Gases

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Kinetic-Molecular Theory Noun

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[ki-net-ik mo-lek-yuh-ler thee-uh-ree]

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Kinetic-Molecular Theory

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A model describing the behavior of matter, particularly gases, as a collection of particles in constant, random motion.

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Example: A gas consists of tiny molecules in constant, random motion. They move freely within a container, colliding with each other and the container's walls.

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Kinetic Energy Noun

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[ki-net-ik en-er-jee]

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Kinetic Energy

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The energy that an object possesses due to its motion, determined by its mass and its velocity.

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Example: This image shows kinetic energy by depicting a soccer ball in motion after being kicked, contrasting it with the stationary ball's potential energy.

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Elastic Collision Noun

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[i-las-tik kuh-lizh-uhn]

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Elastic Collision

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A collision between particles in which the total kinetic energy is conserved, though it may be transferred between particles.

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Example: This diagram shows two particles (A and B) colliding and bouncing off each other. This represents an elastic collision, where particles rebound without losing energy, just like gas molecules.

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Temperature Noun

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[tem-per-uh-cher]

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Temperature

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A measure of the average kinetic energy of the particles that make up a sample of matter.

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Example: This image shows a thermometer, a tool used to measure temperature in degrees Celsius (C) or Fahrenheit (F), indicating the degree of hotness or coldness.

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Diffusion Noun

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[di-fyoo-zhuhn]

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Diffusion

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The movement of one material through another, caused by random particle motion, from high to low concentration areas.

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Example: This image shows a container with gas particles unevenly distributed, creating an area of high concentration and an area of low concentration, known as a concentration gradient.

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Effusion Noun

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[i-fyoo-zhuhn]

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Effusion

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The process by which a gas escapes from its container through a tiny opening into a vacuum.

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Example: This diagram shows effusion, where gas particles escape from a container through a tiny pinhole into an empty space (an evacuated chamber).

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Graham's Law of Effusion Noun

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[grams law uv i-fyoo-zhuhn]

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Graham's Law of Effusion

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A law stating that a gas's effusion rate is inversely proportional to the square root of its molar mass.

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Example: This image shows that lighter gas particles, like Helium, effuse (escape) through a pinhole faster than heavier gas particles, like Ethylene oxide.

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Pressure Noun

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[presh-er]

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Pressure

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The amount of force exerted per unit of area, which for gases is caused by particle collisions.

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Example: This image shows that atmospheric pressure is lower at high altitudes because there is less air (gas) pushing down from above.

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Atmospheric Pressure Noun

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[at-muh-sfer-ik presh-er]

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Atmospheric Pressure

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The pressure exerted by gas particles in Earth's atmosphere, which decreases as altitude increases.

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Example: This diagram shows that atmospheric pressure, caused by the weight of air particles, is highest at sea level and decreases as altitude increases.

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Barometer Noun

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[buh-rom-i-ter]

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Barometer

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A scientific instrument specifically designed and used for the measurement of atmospheric pressure.

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Example: This diagram shows a simple barometer. The pressure of the surrounding air (a gas) pushes down on the mercury, holding up a column in the tube.