In a sol, solid particles are dispersed in which medium?

In a sol, solid particles are dispersed in which medium?

• A. A liquid.
• B. A gas.
• C. A vacuum.
• D. A solid.

Answer: (A)

In a sol, solid particles are dispersed in a liquid. The particles are small enough to stay suspended in the liquid thanks to Brownian motion and stabilizing interactions, preventing rapid settling. This combination—solid dispersed phase in a liquid continuous phase—defines a sol. If the medium were a gas, you’d have a solid in a gas (an aerosol) rather than a sol. If the medium were solid, you’d have a solid-in-solid dispersion, which is a different type of colloid. A gel, by contrast, is a liquid dispersed within a solid network. So the medium must be a liquid.

In a sol, solid particles are dispersed in a liquid. The particles are small enough to stay suspended in the liquid thanks to Brownian motion and stabilizing interactions, preventing rapid settling. This combination—solid dispersed phase in a liquid continuous phase—defines a sol. If the medium were a gas, you’d have a solid in a gas (an aerosol) rather than a sol. If the medium were solid, you’d have a solid-in-solid dispersion, which is a different type of colloid. A gel, by contrast, is a liquid dispersed within a solid network. So the medium must be a liquid.