Mixture

• Mixtures are formed by mixing of 2 or more substances without chemical combination
• These substances may be elements or compounds
• A mixture has variable composition ; the ratio of 2 or more substances may not be same
• A mixture shows properties of constituent substances  
  

Example : Sugar in Water is a mixture, Air is mixture of Oxygen, Nitrogen

Now,

• Sugar in water is a mixture. We can add any amount of sugar in a glass of water, and call the resultant a mixture. 
• The amount of either of the things doesn't matter.
• The property of the mixture is the same as that of the constituents sugar and water.

Activity to Show Preparation (and Properties) of a Mixture

• Take some Iron filings and Sand
• Mix and crush them
• Bring a magnet near the mixture
• We see that Iron fillings get attracted to it

This means that it is a mixture as it still shows properties of Iron (to be attracted by a magnet)

Also, the mixture can be separated using physical methods like magnetic separation .