You've probably never given much thought to the ice cube swirling amid the contents of your Cuba Libre. When watching Titanic, you probably don't ponder how the iceberg that did the ship in is actually a great example of why we have life on earth. We all know that water is kind of important. While not the most exciting of drinks, just try going more than a few hours without taking a sip. But there's something extra-special about water that makes it one of the strangest substances on earth.
To understand water's wackiness, you first need to understand how things are "supposed" to work. Think back, way back, to science class and you might remember talking about the three states of matter: Solids, liquids and gases. The molecules of a gas are very bouncy and far apart. As the gas cools, the molecules get closer together, condensing into a liquid. Cool that liquid even more and the molecules squeeze even more tightly together into a solid.
But water is weird. Unlike almost every other substance on earth, as it freezes it actually expands, making it lighter than its liquid counterpart. To get a really clear view of this, put on your science pants and try the following experiment: Add a few drops of food colouring to the bottom of a large glass. Next, fill the glass a little less than halfway with vegetable oil. Now slowly pour in some baby oil, leaving a few centimetres of space at the top of the glass. You can't really see it, but the baby oil will sit on top of the vegetable oil (for an explanation of why this happens, check out this column).
Drop an ice cube into the oil mix and it will settle in the middle. Now you have to wait. But your patience will be rewarded. Eventually, you will see a drop of water start to peel off the ice as it melts. Eventually it will be joined by more drops that will settle on the bottom of the glass, mixing with the food colouring and demonstrating that liquid water is more dense than ice.
This property is great news for us. If water behaved like other liquids oceans and lakes would freeze solid, turning the earth into a giant ball of ice with no chance for life as we know it. There is however a downside. Living things tend to have cells containing lots of water. If cells freeze, the icy expansion means they get damaged causing a potentially fatal case of frostbite.
But some critters that live in places like the Arctic have found a way around this by making stuff that acts like antifreeze in their blood. One day researchers may find a way to adapt this for use in humans. Who knows? This might be the ticket to sending sleeping astronauts to far-flung galactic destinations. And it gives you plenty to think about while you sip on that highball.
You Will Need:
- Large Glass or Beaker
- Baby Oil
- Vegetable Oil
- Ice Cube
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