Science - The Earth's Atmosphere

Weather

the condition of Earth's atmosphere at a particular time and place.

oxygen molecules

Have to oxygen Atoms

Density

If there are more molecules in a given volume, the density is greater. If there are fewer molecules, the density is less

water vapor

Water vapor is water in the form of a gas. Water vapor is invisible. It is not the same thing as steam, which is made up of tiny droplets of liquid water. Each water molecule contains two atoms of hydrogen and one atom of oxygen.

Molecules

are made up of two or more atoms.

Oxygen and nitrogen

make up 99 percent of dry air. Argon and carbon dioxide make up most of the other one percent. The remaining gases are called trace gases because only small amounts of them are present.

How does the atmosphere protect the earth

In addition, Earth's atmosphere protects living things from dangerous radiation from the sun. The atmosphere also prevents Earth's surface from being hit by most meteoroids, or rocks from outer space.

Air Mass

It may seem to you that air has no mass. But in fact, air consists of atoms and molecules, which have mass. So air must have mass. Because air has mass, it also has other properties, including density and pressure. The amount of mass in a given volume of air is its density. You can calculate the density of a substance by dividing its mass by its volume

Use Oxygen

Plants and animals take oxygen directly from the air and use it to release energy from their food. Any fuel you can think of, from the gasoline in a car to the candles on a birthday cake, uses oxygen as it burns

Ozone layer

Protective layer in atmosphere that shields earth from UV radiation.

Water Vapor - Weather

Water vapor plays an important role in Earth's weather. Clouds form when water vapor condenses out of the air to form tiny droplets of liquid water or crystals of ice. If these droplets or crystals become heavy enough, they can fall as rain or snow. There is very little water vapor in the air over the desert where this lizard lives. In the tropical rain forest (right), where the frog lives, as much as four percent of the air may be water vapor.

When fuels such as coal and gasoline are burned, they release?

carbon dioxide. Burning these fuels increases the amount of carbon dioxide in the atmosphere.

Pure air

contains only gases. But pure air exists only in laboratories. In the real world, air also contains tiny solid and liquid particles of dust, smoke, salt, and other chemicals. You can see some of these particles in the air around you, but most of them are too small to see.

Units of Air Pressure

f the column of mercury in a mercury barometer is 30 inches high, the air pressure is "30 inches of mercury" or just "30 inches." National Weather Service maps indicate air pressure in millibars. One inch of mercury is approximately 33.87 millibars, so 30 inches of mercury is approximately equal to 1,016 millibars. At the top of a mountain, the air pressure is less than the air pressure at sea level

Altitude's affects on Density

the density of the air decreases. This means the gas molecules that make up the atmosphere are farther apart at high altitudes than they are at sea level. If you were near the top of a tall mountain and tried to run, you would quickly get out of breath. Why? The air contains 21 percent oxygen, whether you are at sea level or on top of a mountain. However, since the air is less dense at a high altitude, there are fewer oxygen molecules to breathe in each cubic meter of air than at sea level. So you would become short of breath quickly at high altitudes. The density of air decreases as altitude increases. Air at sea level has more gas molecules in each cubic meter than air at the top of a mountain.

nitrogen

the most abundant gas in the atmosphere. It makes up a little more than three fourths of the air we breathe. Each nitrogen molecule consists of two nitrogen atoms.

Air Mass

A large body of air throughout which temperature and moisture content are similar

Mercury Barometers

A mercury barometer consists of a glass tube open at the bottom end and partially filled with mercury. The space in the tube above the mercury is almost a vacuum—it contains very little air. The open end of the tube rests in a dish of mercury. The air pressure pushing down on the surface of the mercury in the dish is equal to the pressure exerted by the weight of the column of mercury in the tube. When the air pressure increases, it presses down more on the surface of the mercury. Greater air pressure forces the column of mercury higher. At sea level the mercury column is about 76 centimeters high, on average. Air pressure pushes down on the surface of the mercury in the dish, causing the mercury in the tube to rise. The air pressure is greater on the barometer on the right, so the mercury is higher in the tube

Gases In Dry Air

Dry air in the lower atmosphere generally has about the same composition of gases.

Living things need warmth and liquid water.

