What Is Air Made Of
Air is the invisible world we live in — it surrounds us every day, providing a medium for all sorts of chemical reactions to take place. It allows us to breathe, it keeps our bodies alive and well, and it helps make life on this planet possible. But what exactly does air consist of? The answer may surprise you.
In an average American home, there are about 2 million tons (1.8 million kilograms) of various kinds of airborne particles floating around. These include tiny bits of dust and dirt that are suspended in the air by water vapor, pollen grains from plants, smoke particles released from cigarettes or cigars, bacteria and viruses, and even microscopic droplets of liquid water. In fact, if you lived in New York City’s Central Park, your home would be surrounded by more than 6 billion living organisms each year!
This abundance of organic matter makes the air an ideal environment for many different types of microorganisms. Some can be harmful to humans and animals; others serve beneficial functions like breaking down waste products and helping recycle nutrients. All play important roles in creating healthy conditions on earth.
But how do these particles form? And why don’t they just dissolve into nothingness when exposed to the sun and wind? Read on to find out.
Air Pollution
One of the most common sources of pollution comes from the burning of fossil fuels, which releases greenhouse gasses like carbon dioxide and methane. When combined with sunlight, these molecules release heat energy, causing global warming and rising temperatures. This is one reason why scientists have been concerned with cleaning up the air since the industrial revolution began. A lot of work has gone toward finding ways to reduce levels of these pollutants.
Another source of air pollution comes from car exhausts, factories, power plants, and incinerators. Many of these facilities burn fossil fuels like coal and oil to produce electricity and fuel for heating and transportation. However, their operations often emit harmful chemicals like sulfur oxides, nitrogen oxides, and carbon monoxide. Other polluting compounds, such as ozone, come from chlorinated hydrocarbons used to make pesticides and solvents. Ozone forms naturally, but man-made emissions contribute greatly to its presence in the air.
Particles in the air can cause eye irritation and respiratory problems, especially when they’re inhaled deeply. Small particles tend to get lodged deep within the lungs, where they irritate the mucus membranes and cause infections. Larger particles stick close to the surface of the lungs, irritating only those tissues at the top. Both types can trigger asthma attacks.
Smoke particles absorb solar radiation, causing them to grow larger and heavier over time. Eventually, they become so large and heavy that gravity pulls them back toward the ground. They fall through the air before being deposited onto surfaces like grass and roads. As these particles settle, they pick up additional substances and contaminants.
Other pollutants can harm the skin, eyes and nervous system. For example, chlorine gas is commonly used to disinfect drinking water. If breathed directly into the lungs, it could kill someone instantly. Other examples of toxic air pollutants include ammonia, benzene, cadmium, carbon tetrachloride, lead, mercury, methyl chloride, nitrous oxide, perchloroethylene, polycyclic aromatic hydrocarbon, trichloroethene and vinyl chloride.
When inhaled, some of these toxins cause cancer, birth defects, miscarriages, blindness, lung diseases, kidney damage, nerve disorders, heart disease, liver damage and premature death. Children, elderly people and those already suffering from health problems are particularly vulnerable.
So far we’ve discussed the physical components of air. What happens once it gets into our homes? Find out next.
Nitrogen Makes Up More Than Half of Our Atmosphere
About 78 percent of the mass of the Earth’s atmosphere is comprised of two elements: nitrogen and oxygen. Although neither is actually a “gas,” both combine chemically to create the compound N2. Nitrogen atoms bind together via covalent bonds, sharing electrons between them. Oxygen, meanwhile, takes part in ionic bonds — strong chemical bonds formed by sharing electrons between atoms.
Both oxygen and nitrogen are essential to human life. We need oxygen to keep our cells running properly and nitrogen to build proteins and DNA. Without either, plant and animal life couldn’t exist. Plants use nitrogen to convert carbon dioxide into glucose and carbohydrates, while animals need it for protein formation.
Oxygen helps remove waste products from the body and converts them into carbon dioxide, allowing aerobic organisms to continue metabolizing. Humans breathe in oxygen during respiration and exhale carbon dioxide.
