Question

Wait why when finding relative density we only use water at 4°C?​

Answer 1

Because

Why is relative density measured at 4 degrees Celsius?

For liquids, the reference is almost always water at its densest temperature (4 °C or 39.2 °F); for gases, the reference is air at room temperature (20 °C or 68 °F). In scientific circles, the phrase "relative density" is frequently used. A material sinks if its relative density is larger than one.

Answer 2

Answer:

The clusters still have empty spaces, so they decrease the density of the liquid. The molecules of the water are closer together, and this increases the density of the liquid. As the temperature of warm water decreases, the water molecules slow down and the density increases. At 4 °C, the clusters start forming.