As all your students surely know, water is one of the most important requirements for living things. People, cows, birch trees, flounders, goats, owls, panda bears, mustard plants, alligators—if it’s alive, it needs water to stay that way.
As some of your less stupid students may know, something like 71% of Earth’s surface is covered in water. That’s a lot of water, but how much of it is actually drinkable? Well, you can drink any and all of it, obvs, but how much of that water is safe to drink?
This quick and easy Demo Science science demo will help kids (or whoever) visualize just how little safely drinkable water there is on this big blue-green marble of ours.
Water > Apple Juice
For this demo, you’ll need just two items: (1) an apple, the bigger the better; (2) a cutting implement of your choosing—I would recommend a huge, two-handed broadsword, but you do need to be rather precise in your chopping, so I guess we’ll just have to be nerds and use a regular kitchen knife. Boring!
From there, it’s as easy as slicing an apple, because that’s exactly what you’ll be doing. First, explain to your students that the apple represents all the water in the world, both fresh and salt (ocean) water. Cut the apple into four equal pieces (quarters, if you will [or even if you won’t—they’re still quarters whether you call them that or not]).
Then, cut one of those quarters in half—these pieces of apple now each represent roughly 12.5% of the whole. Now, cut one of those halves in half again, representing 6%. Cut one of those smaller pieces in half yet again, giving you a wee 3%. Explain that this tiny slice represents all of the world’s fresh water, while the rest of the apple (in all its now-many pieces) represents the world’s salt water. Be sure to mention how most living things cannot drink salt water without severely negative consequences, leaving fresh water as the only viable option.
Finally, chop one of those little slices into roughly 1/3 and 2/3 sections—you now have two very small pieces that are roughly 1% and 2% of the whole. Explain to your students how this final, miniscule, 1% chunk o’ apple represents all the actually usable fresh water in the world. If they’re not at least moderately surprised by that fact—that only one one-hundredth of the Earth’s water is safe for our planet’s billions of living organisms—you’ve got some hard, cynical little punks in your classroom.
What Happened to the Other 99%
All kinds of things, really. Pollution, misuse and waste, being saltwater… What you want students to learn from this, about conservation and environmentalism and whatever, is totally up to you. I can’t do your whole dang job for you, jeez.