Thursday, August 8, 2013

The Law of Conservation of Whining

[I acknowledge that the problem detailed below is of my own making. I walked into this one. I'm also chuckling about it. Still, I'd still really, really appreciate help extracting myself from this sewer of scientific statistics in which I now find myself sinking...]

In a recent science lesson, I was discussing the difference between chemical and physical changes. We discussed cutting wood versus burning wood, crumpling paper, breaking glass, stretching rubber bands, and crushing ice versus melting ice.

That's when we hit the sticky point. See, Daniel believed that crushing an object should change its mass. I said no. He argued that if we spread it out more, it would weigh more. (Maybe he was thinking that air would get mixed in...? I'm not sure what exactly was happening in his head.) I argued otherwise, but I wasn't convincing him.

Finally I proposed an experiment: we could take beef bouillon cubes, place them in a ziploc bag, weigh them on my kitchen scale, crush them, and weigh them again. This simple exercise would settle the issue conclusively in my favor.

Daniel upped the stakes: he'd cooperate, but if I lost, I had to admit my fallibility. This was a huge deal, since I've been brainwashing the kids since birth that "Mom is always right." Was I willing to risk that status? Well, I was really dang confident, so sure.

Then Eric, who had been supporting my assertions, suggested that I reciprocate by demanding a stake from Daniel. Brilliant idea! I told Daniel that if he lost, he was not allowed to whine AT ALL for 24 straight, glorious hours.

Gleefully anticipating my victory, I put the kids to work.

Three uncrushed cubes weighed in at 0.5 oz. After crushing, they came in at...[drumroll] 0.6 ounces???

"Wahaha!" shouted Daniel. "I knew I was right!"

I tried to explain, but I got the distinct impression that Daniel was tuning me out. "[Babble] small sample instruments with poor precision...round-off error...[static noise]...scientific method...repeatability...charts and graphs...blah blah blah...user error...imperfect testing conditions...independent confirmation..." I think it mostly washed over him meaninglessly.

I did finally negotiate a second attempt. We took 10 buillion cubes, not 3. We agreed to take multiple measurements (I wanted 10 each; Daniel, taking unscrupulous advantage of not having lost his whining privileges yet, bargained me down to 3). We set the scale to grams, not ounces.

Daniel was impatient about the whole thing, but acquiesced. Eric pontificated, naturally, but also helped.

We even made a nifty little chart. It looked like this:

Uncrushed | Crushed

44g            44g
44g            44g
44g            45g (The scale flickered between 44 and 45 grams; Mom suspects round off-error again.)

"Wahaha!" shouted Daniel. "I knew I was right!"

I argued that I did not interpret the data the same way he did. He retaliated by calculating the average of each set of measurements. "The average of the uncrushed weights is 44 grams," he said, "And the average of the crushed weights was 44 and a third grams. So the second set of measurements is bigger and I WIN!!!"

I wondered, fleetingly, if he was being difficult on purpose, if he knew he was wrong but refusing to admit it. He seemed genuinely convinced, though. All of my pleas about "let's try this again, with a really large sample size, maybe 20 measurements each" were to no avail.

Yes, I should have insisted on either "cleaner" laboratory conditions or on lots of repeated measurements. I am not surprised that my $10 kitchen scale is imperfect, but I didn't expect it to let me down quite this badly.

It doesn't help that science is my weakest subject and Daniel knows it. If I tried to explain something about a rare exception to a rule of grammar, he would probably accept my Authority. Not so here. On the other hand, Eric argued with him and Jon lectured him, but he refused to listen to them, too. I think he's really, really enjoying having "proven" us know-it-alls "wrong."

Now I'm completely out of beef broth stock, and I have a kid who doesn't believe in one of the most basic principles of physical science, "The Law of Conservation of Mass and Energy."  (I was going to say "The Law of Conservation of Matter, but Jon made me change it.) The best outcome I've been able to negotiate is a truce in which neither Daniel nor I "collect" the bet from the other.

So, to any chemists, pharmacists, mechanical engineers, or science teachers out there...


1 comment:

Jon said...

We really should have explained better how test and measurement equipment works in reality before you did your experiments.