Question

Cork is a colloid of:

• A. Solid in solid
• B. Liquid in solid
• C. Solid in liquid
• D. Gas in solid

Hint:

Cork is an example of a solid matrix with gas trapped inside, forming a colloidal solution.

Answer 1

The Correct Option is D

Compare cork with a slice of bread, which also feels light because of tiny air pockets baked into its solid structure.

1. Solid in solid: that pairing fits something dense like an alloy, not a light, airy material like bread or cork.
2. Liquid in solid: that pairing fits something moist like cheese, not a dry, rigid material like cork.
3. Solid in liquid: that pairing fits a runny mixture with solid bits in it, nothing like the dry, floaty texture of cork.
4. Gas in solid: bread feels light and spongy because of air pockets trapped in its baked structure, and cork is light and buoyant for the same reason, air trapped in a solid cellular network.

Since cork behaves like bread, light because of trapped air in a solid structure, the correct answer is gas in solid.

Answer 2

Identify the state of cork's overall structure and the state of whatever is trapped inside its cells.

1. Solid in solid: here the trapped component would need to be a second solid, but cork's cell walls do not enclose another solid material.
2. Liquid in solid: here the trapped component would need to be liquid, but cork does not carry moisture the way a gel-like material does.
3. Solid in liquid: here the overall medium would need to be liquid, which cork clearly is not, since it stays rigid and dry.
4. Gas in solid: cork's overall structure is a rigid solid, and its cell walls enclose tiny pockets of trapped air, a gas, matching this pairing exactly.

Since cork's solid structure traps air inside it, the correct answer is gas in solid.