Miracle insulator

The season's first substantive snowfall has laid a light but unbroken carpet across the city. Yesterday's flurries continue into today. The Eramosa River, slender and languid between banks of bare trees, shudders slightly as it pulls an ice coat across, surface streaked by last night's crystal wind.

Miracle compound

This is the time and place where life's most vital substance, water, takes solid form. H₂O is the only chemical that naturally exists on Earth in all three physical states: solid, liquid and gas. This along with water's many other unusual properties makes it essential for the development and sustenance of life as we know it.⁽¹⁾

1. Made of one oxygen and two hydrogen atoms, the water molecule has unique electrochemical qualities because of the way they fit together. The hydrogen atoms are skewed to one side, giving the molecule a slight positive charge on one end, and negative on the other. This polarity causes a strong bond between water molecules.
2. This polarity makes water a powerful solvent, carrying nutrients and other chemicals through ground water and living organisms.
3. The way the molecules attract one another also accounts for water's strong surface tension. This makes it adhesive and elastic. Water can hold together and form waves, rather than spreading out more readily. Droplets cling to a solid surface, resisting gravity. And surface tension allows plants to draw water and nutrients up their stems, against gravity.
4. Water has a high specific heat, which means lots of energy is required to raise its temperature. Water absorbs or gives off a large amount of heat without changing much in temperature.
5. Water conducts heat more readily than any liquid except mercury, so large volumes of water readily maintain a uniform temperature.
6. The most unusual property is that water expands on freezing. Water changing from a liquid to a solid forms a highly organized grid structure that forces the molecules apart. Every other substance on Earth is densest as a solid. If water was like them, ice would sink. But water is densest at slightly above freezing, 4ºC (39ºF), so ice floats on top.⁽²⁾

So ice, rather than sinking to the bottom of our oceans and lakes, forms a protective, insulating crust on the surface. Without this protection, bodies of water would freeze solid. But even glaciers can have flowing water underneath.

Remarkable insulator

Liquid water is the miracle chemical, dissolving and bringing together the compounds that built primordial life, allowing the chemical reactions that keep our bodies and all others alive. But in winter, water provides double service. Ice itself protects the earth from environmental extremes that would eliminate liquid water.

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