dadlab #1: Bouyancy!

Hey there, loyal readers of Following Footprints!  I’m Scotty, a guest contributor to the blog.  I’ll be doing posts on dadlabs, a bunch of physical science lessons with an emphasis on hands-on learning.

Wait, who is this guy?

My credentials are thus: I’m married to the blog’s author, so I get to post on her blog.  If you want to blog here, you’ll have to marry her, too.  I wonder how long before she’ll make me edit that sentence out.

The lab

Today’s dadlab is on bouyancy, and the magical stuff that happens to fluids that are heavier or lighter than other fluids.


We did this dadlab opportunistically, based on the fact that we came across some helium balloons.  And because we were in a supercharged muscle car that simply jumped off the line.

It's important to coordinate your science with your wardrobe

Princess K with some lab equipment.

Your jealousy is entirely understandable

State-of-the-art mobile science laboratory

And because helium balloons in cars are awesome.  If I had planned it better, we would have tied a non-helium balloon to a string as well, but we made do.

Time for Science!

We first established inertia, that is, the tendency of matter to resist acceleration.  Naturally, we did so without using the words inertia, matter, or acceleration.  Tragically, X-man’s balloon had already popped, but it provided a good example of inertia.  I had him hold his broken balloon by the string as still as he could, so that it dangled straight down.  I hit the accelerator from a standstill, and the kids observed how the balloon swung backward.  On another pass, I had the kids try to sit forward (not very easy in 5-point harnessed carseats), and observe how they get pushed back into their forward-facing seats.  The baseline was established: when the car speeds up, stuff goes back.

So what happens when a helium balloon is floating freely in the middle of the car?  When daddy hits the gas, where does it go?  The kids were cautious about their hypothesis that it, too, would go to the back of the car.  So I put the pedal to the carpeted flooring.

That balloon raced to the front, and then promptly popped loudly.  Science is exciting!

We discussed the results.  We talked about how the balloon really wanted to rush to the back of the car, but that the air in the car wanted to do so even more, because it was heavier.  “That, kids, is called buoyancy!”


“Never mind.”  I need to remember to keep things age-appropriate.  I remember how confused I got about density from watching Eureka!  at too young an age, and had to relearn it much later.

Beyond Balloons

Later that day, we looked at an example of liquid buoyancy.  I poured some canola oil in a cup, and some water (with food coloring in it) in another container.  I looked up the specific gravity of canola oil (0.91 if you must know), so I knew what to expect.

I asked the kids what would happen when I poured the water over the top of the canola oil.  Would the water sit on top of the oil?  Would they mix together?  The kids stated their hypotheses, and then we poured!

"Oh, you both have layers. Oh. You know, not everybody like onions. What about cake? Everybody loves cake! "

Canola oil floats on top of food-dyed water

To our budding scientists’ surprise, the water went to the bottom, and left the oil on top!  Then I sealed the top of the cup and turned it upside-down.  The oil stayed on top!


We talked about the connection between the cup of liquid and the balloon in the car.  What’s the common principle?  Heavy stuff goes down and pushes lighter stuff up.  For a 4- and 5-year-old, that feels like just the right amount of detail.  We didn’t go into why the water and oil didn’t mix.  We DID go into what helium balloons would do on the moon.  You know, the important stuff.

This lesson was lots of fun, and hopefully didn’t try to take on too much.  It was my first dadlab, so I’ve got some refining to do.  But the kids seemed engaged, and the lightbulbs did seem to turn on without too much trouble.  Frankly, if I’d had to explain too much, it probably would have killed the fun of the lesson.

I look forward to the next dadlab, and when we do it, I’ll be back!

I’m out!


3 thoughts on “dadlab #1: Bouyancy!

  1. Scott, you’re a hit!! Great job, great entertainment, great science (even I understood it), great dadlab, great dad!! Hurry back soon. Need more input, Stephanie.

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