Saturday, September 28, 2019

What to Do When Science Experiments Don't Work Out

One of the biggest problems I have with Science instruction is when an activity is billed as an experiment but it truly isn't. VERY RARELY does a book of Science Experiments for children actually have experiments in it. In fact, I think Asia Citro's The Curious Kid's Science Book is the only one I've seen.

The Curious Kid's Science Book

by Asia Citro

Most books have Demonstrations... they tell you what materials to collect, they tell you what procedures to follow, they tell you what will happen, and they tell you why it is happening. It's a demonstration of a scientific idea and it's been carefully crafted to work and to help you understand that idea.

I'm sorry, but that's not really an Experiment.

"Is slug slime as strong as a glue stick?"
I totally want to know the answer to that question (Asia doesn't tell us) and I would dearly love to design the experiment that would help me figure it out.

Think about it from the child's point of view.

An Experiment is when you do not know what will happen. It is when maybe even your teacher does not know what will happen. It is when you and everyone who is doing it with you are actually thinking like scientists. It is when you are testing your ideas and taking notes and thinking it through and tweaking something in your materials or your procedure (changing only one variable at a time, of course) and then testing your ideas again.

When an experiment does not work out, rejoice! It's an opportunity to really model scientific inquiry. This week in Science Club we were blessed with two experiments that did not work out. And we had two demonstrations.

Friday, September 27

The astute observer will notice that we switched Sean Connolly books!

We started Science Club this year with the Periodic Table of the Elements. Now we are looking further at combinations and determining whether they are simply a mixture (like the iron filings and sand, which we mixed with a spoon and then separated with a magnet covered in plastic wrap) or an actual chemical reaction (like baking soda and vinegar reacting and carbon dioxide gas being formed in the process).

I demonstrated a mixture with the iron filings and sand; I demonstrated a chemical reaction with the baking soda & vinegar in "Frankenstein's Hand."

We also reviewed last week's demonstration, "On the Trail of Cavendish," where we had seen a chemical reaction in action. We found water vapor inside a glass which had been placed over a burning candle and left there until the candle went out. Our experience was that the combustion had been a "bond breaker"; the water vapor appeared because the bonds between the carbon and hydrogen in the candle wax had been broken and so hydrogen was able to join with the oxygen in the air to make water. Carbon was also able to join with the oxygen to make carbon dioxide. Bonds were broken. New bonds formed. We acted this out in our group with handshakes.

Now it was time to do two more messy and fun chemical reactions, both of which required us to be outside and both of which were perfect for a hot and sunny late September day.

My students have been begging me to do baking soda & vinegar volcanoes and test tube rockets. So we did. That's the whole point of the wishlists!

However, after carefully making our volcano model (digging clay from the back yard, soaking it in a tub of water to soften it, and then slapping it up the sides of a 1 L water bottle) and carefully following the amounts of baking soda, vinegar, and dish detergent in Connolly's book, we found NO ERUPTION. The mixture didn't bubble enough to come out of the bottle.

Great! Now we could tweak the recipe and come up with a better one. Doubling the baking soda and then tripling the vinegar gave us a very satisfying reaction, one which worked so fast that we could barely get the funnel out of the way before ooze was coming out of the volcano's opening.

After messy clay digging & volcano building fun, it was time for the final project. The famous Mentos and Diet Coke eruption was something I had been dreading (a bit) because it was 12 Mentos and a 2 L bottle of Diet Coke... which is supposed to be quite impressive. Of course, as the teacher I was the one in charge of loading the test tube with a dozen Mentos, balancing it upside down on a 2 inch square piece of cardboard placed over the open mouth of the soda bottle, pulling the cardboard out of the way, and sprinting to safety before I got dramatically sticky & wet.

In preparation for this experiment, I went ahead and got the test tubes and test tube rack which I have had on my Amazon wish list for several years.

They are beautiful test tubes and I'm truly glad that I have them... but I didn't measure a Mentos before buying them. Connolly said "test tube" so I got some. Turns out that the diameter of said tubes (20 mm) is not as big as the diameter of the candy (> 20 mm).

Ok, time to brainstorm.

After some discussion we decided to use a toilet paper tube instead. We stacked the Mentos in the toilet paper tube balanced on the cardboard square, and then I pulled the cardboard away and dashed to the sidelines.

As it turns out, only about four Mentos went into the bottle (we still got a pretty cool geyser but it wasn't as big as it would have been with three times as many Mentos). Most of them just fell into the grass.

Great! Now we could tweak the candy delivery system and come up with a better one. Time to get out Science notebooks and brainstorm and sketch...

If you have any ideas to share for this, please feel free to comment. And I'll let you know what happens next week when we tackle this problem again!

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