I was getting T. ready for bed the other night when she asked suddenly if I knew what an hypothesis was.
"Tell me," I said.
She paused for a minute, to recall the information, and said, "it's an idea you can test!"
I don't know where she heard that (probably from Sid the Science Kid on her beloved PBS Kids website) but she was right--a hypothesis IS an idea you can test. Even though she had the definition down pat, I was curious if she could apply the concept in real life. I try to encourage both kids to imagine what might happen before they try something out (even "what do YOU think might happen if you tip that chair?")--the problem always was that L. knew in no uncertain terms what would happen and he often didn't give T. a chance to form her own hypothesis. Now that he's back in school, I decided to fit in one more summer science activity that would help cement in T.'s mind just what testing out a hypothesis might mean.
We decided to test out an oldie but goodie of a science experiment--rescuing an ice cube from a bowl of water using only a thin piece of yarn, and some table salt. There's one rule: you can't use your hands to attach the string in any way to the ice cube. I love this experiment because it's wonderful to watch small children's minds at work figuring this one out, and to catch that a-ha! moment in action when they do.
First we had fun imagining how to do it. I asked T. for ideas about how we might do the experiment and we talked these through, and came up with our own hypotheses about how what would work, and why. Her first idea was to sprinkle salt on the yarn, so we tested this out, and discovered pretty quickly that you can't get the salt to stick to the string.
Then, she decided we should sprinkle the salt onto the ice cube.
She worked out (with some nudging) that the trick was to get the yarn to re-freeze onto the surface of the ice after the salt melts the top layer, but she had to learn that patience was a critical step in the whole process: pull the string up too soon, and you lose the cube.
It took only a few attempts of testing out various angles and ideas for T. to get the experiment to work:
In all, I think the experiment took us only about 20 minutes to work through, then T. spent a good ten minutes playing with the rapidly melting ice cubes. After we had cleaned up the salt and the watery tupperware (and T.'s hands) I asked her what she thought about summer science, in general.
"Is it done?" she asked, looking woeful.
"Summer science might be," I told her. "Summer is almost over."
T. held up one finger in the air, the way she does when she has an idea. "I have an hypothesis to test out!"