Chemistry and Gases Help

By — McGraw-Hill Professional
Updated on Aug 29, 2011

Introduction to Gases

Gases have always been a mystery. Ancient humans saw bubbles of gas form when they brewed ales and spiced ciders from grain and fermented fruit. Some tribes believed intestinal gases were somehow connected to the spirit. When the spirit was unhappy, ill humors (sickness) would plague a person with an excess of gas. When naturally occurring pockets of natural gas from the earth were discovered, it was thought the earth’s spirit was releasing the errors of the people upon the land.

Until the 1700s, spontaneous combustion, the explosive occurrence of fire, was thought to be caused by mice, since the sudden combustion of stored grain in barns always seemed to happen when there were lots of mice around.

Modern chemists have learned a lot since then. With the development of precise equipment that can measure minute amounts of elements, accurate information about gases can now be gathered and studied.

The gas club is a lot more active than the liquid or solid clubs. Gases have livelier characters and no set boundaries. When allowed to escape from a container, they spread out into whatever space there is. If the space is the size of a room, they expand to fill the space. If the space is the outside atmosphere, they spread out infinitely, contained only by temperature changes and directed by wind currents.

Gases are the least compacted form of matter.

Gases are known for preferring to be as far as possible from each other, with no special shape or volume. Unlike solids and liquids, they are independent of one another.

Some common gases found in this free form club include nitrogen, oxygen, air, steam, carbon dioxide, helium, and argon. The air we breathe is a gas, except on very humid summer days when the air seems so loaded with water as to be nearly a liquid.

The table below gives some of the general characteristics of gases.

Table 17.1 Gases are the wild and carefree members of the three matter forms.


No set shape or volume

Expand to fill shape of container

Can be compressed by increasing pressure

Mix completely and spontaneously

Move constantly, quickly, and randomly

Smaller mass gases move more quickly than gases with larger masses

No strong molecular forces between particles

When particles collide, no energy is lost

All collisions are elastic

Low density

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