A solution is a homogeneous mixture of two or more substances. You come across various types of solutions in your daily life. Lemonade,
soda water etc. are all examples of solutions.
Usually we think of a solution as a liquid that contains either a solid, liquid or a gas dissolved in it. But, we can also have solid solutions (alloys) and gaseous solutions (air). In a solution there is homogeneity at the particle level. For example, lemonade tastes the same throughout. This shows that particles of sugar or salt are evenly distributed in the solution.
A solution has a solvent and a solute as its components. The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent. The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.
Examples:
(i) A solution of sugar in water is a solid in liquid solution. In this solution, sugar is the solute and water is the solvent.
(ii) A solution of iodine in alcohol known as ‘tincture of iodine’, has iodine (solid) as the solute and alcohol (liquid) as the solvent.
(iii) Aerated drinks like soda water etc., are gas in liquid solutions. These contain carbon dioxide (gas) as solute and water (liquid) as solvent.
(iv) Air is a mixture of gas in gas. Air is a homogeneous mixture of a number of gases. Its two main constituents are:
oxygen (21%) and nitrogen (78%). The other gases are present in very small quantities.
Properties of a solution
• A solution is a homogeneous mixture.
• The particles of a solution are smaller than 1 nm (10-9 metre) in diameter. So, they cannot be seen by naked eyes.
• Because of very small particle size, they do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
• The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.