92 Get Cool, Stay Cool!-High

Get Cool, Stay Cool! FOCUS Question How can we control heat energy to get cool and stay cool during hot weather?

It's Too Hot! Your body is warm— about 37 degrees Celsius (98.6°F). This is the temperature your organs and muscles need to be healthy and active. To stay at this temperature, your body gives off heat as your body systems work. The warmer it is outside, the harder it is for your body to give off heat. This is why you might feel hot even when the air is cooler than your body temperature. How do you cool off in hot weather? You might enjoy a sprinkler, a cool drink, or an air-conditioned room. In each example, you are cooling off by transferring heat from one place to another. So, what is heat? All objects are made of tiny particles that are always moving, or vibrating. This motion is heat. Particles that are moving fast are hot. Particles that are moving slowly have less heat. Fast-moving particles transfer some motion to slower-moving particles nearby.

Move That Heat! The different speeds of particles cause heat to naturally move from warm areas to cool areas. You cool off by moving heat away from your body or home. You can move heat in three ways: Conduction occurs when heat moves through objects that touch each other. If you touch a cool glass of ice water, heat moves from your warm hand to the cool glass. Convection occurs when a liquid or gas moves around, carrying heat with it. The movement of the hot air or liquid heats the space around it. When you open an oven, the hot air that pours out rises and heats the air in the kitchen, thanks to convection. Radiation occurs when energy travels in waves. It does not need to pass through any material. Radiation is what makes sunshine feel hot, even from such a great distance. You can use all three ways to move heat and keep cool.

A Cool Home On a hot, sunny day, what's the simplest way to stay cool? Get in the shade! Objects that make shade block some of the Sun's radiation. In warm climates, houses are designed to get lots of shade. The roof stretches out past the walls to shade the windows. People build porches and plant trees to create shady spaces outside. In some of the hottest places, people build houses partially underground. The soil blocks the Sun's hot rays. People also build houses to catch cool breezes. Some houses have courtyards— open spaces in the center. Others have one passage, or breezeway, that opens at both ends. Cool air blows straight through.

On really hot days, shade isn't enough to keep a home cool. Air-conditioning uses electricity to cool a building. When turned on, it uses conduction and convection to change the condition of the air from warm and humid to cool and dry. An air conditioner has a special part called a compressor. This part makes pipes within the air conditioner very cold. A fan pulls warm air from the building across the cold pipes. The warm air loses heat and cools down. The fan returns the cold air to the building. Science in Your World As air-conditioning became popular in the 1950s and 1960s, millions of people moved to the "Sun Belt"— warm, sunny places such as Florida and Arizona.

A Cool Body Of course, you can't stay in an air-conditioned building forever. Many places don't have air-conditioning at all. To get cool, you must cool your body. Fortunately, your body has its own cooling system. When you get too warm, you sweat. Just as the liquid in the pipes of an air conditioner evaporates, the sweat on your skin evaporates into the air and releases heat. In places with a dry climate, sweat is very good at cooling you off. But when the air is humid, sweat doesn't evaporate as well since the air is already full of moisture. You need something more to keep cool. Iced drinks help cool down your body and replace the fluids you lose while sweating. Fact or Fiction? You might hear someone say, "I'm sweating like a pig!" But pigs don't sweat to cool off. They roll around in water or mud. The moisture evaporates keeping them cool.