Penny Science Experiment

Science has always intimidated me, especially since those awful days of high school chemistry.

So, today, when I arrived in a second grade classroom and discovered I would be conducting a science experiment in front of twenty students, I got a little nervous. And I'd be doing the experiment, not with my own students, but with the second graders next door. (My students were going to the teacher next door to practice playing Jingle Bells on their recorders.)

Needless to say, I was a little anxious. I read through the six directions, though, and everything seemed rather straightforward. Maybe even fun! Now, if only I could locate the necessary supplies in the back cupboard. Thankfully, the teacher I was substituting for, keeps all of her science materials in one spot and it is easily accessible. From the cabinet, I pulled out an empty canning jar, a set of measuring spoons, a container of salt, and a plastic jug of vinegar. The teacher had also provided me with six dull pennies.

To begin, the students listed the materials on their papers. Just to recap, the materials included: vinegar, salt, measuring spoons, pennies, and a glass jar.

Next up, each student selected a hypothesis from one of the four options below.

a) The pennies will bounce up and down.
b) The pennies will not change.
c) The pennies will make popping noises.
d) The pennies will be shiny.

Then, we graphed the students' hypotheses. Each student received a paper penny, which they taped up onto the graph. Two students guessed A; three students chose B; two students chose C; and thirteen students selected D.

Now for the really good part...the experiment itself, which was broken down into three parts.

First, I dumped some salt onto a penny to see if anything happened.
(Normally, I would have had a student come up and help, but I was under a bit of a time crunch.)

Nothing happened. Nada.

Next, I poured some vinegar onto another penny.

Again, nada.

Third, I grabbed the glass jar and filled it with 6 tablespoons of vinegar and 2 tablespoons of salt.

Then, I dropped all six pennies into the jar and stirred the concoction around for about a minute.

As I was stirring, I said, "The pennies are taking a bath." Several of the kids chuckled. At that moment, the Rubber Duckie song from Sesame Street entered my head, so I started singing it aloud for the kids. You know the one...Rubber Duckie you're the one, you make bath time so much fun, Rubber Duckie I'm awfully fond of you, Doo doo doo doo, doo doo...

That's as much of it as I remember...and I know, I know, I'm so s-i-l-l-y, but the kids laughed and that makes me happy!

As we were singing and stirring, the vinegar and salt mixture instantly turned the pennies shiny...and the kids were very impressed! Talk about instant gratification!

To finish up the lesson, I explained that the pennies looked dull and dirty because they were covered with copper oxide. Copper oxide is formed when copper atoms (from the penny) and oxygen atoms (from the air) combine. Copper oxide dissolves, though, in a mixture of acid and table salt. (In this case, vinegar was the acid, but lemon juice or orange juice would have worked, too.)

But the story doesn't stop there...

Later on in the day during third recess, I ducked into the girl's bathroom to use the restroom. (The staff bathroom was occupied and the recess bell was due to ring soon.) As I was washing my hands, a little girl from the science experiment class walked in and headed toward the back stall. She turned around and said, "Hi, Ms. H." I turned toward her and said, "Hey, how's it going?" She said, "Good." She continued, "That was so fun--that experiment. First, we tried the salt," shaking her head, "but it didn't work." She paused and continued, "Then, we tried the vinegar, but it didn't work either." The disappointed look on her face was replaced with a hint of a grin as she said, "Last, we tried both and bam, they got all shiny!" As she uttered those words, her face just lit up! I felt a big smile flash across my face as I replied, "Yes, they did."

What a penny-perfect experience!