How much do you know about water? Check back to the quiz for the questions.
1. Generally the solid form of something is heavier than the liquid because it’s packed together more tightly and there’s more in it. But ice is less dense than water, which means for the same volume there are less molecules in it. This makes it lighter and it floats on top (which, incidentally, does things like making life possible in lakes).
The reason it is less dense is because of something called hydrogen bonds. Water molecules are made up of one oxygen and two hydrogen atoms, and when it is cold the hydrogens can form a bond with an oxygen from another molecule. This means they make a stiff crystal lattice and moves them further apart, making ice less dense.
Hydrogen bonds in water are also important for life in another way – they make water molecules ‘stickier’ and mean they need more energy to boil, and so a higher temperature. This very big gap between freezing and boiling where we have liquid water is what gives us the ‘space’ for life. And I’ve even found a ‘Hydrogen Bond Song’ down the bottom 🙂
2. Yes, there is water on the moon in the form of ice. Generally the problem on the moon is that when it is in direct sunlight it is extremely hot and anything like water would have boiled off into space long ago. But there are some craters in the southern polar region that are so deep they are always in shadow. This makes them the coldest place in the solar system and means that ice has survived there.
3. The Dead Sea is the lowest place on earth that isn’t covered by water – the shores are 423m below sea level. It is called the Dead Sea because it is so salty that very little can live there, only small numbers of algae and bacteria. It’s more than 8 times saltier than the ocean. The reason it is so salty is because of the low elevation – water flows in but it can’t flow out because there is nowhere else to flow down to. It evaporates in the heat, leaving its burden of minerals behind.
In addition, the area is covered in halite or rock-salt, including the biblical Mount Sodom. Millions of years ago the Dead Sea was a long inlet of the Mediterranean. It’s in an active fault zone where Arabia and Africa are moving apart and the movements cut it off from the rest of the sea. Over the millennia the sea water evaporated and left large salt deposits underneath what would become the Dead Sea.
The Dead Sea is shrinking because of diversions of its inflow, the Jordan River. There are plans to use water from the Red Sea and desalinate them for use in the surrounding areas, then pump the waste brine into the Dead Sea to help maintain it.
4. You don’t need to drink 8 glasses of water a day. You do need roughly a litre to replace what is lost through urine, sweat and breathing, but a lot of that can come from food. In fact with a water rich diet of things like fruits you may not need to drink at all. Anything extra just works your kidneys and bladder, it doesn’t clear extra toxins out of you or anything like that.
One of the easiest ways to track your hydration level is through headaches. If you get dehydrated it lowers the volume of cerebro-spinal fluid around your brain and spinal cord ever so slightly. This irritates the nerves and causes a headache. If you have a headache with no obvious cause, a glass of water is the first thing to try.
5. The picture above is a Coolgardie Safe. This was a way of keeping food cool and fresh with no electricity. It wasn’t as good as an ice-chest but in the goldfields it made a big difference to the taste and safety of food.
The sides are hessian and the container at the top held water, which dripped down onto the hessian and wet it. Then as the water runs down it cools by evaporation. It takes energy to evaporate water, which comes from the surroundings and cools them. Simple but effective.
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