Cheap and Quick STEM Lesson Your Kids will Love #2

This STEM lesson was more fun than I had anticipated.  We picked up ice cubes with a piece of string.  There are few materials needed.  The materials are cheap and it doesn’t take long to carry out the lesson in the classroom.

You will need:

• an ice chest or freezer
• ice cubes (the kind you freeze in ice trays) make about 5 per student to make sure you have enough
• string (like the kind you fly kites with)
• styrofoam bowls
• table salt (one container should be enough for a class of about 20)
• small cups or containers to distribute the salt
• paper towels
• water

First, we watched a video about how salting roads helps salt trucks melt ice and snow on roadways here:

Then I explained to the students that we were going to make a string stick to an ice cube and that they would be able to pick it up.  I had the students predict how long they thought that it would take to attach the string to the ice.  I realized mid lesson that the kids thought I wanted them to literally tie a string around the ice cube.  I had to clarify that we were not lassoing the ice cube, but that the salt would make it stick if they were patient (insert lesson about perseverance and patience here, wink wink).

These are the student directions in order.

• In your bowl of water put 1 ice cube (I passed these out when I was ready for them to begin).
• Put a pinch of salt on top of the ice cube
• Lay the string on top of the ice cube
• One team mate needs to watch time (I had this on smart board). The other team mate needs to watch the ice cube and pull on the string when the predicted time is up.
• If your string doesn’t stick, make a new prediction and try again. Switch partners.

I had a sheet in which the students predicted, and I also took some of their predictions and wrote them on the board.  Some students predicted up to 30 minutes.  Eventually, I reeled this in and said it wouldn’t take 30 minutes.  In honesty it takes somewhere between 30 seconds and a minute.  Also, I reminded students that they would only need a pinch or so of salt on the ice cube.  Some students think that the more salt they use the better the string will stick and end up using WAY TOO MUCH!  The important part of this experiment is the waiting.  I told students that if they added salt that they would need to add it a pinch at a time.

For those students who are successful, I challenge them to make more than one ice cube stick and predict how long it will take for more than once ice cube.  I walk around with a ziplock full of ice cubes during this time.  When students get more than one ice cube to stick it becomes a contest about who can get the most ice cubes to stick at one time.  The most I had students able to stick was 5 ice cubes.  Not many kids were able to do this.

After this experiment, it is fun to discuss more of the science behind why this activity works.  Because I did this during a 30 minute slot at a summer camp, we didn’t really have time to talk much.

I hope you can enjoy this experiment with your students, too!