Which among the following mixtures show the Tyndall Effect? A mixture of: (a) air and dust particles (b) copper sulfate and water (c) starch and water (d) acetone and water. Choose the correct options, and explain the reason for the correct and incorrect options.
Explanation
The correct option is (iii). The Tyndall effect is the scattering of light by particles in a mixture. Mixtures like (a) air and dust particles, and (c) starch and water, are colloids or suspensions. Their particles are large enough to scatter light, making the path of a light beam visible.
Options (b) copper sulfate and water, and (d) acetone and water, are true solutions. In true solutions, the particles are too small to scatter light, so the path of light is not visible. Hence, they do not show the Tyndall effect.
Solution Steps
Step 1: Identify the nature of each mixture. (a) Air and dust particles is a suspension/colloid; (b) Copper sulfate and water is a true solution; (c) Starch and water is a colloid; (d) Acetone and water is a true solution.
Step 2: Recall that the Tyndall effect is the scattering of light by particles, which is exhibited by colloids and suspensions, but not by true solutions.
Step 3: Select the mixtures that are colloids/suspensions. (a) and (c) show the Tyndall effect, corresponding to option (iii).