In a freezer, the temperature falls by 2`c every 5 minutes. In how much time water at 36`c will freeze into ice?

Solution:

In the freezer ice will form from water at 0oC Since the water is at 36oC, so the temp. required to fall will be 36oC - 0oC = 36o.

In the freezer temp falls @ 2oC at every 5 mins.

The temp. to fall 2o time taken = 5 mins.

Then the temp. to fall 36o the time taken = 5 / 2 x 36 mins = 5 x 18 mins - 90 mins = 1 hr 30 mins.

Ans: 1 hr. 30 mins.