We normally consume enough oxygen to meet our needs, but sometimes we’ll go beyond. Athletes who exercise intensely will temporarily require extra oxygen to supply muscles with energy. People under stress may experience shortness of breath. And occasionally, people suffer from hypoxia, in which they receive less oxygen than normal. Hypoxia causes dizziness, headaches, nausea, loss of consciousness, fainting, breathing difficulties, muscle pain and fatigue.
Exercising outdoors reduces the concentration of atmospheric nitrogen. Instead, the air becomes composed mostly of oxygen. At higher altitudes, the ratio of nitrogen to oxygen increases because there is less nitrogen in the air.
How does this affect us? We usually refer to high concentrations of nitrogen as “fog” or “smoke.” On days when a thick fog descends upon a city, traffic slows significantly due to visibility issues. Similarly, on clear days at sea level, aircraft flying below 10,000 feet (3,048 m) encounter reduced visibility caused by low oxygen content.
On the next page, learn more about one of the most prevalent gases in our atmosphere.
Nova Particles Formed From Gas Giants
There’s no question that oxygen constitutes the majority of Earth’s air. That said, there’s another element that floats around us every day, though not nearly as widely: argon. Argon is lighter than both nitrogen and oxygen, making it the fourth major constituent of the atmosphere. It was discovered in 1774 by French chemist Michel Louis Calvet.
Argon is typically found at extremely low densities in the upper parts of the atmosphere, where it serves as a buffer against changes in barometric pressure. Because it is relatively rare, it has long served as an indicator of weather patterns. For instance, on hot summer nights, the temperature of the lower layers of the atmosphere drop precipitously, prompting clouds to form. During rainy periods, however, warmer air tends to rise, causing the lower strata to dry out. This results in the development of rain showers.
These patterns change as new weather systems develop. Early storms can bring warm moist air rushing downward, condensing water vapor and producing lightning strikes. During severe thunderstorms, however, cold fronts sweep across the area, forcing cooler air upward. This prevents moisture from reaching the ground and limits the number of electrical discharges.
Like nitrogen, argon exists in several isotopes, ranging from 36Ar to 44Ar. There are also three stable isotopes of helium: 1He, 2He and 3He. Argon is unusual among the gases in our atmosphere because it contains no hydrogens. Hydrogen atoms join with oxygen to form water vapor, the main component of humidity. Argon atoms cannot react with any other elements.
Learn more about the processes that shape the makeup of the Earth’s atmosphere on the next page.
Gases are classified according to whether they contain fixed nuclei or electrically charged ions. One method for classifying them uses the prefixes denoting the respective number of protons. For example, diatomic nitrogen is referred to as N2.
Earth Gases
The vast majority of the atmosphere consists primarily of nitrogen and oxygen. The balance includes other gases such as water vapor, carbon dioxide and methane. Here’s a list of the five most abundant gases in the Earth’s atmosphere:
Water Vapor – 77%
Carbon Dioxide – 5%
Methane – 4%
Nitrous Oxide – 2%
Fluorine – 0.1%
Most of the carbon dioxide in the atmosphere is absorbed by trees and crops. Only a minuscule portion reaches the oceans and atmosphere. While carbon dioxide contributes to global warming, it is essential to photosynthesis and therefore plays an essential role in maintaining the balance of nature. Methane is produced naturally by microbes and decomposing land vegetation, but it is also emitted from natural sources like volcanoes and wetlands. Water vapor is the largest contributor to Earth’s greenhouse effect.
Humans have changed the composition of the atmosphere considerably over the past century, altering the amount of carbon dioxide and methane present. The United Nations estimates that the increase in CO2 resulting from human activity is equivalent to adding four Olympic pools worth of gas to the atmosphere every year!
While the exact effects of these changes aren’t fully known, we can safely assume they are significant. Scientists predict that climate change induced by increased greenhouse gasses could alter rainfall patterns in tropical areas, causing droughts in the Americas and flooding in Africa. Rising temperatures could also melt polar icecaps, raising sea levels worldwide.
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