Evan and I had chemistry class today. Chemistry class right now consists of his Magic School Bus Chemistry Kit.
Today we did card #29, a demonstration of the bonding behavior of water molecules. In this lab activity, the young scientist counts the number of drops of water he can place on top of a penny before the water spills over the side. He then repeats the process, but first he puts a drop of liquid dish soap on the penny. I sat beside Evan as he followed the instructions, and I saw nothing amiss in the execution. On the first penny he counted 13 drops of water. On the second penny (the one with the liquid soap) he counted 21. Why the difference? We turned over the instruction card and read this explanation:
A penny can hold many drops of water because the water molecules like each other and form special bonds between each other. On the surface of the water, the molecules are held together by this surface tension. When too many drops are added, the surface tension is broken and the water spills over. Fewer drops can be put on the penny with the soap because soap decreases the surface tension and the water spills much sooner. [emphasis added]
Yeah . . . right . . . .
I really don't know how we manage to do this. But over and over again, our science experiments turn out with something far afield of the expected result. Just one of our many family talents, I guess.
5 comments:
This is hilarious. I do wonder what made it fail though.
I can't figure it out, Anonymous. It is so weird!
I just needed to respond to this - the old science teacher in me came to the fore.
The conclusions from scientific experiments are based on multiple trials. My first suggestion is to try the experiment a few more times.
You should not have had that large a difference in the number of drops between the two pennies, no matter what. That probably means that the drops were not uniform in size. It is difficult to regulate that, but not impossible.
Other factors that may be involved: any contaminate in the dropper (maybe it had soap in it from a previous experiment); different pennies (newer pennies might have a larger surface); the type of liquid soap; any substance that may be on the pennies before hand - that is just a few possibilities.
Judy
Thanks for the insight, Judy. It is probably one of those variables you mention. Sometimes I wonder what the point of these experiments is--it is so hard to get them to come out right! Sometimes it seems to make more sense just to read through the instructions and see how they are supposed to turn out and let that be that. Good news is that today we made "lava" by drizzling butter over a flour mountain. Pretty hard to mess that one up! :-)
Lol, Cheryl. We had similar problems, and I can clearly remember opting for the "let's not and say we did" approach to experiments. They are so fascinating in theory, but so fickle in practice!
We dissected a fish once, and it looked NOTHING like it was supposed to. I suspected it was a female full of eggs, so I took a picture and sent it to Jay Wily. I was right! I'm still rejoicing over guessing right on that!
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