You have had something simmering in a covered pot on the stove ...

[kamilo84]

You have had something simmering in a covered pot on the stove and then turn off the heat. Some time later you return to the pot and find that you have trouble lifting the lid. Why?
 
  What will be an ideal response?

Question 2

The activity of a sample reduces from 7.55  109 Bq to 5.11  109 Bq in 5.50 months.
 
  (a) What is the half life?
  (b) How many months must one wait for the activity to decrease to 10?

[trog]

Answer to Question 1

During simmering, the vapor pressure of the water is sufficient to lift the lid a small amount so that steam can escape, so it is slightly above atmospheric pressure. Once the contents of the pot have cooled, the vapor pressure is reduced considerably, and, if the pot is sealed by the lid so no air can leak in, there will be a significant difference in pressure between the inside and the outside, making it difficult to lift the lid.

Answer to Question 2

(a) 9.77 months
(b) 32.4 months

[kamilo84]

Excellent

[ecabral0]

Thanks for the timely response, appreciate it