Ice Ice, Baby!
Outside science came inside today as we explored the effect of salt on ice. Just why do we use it on the paths and roads in icy, frosty weather conditions?
To begin our exploration, we tried to pick up the ice blocks without using our hands, simply using water, string and salt.
Some boffin brains were quick to work out that the string can be made wet then draped over the ice and covered in salt. With a little dose of patience, the salt melts the ice around the string but then a small layer of water freezes over the string again, holding it in place.
Voila! You have lifted the ice without using your hands!
Then, we dropped UV watercolour paint onto the ice block and used a black light to track the burrows and cracks the salt had melted through the ice. This was a great way to see just how far the salt can travel through the solid water in a short span of time.
But what is the science behind it?
Water freezes at 0ºC. Salt lowers that freezing point to around -15ºC, therefore the ice melts when in contact with the salt.
Salt (Sodium chloride) dissolves in water and separates out in to its component elements - Sodium and Chlorine. These additional ions get in the way of the elements of water - Hydrogen and Oxygen - and therefore stop the water molecules from being able to form their rigid 'solid' bonds.
Clever stuff, huh?!