Like Walking on Water

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

Like Walking on Water

December 26, 2014

As winter hits many parts of the world, it becomes cold enough to freeze water into ice. You might have patches of it on your street or sidewalks, or teeny frost crystal designs on your windows. You might also live near a lake where the top of the lake freezes — and if it freezes to at least 4 inches thick, people can skate safely on it (but only if it’s at least that thick, and even then you have to be careful!). When lakes freeze, the ice usually comes out white because it’s full of little air bubbles. But some hikers in Slovakia came to a lake that had frozen completely clear. As the video shows, they can look down past their feet and see all the way to the bottom, as if they were walking on water! It must have felt pretty freaky to see rocks and sand dozens of feet below, and just float above it all like that. But bluish or clear ice is the strongest compared to white, gray or black ice, so at least they knew they could stay afloat.

Wee ones: If the ice on one lake is 7 inches thick and on another it’s 9 inches thick, which one is thicker?

Little kids: Water freezes at 32 degrees F. If it’s just 1 degree warmer than that outside, what’s the temperature?  Bonus: Ice that’s 8 inches thick across a lake can hold up a car, and ice 4 inches thicker than that can hold a small truck! What thickness ice can hold a truck?

Big kids: If every 2 days the ice on your lake freezes an inch deeper, how much thicker will it be 2 weeks from now?  Bonus: If the lake the hikers found was 26 feet deep and was frozen halfway down, how thick was the ice?




Wee ones: The 9-inch ice.

Little kids: 33 degrees F.  Bonus: 12 inches thick.

Big kids: 7 inches thicker, since it will take 14 days.  Bonus: 13 feet.

And thank you Catherine M. for sharing such a cool (actually freezing cold) video!

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About the Author

Laura Overdeck

Laura Overdeck

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.

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