En anglais

Why Some Gases Trap Heat and Others Don't

Science · Weather & Climate · ages 11-12

Name ______________________ Date ____________

Which pair contains two greenhouse gases that absorb some of Earth's outgoing infrared?
- Nitrogen gas and oxygen gas
- Carbon dioxide with methane
- Water vapor with oxygen gas
Which description fits incoming solar radiation compared with radiation emitted by Earth's surface?
- Short-wave radiation, including visible light
- Long-wave radiation, including infrared light
- Mostly radio waves longer than infrared light
Without any greenhouse gases, Earth's average surface temperature would stay the same.
Circle one: True False
Use historical 100-year warming scores of 1 for CO2 and 28 for methane, without climate-carbon feedbacks. For equal released masses, methane's estimated warming effect is how many times as large as CO2's?
Answer: ______________
A CO2 molecule absorbs infrared at a wavelength that matches a suitable vibration. What can happen to the absorbed energy?
- It reflects infrared to space without taking in any of its energy
- It holds absorbed energy forever and never shares any with others
- It can pass vibration energy to other air molecules in collisions
Which statement describes the enhanced greenhouse effect?
- Human emissions add gases that strengthen the natural warming effect
- Human emissions remove all gases absorbing Earth's outgoing infrared
- Human emissions produce sunlight that replaces solar energy at Earth
Nitrous oxide has a higher 100-year warming score per kilogram than CO2. Why does that score alone not tell us which gas contributes more warming from human activities?
- We must count only the gas with the higher score as a warming gas
- We must assume CO2 stops absorbing infrared if any N2O is present
- We also need to know how much of each gas people release and when
Ravi says every molecule that vibrates must absorb Earth's infrared. Why does nitrogen gas (N2) show that his rule is incomplete?
- Its atoms stop all motion when infrared reaches the surface
- Its vibration does not change its electric dipole as needed
- Its molecules leave the air before Earth emits any infrared

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

Carbon dioxide with methane · Carbon dioxide and methane both absorb some outgoing infrared. Nitrogen and oxygen absorb very little; water vapor is a greenhouse gas, but oxygen is not a significant one.
Short-wave radiation, including visible light · Sunlight includes visible light, ultraviolet and near-infrared. These wavelengths are shorter than most infrared emitted by Earth's cooler surface.
False · The natural greenhouse effect keeps Earth's surface warmer than it would be without greenhouse gases. Removing that effect would leave the average surface colder.
28 · Divide the methane score by the CO2 score: 28 ÷ 1 = 28. The comparison uses equal released masses over 100 years, not individual molecules.
It can pass vibration energy to other air molecules in collisions · Absorption adds vibration energy to the CO2 molecule. A collision can transfer energy to another air molecule. Immediate emission by the same molecule is not required.
Human emissions add gases that strengthen the natural warming effect · Human activities add greenhouse gases. With incoming sunlight unchanged, these gases initially reduce energy escaping to space and cause extra warming.
We also need to know how much of each gas people release and when · An equal-mass score does not describe actual emissions. How much of each gas people release, and when, also affects its total warming contribution.
Its vibration does not change its electric dipole as needed · N2 can vibrate, but its ordinary stretching vibration does not change its electric dipole. Vibration alone is not enough for strong infrared absorption.