1 to 2 class periods Less than $10 per class.

Students test whether the color of a material affects how much heat it absorbs. They leave ice cubes placed in boxes made of colored paper (one box per color; white, yellow, red and black) in the sun, and predict which colored box melts an ice cube first. They record the order and time required for the ice cubes to melt.

The study of light and its behavior is an important component in the design of many items, everything from optical instruments to roofing materials to solar cells. The performance and characteristics of light guide engineers to come up with different forms of light detection for lenses in cameras, microscopes, CD players and medical devices. Different sources of light carry different quantities of energy. For example, powerful lasers can cut through stone or even metal. color heat energy light light absorption melting solar sun Certain colors absorb light better than others. The sun produces heat and light. Why ice cubes melt. (optional) The purpose of solar panels. 4 sheets of colored paper per group (white, yellow, red, black) newspaper scissors (1 per student if you want the class to cut out the boxes) 4 ice cubes per group sunny day or a heat lamp Imagine that it is 100-degrees outside. How do you stay cool? What kinds of clothing do you wear? Any thought to color? (Listen to student ideas.) What might be the influence of color and its relationship to heat? Can you think of any instances in which the color of something makes a difference in how hot it gets in the sun? (Listen to student ideas. Possibilities: Wearing white vs. black clothing on super hot days. Flat rooftops sealed in black tar vs. white polymer material. Walking barefoot across a black asphalt roadway vs. lighter concrete roadway. Choosing a white car instead of a black car if you live where it is sunny and hot all the time.) The sun emits energy in the form of electromagnetic waves. We see part of the electromagnetic wave as light and we feel part of it as warmth. Darker colors absorb more sunlight than lighter colors, which is why darker colors get warmer more quickly in the sunlight than lighter colors. The lighter colors reflect more of the sun's radiant energy, so they remain cooler to touch in the sunlight. Let's do our own testing to find out. A form of energy that causes substances to rise in temperature or to go through associated phase changes (as melting, evaporation, or expansion). Energy derived from sunlight. A photo-electric cell that converts sunlight directly into electrical energy and can be used as a power source. A group of solar cells forming a flat surface (as on a spacecraft). The capacity for doing work; raising weight, for example. To take in; to transform (radiant energy) into a different form usually with a resulting rise in temperature. To bounce waves of light, sound, or heat off a surface. Energy (as heat waves, light waves, radio waves, x-rays) transmitted in the form of electromagnetic waves. Make enough ice cubes so that each group can have four. Try to make them the same size for experiment consistency. To save time, pre-cut and assemble (using tape) the colored paper into five-sided boxes each big enough to fit an ice cube. Otherwise, have students cut, fold and tape together their own boxes. Gather the rest of the materials. Make copies of the Activity Worksheet, one per group. With the class, talk through the Introduction/Motivation section. Once the class is thinking about the influence of color and its relationship to heat, divide the class into small groups. Give each group four sheets of colored paper (white, yellow, red, black) and have them cut and fold their sheets into boxes. Hand out newspaper and have each group spread the newspaper in an exposed, sunny place outside, or under a heat lamp. On the newspaper, place the boxes side by side with the opening facing away from the sun/light so students can see inside. Give each group four ice cubes and instruct them to place one ice cube in the center of each colored box. Let the ice cubes sit in the sun until they have melted. Have students check them every few minutes and record which ice cubes melted first, second, third, and fourth. Instruct groups to record their data in the chart on the worksheet. Discuss with the class their observations, touching on the different colors and their ability to reflect light and heat. Also, talk about how these color characteristics help to melt the ice. Ask students the Investigating Questions. Discuss some real-world examples in which engineers use their understanding of how different colors reflect light and heat to design products and find solutions. (Example: Asphalt roads and tar roofs are dark surfaces that absorb heat from the sun. Measurements show that white roofs reflect some of the sun's heat back into space and cool temperatures, much as wearing a white shirt on a sunny day can be cooler than wearing a dark shirt. So, designing white roofing materials or paint for roofs has the effect of cooling temperatures within buildings.) Activity Worksheet (pdf) Activity Worksheet (doc) Why do ice cubes melt? How does the sun affect ice? What kind of clothes do people wear outside in the winter? In summer? On which color did the first ice cube completely melt? Why? If an ice cube was placed on a blue piece of paper, how much time do you think it would take to completely melt? Which color absorbs heat the quickest in the sun? Which color would be the best to help keep ice cubes from melting too quickly in the sun? Rubric for Performance Assessment (doc) Rubric for Performance Assessment (pdf) For a more challenging activity, add a discussion of heat as a form of energy, including the solar panels and solar energy. Cool Roof Resources for Federal Agencies. Federal Energy Management Guide, US Department of Energy. http://www1.eere.energy.gov/femp/features/cool_roof_resources.html Do Different Colors Absorb Heat Better? Grades PreK-2. Education Resources Information Center. Office for Technology and Industry Collaboration, Tufts University and Department of Education. (alternate online location for activity) http://www.eric.ed.gov/ERICWebPortal/search/detailmini.jsp?_nfpb=true&_&ERICExtSearch_SearchValue_0=ED480661&ERICExtSearch_SearchType_0=no&accno=ED480661 Richards, Roy. An Early Start to Technology from Science London: Simon & Schuster, 1990, page 64. White Roofs May Successfully Cool Cities: Computer model simulates impact of white roofs on urban areas. Posted January 28, 2010. Press Release 10-016, National Science Foundation News. http://www.nsf.gov/news/news_summ.jsp?cntn_id=116283