Question
Assertion : A beaker is completely filled with water at $4^{\circ} \mathrm{C}$. It will overflow, both when heated or cooled.
Reason : There is expansion of water below and above $4^{\circ} \mathrm{C}$.

Answer

(a) Water has maximum density at $4^{\circ} \mathrm{C}$. On heating above $4^{\circ} \mathrm{C}$ or cooling below $4^{\circ} \mathrm{C}$, density of water decreases and its volume increases. Therefore, water overflows in both the cases.

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