The kinetic molecular theory of gases is based on several postulates that describe the behavior of ideal gases. Here are the five main postulates, along with simple examples for each:
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Gas Particles are in Constant Motion:
- Postulate: Gas particles are in continuous, random motion in all directions. Their speed increases with temperature.
- Example: If you open a perfume bottle in one corner of a room, the scent spreads throughout the room as the gas particles move freely and quickly in all directions.
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Negligible Volume of Gas Particles:
- Postulate: The volume of gas particles themselves is negligible compared to the total volume of the gas. The actual size of individual gas molecules is very small relative to the spaces between them.
- Example: In a balloon filled with air, the amount of space taken up by the air molecules themselves is minuscule compared to the volume of the balloon.
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No Intermolecular Forces:
- Postulate: There are no significant forces of attraction or repulsion between the gas particles. They do not interact with each other except during collisions.
- Example: In a container of neon gas, the neon atoms move independently without exerting any attractive forces on one another, allowing them to flow freely.
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Elastic Collisions:
- Postulate: Gas particles collide with each other and with the walls of their container in perfectly elastic collisions, meaning that there is no net loss of kinetic energy in the system.
- Example: When a gas molecule collides with the wall of a container, it bounces off without losing energy, so the pressure exerted by the gas on the wall remains constant.
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Average Kinetic Energy Related to Temperature:
- Postulate: The average kinetic energy of gas particles is directly proportional to the absolute temperature (measured in Kelvin) of the gas.
- Example: When you heat a closed container filled with gas, the temperature increases, which means the average speed of the gas particles increases, causing more collisions with the walls and increasing the pressure.
These postulates provide the foundation for understanding the behavior of gases and are essential in various applications within chemistry, physics, and engineering.