Which one among the following statements is NOT a property of "colloid"?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → The solute particles settle down when left undisturbed, that is, a colloid is unstable.
A colloid is a mixture whose particles are bigger than those of a true solution but smaller than those of a suspension (about 1 to 1000 nm). Milk, fog and ink are colloids.
Option (1) It is a heterogenous mixture. — A property of a colloid (Incorrect). It looks uniform, but its particles form a separate phase, so it is heterogeneous.
Option (2) The solute particles settle down when left undisturbed, that is, a colloid is unstable. — Not a property of a colloid (Correct). Colloidal particles do not settle when left alone, so a colloid is stable; settling is the mark of a suspension, such as muddy water.
Option (3) The size of particles is too small to be individually seen by the naked eyes. — A property of a colloid (Incorrect). The particles cannot be seen one by one with the naked eye.
Option (4) Colloids are big enough to scatter a beam of light passing through it and make its path visible. — A property of a colloid (Incorrect). This scattering is the Tyndall effect, seen when sunlight enters a dusty room or a forest.