Water: Our essential chemical

By Al Lowe
Contributor

We all know all about water, don't we? We drink it - we wash in it - we give it to our animals - we water the garden - water is all over the place.
But I just bet that there are a few things which you don't know about this almost universal substance.
We all know that the formula for water is H2O. Two atoms of hydrogen and one of oxygen. There are two of the most common elements on earth. The water molecule itself has an odd look. According to some, its like the head of a very very tiny teddy bear.
One of the strange things about water is that it exists in all three states of matter within a fairly small range of temperatures. Solid - it's ice. Liquid - it's just water. And gas - water vapour or steam. All of these occur within a temperature of a bit more than 100 Celsius degrees. Can you think of any other substance which acts like that? I didn't think so.
Now here is another one. Almost all substances shrink when they cool down, and expand when they warm up. Most solids, liquids and gases behave like this. Now consider water. Take some water at an ordinary temperature, and cool it down. It shrinks just like everything else. But just a minute now! When water gets down to +4C, it stops shrinking, and starts to expand! As it gets colder, it keeps on expanding until it gets to 0 degrees Celsius, and then it freezes - ice! So ice is less dense than the water around it, so it floats.
And it's a good thing that it does. It means that the ice forms on the top of the water. If it didn't, all of our lakes and streams here in the north would freeze from the bottom up. The ice would never melt, and life would not be able to exist in many parts of the world. One of those parts is us, here in Northwestern Ontario.
Another odd thing about water is that so very many other things dissolve in it. That also includes solids, liquids and gases.
Sea water has all sorts of stuff dissolved in it. There are many other salts besides our common salt, lots of minerals, and a huge number of other chemicals.
The percentage of sodium chloride (common salt) in sea water is about 35%. That means that each litre of sale water contains about 35 grams of salt. Other things make up much small amounts. Actually, sulphates, magnesium, calcium and potassium make up most of the rest of what are called 'sea salts.'
There are tiny amounts of other things in sea water, including silver, copper and gold. So far, no simple and inexpensive way has ever been found to extract any valuable minerals from sea water.
Quite a lot of gases are dissolved in water also. Chief among them is oxygen. Without this oxygen in the water, none of our aquatic animals would be around. No fish! Carbon dioxide and nitrogen are also easily dissolved in water.
In almost all cases, the warmer the water, the more will dissolve in it. So if you want to dissolve something in a hurry, use warm water.
So, that's water. Likely the most common chemical on earth. But if it didn't have those three peculiar things about it - well, the earth would be different, and we wouldn't be here.
Water is our most valuable material. We should be very careful about how we treat it.