Soil and energy don't go together, right? One seems natural and a bit on the messy side while the other is a mysterious force that powers everything from our toasters to our cars. What two things could be more different?
Well, science is all about testing what we think of the world. In this experiment, we'll discover if any type of soil can conduct, or carry, an electric current. Soil electrical conductivity? Perhaps soil and energy aren't such a bizarre pairing.
What kind of soil conducts electricity the best?
- 3 containers with lids
- 1/2 cup of clay soil
- 1/2 cup of sand
- 1/2 cup of potting soil
- 1 cup distilled water
- DC 12 volt battery
- 3 jumper wires with crocodile clips
- 2 copper electrodes
- 1 milliammeter
- With your marker, label the three containers A, B, and C.
- Put 1/8 cup of sand into container A.
- Put 1/8 cup of clay into container B.
- Put 1/8 of potting soil into container C.
- Pour 1/8 cup of distilled water into each container.
- Take a look at the contents of each container. Think about what you know about electricity and sand, clay and potting soil. What do you think makes a substance conduct electricity or not?
- Remember the "problem" of this project: What kind of soil conducts electricity the best? Write down your best guess, or hypothesis, in your notebook.
- Secure the lid on to each container.
- Shake container A.
- Take the top off of container A.
- Have your adult helper insert 2 copper electrodes into the sand about 5 centimeters apart.
- Then, have your adult connect the ammeter and the DC 12 volt battery to the electrodes.
- Read the meter.
- Record the current measurement in your notebook.
- Repeat steps 7-12 with containers B and C.
- Look at your notes. Which material conducted electricity the best?
You should have recorded the highest meter rating for the potting soil.
Electrical conductivity is often determined by the presence of nutrients and ions. Whenever you have a group of nutrients and a group of ions, the ions are instantly attracted to their nutrient neighbors. This attraction equals energy. Potting soil has tons of nutrients and ions, so it produces tons of energy. Your measurement tools picked up on this, and that's why you recorded such high numbers. On the other hand, clay soil and sand barely have any nutrients or ions, resulting in little energy.
How can you use this new knowledge? Well, the better soil electrical conductivity, the better home for plants -- plants love nutrients and ions! Try checking your backyard for plants that are doing well and for plants that are dying. Do you think your soil test could explain why some plants look better than others? Keep guessing and testing new ways to experiment. You know what kind of people do that everyday? Scientists!