Science Fenns K-5Grades K to 5
A flashlight on a dark table sending a bright beam, with its batteries glowing in a cutaway sketch.

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Energy Changes Form

Chemical to electrical to light in a flashlight.

Lesson 18 of 41

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Before we start

Today’s story

Energy Changes Form

Click a flashlight on and the dark goes away. Click it off and it returns. The batteries seem to do all the work.

Inside the batteries, chemicals hold stored energy. When the circuit is closed, that chemical energy changes into electrical energy. In the bulb, the electrical energy changes into light and heat.

We call this an energy transformation. Energy changes form, yet the total stays the same. Let us follow one.

See it

Five steps. Every time.

    Hands on

    Energy Detective

    20 minutes · Do this with a grown-up nearby

    You need

    • Flashlight
    • Hand-crank radio or toy
    • Paper
    • Pencil

    Do this

    1. Turn the flashlight on and off.
    2. Write the energy forms you can name.
    3. Hold the bulb end near your hand and feel for warmth.
    4. Crank a hand-powered toy and note the forms.
    5. Draw an arrow chain for each device.
    6. Share your chain with a partner.
    Write or draw: Two arrow chains such as chemical to electrical to light.

    Watch for: Did you feel heat from the bulb? Where else did energy go?

    Safety: Do not use wall power. Batteries only.

    Same every time

    Three rules

    Rule 1Name each form

    Chemical, electrical, light, heat, sound, motion.

    Rule 2Follow the chain

    Energy goes from one form to the next.

    Rule 3Energy is not lost

    It changes form or place.

    Grandpa Fenn’s notebook

    Say it like a scientist

    energy
    The ability to cause change.
    transformation
    A change from one form to another.
    chemical energy
    Energy stored in matter.
    electrical energy
    Energy of moving charge in a wire.

    Poppy’s quiz

    Six questions

    Tap an answer. Green means right. You will see why.

    Talk about it

    Say it out loud

    • How do you know energy changed form?
    • Where do you see energy change form at home, like a toaster or a lamp?
    Did you know

    Your body also changes energy, turning the chemical energy in food into motion and warmth.

    Someone who does this

    An electrical engineer designs devices that change energy efficiently.

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