CHAPTER 2. ATMOSPHERIC PRESSURE
The units of pressure that are used are pascal (Pa), standard atmosphere (atm), and torr. 1 atm is The Gas Laws: Pressure Volume Temperature Relationships. Standard conditions for temperature and pressure are standard sets of conditions for . The molar volume of gases around STP and at atmospheric pressure can be The relationship between the two constants is Rs = R / m, where m is the. What is the relationship between atmospheric temperature, pressure and wind? Examples of temperature winds are the land/sea breeze and the valley winds.
However, gravitational separation of the air mixture takes place by molecular diffusion, which is considerably slower than turbulent vertical mixing of air for altitudes below km problem 4. Turbulent mixing thus maintains a homogeneous lower atmosphere.
Pressure and Temperature
Only above km does significant gravitational separation of gases begin to take place, with lighter gases being enriched at higher altitudes. During the debate over the harmful effects of chlorofluorocarbons CFCs on stratospheric ozone, some not-so-reputable scientists claimed that CFCs could not possibly reach the stratosphere because of their high molecular weights and hence low scale heights.
In reality, turbulent mixing of air ensures that CFC mixing ratios in air entering the stratosphere are essentially the same as those in surface air. Exercise The cruising altitudes of subsonic and supersonic aircraft are 12 km and 20 km respectively.
Pressure and the Gas Laws
What is the relative difference in air density between these two altitudes? The air density at 20 km is only a third of that at 12 km. The high speed of supersonic aircraft is made possible by the reduced air resistance at 20 km.Effect of Pressure on the Boiling Point of Water
Consider a coastline with initially the same atmospheric temperatures and pressures over land L and over sea S. Assume that there is initially no wind. In addition, because the density of liquids does not change with height most liquids are incompressiblesuch an equivalent liquid column has a well defined upper boundary below a vacuumOne of the heaviest liquids at room temperature is mercury Hg and the height of the Hg-column that is equivalent to normal pressure mb is only mm long For this reason, columns of mercury, "hanging" in an inverted vacuum tube, can be used as practical instruments to measure atmospheric pressure see FigureLutgens and Tarbuck, If water were used instead of mercury, the height of the column equivalent to normal pressure would be The Gas Laws The example of the gas-filled balloon can also be used to explore the basic gas laws see also Appendix D, p.
In the following, lets assume that the balloon is tight, so that the amount or mass of air in it stays the same: With density being the ratio of mass per volume, the gas density of the balloon thus varies only with its volume when mass is held constant.
If we squeeze the balloon, we compress the air and two things will happen: Since density is mass over volume, and the mass stays constant, the rise in density means that the volume of the balloon decreases: For two states of pressure P1, P2 and two corresponding volumes V1, V2this is stated mathematically: This in turn increases the rate at which the gas molecules bombard the skin of the balloon.