Density anomaly of water
= Density anomaly of water
Fresh water reaches maximum <mass density> near $4\,{}^\circ\mathrm C$ at atmospheric pressure. A useful local <equation of state> is
$$
\rho=\rho_m\left[1-\alpha(T-T_m)^2\right],
$$
so water becomes less dense when its temperature moves either above or below $T_m$.