Science Content Knowledge
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Heat Transfer. Photo courtesy of Wifer X, Flickr.
reason a car heats up on a sunny day - the energy from the sun is transferred to the car. Some animals, like snakes, can see in the dark by sensing infrared light. Rescue workers use infrared sensors to find people in emergency situations. KEEPING WARM How do we keep warm in an Arctic winter? People are sources of heat - the food we eat helps to fuel our body's furnace. (People in cold climates eat about twice as many calories as those in warmer climates.) We feel cold when we lose more heat energy than our body can produce. To stay warm, we must reduce the flow of heat away from our body. Blankets, coats, and houses are ways that we reduce heat transfer (from
conduction, convection, and radiation) from us to the outdoors. Evaporation is another way that we lose heat. Hypothermia is what happens when our body temperature drops because the heat flow out from our bodies is more than the body can replace. Hypothermia makes people dizzy and confused, can turn their skin blue, and can be fatal. Frostbite is when some part of the body like the fingers - freezes, because the body stops circulating blood to that area in order to conserve warmth. Warm clothing has changed over time. Native peoples wore animal skins, like seal, caribou, polar bear, wolf and fox, to stay warm. Animal skins keep people warm because the fur traps air,
and air is a good insulator. A down jacket keeps you very warm because the feathers trap air. Early explorers to the Arctic used fabrics like wool and cotton, which did not insulate them well enough and were heavy and bulky. Modern outdoor gear is made of light synthetic fabrics worn in layers: long underwear covered with a warm shirt, a jacket, and a windbreaker. Each layer traps air, providing extra insulation. We use boots, socks and mittens to protect the parts of our body that are far from our heart, which provides warmth through blood circulation. Igloos are also used to provide shelter and warmth for travelers and hunters. But how can an igloo keep you warm when it's made of snow and ice? Snow and ice are actually good insulators. The igloo blocks the wind and, more important, keeps your body heat inside the structure's air space. The snow on the inside of the igloo typically melts and refreezes, making a protective layer.
Igloo. Icon courtesy of Iconshock, Iconfinder.
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