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What is a Gas?

February 25, 2013

Hi, my name is Emerald Robinson, and in this “What Is” video, we’re going to investigate the state of matter called a “gas.”

Gases are materials that have a no definite volume and no specific shape. In other words, gases can easily flow into and take the shape of a container, and will expand, redistributing themselves to evenly fill that container.

Although there are many types of gases, there are few characteristics that they have in common.

First, particles in a gas have no real arrangement. They can move over and past one another, and the space between the molecules can increase or decrease. Molecules in a gas collide with one another, and move more quickly or more slowly based on factors like temperature and pressure, but they will always spread out fairly equally to fill the space that they’re in. All of this molecular movement means that gases hold a lot of kinetic energy – energy caused by motion.

Second, gases can be compressed. Because there is space between the molecules in a gas, it can be placed under pressure and squeezed so that the particles are forced to be close to one another.

Third, gases can flow from one area to another, although the direction of flow is not directly affected by gravity. This ability to flow means they are sometimes referred to as “fluids.”

Last, gases have melting points and boiling points that are below room temperature.

For the most part, we are unable to see gases because of the space between their particles. Scientists have to use characteristics like pressure, volume, number of particles per unit area, and temperature to discuss and identify them. Gases are commonly used in things like cooking, health care, and scientific research and they even make up the air we breathe.



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