Consider the following statements: I. A colloid and a suspension are heterogeneous mixtures. II. Colloids can be separated from the mixture by the process of centrifugation. III. Particles of colloids and suspensions can be seen by naked eye. IV. The aqueous solution of copper sulphate does not show Tyndall effect; however, the mixture of milk and water shows Tyndall effect. Which of the statements given above is/are correct?

Statement I is correct: colloids and suspensions are both heterogeneous mixtures (true solutions are homogeneous). Statement II is correct: colloids can be separated by centrifugation, which sediments colloidal particles by high-speed rotation. Statement III is incorrect: colloidal particles (1–1000 nm) cannot be seen by the naked eye; only suspension particles (>1000 nm) can be seen. Statement IV is correct: copper sulphate solution is a true solution (no Tyndall effect), while milk-water is a colloid that shows the Tyndall effect (scattering of light). So statements I, II and IV are correct.