Q. It is known that wax contracts on solidification. If molten wax is taken in a large vessel and it is allowed to cool slowly, then
A) It will start solidifying from the top to downward
B) It will start solidifying from the bottom to upward
C) It will start solidifying from the middle, upward and downward at equal rates
D) The whole mass will solidify simultaneously
Explanation
(b) Substances are classified into two categories
(i) water like substances which expand on solidification.
(ii) $CO_{2}$ like (Wax, Ghee $etc.$) substances which contract on solidification.
Their behaviour regarding solidification is opposite.
Melting point of ice decreases with rise of pressure but that of wax etc increases with increase in pressure. Similarly ice starts forming from top to downwards whereas wax starts its formation from bottom to upwards
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.