Concept:Water shows anomalous expansion, so its density does not change uniformly with temperature.
Explanation:When a quantity of water at
0∘C is heated, its volume first contracts for a small range of temperature.
From
0∘C to
4∘C, the water contracts, so the same mass occupies a smaller volume.
Using
ρ=Vm, a smaller volume at constant mass makes the density rise.
At
4∘C, water attains its maximum density.
From
4∘C to
30∘C, water expands on heating, so its volume increases.
For a fixed mass, an increase in volume causes the density to fall.
Therefore, for each degree rise from
0∘C to
30∘C, the density first rises and then falls.
Answer:D. rise and then falls