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To understand how color affects the absorption of solar radiation.
Solar heating systems may be passive or active. In an active solar heating system, special equipment, in the form of a solar collector, is used to collect and distribute the solar energy. In a passive solar heating system, a home or building is designed to let in large amounts of sunlight. The heat produced from the light is trapped inside.
Both active and passive solar heating systems convert solar radiation into thermal energy, or heat. All substances have thermal energy. It is caused by the vibration and movement of atoms and molecules within them. The faster the molecules in a substance move or vibrate, the more thermal energy is in that substance. When solar radiation strikes a substance, it causes its atoms and molecules to vibrate and move faster, increasing the thermal energy of the substance. If a substance is in contact with a cooler substance, collisions between adjacent vibrating atoms and molecules in the two materials cause the energy of the vibrations to even out, cooling the hot substance and warming the colder one. Substances with darker surfaces absorb a greater percentage of solar radiation than substances with lighter surfaces.
In an active solar heating system, solar radiation strikes the bottom of the solar collector box and increases its thermal energy. The bottom of the box transfers this energy to any air, water, or other liquid that is passed through the box. Likewise, a building with a passive solar heating system is designed to absorb solar radiation and transfer the heat generated to other parts of the building. For example, an outside wall might be made of materials that heat easily in sunshine and then transfers its heat to the inside of the house.
Students determine how the temperature of water in three metal containers (one black, one white, one shiny) changes over time when heated.
Three cylindrical metal containers (all alike), black paint, white pain, aluminum foil, masking tape, graduated cylinder, water, stirrer, three thermometers, three heat lamps
|After 4 min.|
|After 8 min.|
|After 12 min.|
|After 16 min.|
|After 20 min.|
|After 24 min.|