Thursday, April 18, 2019

Homeschool Science: The Chicken Egg Osmosis Experiment

When Syd and I played with gummy bear osmosis, I wanted her to observe water passing into the gummy bear and causing it to expand.

It did. It was cool!

With this chicken egg osmosis experiment, I wanted the kids to understand that osmosis can go both ways through a semi-permeable membrane. If the more concentrated solution is inside the cell, water goes there. But if the more concentrated solution is outside the cell, then that's where the water goes.

Bring on the naked egg!

You can dissolve the shell from an egg as a simple, hands-on demonstration with little ones, as an early elementary human biology lesson (and demonstration of why we brush our teeth!), and as one of the projects in an acids/bases unit of a chemistry study--we've done all of these, so it's old news but still always fun.

And if you have sensory-seeking kids, there's nothing like the feel of a chicken egg with its shell dissolved away:

And speaking of sensory-seeking kids...

I promise that, current evidence to the contrary, she is very intelligent. Just don't try this at home, okay?


So as you've gathered, before we violated every lab safety standard and Licked the Science, we soaked the eggs in vinegar for long enough to get them nice and bloated, as osmosis equalized the water inside the egg with the water outside it. The kids' challenge was to find a solution to soak the eggs in that would cause water to migrate FROM the egg TO that solution, thus shrinking the egg and lowering its mass.

The kids weighed their eggs in grams, labeled jars and put the eggs in--

Guess whose jar belongs to Syd?
--and then went in search of a solution with the proper characteristics. Will chose canola oil (spoiler alert: it worked); although I encouraged Syd to use her notes from the gummy bear osmosis experiment to inform her choice, her first idea was baking soda dissolved into water and dyed blue. This had the opposite of the desired effect, as you can see from the fact that her egg is now blue:

It looks really cool, though! It would perhaps be a fun continuation of this project, when done with small children, to dye the water a rainbow of colors.

I stopped photographing the eggs at this point because they were soooo gross (and Will did NOT lick one again), but you'll be pleased to learn that for Syd's second try, she chose dish soap. Success!

If you've got even more time to play, you can do this similar but more academically rigorous osmosis experiment with potatoes, instead. You can also watch this neat little animated model of a cell membrane in action.

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