The correct option is (c).
Explanation
Colloids are mixtures where the particle size is intermediate between true solutions and suspensions. They are classified based on the physical states of the dispersed phase and the dispersion medium.
Statement 1 is Correct:
Emulsions are colloidal systems in which both the dispersed phase and the dispersion medium are liquids. Common examples include milk (liquid fat dispersed in water) and emulsified oils.
Statement 2 is Incorrect:
Sponge and pumice are not examples of emulsions.
- Pumice is a solid foam, formed by a gas dispersed in a solid medium.
- Sponge is also classified as a solid foam (gas dispersed in a solid).
Statement 3 is Correct:
Colloids, including emulsions, are heterogeneous mixtures. While they may appear homogeneous to the naked eye due to the small particle size (1 nm to 1000 nm), the distinct phases exist and can often be distinguished under a microscope or through light scattering (Tyndall effect).
Key Takeaway:
An emulsion is defined as a liquid-in-liquid colloid (e.g., milk, face cream), distinct from foams (gas-in-liquid/solid) or sols (solid-in-liquid).