For water at $0^{\circ} C$,it takes one hour for the first $3 \ mm$ of ice layer formation. How many hours will it take for the next $6 \ mm$ of ice formation?

The heat is flowing through a rod of length $50 \ cm$ and area of cross-section $5 \ cm^2$. Its ends are respectively at $25^\circ C$ and $125^\circ C$. The coefficient of thermal conductivity of the material of the rod is $0.092 \ kcal/m \cdot s \cdot ^\circ C$. The temperature gradient in the rod is

Assertion: $A$ thermos bottle consists of a double-walled glass vessel with the space between the two walls evacuated,so that the heat transfer between the contents of the bottle and the outside is minimized.
Reason: The vacuum between the two walls inhibits the heat transfer by the radiation mechanism.
Which of the following is correct?

Two thin blankets keep more warmth than one blanket of thickness equal to these two. The reason is

Under steady state,the temperature of a body

$Assertion:$ Two thin blankets put together are warmer than a single blanket of double the thickness.
$Reason:$ Thickness increases because of the air layer enclosed between the two blankets.