Nature of Solutions and Suspensions

There are different types of mixtures. Solutions and suspensions are two of them.

Solutions

A solution is a mixture formed when one or more solutes dissolve in a solvent. The solute is the substance that dissolves. The solvent is the substance which the solute dissolves in, and it usually forms the main part of the solution. For example, common salt (solute) dissolves in water (solvent) to form salt solution.

Water is a common solvent. A solution in which water is the solvent is known as an aqueous solution. Fizzy drinks and mineral water are examples of aqueous solutions.

Besides water, there are other types of solvents. Solvents can be in any physical state. Similarly, solutes may be solids, liquids or gases.

Diversity of Solutions

Suspensions

A suspension is a mixture in which solid or liquid particles are suspended in a liquid or a gas. Muddy water, for example, is a suspension of mud in water.

Muddy water is a suspension

Tests to distinguish a suspension from a solution

Appearance

Compare the appearance of the two types of mixtures.

Which is clear and uniform? Which is cloudy and uneven?

The chalk in the suspension is not uniformly distributed in the water. This makes the suspension uneven. This nature of the suspension is called as heterogeneous. The chalk powder suspends in the water, making the mixture cloudy. If left to stand, the powdered chalk settles to the bottom of the beaker.In contrast, common salt dissolves in the water to form a clear solution which is uniform throughout. Such a mixture is called Homogenous

LightCompare the difference in the nature of strong beam of light on the side of the two beakers would the light be able to pass through the beaker.

The light passes through the salt solution and is seen on the table surface in the Figure (a), but no light passes through the suspension Figure (b).

Filtering

Figure Salt solution and a suspension of powdered chalk and water

Figure (a) Light Passes (b) Light cannot pass through a solution through a suspension

Considering the size of the solute in a solution and the suspended particles in a suspension, predict which — salt solution or chalk suspension — would leave behind a residue when filtered.

The suspended particles are left behind as residue when a suspension is filtered as they are too large to go through filter paper Figure (b). No residue is obtained when salt solution is filtered as they completely dissolve in solvent forming a clear solution Figure (a)