Question

• Take an empty bottle of the sort in which bottled water is sold. Pour about 5-10 mL of water into it and close the bottle tightly. Shake it well or leave it out in the Sun for ten minutes. This causes the air in the bottle to be saturated with water vapour.
• Now, take a lighted incense stick. Open the cap of the bottle and allow some of the smoke from the incense stick to enter the bottle. Quickly close the bottle once more.Make sure that the cap is fitting tightly. Press the bottle hard between your hands and crush it as much as possible. Wait for a few seconds and release the bottle. Again press the bottle as hard as you can.
• • When did you observe that the air inside seemed to become foggy?
  • When does this fog disappear?
  • When is the pressure inside the bottle higher?
  • Is the fog observed when the pressure in the bottle is high or when it is low?
  • What is the need for smoke particles inside the bottle for this experiment?
  • What might happen if you do the experiment without the smoke from the incense stick? Now try it and check if the prediction was correct. What might be happening in the above experiment in the absence of smoke particles?

Answer 1

1) When the air inside the bottle is saturated with water vapour and the smoke of the incense stick is inserted in it.The smoke particles acts as a nucleus for the water vapours and thus cloud formation takes place.

2)When these droplets will become heavier they will come down as a water and thus fog will disappear.

3)When pressure is high it causes condensed droplets to come down thus disappearing fog.

4) The fog is observed inside the bottle if the pressure inside the bottle is low.