What Is Air Made Up Of
Air contains a lot more than just oxygen and nitrogen. It also contains many different types of molecules that contain various combinations of the two main components — oxygen and nitrogen. The atoms within these molecules are arranged differently from one another, and they each have their own special functions. Each molecule plays an important role in our environment and is essential for life on Earth.
Carbon Dioxide (CO2) is the second-most common gas found in air at about 0.14 percent by volume. It is colorless, odorless, soluble in water and nonflammable. Carbon dioxide comes from burning fossil fuels like coal or oil to create energy, or when organic material breaks down in the presence of bacteria or fungi. However, it can be produced naturally through photosynthesis. Plants do this by using carbon dioxide and sunlight together to produce sugar. When animals eat plants or breathe them in, they consume CO2. The human body uses some of this carbon to make proteins needed to function, but most goes into making blood cells and muscles. A large part of the rest gets converted into fat. In fact, humans burn off about 1,000 pounds (453 kilograms) of food every day to produce enough energy to sustain themselves. That means we’re responsible for producing nearly half of all the CO2 released into the atmosphere each year. This amount would fill up 12 million cars.
Ozone is another compound commonly found in air. Its name sounds similar to “oxygen,” so what exactly does it do? Ozone actually protects us against ultraviolet rays. Ultraviolet light waves pass right through matter, including ozone. They can even break apart molecular bonds. This is why you need sunscreen to protect your skin from UV radiation. But if there is no ozone present, then these harmful rays can damage DNA and cause cancer. Fortunately, ozone exists naturally and helps filter out the suns’ dangerous UVB rays. Without it, the sun’s rays could cook us in minutes.
Nitrogen Oxide (NOx) is usually found in smoggy areas where factories release polluted fumes. Nitrogen oxide combines with moisture and sunlight to form nitric acid, which can burn the lungs and lead to respiratory problems. Pollution often refers to manmade materials introduced into the natural world. In the case of NOx, it originates from the combustion process used to generate electricity or heat homes. Electric utilities use natural gas to operate generators. When burned, natural gas produces carbon dioxide and water vapor along with traces of methane and sulfur compounds. Manure, garbage, and wood chips are also added to help speed up the reaction between the fuel and oxygen. These emissions become contaminated particles called particulates, which can settle on roofs, inside walls, and in the lower layers of the atmosphere. As a result, people may suffer lung ailments, eye irritation, and headaches while breathing polluted air.
Hydrofluorocarbons (HFCs), known as “super greenhouse gases” because they trap heat well in the atmosphere, were developed specifically to replace chlorofluorocarbons (CFCs). HFCs are now being phased out under the Montreal Protocol in order to save the earth from catastrophic global warming.
Methane (CH4) is a flammable, foul-smelling, highly combustible hydrocarbon. Methane is primarily generated during the digestive processes of cows and sheep and the digestion of waste by microbes in landfills. Although it doesn’t contribute much to climate change, methane is a major contributor to the formation of smog. Burning methane releases potent carcinogens known as polycyclic aromatic hydrocarbons (PAHs). PAHs can harm the lungs and immune systems and cause birth defects.
Water Vapor, although not considered toxic, is still classified as a greenhouse gas. Water vapor is released when water evaporates from lakes and rivers, wetlands, and oceans. Because water vapor traps heat well, its contribution to global warming cannot be ignored.
In addition to containing gases, air is mostly composed of tiny droplets of liquid and solid particles. At room temperature, air is almost completely saturated with water vapors. The mixture is called atmospheric water vapor and accounts for roughly 71 percent of the weight of air. Most of the remaining mass consists of nitrogen (24 percent), oxygen (20 percent), argon (3 percent), and trace quantities of other gases. Particles include dust, pollen, smoke, volcanic ash, snowflakes, ice crystals, sea spray, clouds, fog, and pollution.
Atmospheric water vapor is distributed evenly throughout the atmosphere. Scientists believe that the average person breathes around 6 gallons (21 liters) of water per day. The humidity depends upon location. For example, heavy rainfall will increase the humidity in certain regions. Humidity affects how easily heat moves through the atmosphere. Heat rises and decreases in density when it expands. Higher humidity slows the transfer of heat across long distances, causing temperatures to remain higher near the ground.
