What’s that smell?

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Smelly things are all around us. Some smell nice, others smell horrible. But what makes a smell? And why are some things smellier than others?

Smells happen when molecules of a chemical or substance float through the air and end up inside your nose. Lots of things can smell: flowers, foods, perfume, even our bodies! Smell molecules come from chemicals that are ‘volatile’, which means they can evaporate (turn into a vapour) easily. And the more volatile chemicals that something releases into the air, the smellier it is.

Smells can be affected by temperature because heat makes volatile chemicals evaporate even more easily. So, a stinky cheese will be smellier if it’s left out on the kitchen table on a warm day than if it’s kept in the refrigerator. And, have you ever noticed a funny smell outside after it’s been raining? Well, that’s caused by molecules evaporating from wet soil as part of the water cycle. So, water can affect smells, too!

Have you ever wondered, how our noses smell things? At the back of your nose you have millions of special cells called ‘sensory neurons’. These cells detect smell molecules and send messages to your brain. Your brain uses these messages to tell you about what you are smelling – like, whether it’s nice or nasty, safe or harmful, tasty or yucky.

Many animals are good at smelling, including my mum’s dog, Teddy (in the photo above). Here’s a list of the top-10 best smellers in the animal world. I’ll bet you can’t guess which animal is a number one!