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 –

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.