Humans breathe air, but why do we inhale anything at all? Breathing allows us to take in nutrients and expel wastes. Our bodies require oxygen to convert glucose from starches and carbohydrates into energy. We exhale carbon dioxide, water vapor, and sometimes sweat. Sweat is mainly water and salts, but it also includes urea, lactic acid, and other chemicals. Some of these substances are necessary to maintain bodily functions. Others are metabolic products of normal daily activities. Bacteria in our mouths convert sugars into acids, which kill bad breath germs. Urine mixes with ammonia to neutralize excess sodium and control fluid levels. And saliva coats the mouth cavity to lubricate food intake and prevent tooth decay.
All organisms must spend time finding food and avoiding predators. Animals must locate mates, find suitable nesting sites, defend territories, and reproduce successfully. Many species travel great distances to get to specific locations. Birds migrate thousands of miles to reach warmer climates; fish swim hundreds of miles upstream to spawn. Even insects fly several hundred miles over ocean currents to new breeding grounds. Humans do this too. They move from city to city searching for jobs and housing. If they didn’t, they’d never meet potential spouses.
Scientists once believed that birds had wings to keep warm. Now researchers think that flying keeps mammals cool. Flying provides insulation from cold winds and extreme weather conditions. The same principle applies to bats, whales, and gliding possums.
When scientists first discovered bird feathers in amber fossils dating back 100 million years ago, they wondered why feathered dinosaurs hadn’t evolved flight. One theory was that flying kept them warm. Today, however, experts have determined that flight alone wouldn’t provide sufficient lift to support flight. Instead, they propose that feathers helped regulate body temperatures and retain fluids. They say that the combination of feathers and wing membranes created a thermally insulating layer that provided extra warmth without overheating. Another idea is that feather structures act as solar collectors to absorb heat from the sun. Yet others suggest that feathers improve aerodynamics by reducing drag.
Although birds don’t wear clothes like penguins, they do cover themselves with oily secretions from glands located beneath their wings and tail. This waterproofing substance prevents evaporation, thus keeping them dry. Researchers have named this substance “keratin.” Keratin is a protein unique to birds. It takes millions of years for keratin to decompose. By covering their eggs, chicks acquire a protective outer coating that enables them to survive harsh winters.
On the next page, learn about how astronauts stay alive in space.
Astronauts’ Diet in Space
Space Food Labels Explained
Spacesuits
Food Labels in Space
Gravity plays a huge factor in staying healthy. On Earth, gravity pulls objects toward the center of our planet. Astronauts aboard the International Space Station (ISS) experience zero gravity. Their bodies don’t know whether to hold onto vital organs or float away in search of open spaces. To avoid confusion, scientists designed a diet called the Reduced Gravity/Microgravity Pregnancy Nutrient Requirements Study. NASA says that astronauts should follow a low-calorie diet that mimics what happens on Earth after prolonged periods of weightlessness. According to the recommendations, astronauts who weigh less than 110 pounds (49 kilograms) shouldn’t exceed 2,200 calories per day. Those who weigh more than 130 pounds (59 kilograms) should limit their calorie consumption to 1,800 calories per day.
NASA also recommends that astronauts drink plenty of fluids. Drinking water and maintaining proper hydration is crucial for health. The recommended intake is eight glasses of liquids per day but varies according to age and medical needs.
Since astronauts lose muscle mass and bone density when exposed to microgravity, NASA encourages exercise. The ISS offers workout equipment, televisions, and computers. Crew members also attend classes and lectures on topics like nutrition, psychology, health care, and science.
One thing astronauts miss out on is pizza. Pizza Hut offered a limited edition menu item, the Sputnik Chocolate Chip Cookie Panini, in honor of the 50th anniversary of the Soviet Union launching the first artificial satellite.
If you’ve ever seen a commercial airline meal, chances are good that you’ll see a label indicating how much salt, cholesterol, and trans fats are included in the fare.
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