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9 Cards in this Set
- Front
- Back
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Kinetic model of matter |
The kinetic model of matter states that the tiny particles that make up matter are always in continuous random motion. |
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Solid
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Particle arrangement: - closely packed together, usually in a regular pattern, occupying minimal space - large number of particles per unit volume - has the highest densities as a result Particle movement: - vibrate about their fixed positions - held in position by very strong attractive forces between the particles - has a fixed volume and shape as a result |
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Liquid |
Particle arrangement - randomly arranged with the particles slightly further apart than in solids - slightly smaller number of particles per unit volume compared to solids - has relative high densities as a result Particle movement - free to move about within the liquid, attractive forces between the particles - has a fixed volume, but take the shape of the container |
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Gas |
Particle arrangement - randomly arranged and very far apart from one another - small number of particles per unit volume has very low densities as a result Particle movement - particles have very little attraction between them, move about randomly at very high speeds, occupy any available space - has no fixed shape or volume, highly compressible as a result |
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Evidence of molecular motion and the effects of temperature on molecular motion. |
Brownian motion is the random motion of particles that are suspended in a fluid. When temperature increases, the particles in the fluid are observed to move faster and more vigorously. This is because when the temperature of air increases, the average kinetic energy of the air molecules increases. This means that the faster-moving air molecules bombard the smoke particles more vigorously and frequently. This causes the smoke particles to move faster and change direction more frequently. Brownian motion serves as evidence for the kinetic model of matter. |
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Pressure in gases |
So how do the air molecules inside the container produce a pressure on the container's walls?
Due to the numerous collisions between air molecules and the wall, the force per unit area gives rise to the pressure exerted by the molecules on the walls of the container.
From this, we can conclude that the pressure of a gas is due to the collisions of the gas molecules with the walls of the container. |
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Pressure-temperature relationship |
The pressure of a fixed mass of gas is directly proportional to its temperature, provided its temperature remains constant.
For a fixed volume and mass of a gas, a rise in the temperature of the air causes an increase in the average speed of the gas molecules. The gas molecules bombard the surface of the container more vigorously and more frequently. The average force per collision between the gas molecules and the wall of the container increases. Since the volume of the container stays constant, the pressure inside the container increases. http://www.schoolscience.co.uk/site/scho/uploadedresources/pressure-law2.gif |
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Pressure-volume relationship |
The pressure of a fixed mass of gas is inversely proportional to its volume, provided its temperature remains constant.
For a fixed mass of gas at a constant temperature, decreasing its volume results in a proportionate increase in its pressure. A decrease in the volume of the gas means that the number of molecules per unit volume increases. Therefore, the gas molecules collide more frequently with the inner surface of the container and this results in a greater force. Since p=F/A, gas pressure increases. http://ibphysicsstuff.wdfiles.com/local--files/ideal-gases/PressVol.jpg http://www.kentchemistry.com/images/links/gases/Boyle_3.gif |
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Volume-temperature relationship |
The volume of a fixed mass of gas is directly proportional to its temperature, provided its pressure remains constant.
For a fixed mass of gas at constant pressure, increasing its temperature results in a proportionate increase in its volume. The heated gas molecules collide more vigorously and more frequently with the inner surface of the container. Gas pressure increases, and when it exceeds atmospheric pressure a net upward force acts on the container.
http://www.kentchemistry.com/images/links/gases/ideal_s2_11.gif |
