I'm thinking about to color 70% of the body of my children (3-4 years old) with blue ink in order to show that 70% of his body is constituted of water. The problem is maybe they could think that the upper part of his body doesn't have water (see picture).

Do you think this activity is the best activity to show that?

I'm looking for suggestions of activities in order to show them that his body has 70% of water as well.


  • I'm not sure that this is really Parenting related, but I also can't think of a much better fit (is there a childhood education SE yet?)...
    – Acire
    Commented May 31, 2015 at 20:53
  • @Erica yes, that's exactly what I've been thinking.
    – user26832
    Commented May 31, 2015 at 21:41
  • Bake a chicken until it's completely dry, weighing it before and after? I've never actually tried this experiment, so I can't say it will work smoothly. Commented Jun 1, 2015 at 8:01
  • 1
    @Erica I think it's parenting allright, a bit specific, but still well within the scope.
    – Dariusz
    Commented Jun 1, 2015 at 9:46
  • 2
    @200_success You'd have to burn the chicken, basically, to get it to that point; you'd still have a lot of water in it when baked as dry as you can get it. However, you're actually losing oil as well as water. I guess the best thing to do is to combust it, evaporating the water in the process, and re-condense the water (using a method similar to a still). That would be ... very hard, though. And you'd never get the right amount because chickens have had their blood drained already (unless you're butchering it yourself, in which case maybe not a good experiment for a 3 year old)
    – Joe
    Commented Jun 1, 2015 at 16:38

1 Answer 1


Make beef jerky

A tasty lesson about how important water is in living organisms.

The fact that the human body is 70% water is pretty well known, but really on its own it's just a simple factoid. It doesn't teach you much. Instead, make the knowledge part of a lesson in biology revolving around the importance of water to (all!) life.

Since practical lessons tend to stick much better, this lesson uses all of the senses and lets the children get involved with the proces to make sure it sticks.

Observing ordinary meat

Start by getting a slab of ordinary meat to make jerky from. Show it to the kids; talk a bit about how water is important to living things. Let them handle the meat and ask them to write down what it looks, feels and smells like.

Making predictions

Next, tell them you're going to remove the water from the meat. (Don't tell them it becomes jerky, that might make them cheat in the next steps) Let them predict how much of the meat is water (their own best guess) and write it down. Also let them predict what will happen to the meat, using the same descriptors as in the first step (looks, feels, smells).

End lesson, make jerky

End the first part of the lesson. Use a very bland marinade to prep the jerky and then weigh the end result and write down the number. The reason for using a bland marinade is that you want to change the smell as little as possible! You can let the kid watch in on this part and/or turn it into another lesson, of course.

Prepare next lesson

Once the jerky is complete, start the next lesson. Tell the kids the total weight at the start. Then, let them weigh the end result and let them figure out how much of the initial weight was water that has now been removed.

Draw conclusions

Let them handle the meat again and write down the look, feel, smell, etc. Recover the earlier writings. Compare their predictions (both in water content % vs real and the predicted look/feel/smell vs the actual) and discuss the results. Then talk a bit about what has happened to the meat and where the differences are coming from.

Closing up

Take questions, if any remain. Then, eat the jerky together.


  • letting kids explore the proces with all their senses means things will stick better
  • teaches children about the scientific method; make predictions, do experiments, see if you were right, figure out what happened
  • learn about how things are prepared and that food isn't just produced in a factory


  • material might be expensive and can only be used once
  • lesson is split in two parts due to preperation proces of jerky
  • not suitable for vegetarians (but try dried fruit instead; works about the same although it's a little further removed from the feel of human flesh)
  • Basically a brilliant idea, but I'm not sure whether a 3-4 yo can grasp the math as you suggested. My son is gifted in math (tested, not bragging parent speaking) and would have had difficulties with this at that age. If the 2/3 water aspect can be neglected and translated to "contains a lot of water" it works at that age, but OP needs to decide what precisely the goal is. Upvoted anyway, also for the excellent description of the process.
    – Stephie
    Commented Jun 1, 2015 at 10:40
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    A nice idea, but given the blood is not in the beef pre-beef-jerky making, it won't come to 70% by any means (though given the bone is also not there, maybe it will by chance, who knows). I don't think beef jerky is entirely devoid of water, either, though it's probably as close as you can get without combusting the beef. But as a general lesson about 'a lot of water in the body', without worrying about the specific proportion, I think it's good.
    – Joe
    Commented Jun 1, 2015 at 16:40

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