Question

Explain the following giving examples:
The saturated solution, pure substance, colloid.

Answer 1

Hint: A saturated solution contains the maximum amount of solute that can be dissolved in the solution at the conditions of temperature and pressure at which the solution is being prepared. Pure substances are built of only one kind of particle. Colloids are mixtures in which the particles of one substance are dispersed throughout a second substance.

Complete step by step solution:
Let us first start with the saturated solution.
-Saturated solution: A saturated solution contains the maximum amount of solute that can be dissolved in the solution at the conditions of temperature and pressure at which the solution is being prepared. If to a saturated solution, more solute is added then either a precipitate or a gas will be produced. Hence there will be a dynamic equilibrium between the solute in the solution phase and the solute in the solid precipitate form. For example carbonated water. If we increase the temperature, then the solubility of the solute will increase and hence more solute can be added to it to give a saturated solution. For a saturated solution, the rate of crystallization and the rate of solubility of the solute are the same.
Now let us take up pure substance.
-Pure substance: Pure substances are built of only one kind of particle. They have a uniform structure. They are divided into elements and compounds. An element is only made up of only one type of atom. An Element could be a metal, non-metal or a metalloid. For example silicon, iron etc. Compounds are formed from elements when they combine in a fixed ratio. For example, potassium chloride is a compound.
Now let us look into colloids.
-Colloids: Colloids are mixtures in which the particles of one substance are dispersed throughout a second substance. The substance whose particles are dispersed is called the dispersed phase and the substance in which the particles of another substance are dispersed is called dispersion medium. The size of the colloidal particles is generally between 1 micro-meter and 1 Nano-meter. Both the dispersed phase and the dispersion medium could be solid, liquid or a gas. The formation of colloids could be reversible or irreversible. Colloidal solutions display Tyndall effect (when beams of light are incident on a colloidal solution, they get scattered). For example milk, butter and vanishing cream.

Note: Stable colloids are also called lyophilic sols since strong forces of attraction are present between the dispersed phase and the dispersion medium. Colloids are classified based on a number of parameters such as physical state, the dispersion medium, interactive forces present and properties of sol particles.