In places with cold winters, salt trucks are a common sight this time of year. These trucks put down salt during winter storms. Winter storms dump snow and ice onto the roads. You may have seen people put salt on icy or snowy sidewalks too. Is it the same salt we put on our food? How does it work?
The salt used on roads is very similar to the type we use on our food. It is the same substance [type of matter], but has not been purified, so it may be a different color.
Salt makes the roads safer by helping to melt the snow and ice. Snow and ice can be slippery. When salt mixes with water, it lowers its freezing point [the temperature at which a liquid changes into a solid]. The freezing point of pure water is 32° F (0° C). Saltwater freezes at a lower temperature than pure water. This means that water remains a liquid at lower temperatures. Instead of being ice or snow, it is liquid water. When water is liquid, the roads are safer. Cars can travel safely!
What Can You Do? Sprinkle table salt onto an ice cube. Observe what happens. (Hint: Adding a drop or two of food coloring will make observation easier.)
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