Greenhouse Gas Science · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Why Some Gases Trap Heat and Others Don't

Science · Weather & Climate · ages 11-12
Name ______________________   Date ____________

  1. Scientists find a gas whose molecules are each two identical atoms joined by one simple bond, just like O2. What will this gas most likely do when infrared light hits it?

    • Catch the infrared with a bending bond, like CO2 does
    • Let the infrared pass right through without absorbing it
    • Break apart into two single atoms

  2. Which kind of light does the Sun mainly send toward Earth?

    • Short-wave light
    • Long-wave infrared light
    • Radio waves

  3. The natural greenhouse effect is a bad thing that only causes harm.

    Circle one:   True   False

  4. Look at the bar chart. About how many times more heat does one methane molecule trap than one CO2 molecule?

    CO21Methane28

    Answer: ______________

  5. A CO2 molecule bends and stretches when infrared light hits it. What happens next?

    • It reflects the infrared straight back to space with no change
    • It turns into oxygen gas
    • It absorbs the energy, then re-emits infrared in a new direction

  6. Which statement best describes the enhanced greenhouse effect?

    • Extra heat-trapping caused by human-added gases on top of the natural effect
    • The complete absence of any greenhouse gases
    • A greenhouse effect that only happens on other planets

  7. Nitrous oxide (N2O) traps about 265 times more heat per molecule than CO2, but there is far less N2O in the air than CO2. Why can CO2 still matter more overall to warming?

    • Because N2O molecules cannot absorb infrared light
    • Because CO2 is not a greenhouse gas at all
    • Because CO2's huge total amount in the atmosphere can outweigh its lower potency per molecule

  8. Ravi says nitrogen gas (N2) must trap heat too, since it's a gas in the air just like CO2. What is wrong with his reasoning?

    • N2 is actually colder than CO2, so it can't trap heat
    • N2's two identical atoms form a bond that doesn't flex to absorb infrared, unlike CO2's bond
    • N2 only exists at night, so it never meets sunlight
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Answer key

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

Why Some Gases Trap Heat and Others Don't W1-mt_EQQWKz03P8-s1

  1. Let the infrared pass right through without absorbing it · Two identical atoms joined by one simple bond cannot stretch and bend the way CO2's bonds can, so infrared passes straight through, just like with O2 and N2.
  2. Short-wave light · The Sun is very hot, so it sends out mostly short-wave light, including the visible light you see.
  3. False · The natural greenhouse effect keeps Earth warm enough for life. The problem is the extra, human-added effect on top of it.
  4. 28 · The methane bar is about 28 times as tall as the CO2 bar, showing it traps about 28 times more heat per molecule.
  5. It absorbs the energy, then re-emits infrared in a new direction · The bending motion absorbs the infrared energy, and the molecule releases it again, sometimes sending it back toward the ground.
  6. Extra heat-trapping caused by human-added gases on top of the natural effect · Burning fossil fuels adds extra CO2 and methane, which trap more infrared heat beyond the natural balance.
  7. Because CO2's huge total amount in the atmosphere can outweigh its lower potency per molecule · Total warming depends on both how potent a gas is per molecule and how much of it is actually in the air.
  8. N2's two identical atoms form a bond that doesn't flex to absorb infrared, unlike CO2's bond · Being a gas isn't enough. What matters is whether the molecule's bonds can stretch and bend to catch infrared, and N2's simple bond can't.
Worksheet · LightMySky