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Favorite classroom science experiments? Answered

I've been wanting to document some simple and effective science experiments, so I'd love to hear favorites from the community!

The most popular experiments at my elementary school were definitely lemon and potato batteries. I have no idea why, but tiny-me really enjoyed seeing that light bulb start glowing

Or the time we dyed carnations using food coloring in the water in middle school! It was really neat to see the flower change a little more every day during the week.

What's your favorite? :D

Discussions

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Jack A Lopez

18 days ago

It occurred to me, about a month ago someone here wrote me a PM asking for advice regarding a demo with pH indicator electrolysis, like this one,

https://www.exploratorium.edu/snacks/indicating-el...

I actually tried this myself, using purple cabbage juice as the indicator, and the results were colorful. Some pictures of this are attached to this post.

Also the user who wrote me the PM never wrote back: another drive-by question asker.

indicator-electrolysis-p11-23minutes-later.jpgindicator-electrolysis-p08-8minutes-later.jpgindicator-electrolysis-p05-seconds-later.jpgindicator-electrolysis-p03-magnesium-sulfate-heptahydrate-epsom-salt.jpgindicator-electrolysis-p02-indicator-from-red-cabbage.jpgindicator-electrolysis-p01-electrodes-from-AA-batteries.jpg
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WeTeachThemSTEMJack A Lopez

Answer 16 days ago

This is awesome and your results are definitely really colorful. I know some students who would love to see this experiment in action and can only imagine their excitement as those colors develop and spread. It looks like you used the anodes from a battery, is that what caused the unique colors?

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Jack A LopezWeTeachThemSTEM

Answer 16 days ago

The colors are due mostly to the cabbage juice, which is different colors at different levels of pH. The different levels of pH are due to the electrolysis reactions.

Essentially the cathode is making the water near it more alkaline, by reducing (giving electrons) H+ to hydrogen gas.

2 e- + 2 H+ = H2
(or 2 e- + 2 H2O = H2 + 2 OH- )

The anode is making the water near it more acid by oxidizing (taking electrons) OH- to water and O2.

2 OH- = 2 e- + H2O + 0.5 O2
(or H2O = 2 e- + 2 H+ + 0.5 O2 )

I wrote, "due mostly to the cabbage juice," because there are other things that could be adding color to the water.

One thing that comes to mind is oxidation of the anode, particularly if it is made of some kind of metal, especially some kind of transition metal, since the ions of those tend to be colorful.

The Exploratorium author, in that page I linked previously, used stainless steel bolts, for both electrodes, and I tried that too, but the colors seemed to look better using carbon electrodes (removed from zinc-carbon batteries).

I think the reason why the colors were different, was because the stainless steel was oxidizing, and adding some color to the water.

The obvious way to test for this, is to just perform the same setup, but without pH indicator coloring the water.

I tried a few different anode materials: stainless steel bolt, ball of nichrome wire, piece of tin-lead solder alloy, lead fishing weight. Some pictures of these are attached.

It occurs to me now, I did not take a picture of a carbon anode, without indicator, to see what colors, if any, were happening with that, and I should, because I suspect that is the best, easy to find, anode material to use for this demo, with respect to not adding unwanted colors.

Also I am kind of guessing the carbon anode is probably least toxic, although, I have to admit I don't actually know what is in those carbon electrodes, if anything besides carbon.

electrolysis-colors-stainless-steel-anode.jpgelectrolysis-colors-nichrome-wire-anode.jpgelectrolysis-colors-tin-lead-solder-anode.jpgelectrolysis-colors-lead-fishing-weight-anode.jpg
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WeTeachThemSTEMJack A Lopez

Reply 14 days ago

Thanks for explaining and adding the additional images of the tests using different materials. It's really great to see the variations resulting from each material.

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Jack A Lopez

18 days ago

There is a simple physics experiment, in which a steel ball rolls down a ramp, of vertical height h1 above a table. Then the ball rolls across the table for some distance. Then the ball rolls off the edge of the table, and falls a vertical distance h2 to the floor.

The ball also moves some horizontal distance x in its fall to the floor.

The goal of this experiment is to predict where the ball is going to land; i.e. calculate the horizontal distance x. Then measure that distance on the floor, and place a cup there to catch the ball.

A crude picture of this setup can be found here,

https://cdn.instructables.com/FFJ/3U5P/FZHLB97A/FF...

and that picture is attached to a forum topic from 10 years ago, here,

https://www.instructables.com/community/Epic-Scien...

I think the reason I like this one, is because it demonstrates the power of physics to predict an event, in this case: when and where a ball will land, just from a few simple calculations.

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WeTeachThemSTEMJack A Lopez

Answer 16 days ago

That sounds like a really fun way to introduce making predictions in science, as well as math and ELA. Such a great idea! I love when fun, hands-on projects can be used to reinforce cross-curricular concepts.

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Jack A LopezWeTeachThemSTEM

Answer 16 days ago

I learned about this demo by doing it as a lab, in high school, in Physics class, years ago. I guess it made an impression on me.

By the way, what does "ELA" stand for?

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WeTeachThemSTEMJack A Lopez

Reply 14 days ago

I love that certain labs and lessons stick with us! :) ELA stands for English Language Arts

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bekathwia

19 days ago

Two fun projects that use the power of the sun: solar balloons and solar engraving. For the balloons, students can try different balloon shapes to find the optimal ratio of surface area to mass, and using a engraving with a magnifying glass can teach about different absorption/reflection and conductivity properties of materials based on how easy they are to etch.

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WeTeachThemSTEMbekathwia

Answer 16 days ago

I love school solar projects! Solar ovens were my favorite as a student and teacher. Solar balloons are really popular among my fourth-grade teacher friends, but the solar engraving is such a great project and I haven't seen it at the elementary level... I'm thinking a full day of solar energy exploration is in order and these are perfect activities to set up as a station rotation. :)