BS: Why don't we make water?

Subject: RE: BS: Why don't we make water?
From: Steve Shaw
Date: 18 Oct 15 - 08:02 PM

I read to my horror the other day that every single Californian almond that I eat took nine gallons of water to grow.

Subject: RE: BS: Why don't we make water?
From: Steve Shaw
Date: 18 Oct 15 - 07:58 PM

You could tell your grandson that water has some amazing properties, without which we wouldn't be here. It has the highest thermal capacity of any substance, meaning that the oceans can hold huge amounts of heat which keeps the whole planet equable. Most substances contract when they are cooled. Water does the same....until it reaches 4 degrees C, when, weirdly, it starts to expand again as it cools down. The upshot of this is that ice is less dense, instead of more dense as you might expect, than liquid water. That's why ice floats on top of your drink. That's also why ice forms on top of lakes in freezing weather. If ice followed the "normal rules" it would sink to the bottom and, eventually, the whole lake would freeze solid and everything in it would be killed. Instead, the ice on the surface actually prevents heat loss from the liquid water underneath by insulation. It's been calculated that if ice were heavier than water and sank, all the oceans of the earth would freeze solid and life on earth would not be possible. Clean water also has a film on its surface made of a single layer of water molecules holding hands. The force is so strong that this invisible, super-thin layer can float a steel needle or a pond skater. This surface tension is vital to plants as it helps water to grip the sides of the tiny tubes in the stem and move up through the plant, without which the plant couldn't exist. Pretty important when you consider how much the earth relies on plant life. Another unusual feature of water is that, unlike other substances, it can easily exist on earth as solid, liquid and gas in huge amounts at the same times. The interchange among the three is what drives our climate. Good stuff is water, and I haven't even mentioned its value as one of the best solvents in the universe.

Subject: RE: BS: Why don't we make water?
From: Joe Offer
Date: 18 Oct 15 - 07:33 PM

Let the record reflect that I agree with Steve Shaw.

There's a huge desalination plant coming online soon in San Diego. That's a ray of hope.

-Joe-

Subject: RE: BS: Why don't we make water?
From: Steve Shaw
Date: 18 Oct 15 - 07:25 PM

To make water, you need a lot of hydrogen. There's very little of that in the atmosphere. The only viable source of it is...water. We can make hydrogen from water by splitting the water molecule. Unfortunately, this takes a lot of energy. Though it's doable, a really large-scale economical method has yet to be devised. I think that one day we'll be able to use solar energy to power water-splitting. We can split water on a very small scale in the lab, and your grandson may well have seen it. We called the piece of kit Hoffmann's Voltameter when we were at school. You fill it with acidified water and apply a current to the platinum anode and cathode. The water is split and you get oxygen at one electrode and hydrogen at the other. There is twice as much hydrogen, nicely demonstrating H2O. The best way to get pure water is to purify water from reservoirs, rivers or the ocean. Getting pure water from sea water requires a lot of energy, and only a few countries do it, mostly those with very dry climates. If we could get hydrogen cheaply it would solve our energy problems and probably stop global warming, because when you burn it it releases a lot of energy, and all you get as waste product is water. It's a bit hard to handle, though, as it is very explosive in the presence of oxygen, but, one day, I think it will be a major energy source.

Subject: BS: Why don't we make water?
From: michaelr
Date: 18 Oct 15 - 07:03 PM

So my grandson, who is 11, asked the other day: If we're in such dire need of water, why don't we make it ourselves? After all, it's a simple molecule - some oxygen, some hydrogen, mix `em together, and bingo.

I did not have an answer. I think I remember that those elements are quite combustible, but my recollection of high school chemistry is too vague to tell him anything useful. Who can help?