Script

Prepreparation

Cut small slits in the lemons using a sharp knife for students to insert electrodes in.

Introduction (10 minutes)

Introduce yourself, assistants.

Today we are going to talk about electricity. Where can we get electricity? Ideas they could come up with include batteries, power plants.

Explain that electricity is a kind of energy, that energy can be converted from one form to another. Can they think of a form of energy that electricity can be converted to? Perhaps motors (mechanical), lights (heat), buzzers (vibrational).

Main idea, write on board: energy transfer

Where do they think the electricity energy comes from? Burning coal (chemical), wind turbines (mechanical), dams (mechanical).

What about batteries? What kind of energy does battery electricity come from?

Main idea: batteries use chemical energy to generate electricity. They have two different metals or other materials and an acid.

Write on board: chemical energy

Lemon battery introduction (5 minutes)

So we mentioned acid in batteries. People usually call lemons acidic. Do the students predict that a lemon can be used as the acid source for a battery? What else will we need for a battery? Different metals. Can the students think of anything that we might be able to use for the metals?

We need an acid and two metals. These can be our variables. What would the students like to test? Options could be:

• different fruits
• different combinations of metals
• spacing of electrodes
• squeezing lemon vs. not squeezing

How will we measure the data? Show the student a multimeter. Explain that it can measure the current (how much

Activity 1: Lemon battery experiments (15 minutes)

Students should choose a question to test. Let them have access to paper and markers so they can note the multimeter values for the variables they test.

Volunteers should visit the groups to measure the current and voltage with the multimeter. As students work, ask questions such as

• What have you tried?
• What happened?
• What happens with different metals?
• Have you tried hooking your lemon up with your neighbors’? What happens to the measurements then?

If students have questions, the leader should try to guide them to a way to figure it out themselves or to another group that has an idea.

Discussion (10 minutes)

Have students come back to the front of the room to report their results and conclusions. All students should be expected to listen to the others presentations.

Challenge (15 minutes)

A typical LED uses 1.8 volt, 20mA. Based on the students’ results (including observations about hooking up lemons in series), can they predict how many lemons it might take to light an LED?

Wrap Up (5 minutes)

Ask the students if they have any final questions. Ask them to vote on which fruit you should use to power the clock. Have a student volunteer help hook the clock up. Have them predict how long they think the clock will work. Do they think lemon batteries are a good (environmentally sound, inexpensive) alternative to other batteries? Remind them of the energy needed to grow a lemon, the cost of a lemon.