Because the atmospheric pressure at sea level is variable, it is not a consistent unit of pressure.It is caused by gas particles hitting the walls of their container. A pressure of 0.887 atm equals how many pascals?.How many millimetres of mercury are in 334 torr?.How many millimetres of mercury are in 0.334 atm?.What units of pressure are equal to each other?.Explain why the original definition of atmosphere did not work well.If a force of 2,546 N is pressed against an area of 0.0332 m 2, what is the pressure in pascals?. If a force of 16.7 N is pressed against an area of 2.44 m 2, what is the pressure in pascals?.Define and relate three units of pressure.Relating these to the formal SI unit of pressure, 1 atm = 101,325 Pa. Published by Houghton Mifflin Harcourt Publishing Company. The American Heritage Science Dictionary Copyright 2011. The scientific notation for 10,492, for example, is 1.0492 X 10 4. We can use these equivalences as with any equivalences-to perform conversions from one unit to another. scientific notation A method of expressing numbers in terms of a decimal number between 1 and 10 multiplied by a power of 10. An equivalent unit is the torr, which equals 1 mmHg. (The torr is named after Evangelista Torricelli, a seventeenth-century Italian scientist who invented the mercury barometer.) With these definitions of pressure, the atmosphere unit is redefined: 1 atm is defined as exactly 760 mmHg, or 760 torr. A more reliable and common unit is millimetre of mercury (mmHg), which is the amount of pressure exerted by a column of mercury exactly 1 mm high. However, “average atmospheric pressure at sea level” is difficult to pinpoint because of atmospheric pressure variations. A common unit of pressure is the atmosphere (atm), which was originally defined as the average atmospheric pressure at sea level. However, this is usually too small in magnitude to be useful. The formal, SI-approved unit of pressure is the pascal (Pa), which is defined as 1 N/m 2 (one newton of force over an area of one square metre). The pressure of the atmosphere is 101,325 Pa. Even our atmosphere exerts pressure-in this case, the gas is being “held in” by the earth’s gravity, rather than the gas being in a container. Pressure ( P) is defined as the force of all the gas particle/wall collisions divided by the area of the wall:Īll gases exert pressure it is one of the fundamental measurable quantities of this phase of matter. The accumulation of all these forces distributed over the area of the walls of the container causes something we call pressure. Although collisions with container walls are elastic (i.e., there is no net energy gain or loss because of the collision), a gas particle does exert a force on the wall during the collision. The kinetic theory of gases indicates that gas particles are always in motion and are colliding with other particles and the walls of the container holding them. Learn the units of pressure and how to convert between them.
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