The density of water is 1000 kg/m3 at 4°C. This is because water has its maximum density at 4°C. At temperatures below 4°C, water molecules start to form ice crystals, which are less dense than liquid water. At temperatures above 4°C, water molecules start to move around more, which makes the water less dense.
Option A: 0°C is the freezing point of water. At this temperature, water molecules start to form ice crystals, which are less dense than liquid water. Therefore, the density of water is not 1000 kg/m3 at 0°C.
Option B: 0°K is absolute zero, the temperature at which all molecular motion ceases. At this temperature, water molecules would be completely still, and the density of water would be infinite. However, this is an unrealistic scenario, as it is impossible to reach absolute zero. Therefore, the density of water is not 1000 kg/m3 at 0°K.
Option C: 4°C is the temperature at which water has its maximum density. At this temperature, water molecules are arranged in a way that makes the water as dense as possible. Therefore, the density of water is 1000 kg/m3 at 4°C.
Option D: 20°C is a temperature that is above the freezing point of water. At this temperature, water molecules are moving around more, which makes the water less dense. Therefore, the density of water is not 1000 kg/m3 at 20°C.