Question

Cheese is a colloidal solution of:

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

Hint:

Colloidal solutions can have different phases of matter, such as liquid dispersed in solid, like in cheese.

Answer 1

The Correct Option is B

Compare cheese with fruit jelly, another common gel where liquid is locked inside a solid-like network.

1. Solid in solid: that would be more like a metal alloy, two solids mixed at a fine scale, not a soft, liquid-holding block like cheese or jelly.
2. Liquid in solid: jelly holds fruit juice, a liquid, trapped inside a solid gelatin network, and cheese holds water and fat trapped inside a solid casein network in the same way.
3. Solid in liquid: that would be more like a runny paste with solid bits floating through it, not a firm block that holds its shape like cheese or jelly does.
4. Gas in solid: that would be more like a sponge or foam, with air pockets in a solid, not the liquid-holding structure seen in cheese.

Since cheese behaves like jelly, holding liquid inside a solid network, the correct answer is liquid in solid.

Answer 2

Identify the physical state of cheese's overall structure, the medium, and of the component trapped inside it, the dispersed phase.

1. Solid in solid: here both parts would need to be solid, but cheese contains a noticeable liquid component too, so this pairing is incomplete.
2. Liquid in solid: cheese's overall network of casein protein is solid, and the water and fat trapped within it are liquid, matching this pairing on both counts.
3. Solid in liquid: here the overall medium would need to be liquid, but cheese holds a firm solid shape rather than flowing like a liquid.
4. Gas in solid: here the dispersed phase would need to be gas, but cheese's structure holds liquid, not trapped air, as its main dispersed component.

Since cheese's solid network holds a liquid component, the correct answer is liquid in solid.