# Summertime Ice Rescue

June 13, 2014

As the temperature rises, the search is on for activities to beat the heat. Some days are so hot we can imagine how nice it would be to find ourselves surrounded by a chilly substance like ice. While we’d be miserable after just a minute or two, you can easily freeze small toys and trinkets in a block of ice. Once they’re frozen, the kids can become ice excavators, freeing the toys, cooling off, and learning some cool math principles along the way!

Have the kids gather a few small toys that can be submerged in water without sustaining damage. My son chose small super-hero figures. He couldn’t wait to come to the superheroes’ rescue and save them from their frozen jail!

Before your kids can rescue, they’ll need to search.  Have your rescue crew count the total number of small toys and then search out a matching number plastic containers in different shapes and depths to freeze the toys in. Your “Tupperware” cabinet, toy chest, and stash of bath and beach toys are good places to look.

Fill the containers 3/4 full with water and add a few toys to each container. Kids naturally will want to fill the containers to the brim, but this would be a big frozen mistake! Unlike most substances, which contract upon freezing, water expands. If the water expands and our containers are full, what will happen when the water freezes?

Once your containers are full (but not too full!), ask the kids to share some observations. Which container do they think will freeze first, and why?

Set the containers in the freezer and wait for them turn into solid ice. Another interesting property of frozen water is that it becomes less dense as it freezes. While you’re waiting for your containers to freeze, set up a little sink or float experiment. Go on a scavenger hunt around the house and collect a few items that are about the same size as an ice cube. Fill a bowl with water and take turns putting the items in water. Do they sink or float? How about an ice cube?

When your containers are frozen solid, it’s time to begin excavating! Brainstorm some fun ways to speed up the ice melting process. My rescuers came up with a few creative ideas:

• Pouring warm water on the ice bricks
• Squirting them with squirt toys filled with cold water
• Placing ice on warm sidewalk or driveway
• Sprinkling the ice with salt, sugar, or sand

Salt helps to make the ice melt faster by decreasing the freezing temperature of water. Lots of people use sand on ice in the winter, but it doesn’t actually make the ice melt any faster. Instead it creates friction on the surface of the ice that is helpful for walking or driving on it. The friction might help the ice melt, but it’s not due to any special properties of the sand itself. Sugar can also lower water’s melting and freezing points, however it’s not as effective as salt.

Remember how you asked the kids to choose containers of different sizes, shapes and depths? This affects the rate of melting as well. The larger the surface area, the more ice is exposed to heat, and the faster it will melt.

We’d love to see your ice excavators hard at work! Share your photos with us on Instagram and use the hashtag #BedtimeMath to be sure we see it!

Photo courtesy of Angie Six.