Doppler 9&10 STEM: How Does Salt Work?

Teachers & Parents:

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With the unpredictability of winter always trying to come back as we approach spring salt may not be used as much. But throughout winter you may be wondering, why do we use salt trucks to melt ice on the roadways and do other materials work? Well, we are going to show you salt “melting” ice in this week’s STEM and describe how it works.

• Water
• Clear Cups
• Dixie Cups
• Ice
• Ice Tray
• Cookie Sheet
• Baking Sheet (For Larger Ice)
• Salt
• Sand (optional)
• Food Coloring
• Paint Brush
• Glitter

Now let’s make some art, then melt it!

1. Freeze cubes of ice in an ice tray
2. Grab 3 dixie cups and label them 1, 2, and 3
3. Pour warm water into dixie cup 1
4. Pour cold water into dixie cup 2
5. Pour warm water with kosher salt into dixie cup 2
6. Pour food coloring of your choice into each dixie cup, make sure they are different colors.
7. Add glitter too if you would like.
8. Once ice cubes are frozen, take them out and place them on a cold plate (so the ice doesn’t melt right away)
9. Use the paintbrushes to decorate your ice cube.
10. While you are brushing, keep in mind which dixie cup you are using the water from?
11. Ice will start to melt. Which one melts first? Hint: I will be “salty” if this doesn’t work out
12. You can try this with other minerals like sand too!

Now for a little explanation!

So why do the road crews use salt to melt ice? Well as you saw salt melts the ice quicker than just warm water (warm air).

The salt lowers the freezing point of water. In other words, salt makes ice harder to stay frozen when it is applied. The more salt you place on the ice, the faster it will lower the freezing point, the faster the ice melts. Thank goodness road crews know this trick! Other states that are much warmer do not use salt or do not have salt trucks because snow is so rare. Can you imagine not having salt trucks in Northern Michigan?

If your kiddos try this experiment, send us photos of you and your experiment and you might get to see it during weather on The Four on Tuesdays!

Make sure you tune in every Tuesday for a New 9&10 STEM. Send us an email at  or find us on Facebook and at Doppler 9&10 Weather Team if you have a weather question or want something in science explained! It does not have to be weather-related! Anything Science or math-based we’ve got you! You can always get the latest forecast on 9and10news.com/weather as well as interact with us on social media!

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