Question

Which of the following best describes a sol-gel colloidal system?
A. Butter and milk.
B. Blood.
C. Beaten egg whites.
D. Paper.

Answer 1

We know that the colloids have two components, one dispersion phase which is less in quantity, and a dispersion medium which is more in quantity. In solid-sol both the dispersion phase and medium are solid. A colloid is a mixture in which one substance of dispersed insoluble particles is suspended throughout another substance. Colloidal solution refers to the overall mixture.

Complete answer:
Colloidal state of matter is, therefore, a state in which the size of the particles is such $\left( 1\text{ }to\text{ }1000\text{ }nm \right)$ that they can pass through filter paper but not through animal or vegetable membrane. The substance dissolved is called the solute, and the medium in which it is dissolved is called the solvent, similarly, in a colloidal system, the terms solute and solvent are replaced by the terms dispersed phase and dispersion medium respectively. Sol is a colloidal suspension with solid particles in a liquid. An emulsion is between two liquids. Foam is formed when many gas particles are trapped in a liquid or solid. Aerosol contains small particles of liquid or solid dispersed in a gas.
Thus, dispersed phase means the substance distributed in the dispersion medium in the form of colloidal particles and the dispersion medium is the medium in which the substance is dispersed in the form of colloidal particles , the colloidal system thus obtained is sometimes called colloidal dispersion or simply colloid.
Therefore, the correct answer is option A.

Note:
Remember that Foam is the colloid in which the dispersion phase is gas and the dispersion medium is gas, for example, froth, whipped cream. Solid foam is the colloid in which the dispersion phase is gas and the dispersion medium is solid. There is no colloid in which the dispersion phases and medium both are gas.