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December 3, 2015

STEM Fun: Make a Lemon-Powered Clock in 6 Steps

By Christy Crawford
Grades 3–5

    Your students may be buzzing about some of the hot, new STEM toys being promoted this holiday season. Take the opportunity to have kids craft a homemade lemon clock, and learn more about how batteries work.

    For each group of three students, you’ll need:

    • 3 fresh lemons

    • 3 galvanized or zinc nails

    • 3 pre-1982 pennies soaked overnight in an electrolyte solution such as Gatorade or lemon juice and salt to clean*

    • insulated wires with alligator clips

    • digital clock (I used a dollar store clock that runs on a AAA battery.)

    • knife

    *Pennies created before 1982 are mostly copper. Those created after 1982 are coated with zinc and will not work. You can also use copper wire.

    Step 1: Squeeze or roll your lemon vigorously to make an electrolyte solution. This will get the fruit's acidic juices flowing and primed to move electrons between the positive and negative terminals in Step 2. 

    Step 2: Cut a slit into the lemon. Insert a penny or copper wire in the lemon to create the positive terminal. About an inch away or more, insert a galvanized (zinc) nail into the other side of the lemon to create a negative terminal. Ask your young engineers how the lemon compares now to a coppertop battery? 

     

    Step 3: Connect an alligator clip to the penny and another alligator clip to the nail. 

    Step 4: Is one lemon enough to power a clock that runs on a AAA battery (1.5 volts)? One lemon produces 7/10 of a volt. Ask students to predict how many lemons they'll need (at least two). Roll each lemon vigorously and create positive (copper) and negative (zinc) terminals in the additional lemons.

    Step 5:  Let students link lemons in a series by connecting alligator clips from the positive terminal (copper penny) of one lemon to the negative terminal (zinc nail) in each adjacent lemon. (I didn't use fresh lemons — look how many lemons it took to power the clock!)

    Step 6: Remove the battery in the LED clock and connect the alligator clips to the positive and negative terminals in the clock. 

    What else can engineers power with fruit or a potato? Have students check out Lady Ada’s “B is for Battery” to see a lemon-powered LED and discover more about batteries and circuits.

     

    If you're looking for holiday fun, check out my post, "Using Elf on the Shelf in the Classroom."

    Got milk?                              Encourage kindness!

     

    For more holiday fun, use the promo code in the coupon below to enjoy savings at The Scholastic Store!

    Your students may be buzzing about some of the hot, new STEM toys being promoted this holiday season. Take the opportunity to have kids craft a homemade lemon clock, and learn more about how batteries work.

    For each group of three students, you’ll need:

    • 3 fresh lemons

    • 3 galvanized or zinc nails

    • 3 pre-1982 pennies soaked overnight in an electrolyte solution such as Gatorade or lemon juice and salt to clean*

    • insulated wires with alligator clips

    • digital clock (I used a dollar store clock that runs on a AAA battery.)

    • knife

    *Pennies created before 1982 are mostly copper. Those created after 1982 are coated with zinc and will not work. You can also use copper wire.

    Step 1: Squeeze or roll your lemon vigorously to make an electrolyte solution. This will get the fruit's acidic juices flowing and primed to move electrons between the positive and negative terminals in Step 2. 

    Step 2: Cut a slit into the lemon. Insert a penny or copper wire in the lemon to create the positive terminal. About an inch away or more, insert a galvanized (zinc) nail into the other side of the lemon to create a negative terminal. Ask your young engineers how the lemon compares now to a coppertop battery? 

     

    Step 3: Connect an alligator clip to the penny and another alligator clip to the nail. 

    Step 4: Is one lemon enough to power a clock that runs on a AAA battery (1.5 volts)? One lemon produces 7/10 of a volt. Ask students to predict how many lemons they'll need (at least two). Roll each lemon vigorously and create positive (copper) and negative (zinc) terminals in the additional lemons.

    Step 5:  Let students link lemons in a series by connecting alligator clips from the positive terminal (copper penny) of one lemon to the negative terminal (zinc nail) in each adjacent lemon. (I didn't use fresh lemons — look how many lemons it took to power the clock!)

    Step 6: Remove the battery in the LED clock and connect the alligator clips to the positive and negative terminals in the clock. 

    What else can engineers power with fruit or a potato? Have students check out Lady Ada’s “B is for Battery” to see a lemon-powered LED and discover more about batteries and circuits.

     

    If you're looking for holiday fun, check out my post, "Using Elf on the Shelf in the Classroom."

    Got milk?                              Encourage kindness!

     

    For more holiday fun, use the promo code in the coupon below to enjoy savings at The Scholastic Store!

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