Whoever would like to learn about the properties of liquids and, more generally, chemicals, taking water as an example, is likely to incur more than a misunderstanding.
The temptation is definitely great: Water is definitely the most abundant virtually pure chemical substance we are daily in contact with, it is essential to life and, the most important thing is that we all have directly and personally experimented its characteristics and its behavior.
Unfortunately, water contains in itself more than just an anomaly, each of which combining to bring about making the properties of this substance different in several respects, starting with chemical-physical one, from those of the majority of liquids and chemicals in general, even considering the tens of thousands chemical species known nowadays. The intersection of these anomalies makes the most abundant and “known” substance on our planet a “bad friend” for those who want to approach knowledge of liquid substances and their properties following an inductive method.
Density of the solid state compared with the liquid state
It is certainly not the only case (for example the cast iron is another one), but there are very few chemicals that, like water, show a density at the solid state lower to that at the liquid state.