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Monday, July 27, 2009

Water: an amazing substance

Water is a very common substance, so common that we take it for granted, but it is also unusual. How so? Why is that important?

1. Water is the only common substance that may be found in all three states under common conditions. This means that we can have a water cycle, wherein water moves all over the earth in the gaseous state, and precipitates in the liquid or solid state. If it weren't for that, agriculture would be mostly impossible. It also means that we can have snow and ice, which are important for many reasons, including the fact that snow and ice insulate organisms that live under them, greatly slowing heat loss from bodies of water with ice and snow covering them.

Mars is the only planet, other than Earth, in our solar system where conditions are enough like earth that all three states might occur there, but there doesn't seem to be much water on Mars at all now (there may have been in the past). There may be water on Enceladus, a satellite of Saturn.

2. Water is the only common substance that becomes less dense when it becomes a solid. This means that ice floats. If it didn't, polar bears would have a hard time, and bodies of water (except for very shallow ones) would be mostly solid, even in the summer, because the ice would be denser, and would stay on the bottom, where the sun wouldn't melt it. If that were so, many water-living organisms couldn't exist.

3. Water is unique in that it becomes most dense at 4 degrees Celsius (approximately the temperature inside a refrigerator) when it is still liquid. This means that bodies of water tend to become uniform in temperature when they cool in the fall, and when they warm up in the spring, as liquid water, either colder or warmer than 4 degrees, rests on top of the 4 degree water, until it either cools to 4 degrees in the fall, or warms to 4 degrees in the spring, so that eventually the whole body of water is at 4 degrees. The resulting uniformity means that nutrients that have sunk to the bottom can be stirred by the wind while the body of water is uniform. Again, if this were not true, many water-living organisms couldn't exist. (for more on this topic, see here)

4. Water is transparent. This means that your eye can see, as light goes through the eye (which is mostly water) to the retina. It also means that fish can see, and that plants below the surface of a body of water can carry out photosynthesis, the food-making process that requires light.

5. Water has a high specific heat, meaning that it takes a lot of energy to change the temperature of water without changing its state.

6. Water has a high heat of fusion, meaning that it takes a lot of energy to melt ice, or that you must remove a lot of energy for water to freeze.

Properties 5 and 6 help to stabilize the climate near bodies of water. They also allow fruit-growers to protect their crops from freezing by spraying them with water when a freeze is predicted.

7. Water has a high heat of vaporization, meaning that it takes a lot of energy to vaporize water, ("A watched pot never boils") or that you must remove a lot of energy to condense vapor. Properties 5-7 mean that water stabilizes temperature. For example, a human at 37 degrees C (normal body temperature) can remain in air at 45 degrees C or 0 degrees (freezing temperature) for a long time without damage. It also means that deserts are subject to a great deal of temperature fluctuation compared to areas near large bodies of water.

8. Water makes up most of the mass of most living things, including green plants. It is, of course, made of molecules with two Hydrogen atoms and one Oxygen atom. One reason that this is vitally important is that water is one of the raw materials of photosynthesis, the process by which green plants make food for the rest of living things. Photosynthesis attaches the Hydrogen from water to Carbon from Carbon Dioxide.

9. Water is self-attractive, which means that it makes drops -- water molecules sticking together. This property helps tall plants get water up to their tops, and also makes it possible for some organisms to walk or run on top of the surface of bodies of water.

Some would argue that these, and other properties of water, are so unique, and so important, that water must necessarily have been specially created as it is. I believe that God designed water with these, and probably other, unique properties, but don't believe that I can prove this. In the Bible, Hebrews 11:3 implies that we understand God's creative power by faith.

Thanks for reading.

See this post on the times that water is mentioned in the book of John. Here's a post on the importance of water, from a different author.

This is a re-post from July 26, 2007, changed slightly.


Anonymous said...

thanyou for the info as i have just been given an essay on water to do and had no idea where to start or what to include i hope it is okay to use sections of this as i have referenced back to this site

Martin LaBar said...

That's fine. Glad to be of help.

Keetha Broyles said...

I love teaching my students about water - - - I have the privilege of being the FIRST to ever tell them about water's amazing temperature stabilizing qualities - - - oh, and polarity too - - - until they have me they think being polar is a form of depression. Hehehehehehehe

Martin LaBar said...

It is a privilege, I'm sure.

Thanks, Keetha.