A solid dispersed in a liquid.
Explanation
A colloid is a heterogeneous mixture where one substance (the dispersed phase) is suspended throughout another substance (the dispersion medium). The classification of colloids is primarily based on the physical states (solid, liquid, or gas) of the dispersed phase and the dispersion medium.
Option Analysis
- A solid dispersed in a gas. is incorrect: A solid dispersed in a gas is known as an Aerosol. Common examples include smoke and volcanic dust.
- A solid dispersed in a liquid. is correct: A Sol is a colloidal system in which the dispersed phase is a solid and the dispersion medium is a liquid. Examples include paints, cell fluids, and muddy water.
- A liquid dispersed in a solid. is incorrect: A liquid dispersed in a solid is known as a Gel. Examples include cheese, butter, and jellies.
- A gas dispersed in a liquid. is incorrect: A gas dispersed in a liquid is known as a Foam. Examples include whipped cream and soap lather.
Key Takeaway
In colloidal chemistry, a Sol specifically refers to solid particles dispersed within a liquid medium, distinct from a Gel (liquid in solid) or an Aerosol (solid/liquid in gas).