Why is Water 'Weird'?

Water is the most common liquid on the planet, yet its strange properties continue to baffle scientists.

Why is Water So Strange? The short answer, according to Dr. Mark Lorch at Science Focus:

Water's strange properties are all down to its molecular charges.

Water has many strange properties, including a high surface tension, an ability to dissolve more things than any other common liquid, and a solid state (ice) that floats. These strange properties come from water’s simple structure. Its atoms form a chevron shape with a slightly negatively charged oxygen and positive hydrogens. This allows water to bind to and dissolve both negatively and positively charged molecules.

Meanwhile, the hydrogen of one water molecule is attracted to the oxygen of another. Within a liquid these attractions briefly hold the molecules together, generating the high surface tension. This network is frozen in place when the water is cooled, leaving large gaps. As a result, the sponge-like ice floats on the liquid. In contrast, other chemicals form tightly packed solid crystals that are more dense than the liquid and so sink. The Weirdness of Water The long answer, according to Rachel Brazil at Chemistry World: Water's strange properties are all down to its molecular charges. Water, the most commonplace of liquids, is also the strangest. It has at least 66 properties that differ from most liquids – high surface tension, high heat capacity, high melting and boiling points and low compressibility. One school of thought is that water is not a complicated liquid but ‘two simple liquids with a complicated relationship’. For some, this statement contradicts the basic principles of physical chemistry; for others it explains just why water behaves in such an anomalous way. Over the last decade the academic arguments have reached boiling point. ‘[It’s] bringing out very strong, almost religious opinions among different scientists,’ says Anders Nilsson, a chemical physicist with appointments at Stockholm University in Sweden and Stanford University in the US. Chemists have attributed water’s strange properties to the tetrahedrally arranged hydrogen-bonding networks that it forms, but exactly what is going on, particularly when water is in a supercooled state, is still up for debate. Read more >>>