The weather in the UK over the past week or so has been, shall we say, a little chilly. In northern parts of Scotland it hit around -19 degrees Celsius (that’s about -2F) and the snow was knee deep.

But have you ever wondered why they put salt on the roads to help get rid of ice? It’s quite simple, really.

Every substance has 3 possible states – solid, liquid or gas. Water at a normal temperature is a liquid – heat it up sufficiently and it turns in to a gas, cool it down and it turns to a solid – ice. The molecules within water virtually stand still at 0 Celsius, hence it becomes solid.

However, adding salt to the mix destabilizes the molecules – salt DOES NOT freeze at 0C. Salt water won’t freeze until it hits somewhere between -10 and -20C (depending on the salt-to-water ratio) and is therefore a liquid at 0C. If you sprinkle some salt on a patch of ice, you will see the ice melt from the area you started in and gradually melt further and further out – this is caused by the slat molecules spreading throughout the water/ice.

Of course, when the air temperature is -20C to start with, you may have to consider breaking out the pick-axe…