This unit investigates the origin of colors in materials, including gasses, liquids, and solids. "Color in gasses" includes experiments that explore the color of fireworks, the origin of smog, the cause of rainbows, and why the sky is blue. The "Color in liquids" section includes investigations into why plants are green, the color change of acid/base indicators, why objects change color when they rust, and how glowsticks and fireflies produce colored light. The section dealing with "Color in solids" examines how colors are produced by the interference of light using an audio CD, how UV light can be detected using fluorescence, and how light emitting diodes work. Investigations are also performed with materials that change color in response to temperature (thermochromics), which are often used as temperature indicators. The unit concludes with an investigation into materials which change color in response to the application of an electric current (electrochromics).
This unit was also recently presented for the first time at the 1997 San Diego Science Educator's Association (SDSEA) Conference, where it was well received by 30 middle and high school science teachers. Typical written comments by those attending included: "The units are activity based and invite students to discover the concepts." and "Thanks for the planning and for sharing your expertise. It enthuses me to see applications of concepts and begin to understand how they've been developed."
This unit relates to the NSES physical science content standards in grades 5-8: "light interacts with matter by transmission, absorption, or scattering. To see an object, light from that object-emitted by or scattered from it-must enter the eye;" and in grades 9-12: "Electromagnetic waves include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. The energy of electromagnetic waves is carried in packets whose magnitude is inversely proportional to the wavelength. Each kind of atom or molecule can gain or lose energy only in particular discrete amounts and thus can absorb and emit light only at wavelengths corresponding to these amounts."
Photos below were taken at the Chromatics module (and other Explorations in Materials Science modules) presentation at the 1997 California Science Teachers Association Meeting on October 3, 1997.