The Kitchen Lab: Using Vegetables and Fruit in Scientific Experiments
Guest Post by Max Cooper
Experiments featuring vegetables and fruit are a great way to get kids interested in science. By using these everyday edibles to demonstrate scientific reactions, you can spark kids’ imaginations and start them questioning how the world around them works. Here are some simple and safe experiments involving fruit and vegetables that you can use to teach your kids about science.
Potato Power
Potatoes are boring, right? Wrong! You can use a potato as a power source to light up a very small bulb or a light emitting diode (LED), which you can buy cheaply from a hardware shop.
How to Make a Potato Battery
- Push a piece of copper wire and a zinc-plated (galvanized) nail into the potato to act as the electrodes in this experiment. The two objects should be close together, but don’t let them touch.
- Connect the other end of the copper wire to one terminal of the LED, and use more wire to connect the other terminal to the steel nail.
- The LED should light up as current flows through the circuit. If it doesn’t work, try swapping the terminals of the LED. You might have to dim the lights to see the LED light up.
What is happening inside the potato? When the metals come into contact with the potato flesh, a chemical reaction occurs which releases metal ions into the potato. More specifically, potatoes contain phosphoric acid, which reacts with the zinc to form positively charged zinc ions and free electrons. At the other electrode, electrons in the copper combine with the hydrogen ions in phosphoric acid to produce hydrogen gas. The excess of electrons in the zinc electrode and the deficit of electrons in the copper electrode cause electrons to flow around the circuit, powering the bulb.
Polishing Pennies with Ketchup
You can teach kids about acids by using ketchup to make an old penny shine like new. Simply squirt ketchup over some dull brown pennies and leave them for a few minutes, then let your kids rub the pennies between their fingers. When you rinse off the ketchup, the pennies will be shining brightly.
This experiment works because acid in the ketchup reacts with copper oxide, the dull brown coating on the pennies, to form copper acetate. When you rinse the pennies in water, the copper acetate dissolves, leaving a shiny penny.
The Corrosive Power of Cola
Cola is an even more effective cleaner of old pennies. Use cola instead of ketchup in the experiment above to show children just how acidic their favourite soft drink is. Even better, if one of your kids has lost a tooth recently, leave it sitting in a glass of cola. After a few weeks, the phosphoric acid in the cola will have reacted with the enamel of the tooth to turn it black and brittle. There will be visible cracks in the tooth and it will shatter if you hit it with a hammer. Use this experiment to explain to show your kids that they need to brush their teeth after drinking cola to get rid of the dangerous acids.
Max Cooper is a dad, a self confessed science nerd and a freelance insurance writer.
Photo attribution: By Loadmaster (David R. Tribble) This image was made by Loadmaster (David R. Tribble) Email the author: David R. Tribble Also see my personal gallery at Google Picasa (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons
