Leon and Michael usually go swimming in a lake... ... but today, they've gone to the sea instead. Oh, accidentally swallowed some water, did you? And it didn't taste like the water you're used to swimming in? No, sea water contains a lot of salt.
It's the same kind of salt used in cooking - common salt, or table salt. One litre of seawater contains about 35 grams of table salt, or two tablespoons. Sea water is a saline solution. You can dissolve more salt in the water. But only up to a limit.
When there's about 350 grams of salt per litre of water - ten times more than in sea water - the salt just sinks to the bottom, without dissolving. The solution is saturated. Actually there are some lakes - salt lakes - where the salinity is that high: Thirty-five percent. No plants or animals can live there: the water is very clear. Swimming in a salt lake feels a little special.
The more salt the water contains, the higher you will float - salt water has high buoyancy. But it's not good to stay in the salt lake too long - salty water will dry out your skin. Yes, it's true: despite being wet, your skin will lose liquid. Salt has a dehydrating effect. Another thing about salt water is that when it cools down, it freezes at a lower temperature.
The more salty the water is, the colder it will have to get in order to freeze. Pure water freezes at zero degrees Celsius, and sea water at minus two degrees. A saturated saline solution stays liquid down to minus 21 degrees. This can be useful in winter. Here is a road, covered with ice and snow.
It is slippery, and difficult to drive on. But if we put some salt on the road... ... The ice will melt. The ice doesn't melt because it is heated by the salt. In fact, the salt water that is formed is even colder than the ice was to begin with!
Salt both melts - and cools - ice. Table salt consists of two elements: Sodium ... and chlorine. The chemical name is sodium chloride. The body needs to take in some sodium chloride to function properly... ...
but if you eat too much, more than about one teaspoon per day, it can be bad for you. And if you swallow too much in one go, you'll probably feel sick. Okay, Leon... maybe it's time for you to get out of that sodium chloride solution now...