20 Minute Labs: Ice Cube Necklace

STRING AN ICE NECKLACE!

With summer just around the corner, we're looking forward to enjoying icy drinks in the sun. Are you?

In this month's 20 Minute Lab,we'll make an ice cube necklace with just a few items from around the house!

You might think that to make an ice cube necklace, you could just lay a string in an ice cube tray, fill it with water, and then freeze it. Well, that would be one way to do it!

But we’re going to use science to add the string AFTER the ice cubes have frozen! How could that work? Not by tying a knot around each one…. We’ll attach the string to the ice cubes using the power of salt!

Ready? Let’s do science!

What You'll Need

• bowl
• water
• ice cubes (3-5)
• fine table salt
• piece of string or thread about 18 inches long

Let's Get Started!

1. Fill your bowl with water - almost to the top.
   
   
2. Add your ice cubes. (You'll notice they float in the water.)
   
   
3. Arrange the ice cubes so they are close together or touching.
   
   
4. Lay the string over the top of each ice cube (lengthwise works best).
   
   
5. Now pour some salt in a small bowl.
   
   
6. Use your fingers to sprinkle the salt over the string on top of each ice cube. You’ll need to use about ½ teaspoon for each ice cube. (Note: Too much salt or too little salt can prevent the experiment from working, so you may need to experiment a bit to get the amount just right!)
   
   
7. Let the salt sit on top of string and ice for about 30 seconds.
   
   
8. Now pick up the string from both ends and watch the ice cubes come along!
   
   
9. Congratulations! You made an ice cube necklace!

WHAT'S GOING ON?

How did the string become attached to the ice cubes? It's all in the salt. Adding salt to water decreases its freezing point. Normally, water freezes at 32°F – or 0˚ Celcius– this this is called the freezing point.

But when salt is added, water no longer freezes at 32˚F - it doesn’t freeze until the temperature gets colder. The more salt mixed with water, the lower the freezing point!

In this experiment, when you added the salt to the string over the ice cubes, it melted that area of the ice cube, creating a little pool of water.

As the ice melted, the water diluted the salt, which made it less able to lower the freezing point. The freezing point increased, and the ice cube refroze. This time the water froze over the string, trapping the string in the ice cube. So, when you lifted the string out of the bowl, the ice cubes held on and came along!

If you live in a place where you get a lot snow and ice in the winter, you have likely seen salt used in this way to keep the roads safe! Big trucks will spread salt on the roads to prevent water from freezing into ice. This helps prevent cars from slipping and sliding and make the roads safer!

Do you think anything else might lower the freezing point of water? Try some other things like sugar, pepper, or baking soda and see what happens!

SHARE WITH US!

Let us know how your experiments turned out! Share your photos and results with us on Facebook, Twitter, Instagram, or send us an email to info@yellow-scope.com. We love getting your messages!

For more exciting experiments, check out our Yellow Scope science kits on the Shop tab of our website!