I is for Ice Cube Challenge: Can you pick one up with only a string?

Ice Cube Challenge

Yesterday I gave the girls a challenge.  I gave them a bowl of water (with blue food coloring for better visibility), an ice cube, a piece of string and some salt and challenged them to pick up the ice cube with the string. 

Rules are you can’t pick the ice cube up with your hands and you can’t tie a knot in the string. It’s possible, but you have to know a bit of science to figure it out.

Ice cube challenge

The girls tried dangling the string in the water, scooping up the ice with it and twirling it around. Charlie got close by laying the string over the ice, but she wasn’t quite sure how to proceed. It was fun watching the look of concentration on the girls faces.

If you want, get your supplies out and try it yourself.  See if you can do it before you read on. We’ll wait, I promise.

We finally showed them the trick to picking up the ice cube and I’ll share it with you too.

First, lay the string over the ice cube.

Next sprinkle a little salt over the string onto the ice.

Ice cube challenge

Wait 30 seconds to a minute.  Waiting is the hardest part.

ice cube challenge

Finally, pick up your ice cube with a single piece of string!

ice cube challenge

Ta da! Challenge completed successfully.

So, how does this work? Why does the string stick to the ice when salt is added?

Salt lowers the melting point of the ice and lowers the freezing point of the water. This means the salt melted the ice a bit and then as the water cooled it refroze over the string allowing it to stick to the ice cube.

Were you able to pick up the ice cube without reading the trick? Share your experience in the comments!

A to Z Challenge


    • Mary

      As I would tell my girls, great real life application! Yes, that’s exactly why we put salt on the roads, it reduces the freezing point allowing the salt to melt the ice on the roads and keep them from refreezing unless the temp drops to a certain level. We’re horrible with the salt we put down, I think we use too much, because it always seems to pit our driveway. Oh well, it’s giving it character, lol

    • Mary

      I’ll be honest, I know some of my science stuff, but it’s not my strong point. After I wrote this I had to have my husband “check my work” to make sure I understood it. I kinda love doing things like this because it’s reteaching/reinforcing the knowledge I learned years ago. Always good to have a refresher and someone who knows science to keep me in line!

  • Liz Brownlee

    What fun! Wish i’d been home-schooled! I did that for my son when we had to live in Canada for a while while my husband was editing a film, but my children otherwise went to the village school (which was more like a home, really!).

    I am a children’s poet and keep thinking I should get in touch with home-schoolers over here to do some poetry!

    Liz (A-Z) (website)
    Liz Brownlee recently posted…I is for Invisible!My Profile

    • Mary

      That’s awesome Liz! I’d love to feature some of your poetry sometime, just let me know if you’d like to work together on something!

  • Jen

    I’m going to do this with the boys. They would love this! I need to do more at home science projects. I always forget how much I really love science.

    • Mary

      My kids love science and originally my husband went to college for chemistry (he also does a lot of sciency stuff in the military). We are always learning about something and I should be posting even more science ideas. Check out my science board on Pinterest for even more science experiments to do at home. I have a ton pinned.

    • Mary

      Hahaha, those are Tostitos and they are for my homemade salsa (really it’s pico de gallo, but we call it salsa, lol). Mmmmmm, it’s soooo good. I can’t wait to get my salsa garden moving so I can make it out of fresh veggies instead of store bought shipped in stuff.

    • Mary

      Yes! I want to do a bunch of simple science projects with the kids this summer to peak their interest and curiosity. When you start showing them cool things, they eventually start questioning what makes it happen. Love those moments!

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