Connecting Molecular Structure and Bonding to Climate Change

Learning Resources

Describe what the IR absorption spectrum is and how it depends on the molecular structure and bonding of a molecule.
Analyze a gas to see if it has the characteristics of a greenhouse gas and predict how important a greenhouse gas it will be based on its molecular structure and bonds.
Explain how the absorption of IR radiation by a greenhouse gas causes tropospheric warming.

Key ideas 1-4 will provide useful background information, and key ideas 5-6 go further in depth into the connection of molecular structure and bonding to climate change.
The gases unit introduces the composition of air, layers of the atmosphere, properties of gases, kinetic molecular theory, electromagnetic radiation, collisional de-excitation, infrared spectroscopy, greenhouse gases, Earth’s energy imbalance, and the IR spectrum of molecules.
Incorporate the material in this unit into lesson plans and work through embedded examples. (there are worked examples and “your turn” examples which the students can attempt on their own. Both have detailed answers available)

This applet visualizes the infrared spectra of multiple greenhouse gases, and how they overlap with the “IR windows” regions on earth’s black body emission curve where both carbon dioxide and water do not absorb IR. Use the Laboratory Spectra option in the Display Options menu to explore the IR spectra of specific greenhouse gases. In the Display Options menu there is an option to add the Black Body Curve to see the regions where Earth emits the most IR radiation. Add the curve and analyze the different greenhouse gases to let the students visualize which ones absorb the most reflected radiation in the IR windows, and explain how that makes them very strong greenhouse gases.
There are some worked examples that can be used along with this applet in the VC3chem unit on Gases (Key idea 5)

This animation illustrates the absorption of infrared radiation by gases in the troposphere and the collisional loss of this absorbed energy to surrounding N₂ and O₂ molecules. In this animation, the user can sweep through a region of the IR spectrum and excite some of the vibrational modes of various gases listed in the Gas menu. In the Display menu, you can add atmosphere and see the effect that CO₂ vibrations have on molecules of the atmosphere and on temperature with the thermometer visual.
There are some worked examples in the VC3chem unit on Gases that can be completed with this applet. (Key ideas 4 and 5)

Lesson 3, Key idea 3 explores this connection further.
This section of the lesson on the chemistry of the greenhouse effect focuses on the emission and absorption of radiation, specifically infrared. This resource also encourages the use of the KCVS IR windows applet along with questions to strengthen understanding.

This applet allows users to experience the IR spectra of various common greenhouse gases as sound. This allows another dimension of understanding of the fundamental global heating and cooling mechanisms contributing to global climate change. Select various greenhouse gases to display on the IR spectrum and from that group select one to listen to. Slide along the spectra to hear the peaks as sound. The temperature can also be adjusted and its effect on Earth’s black body curve will be observed.