Make a Lemon Volcano, and More Fun Citrus-Based Science Experiments

You don't need a master's degree in chemistry to build a lemon volcano — but don't tell your kids that.

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halved lemons, limes, oranges and other citrus fruit that can be used in science experiments at home...

The following was produced with Sunkist, a cooperative of family-owned farms bringing you the best fresh citrus California has to offer.

You don’t need a master’s degree in chemistry to build a lemon volcano — but don’t tell your kids that. When you combine lemon, baking soda, and soap and let the chemistry take hold, they’re going to think you’re a magician. Kindly correct them and let them know it’s more like the next Louis Pasteur — then tell them all about the advent of pasteurization. This is a learning experience after all, and like all kitchen experiments, a great way to extend what kids get in the classroom.

“The idea that learning stops at the end of the school day is silly,” says Julie Geoghan, founder of the Tiny Scientist, an after-school and summer camp based in Brooklyn. “Educational activities outside of school are the perfect opportunity to show children that knowledge doesn’t exist in an isolated bubble.”

But knowledge (and bubbles) do come out of the off-gassing that occurs when lemon juice meets baking soda. With a few kitchen items and a little guidance, you can have hours of science-based fun. Here are your step-by-step guides to four projects that will test out the complex elements inside of citrus, which just so happen to be the best after-experiment snack in the house.

The “Magic” Floating Orange Trick

What you need:

  • 2 oranges
  • A kitchen scale
  • A glass vase
  • Water

What to do:

  1. Fill the vase up with water, a little more than halfway.
  2. Peel one of the oranges. Leave the peel on the second orange.
  3. Weigh the peeled orange and record the weight. Weigh the unpeeled orange and record its weight, too.
  4. Before putting the oranges in the water, ask your child: Will these oranges float? Which will float? Which will sink? Why?
  5. Put the peeled orange in the water. Does it float? Now switch, and put the unpeeled orange in the water. Does it float?
  6. Discuss with your child why the heavier fruit was the one that floated (a great lesson about buoyancy).
  7. Dry and eat those delicious oranges.

DIY Lemon Spray Bottle

What you need:

  • A lemon
  • A spray bottle or old perfume bottle
  • A knife
  • A penny

What to do:

  1. Cut the top off of the lemon.
  2. Unscrew the top of your spray or perfume bottle, and insert the straw directly into the fruit.
  3. Give the sprayer a few pumps, and watch the juice come out.
  4. Use your new lemon sprayer on a bathroom counter stain or rub a dirty penny with it to clean it up. Talking points to discuss with this step: Why is lemon juice good for cleaning? Explain that lemon juice is high in citric acid, so it makes a good natural cleaner.

Expert’s Pick: Julie G’s Lemon Volcano

What you need:

  • Two lemons and/or two oranges (try both and compare!)
  • Baking Soda
  • Food Coloring
  • Dish soap
  • A Plate
  • Cup
  • Spoons

What to do:

  1. Taste the lemon, just for laughs. “That super tangy taste that puckers up your mouth is a clue that there is acid in the fruit,” Geoghan says. “If you have a lemon and an orange, taste both and talk about which one has more acid.”
  2. Cut the bottom off the lemon (or orange) so it sits on the plate. Turn the fruit over and slice out the inside.
  3. Slice the second fruit in half and juice it. Keep the juice off to the side in a cup.
  4. Place your orange or lemon core on a tray. Use your spoon to muddle and mash the center of the lemon to break the walls of the fruit cells and release the juices. “Keep the juice in the lemon,” she says. “The more you reserve the more fun the experiment is.”
  5. Place a few drops of food coloring into the lemon. (Talking points to discuss with this step: What was the color you squeezed in? Will it change inside the lemon/orange? What color will it change into?)
  6. Squeeze a quarter-sized amount of dish soap into the lemon. Bubbles are evidence of chemical reactions, and the soap makes the reaction more visible and exciting.
  7. Dip your pinky into the baking soda and take a tiny taste. Acids are sour and bases are usually bitter. Add a spoonful of baking soda into the lemon. (Talking points to discuss with this step: What do you observe? “If it starts to fizz, you are watching a chemical reaction,” Geoghan says.)
  8. Take a spoon or craft stick and stir the lemon and lemon juice that you set aside in step 3. “It should start foaming really well as you stir it,” Geoghan says. “After a few moments, ask the kids if chemical reactions last forever and to explain their answer.”
  9. “At the end of experiments like this, I like to tell kids that they have two minutes to try whatever they want,” Geoghan says. “Most people internalize and retain information much more quickly when they are doing, rather than listening.” Watch as they add more baking soda, coloring, dish soap, and the extra lemon juice you set aside earlier and let them learn and see for themselves.

The Classic Lemon Battery

What you need:

  • Four lemons
  • A galvanized nail (coated in zinc)
  • A penny
  • A knife
  • A voltmeter
  • A small LED light bulb

What to do:

  1. Make a small incision on the top of the lemon, near the right end of the fruit. Insert the penny into the incision.
  2. Push the galvanized nail into the opposite end of the lemon.

Repeat Step 1 and 2 for the rest of the lemons.

  1. Explain to your child that the nail and the penny represent the opposite ends of a battery. They are called “electrodes.”
  2. Connect the voltmeter to the corresponding ends of the lemon battery and note the voltage measurement.
  3. Connect the four lemon batteries with a metal wire — making sure to match “+” ends to “-” ends of each lemon battery. This adds the voltage from each cell together—and will be enough energy to light a small light bulb.
  4. Connect the LED light bulb. At the red plastic base of the LED you will notice a “flat spot”— it looks like an indentation. The wire that comes out beside that flat spot connect to the “-” side of a battery, the other wire to the “+” side. Connect the remaining wires of the lemon batteries to the light bulb.
  5. Explain to your child how your circuit works. The electrons flow from the “-” (nail) end of your lemon battery through the light bulb, and back to the “+” (penny) end of the battery. The flow of electrons is what powers the light, thanks to the electrolytes in the lemon.

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