The easiest way to know that Fall is at our doorstep is the raining of pumpkins from the sky.
This is a fun fall craft that is great for both preschoolers and older siblings. Beacsue little hands can help build the pumpkin clock circuit and decorate the pumpkins, kids of all ages can engage in both the science and the art.
What I love about the pumpkin clock (and the potato clock, lemon clock, apple clock.....) is that it doesn't use a battery to power the clock. This can be mind-boggling for kids and it is a great question to ask them. How will this pumpkin clock be powered? Is there a battery? Is it plugged into the wall? Just as babies love balloons because they 'defy' gravity, kids will love this pumpkin clock because it defies everything they know about electronic parts.
This easy Halloween craft can be on your doorstep and ready to go for the upcoming weekend. We'll show you what you need, how to make it, and explain the science behind what makes this fun fall pumpkin clock tick.
How to make pumpkin clock
- Place the two pumpkins on a table near each other.
- Open the potato clock kit and place one copper and one zinc metal strip into the sides of each pumpkin (make sure they don’t touch inside)
- Connect a single wire between a copper strip on one pumpkin to the zinc strip on the other pumpkin.
- Connect the red wire from the clock to the remaining copper strip.
- Connect the black wire from the clock to the remaining zinc strip.
- Set your clock and decorate your pumpkins.
How a pumpkin clock works
Hopefully, as you make this your kids will wonder what exactly is powering the pumpkin clock. You can make an experiment of this by trying out different types of metals instead of zinc and copper.
For example, the hardware store often sells brass and steel strips as well. You could check to see what happens if you replace the silvery zinc with the silvery steel. Is it color that drives the reaction, or something else?
You should find that the type of metal is important. This reaction, called an electrochemical reaction because it produces electricity through a chemical break down, requires the presence of zinc.
Why is zinc important in my pumpkin clock?
The solid zinc can go under a reaction that turns it into two positive zinc ions in solution plus two electrons when it is in a slightly acidic solution (the acid serves to ‘chomp’ away at the zinc). These electrons travel through the wire, through the clock, and then to the copper strip, or electrode. When they reach the copper they combine with hydrogen ions to produce hydrogen gas. Unlike the electrons, which traveled through the wire and powered the clock, the zinc ions will travel through the pumpkin. These zinc ions travel through the pumpkin to the copper strip where they will regain electrons and turn back into zinc metal.
By adding two pumpkins in series, we create a larger voltage or more oomph to our ‘battery’.
In addition to trying different types of metal strips to power your pumpkin clock you can also try:
- Other foods. Will potatoes power a clock? What about lemons? Bread? Turkey? What types of qualities must the food have to be able to conduct electricity and power a clock?
- Timing the clock. How long will your pumpkin clock last? Will it outlast a potato clock? How can you make your pumpkin clock last longer?
- Looking at the electrodes over time. What happens to the electrodes over time? Does the look change from day to day?
- Add lights. If we can power a clock with a pumpkin (or a potato), what about a light? Can we power LEDs?