Is Matter Around us Pure?

• A solution is a homogeneous mixture of two or more substances in which the particle size is smaller than.
• Solution has a solvent and a solute as its components.

SOLVENT: The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent.

SOLUTE: The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute. The following are some examples of solutions:

1. Air is a homogeneous mixture of gases where both the solvent and the solute are gases.
2. Sugar syrup is a solution where sugar is dissolved in water using heat. So, sugar is the solute and water is the solvent and.
3. Tincture of iodine is a mixture of iodine in alcohol. Here alcohol is the solvent and  iodine is the solute.

Properties of a solution:

The important characteristic properties of a solution (or true solution) are as follows:

• A solution is a homogeneous mixture, i.e., particles are evenly distributed.
• The particles of a solution are smaller than 1 nm
  $\left({10}^{–9}\mathrm{metre}\right)$

  in diameter. The size of solute particles in a solution is extremely small.

• The particles of a solution cannot be seen even with a microscope.
• The particles of a solution pass through the filter paper. So, a solution cannot be separated by filtration.
• The solutions are very stable. The solute particles do not settle down when left undisturbed.
• A true solution does not scatter light. This is because its particles are very, very small. So, the path of light is not visible in a solution.

Types of solutions:

• Solution of solid in a solid. For example, brass is a solution of zinc in copper.
• Solution of solid in a liquid. Sugar solution.
• Solution of liquid in a liquid. Vinegar is a solution of acetic acid (ethanoic acid) in water.
• Solution of gas in a liquid. Soda-water is a solution of carbon dioxide gas in water.
• Solution of gas in a gas. Air is a solution of gases like oxygen, argon, carbon dioxide and water vapour, etc.

The maximum amount of a solute which can be dissolved inof a solvent at a specified temperature is known as the solubility of that solute in that solvent (at that temperature).

Effect of Temperature and Pressure on Solubility:

The effect of temperature and pressure on the solubility of a substance is as follows:

• The solubility of solids in liquids increases on increasing the temperature; and decreases on decreasing the temperature.
• The solubility of solids in liquids remains unaffected by the changes in pressure.
• The solubility of gases in liquids usually decreases on increasing the temperature; and increases on decreasing the temperature.
• The solubility of gases in liquids increases on increasing the pressure; and decreases on decreasing the pressure

Saturated and Unsaturated Solutions:

Depending upon the amount of solute present in a solution, it can be called a dilute, concentrated or a saturated solution.

• Unsaturated Solution: A solution in which more quantity of solute can be dissolved without raising its temperature.
• Saturated Solution: A solution in which no more solute can be dissolved at that temperature.

Effecting of ‘Heating’ and ‘Cooling’ on a Saturated Solution:

• If a saturated solution at a particular temperature is heated to a higher temperature, then it becomes unsaturated.
• If a saturated solution available at a particular temperature is cooled to a lower temperature, then some of its dissolved solute will separate out in the form of solid crystals.

Concentration of a solution:

The concentration of a solution is the amount of solute present in a given quantity of the solution. Solute and solvent are present in uneven ratios in solutions.

Concentration of solution = Amount of solute/Amount of solution

Or

Concentration of solution = Amount of solute/Amount of solvent

It can be deducted in the following ways:

• Mass by mass percentage of a solution:

• Mass by volume percentage of a solution:

• Volume by volume percentage of solution: