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Revision Notes on Is matter around us Pure
What is a substance? 
	
	
Anything that cannot be broken into further particles by applying any physical processes is called a Substance.
	
	
	
Matter can be classified into two types of substances – Pure substances and Mixtures
	
What is a pure substance?
A substance that consists of only one type of particle is called a Pure Substance. For Example, Diamond, Salt, Sulfur, Tin. 
What is a mixture?
	
	
When we combine different substances into each other a mixture is formed. For Example, Lemonade is a mixture of three substances, Lemon Juice, Sugar and Water.
	
	
	
Which of these is a mixture or a pure substance?
	
Water, Copper, Chocolate cake, Hydrogen, Soil, Air
Mixture – Chocolate cake, Soil, Air
Pure substance – Water, Copper, Hydrogen
Types of Mixtures
There are two categories of mixtures: Homogeneous Mixtures and Heterogeneous Mixtures
Homogenous Mixtures
	
	
When we add sugar, water and lemon juice together they all uniformly mix with each other. Now it is no possible to separate these substances from the mixture. Such mixtures in which the components mix with each other uniformly are called Homogenous Mixtures.
	
	
	
The ratio of compositions of homogeneous mixtures can be different. For Example, one may add two spoons of sugar in lemonade while someone else may add only one spoon of sugar in their lemonade. Still, lemonade is a homogeneous mixture.
	
Heterogeneous Mixtures
	
	
The components in a heterogeneous mixture do not completely dissolve in each other and we can separate them by physical means. In other words, the composition of such mixtures is not uniform.
	
	
	
For Example, If we mix sand in water the sand settles down in water after some time and we can separate it by filtration.
	
Here are a few differences between homogeneous and heterogeneous mixtures –
							
		
			
Homogenous Mixtures
			
Heterogeneous Mixtures
		
		
			
			
They have a uniform composition throughout 
			
			
			
They have a non-uniform composition
			
		
		
			
			
We cannot separate the components of the mixture through physical processes
			
			
			
We can separate the components through physical processes
			
		
		
			
			
Components cannot be seen through naked eyes
			
			
			
Components can easily be seen through naked eyes
			
		
		
			
			
The mixture is in single phase throughout
			
			
			
The substances can be of two different phases and we may see separate layers of the substances 
			
		
		
			
			
Example: A mixture of water and milk
			
			
			
Example: A mixture of oil in water 
			
		
	
What is a solution?
A solution is nothing but a uniform mixture of two or more substances. Homogenous Mixtures are solutions.
Solution of -
	
	
Liquid into liquid:  Water and Ink
	
	
	
Solid into solid: Alloys
	
	
	
Gas into gas: Air
	
	
	
Solid into liquid: Sugar and Water
	
	
	
Solid into gas: Hydrogen and Metals
	
	
	
Liquid into gas: Carbon Dioxide and Water 
	
What is an alloy? 
An alloy is a mixture of different metals or non-metals and metals that cannot be separated from each other using physical methods. For Example:
Brass – Copper with up to 50% zinc
Bronze – Copper with up to 12% tin
Solution constitutes of two types of substances, a solute and a solvent.
Solution = Solute + Solvent
Solvent – The substance in which another substance is mixed is called the Solvent. For Example, Water is a solvent in which we can mix different substances such as salt or sugar.
Solute – The substance that is added to the solvent to form a solution is called a Solute. For Example, Salt, when mixed in water, acts as a solute for the mixture. 
Properties of a Solution:
	
	
A solution is a homogenous mixture.
	
	
	
We cannot see the particles of a solution through naked eyes as they as are small as 1 nanometer in diameter.
	
	
	
The path of light is not visible through the solution. The particles of a solution do not scatter light through them as they are extremely small.
	
	
	
We cannot separate the particles of a solution by methods of filtration. 
	
What is a stable solution?
A stable solution is a solution in whose particles do not settle down if we leave the solution undisturbed for some time. This is because the particles of a stable solution are homogeneously spread.
						

							
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