Which of the following characterizes a colloid?

• A. Brownian movement
• B. Tyndall effect
• C. Particle sizes greater than 1 μm
• D. Both A and B
• E. All of the above

Answer: (D)

Verified step by step guidance

1. Understand the definition of a colloid: A colloid is a mixture where one substance is dispersed evenly throughout another. The particles in a colloid are larger than those in a solution but smaller than those in a suspension.
2. Examine Brownian movement: This refers to the random motion of particles suspended in a fluid, resulting from their collision with fast-moving molecules in the fluid. Colloidal particles exhibit Brownian movement due to their small size.
3. Explore the Tyndall effect: This is the scattering of light by particles in a colloid. When light passes through a colloidal mixture, the particles scatter the light, making the path of the light visible. This effect is a characteristic of colloids.
4. Consider particle size: Colloidal particles typically range from 1 nm to 1 μm in size. Particles greater than 1 μm are generally too large to be considered colloidal and are more characteristic of suspensions.
5. Evaluate the options: Based on the definitions and characteristics, both Brownian movement and the Tyndall effect are key features of colloids. Particle sizes greater than 1 μm do not characterize colloids, so the correct answer is both A and B.