For your consideration:
I am often amazed at how much more capability and enthusiasm for science there is among elementary school youngsters than among college students.
– Carl Sagan
I, along with a group of my high school math and science program students, conducted the following demonstration for a group of elementary school students, mostly fourth and fifth graders:
To begin, we discussed how the air we breathe is a mixture of several different gases. And how every gas, whether it is an element (such as nitrogen or oxygen), or a compound (a combination of elements in a specific ratio, such as carbon dioxide), has a unique fingerprint, consisting of a set of colored lines, called its spectrum.
After dividing the class into groups of three students each, we handed out paper glasses with diffraction grating lenses, crayons, a ruler, and large pieces of drawing paper. We asked them to draw seven six-inch lines on their paper, making sure there was plenty of space between each. They were to label these lines in order: hydrogen, hydrogen, nitrogen, oxygen, neon, carbon dioxide, and air.
Then, using a spectrum tube high-voltage power supply and the spectrum tubes for air, carbon dioxide, helium, hydrogen, neon, nitrogen, and oxygen, we began the demonstration.
In a darkened room, I instructed the students to put on their diffraction grating lenses. I then proceeded to insert the spectrum tubes of the following gases in order: hydrogen, helium, nitrogen, oxygen, neon, and carbon dioxide into the spectrum tube high voltage supply generating the spectral lines of each. I chose these gases and the order they were placed into the voltage supply because starting with the spectrum of hydrogen, the spectrum build in complexity from left to right. As each gas’s spectrum was displayed, we asked the students to use their crayons and drawing paper to color the spectral lines they observed. We were not concerned with the wavelength of the lines, only the color pattern from left to right.
After turning up the lights, I posed the following question to the students: “Which of these gases do you think are in the mixture that makes up the air we breathe?” While most students, ranging from elementary to high school, and even some college students and adults, can identify some of the gases present, very seldom does anyone know them all. As each group made their guess, we wrote their answers on the board for everyone to see, without any judgment as to whether the answers were right or wrong.
At the end of this part of our discussion, we darkened the room again. This time, I inserted the spectrum tube for air, asking the students again to color the spectral lines they observed.
To finish our demonstration, we asked each student group to compare the lines they colored for air with their spectral lines for the other gases. And to circle which gas’s spectral line pattern matched up with the lines they saw in the spectrum for air. Quickly they began to see that there were several combinations of individual gas’s spectral lines present in the air’s spectrum. We collected each group’s drawings and discussed their results.
Finally we posed the following questions: “What did they learn today?”, “Can you now tell us which gases you believe are present in the air we breathe? And, more importantly, “Did you have fun?”
Commentary
The students’ initial reaction to observing spectral lines through diffraction grating glasses was truly captivating. It felt as though we had opened up an entirely new world for them. There was no immediate need to delve into the scientific explanation behind the spectra’s generation; the demonstration’s primary goal was to cultivate the joy, awe, and wonder inherent in scientific discovery. My experience in the classroom and my years of tutoring often revealed that many high school and college students prioritize grades over a sense of wonder, potentially finding this demonstration “lame” or even boring, a waste of their time. However, sometimes the simplest method for explaining complex phenomena is by nurturing the innate sense of awe and wonder within us all.
