Question

Figure 15 shows a setup used to study Brownian motion in liquids.

 

1. State the function of the hand lens. 
2. State what is observed on the pollen grains. 
3. Explain the observation made in (2). 
4. State and explain what would be observed on the pollen grains if the water is heated. 

Answer 1

1. To magnify/ enlarge the pollen grains for better visibility.
2. They are observed to move in random motion
3. They are being hit/ bombarded by the invisible water molecules which are in constant/ continuous random motion hence also move in random motion.   
4.    
   • Rate of random motion of the pollen grains increases
   • Increase in temperature of water increases the kinetic energy of water molecules, which move with a higher speed thus knocking/ bombarding the pollen grains which in turn move more/ vigorously/ faster.