Educating Risa

Jim did a couple of really simple science activities with the boys on the weekend, using just ice cubes, salt, and string. He emptied an ice cube tray into a large bowl, and then put one cube in each of the boys’ blue bowls, along with a piece of string, asking: “How can I use this string to pick up the ice cube, without tying the string around it?” The boys were stumped. “What if I sprinkle it with salt? Will that help?” The boys thought this was crazy! “What if I say abracadabra while sprinkling?” joked Jim.

“We’ll check back on this in a bit.” He then took out some small ice chips and shavings that had fallen off when cracking the ice cubes from their tray, and put them into a separate bowl. He had the boys observe briefly, and asked them what was happening. “They’re melting,” was the reply. “So what do you think will happen if we sprinkle salt over top of the ice chips?”

The boys observed the ice for a minute or two, and Daegan said, “I think they are melting faster.” Jim confirmed this, and explained a bit about saltwater having a different freezing / melting point that regular water. He also talked about how some places salt roads or sidewalks in winter.

He then got two ice cubes and showed the boys how to glue ice together…without glue!

He pressed the two cubes together, pressing the top cube into the salted side of the bottom cube:

Gareth wanted to help, and got his rubber gardening gloves on to protect his hands from the cold: 

And voila! The cubes stuck! (You have to hold them a while as you need enough time for the salt to melt enough of the cube that then re-freezes to the other non-salted cube above, adhering them together.)

So how about that ice cube and string we started with? (Same reasoning: the salt melts some of the cube, the string gets caught in that water, which then re-freezes, trapping the string in ice):

Unfortunately Gareth tried to lift his string too soon, disrupting the process. But this experiment is cheap and easy to repeat. When we were done the boys took the remaining ice cubes, sprinkled them with salt in a bowl, and re-froze to make a giant iceberg. They wanted to play Arctic Animals again.