By trapping energy from the sun, the atmosphere keeps most of Earth's surface warm enough for water to exist as a liquid.

carbon dioxide

Each molecule of carbon dioxide has one atom of carbon and two atoms of oxygen. Carbon dioxide is essential to life. Plants must have carbon dioxide to produce food. When the cells of plants and animals break down food to produce energy, they give off carbon dioxide as a waste product When fuels such as coal and gasoline are burned, they release carbon dioxide. Burning these fuels increases the amount of carbon dioxide in the atmosphere.

two gases make up most of the air

Each molecule of carbon dioxide has one atom of carbon and two atoms of oxygen. Carbon dioxide is essential to life. Plants must have carbon dioxide to produce food. When the cells of plants and animals break down food to produce energy, they give off carbon dioxide as a waste product.

The atmosphere

Earth's atmosphere is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids. Oxygen and nitrogen together make up 99 percent of dry air. Argon and carbon dioxide make up most of the other one percent. nitrogen is the most abundant gas in the atmosphere. It makes up a little more than three fourths of the air we breathe. Each nitrogen molecule consists of two nitrogen atoms.

Aneroid Barometers

If you have a barometer at home, it is probably an aneroid barometer. The word aneroid means "without liquid." An aneroid barometer (an uh royd) has an airtight metal chamber, as shown in Figure 6. The metal chamber is sensitive to changes in air pressure. When air pressure increases, the thin walls of the chamber are pushed in. When the pressure drops, the walls bulge out. The chamber is connected to a dial by a series of springs and levers. As the shape of the chamber changes, the needle on the dial moves.

Altitude affect on air pressure

Imagine a stack of books. Which book has more weight on it, the second book from the top or the book at the bottom? The second book from the top has only the weight of one book on top of it. The book at the bottom of the stack has the weight of all the books pressing on it. Air at sea level is like the bottom book. Sea-level air has the weight of the whole atmosphere pressing on it. So air pressure is greater at sea level. Air near the top of the atmosphere is like the second book from the top. There, the air has less weight pressing on it, and thus has lower air pressure. Air pressure is greater at sea level and decreases as the altitude increases.

Earth's atmosphere

The envelope of gases that surrounds the planet. Is made up of nitrogen, oxygen, carbon dioxide, water vapor, and many other gases, as well as particles of liquids and solids. If you breathe on the apple, a thin film of water droplets will form on its surface. Earth's atmosphere is like that water on the apple—a thin layer of gases on Earth's surface

Pressure

The force pushing on an area or surface. The weight of the atmosphere exerts a force on surfaces. Air pressure is the result of the weight of a column of air pushing down on an area. The column of air extends upward through the entire atmosphere There is a column of air above you all the time. The weight of the air in the atmosphere causes air pressure.

Atmosphere Weight

The weight of the column of air above your desk is about the same as the weight of a large school bus. So why doesn't air pressure crush your desk? The reason is that the molecules in air push in all directions—down, up, and sideways. The air pushing down on top of your desk is balanced by the air pushing up on the bottom of your desk. Air pressure can change from day to day. A denser substance has more mass per unit volume than a less dense one. So denser air exerts more pressure than less dense air. Even when you take off your pack, your shoulders will still have pressure on them. The weight of the atmosphere itself is constantly pressing on your body.

Ozone

is a form of oxygen that has three oxygen atoms in each molecule instead of the usual two. Have you ever noticed a pungent smell in the air after a thunderstorm? This is the odor of ozone, which forms when lightning interacts with oxygen in the air.

A barometer

is an instrument that is used to measure air pressure. Two common kinds of barometers are mercury barometers and aneroid barometers.

Air Pressure

is the result of the weight of a column of air pushing down on an area. The column of air extends upward through the entire atmosphere,

Altitude

or elevation, is the distance above sea level, the average level of the surface of the oceans. Air pressure decreases as altitude increases. As air pressure decreases, so does density.

oxygen

the second most abundant gas in the atmosphere, it makes up less than one fourth of the volume Plants and animals take oxygen directly from the air and use it to release energy from their food. Any fuel you can think of, from the gasoline in a car to the candles on a birthday cake, uses oxygen as it burns

Atom

the smallest unit of a chemical element that can exist by itself

Ultra violet Rays

we can not see them because we don't have the cones to perceive that wavelength