A student investigates Brownian motion by observing smoke particles in a glass cell under a microscope. The smoke particles appear to move in a random, jerky motion. What causes this motion?

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Question

A student investigates Brownian motion by observing smoke particles in a glass cell under a microscope. The smoke particles appear to move in a random, jerky motion. What causes this motion?

Accepted Answer

Collisions between air molecules and smoke particles — Award 1 mark for identifying that the random motion of smoke particles is caused by collisions with fast-moving air molecules. A is incorrect — convection currents would cause directional, not random jerky, movement. B is incorrect — smoke particles are too far apart for frequent collisions with each other. D is incorrect — vibration would cause regular, not random, movement.

Answer

Convection currents in the air inside the cell

Answer

Collisions between air molecules and smoke particles

Answer

Collisions between smoke particles

Answer

Vibration of the microscope stage

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