Science At Home: Candle Trick and Fire!


If you want to impress your kids, grandkids, significant other, friends, neighbors or your dog, I’ve got STEM science you can do at home! Science is cool and looks like magic. No advanced degrees needed! These don’t require much in the way of materials, either, so you can probably avoid going to the store. Without further ado, here’s an easy STEM science experiment at home!

Listen to the instructions and explanation above!Louie and Microphone

Candle Water Trick

You only need:

  1. A tea candle (or any candle. This could work with a taper if you have a large enough glass to cover it)
  2. Water 
  3. Small plate
  4. Drinking glass or vase
  5. Lighter or matches
  6. Food coloring
Materials for Candle Trick


  1. Add the water to the plate. (1/4 cup or so)
  2. Use a few drops of food coloring to make this more visible and dramatic. (I just realized that I picked blue. I love blue…it is rare in nature. Read about why here!)
  3. Put the candle in the water, but be sure that it can burn without getting wet.
  4. Light the candle
  5. Cover it with the glass 
  6. Observe!

Video of experiment in action below!


Question mark

There is a lot of misinformation online, and this STEM activity is rife with such. Here’s the WHY…

  • As soon as the glass covers the candle, the candle is burning in a closed environment. (Okay, not perfectly closed, but you have to agree it’s close)
  • Because of thermal expansion, (warmed air molecules move more quickly and bounce against each other and move further apart, so they increase in volume or area they take up in space) the air pressure is higher under the glass than in your room.
  • The burning of wax produces about 30% more molecules of carbon dioxide and water than the molecules of oxygen consumed in the reaction.
  • Yes, candle wax or paraffin, burning IS a chemical reaction.
  • Burning is one of the signs of a chemical reaction! which…

    …I outline in my book, Chemical Reactions, coming out in 2021 from Nomad Press




  • The balanced chemical reaction of paraffin and oxygen:  C25H52 + 38 O2 => 25 CO2 + 26 H2O (38 molecules of oxygen on the left versus 25 molecules of carbon dioxide plus 26 of water on the right = 51 molecules, or about 30 percent more product)
  • The increased heat and increased number of molecules under our glass (or the products of the chemical reaction on the right side of the equation above) increases the pressure inside/under the glass. (More heat excites the molecules and more molecules are there to bounce off each other, aka thermal expansion again)
  • When the candle burning reaction (called a combustion reaction) runs out out oxygen and the candle goes out, the temperature decreases again. You’ll agree with a decrease in temperature, the pressure decreases, too. The water vapor created above (see equation up there), begins to condense. This ends up causing a decrease in pressure under our glass, which goes lower than the outside of the glass. 
  • Therefore, despite the fact that water is heavier than air, the water is pulled into the jar, because of a pressure difference again, this time higher on the outside than inside. 

Nature loves equilibrium! Nature wants the pressures equal.



This experiment involves chemistry AND physics! Super cool.

In the interest of keeping this post shorter, my consultants (Louie and Ian) suggest that I stop with one experiment.

Next time, we’ll talk about magnetism and do another easy, cool magical science experiment. This will give me a few more days to find some leaves. Spring is never early in Wisconsin. Pretty but no leaves….


Louie spring flowers

Louie is eager to continue leaf hunting…. 

Let’s go outside!

Try this and please let me know who you impressed! 

Hummingbird on red flowers

If you want to more magical STEM activities to impress your posse, I’ve got a great one here! Just click on the highlighted text!

Hint: it involves flowers. No green thumb needed!

Also…please subscribe! Scroll up and you’ll see the teal box in the sidebar on the right! You’ll make me very happy when you do! 

Jumping with balloons

No, this isn’t me but I’d love to try this someday!


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60 thoughts on “Science At Home: Candle Trick and Fire!”

  1. This is so doable. Love your simple experiment. Yes, one is perfect. But please write another post and give us another one, and please have lovely Louie in there as well.

  2. Love these so much! My partner has a degree in chemistry and I, on the other hand, am absolutely useless so he’s always picking out little experiments like these to blow my mind with. Definitely going to give some of these a go! Great post 🙂

  3. These look like so much fun to try! I need to be more active with making my kiddo’s school at home more interesting. At this point everything but the core classwork is optional. Trying to get her to do the optional stuff to keep her engaged and off Disney+ is hard. These should get her more excited!

  4. Wow I loved the post!! We could really use some science here in the blogosphere and that was really fun to read!!

    You explain very well too. I understood it all in one go. :)))



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Susan Berk Koch author

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