How does water turn to ice?
Like everything else in the world, water is made up of molecules that are constantly moving. When water is in liquid form, its molecules have more energy than in a solid – they move around quickly, essentially bouncing off of one another. As water cools, the amount of this energy is reduced which causes the molecules to move more slowly until – at a temperature of 0°C –
they start to stick together and take a solid form, known as ice.
Perfect for a tall glass of lemonade on a hot day!
When there is salt present in water, however, the freezing temperature goes much lower. In fact, ice actually repels salt molecules, keeping more water from freezing. That’s why they use salt to melt ice on the sidewalks and roads in places where it gets very cold.
Try it out: LET’S GET SALTY
Take two empty plastic water bottles and fill them with tap water.
In one of the bottles, carefully add 2 tablespoons of salt to one of them, shake it to dissolve the salt, and replace both caps.
Use a marker or rubber band to mark which one has the salt water, and put both bottles in your freezer.
Check the bottles every hour or so: which one froze first?
How much longer did the second one take to freeze?
