Concept:The anomalous thermal expansion of water refers to its unique property of contracting upon heating from \( 0^\circ\text{C} \) to \( 4^\circ\text{C} \).
Formula:$$ \text{Density} = \frac{\text{Mass}}{\text{Volume}} $$
Solution:- When ice melts at \( 0^\circ\text{C} \), the open cage-like structure starts to collapse, bringing molecules closer together and increasing density.
- This collapse outpaces the normal thermal expansion of the liquid until the temperature reaches \( 4^\circ\text{C} \).
- Above \( 4^\circ\text{C} \), increased kinetic energy causes normal thermal expansion, making the liquid less dense again. Thus, density peaks exactly at \( 4^\circ\text{C} \).
Why other options are incorrect:At \( 0^\circ\text{C} \) and \( -4^\circ\text{C} \), water exists as less dense solid ice. At \( 1^\circ\text{C} \), the cage structure is still partially collapsing, so the density has not yet peaked.
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