A Simple, Student-Built Spectrometer To Explore Infrared Radiation and Greenhouse Gases

Abstract

In this experiment, students build a spectrometer to explore infrared radiation and greenhouse gases in an inquiry-based investigation to introduce climate science in a general chemistry lab course. The lab is based on the exploration of the thermal effects of molecular absorption of infrared radiation by greenhouse and non-greenhouse gases. A novel feature of the experiment has students building an infrared spectrometer, using a hot plate as an IR source, a sample compartment employing a plastic cuvette holder with open sides (to standardize the path length), and a low-cost infrared thermometer. Students, working in groups, (1) explore a PhET simulation; (2) design a set of experiments in response to a scientific question, “comparing the absorption of infrared light in the presence and absence of each different sample of gas, are there any significant differences that can be observed experimentally?”; (3) reflect on climate science and their experimental results by visiting the American Chemical Society Climate Science Toolkit; and (4) communicate their results in lab by constructing and presenting a poster. Assessment of student responses to a pre- and postexperiment question suggests that the lab has a positive influence on student understanding of the concepts involved in identifying greenhouse gases. Results from postexperiment questions also provide information for what aspects of the online resources students found useful.

Review of Student-Built Spectroscopy Instrumentation Projects

“…Beyond fluorescence and atomic emission instrumentation, several other student-built spectroscopic instruments have been demonstrated, including scattering measurements, , polarimetry, and UV − and IR ,, absorbance spectroscopy. Home-built IR instruments have been applied to greenhouse gases, ammonia, and kerosene-adulterated gasoline (Figure a), and important principles of FT-IR, such as Fourier transformation and interferometry, have been demonstrated using visible light and LEGO blocks . For advanced students, instructors could imagine a broad range of spectroscopic instrument building projects.…”

“…To this end, students can extract the most relevant RGB color channel from cellphone videos, 25 place a filter between the flame and a point detector, such as a photoresistor or photodiode, 109,115 or include a monochromator or commercial spectrometer (costpermitting). 125,131,132 Beyond fluorescence and atomic emission instrumentation, several other student-built spectroscopic instruments have been demonstrated, including scattering measurements, 99,116 polarimetry, 52 and UV 88−90 and IR 113,124,133 absorbance spectroscopy. Home-built IR instruments have been applied to greenhouse gases, 133 ammonia, 124 and kerosene-adulterated gasoline (Figure 4a), 113 and important principles of FT-IR, such as Fourier transformation and interferometry, have been demonstrated using visible light and LEGO blocks.…”

Designing a Remote, Synchronous, Hands-On General Chemistry Lab Course

“…The in-person course includes some “traditional” lab experiments, such as the synthesis of alum, the copper cycle, and measuring the heats of reaction. We also offer a series of inquiry experiments, some of which have been reported previously in this Journal , including an experiment on greenhouse gases and a polymers and cross-linking experiment, which incorporates the CORE approach ( C hemical O bservation, R epresentation, and E xperimentation). − The left side of Table lists typical experiments and activities for our standard in-person lab course, along with a list of selected equipment and chemicals. The features of the redesigned remote lab course are shown on the right side of Table and are discussed in detail in the following sections.…”

Benchtop Global-Warming Demonstrations Do Not Exemplify the Atmospheric Greenhouse Effect, but Alternatives Are Available

“…However, the IR-absorbing property of carbon dioxide is a vital concept for understanding climate science, so a concrete classroom demonstration is useful. An elegantly simple, direct observation of the absorption is possible . The experiment or demonstration requires a laboratory hot plate, an inexpensive infrared thermometer, an empty clear plastic bag, another filled with carbon dioxide and a third filled with air or nitrogen.…”