The halogens include fluorine, chlorine and iodine. You are probably most familiar with chlorine – often associated with the smell of swimming pools. But did you know that the distinctive smell of a swimming pool is not actually caused by chlorine. It comes from compounds known as chloramines, which form when chlorine reacts with sweat, urine and cosmetics!
It is not only humans who love swimming though. There are many animals which love taking a dip. For example, elephants are able to swim up to 20 miles per day, and can use their trunks as snorkels to swim underwater! Sloths, who we think of as lazy creatures, can actually swim 3 times faster than they walk. All pigs swim well, and love to get in the water. Pigs cannot sweat, so not only does this help them cool down, it is also a much cleaner option to rolling around in the mud. In addition, pigs are quite buoyant, due to the level of fat in their bodies, and therefore float well! Cows are also excellent swimmers, with four powerful legs acting as paddles and large buoyant bodies.
The Komodo dragon’s physique probably does not remind you of a champion swimmer, but these reptiles can swim up to 1000 feet. They often swim between islands, and dive underwater to avoid predators. Iguanas have the advantage of using not just their arms and legs – but also utilise their long tails a propellers so they swim even faster! They even tuck their legs in when swimming to reduce the friction on their bodies.
GCSE Science students – you need to be able to describe and explain the properties of the halogens. Our new guide, “How to work with Halogens” can help. Included, as always are questions to try, and answers to check your understanding.
To see the guide, click on the picture below. 
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