Cells That Do Work: Batteries, Fuel Cells and Corrosion · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Batteries, fuel cells, and rust

Science · Chemistry · ages 17-18
Name ______________________   Date ____________

  1. A hydrogen fuel cell powers a small vehicle. What keeps it producing electricity?

    • A sealed store of past charge
    • An overnight recharge
    • Fuel flowing in from outside

  2. Two cells: an alkaline flashlight cell and a lead-acid car battery. Which one can be recharged?

    • The lead-acid car battery
    • The alkaline flashlight cell
    • Neither can be recharged

  3. Driving current backward through a rechargeable cell restores its starting chemicals.

    Circle one:   True   False

  4. A lead-acid battery has fully discharged. What now coats both plates?

    • Pure metallic lead
    • Hydrogen bubbles
    • Lead sulfate

  5. A cell lists 2 volts on paper but reads lower while driving a big motor. Why?

    • The wires add extra voltage
    • Large currents make the voltage sag
    • Motors raise the cell potential

  6. A hydrogen-oxygen fuel cell delivers less than its ideal potential. What limits it?

    • The fuel arriving too quickly
    • Slow electrode kinetics and internal resistance
    • The water product adding voltage

  7. A phone battery holds less charge after hundreds of cycles. Why?

    • Side reactions slowly wear the cell out
    • The lithium turns into lead sulfate
    • Electrons leak through the sealed case

  8. A friend says a rusting nail is nothing like a battery. What is the error?

    • Nails cannot conduct any charge
    • Batteries never involve metals
    • Rusting is the same electrode chemistry in an unwanted cell
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Batteries, fuel cells, and rust W1-mt_NQQzlecX4v-s1

  1. Fuel flowing in from outside · A fuel cell runs as long as fuel and oxidizer keep flowing in.
  2. The lead-acid car battery · Lead-acid is a secondary cell, so current driven backward restores it.
  3. True · Rechargeable reactions run in reverse under an outside current.
  4. Lead sulfate · Discharge converts lead and lead dioxide into lead sulfate.
  5. Large currents make the voltage sag · Heavy loads sag the voltage below the paper prediction.
  6. Slow electrode kinetics and internal resistance · Slow reactions at the electrodes plus resistance losses pull voltage down.
  7. Side reactions slowly wear the cell out · Side reactions consume the cell bit by bit, so capacity fades.
  8. Rusting is the same electrode chemistry in an unwanted cell · Rust is electrode chemistry running where nobody wants it.
Worksheet · LightMySky