Give a more illustrations showing that air needs to be removed from a container before something else can enter it.
Answers
In countless tasks, from running blast furnaces to inflating tires, people use air. Airplanes and kites need it to fly. The sound of thunder or a clap of hands requires air to be heard. Humans and animals would die without air. Trees, flowers, and grass also need it to live.
Human beings are in contact with air every second that they live. It is all around, and it extends upward for many miles as the Earth’s atmosphere. Sometimes, on a windy day, people feel it brushing against their skin. They can hear it move when the wind howls or a tire blows out. Most of the time, however, people are completely unaware of the air, because it has no color, taste, or odor. They even think of a container of air as being empty.
WHAT IS AIR?
This invisible substance called air is really a mixture of several gases. Each gas is present in the form of separate, tiny units called molecules. Molecules are much too small to be seen, but they make up for their small size by being present in tremendous numbers. Scientists estimate that 1 cubic inch (16.4 cubic centimeters) of ordinary air contains about 300 billion billion of them. They are so tiny, however, that there is plenty of space between them.
Under ordinary conditions, each molecule has energy enough to shoot through space at a speed of about 1,000 miles (1,600 kilometers) per hour. Very few molecules, however, travel far in a straight line at this speed. One reason is that the Earth’s gravity holds most of them within a few miles of the ground in spite of their speed. In this space they fly about, colliding with each other at a tremendous rate. In usual situations near the ground, each molecule collides with another molecule about 5 billion times each second.
DIFFERENT ELEMENTS THAT MAKE UP AIR
The molecules of two different elements, nitrogen and oxygen, make up about 99 percent of the air. The rest includes small amounts of argon and carbon dioxide. (Other gases such as neon, helium, and methane are present in trace amounts.)
Oxygen is the life-giving element in the air. It helps plants make food. Oxygen supports fire and other chemical changes in matter. It also causes metals to rust.
Certain compounds of nitrogen help build tissue in living things. Nitrogen also serves to dilute the oxygen in the air. Plants, humans, and animals are used to the diluted mixture and would soon “burn out” if they lived in pure oxygen. Indeed, the living world would soon burn up, for in pure oxygen every spark or flash of lightning would start raging fires.
Carbon dioxide is formed by the union of oxygen and carbon. Every fire produces it, as do the bodies of humans and animals. They give it off in every breath they expel. Plants use the carbon in carbon dioxide for making food and give back the oxygen to the air. Thus they continually renew the supply of oxygen.
Most air contains water vapor. The amount varies greatly from time to time and place to place. Air also contains dust, pollen, spores, bacteria, and other bits of solid and liquid matter.
THE PROPERTIES OF AIR
Air can be greatly compressed. All the air in a space as big as a house can be squeezed into a small tank. On the other hand, air can expand almost indefinitely. If all the air were removed from the inside of a house and then 1 cubic foot (0.03 cubic meter) of air were supplied, the air would expand throughout the building.
This elastic quality comes from the nature of air as a mass of fast moving atoms and molecules. Air can be compressed because there is plenty of space between the atoms and molecules that make up the gases in air. Pressure simply squeezes the particles closer together. A sample of air also will expand to fill any space that is empty.
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An oxygen cylinder is used in hospitals is the illustration showing that air needs to be removed from a container before something else can enter it.
What are factors which affect air pressure?
- The particles of air move freely and they colloid each other then it is a kinetic molecular theory
- The volume of the container is also affected by the pressure of air
- If the volume of any container decreases then the pressure of the air gets increases
- If the pressure of the air increases then the number of gas molecules are also increases