- Age:4+
- Time:15 min
- Difficulty:Easy
- Mess level:Low
- Supervision:No
Science Behind The Dancing Grain Experiment
Do you remember the Orange density experiment? There we talked a lot about what determines what sinks and what floats. As the name implies, it’s all about the density. It’s at the play here as well.
When you first drop grain inside the water, it sinks to the bottom. Why? Because it has a higher density (mass per volume) than water. But then, the magic happens.
Vinegar and baking soda react beautifully and quite explosively in what we call an acid-base reaction. Here the baking soda is a base (NaHCO3) and the vinegar (CH3COOH) is acid. Acid is always trying to get rid of the positively charged hydrogen atom (proton) and the base really wants that proton. So naturally, those two quickly get together to accomplish their goals.
When the baking soda gets that coveted proton, it immediately dissolves into water and carbon dioxide. Those tiny bubbles of carbon dioxide get attached to the surface of our grain. Since their weight is insignificant, the mass of the grain stays the same. But the volume gets quite larger. Do you know what that means? Since the density is mass/volume, that means the density gets lower. So much lower that in fact it’s less than the density of the water and the grain rises to the surface.
Here we see the Archimedes’ Principle at work. It states that the buoyant force exerted on a fluid is equal to the weight of the fluid displaced. Now that the grain has a greater volume, it displaces more water and causes the water to exert a greater buoyant force.
When the grain reaches the surface, carbon dioxide escapes in the air and our poor grain loses its transport. Back to the bottom, it goes. This dance lasts for quite a bit of time and it’s mesmerizing to watch.
Materials Needed For The Dancing Grain Experiment
Water, baking soda, vinegar and a few grains: the whole dancing setup.
All we need is some Vinegar, Baking Soda, Water and some Grain
- Water
- Bowl or glass
- Grain (we used buckwheat but you can experiment with rice or barley)
- Baking soda
- Vinegar
- Food coloring (optional)
Instructions For Making Dancing Grain Experiment
For step-by-step instructions on how to conduct this experiment watch the video at the beginning of the article or continue reading.
Carbon dioxide bubbles lift the grains up, then drop them when they pop.
Adding Vinegar to Water with dissolved Baking Soda will make our grain dance!
- Pour the water into the bowl.
- Put one spoon of baking soda.
- Add a fistful of the chosen grain (we used buckwheat).
- Optionally, add some food coloring.
- Add a spoon or two of vinegar.
- Poof! Enjoy watching the grain dancing. It lasts quite some time.
Why does a grain suddenly float up to the surface?
Make your prediction, then tap an answer to check!
✨ Pro tip
If the grain isn't "dancing" after a minute or two, it's probably too heavy - try a smaller, lighter grain like rice instead. When the dancing slows down, you can revive it with another splash of vinegar.
What Will You Develop And Learn
- Chemistry principles
- What is an acid-base reaction
- What is density and how to calculate it
- Archimedes’ principle
Key takeaways
- Density (mass ÷ volume) decides whether something sinks or floats; the grain starts denser than water, so it sinks.
- Vinegar and baking soda react in an acid–base reaction that produces carbon dioxide gas.
- Bubbles of that gas cling to each grain, adding volume but almost no mass, so its density drops and it rises.
- At the surface the bubbles escape, the grain's density returns, and it sinks again - that's the "dance".
- This is also Archimedes' principle at work: a bigger volume displaces more water and gets a bigger upward push.
Frequently Asked Questions
Why does the grain dance up and down in the water?
Each grain starts out denser than water, so it sinks. Bubbles of carbon dioxide from the vinegar–baking soda reaction stick to it and lift it up. At the surface the bubbles pop, the grain becomes dense again, and it sinks - repeating for a lively "dance".
What is the reaction between vinegar and baking soda?
It's an acid–base reaction. The vinegar (an acid) and baking soda (a base) react, and the baking soda breaks down into water and carbon dioxide gas. Those carbon dioxide bubbles are what make the grains rise.
What grains work best for the dancing grain experiment?
Light grains work best. We used buckwheat, but rice, barley, or even small pasta or lentils can dance too. If a grain is too heavy the bubbles can't lift it, so switch to a smaller or lighter one.
How long does the dancing last and how do I restart it?
It usually keeps going for quite a while, until the reaction runs out of fizz. When the dancing slows, just stir in another spoonful of vinegar (and a little more baking soda if needed) to start it up again.
Is the dancing grain experiment safe for kids?
Yes, it's very safe. Vinegar, baking soda, water, and grain are all harmless kitchen ingredients, and there's no heat or sharp tools involved - perfect for little scientists, with a grown-up nearby to enjoy the show.
What science does the dancing grain experiment teach?
It brings together density, acid–base chemistry, and Archimedes' principle in one mesmerising demo - showing how adding volume (gas bubbles) without much mass lowers density enough to make something float.
If you liked this experiment and want something else, give a try to another kitchen experiment. How about exploring the concept of osmosis in Gummy bears osmosis experiment? Or if you have some leftover vinegar and baking soda, try to use it as a propulsion system to this amazing rocket! Or go for another fan favorite - volcano eruption. Whatever you choose, always remember to have fun, be careful and observe closely. Until the next adventure, dance on!
