron will stick to the magnet -

If you heat the mixture over a Bunsen burner, hot plate or stove, the mixture will start to glow. The elements will react chemically to form iron sulfide which is a compound. Careful! Unlike the mixture, the formation of a compounds cannot be undone so easily

 What you Need

• iron filings 
• sulfur powder
• magnet
• test tube or beaker
• Bunsen burner or hot plate or stove

 A compound is a material that is made up two or more elements chemically joined together.
For example , water is a compound made up of the elements hydrogen  (H) and oxygen (O). 


A compound such as water has particles called molecules.

Water

• We can represent a water molecule by writing a chemical formula: H2O.

• This tells us that a molecule of water contains two atoms of hydrogen joined to one atom of oxygen.
• Water is made up of many identical water molecules. 
• Water is a liquid, so the molecules are close together.

Carbon dioxide

•  Chemical formula: CO2.
•  one carbon atom joined to two oxygen atoms make a molecule of  carbon dioxide
• Carbon dioxide is a gas, so the molecules are further apart than in water

Sodium chloride (common salt)

• Formula - NaCl
• There is one sodium particle for every chlorine particle
• NaCl is a solid, the sodium and chlorine particles in it are close together with strong forces between them

The cards below show information about some materials. Some of them are elements and some are compounds.

Signs of a chemical reaction