Chapter 14 Gases and Plasmas Flashcards
Define Atmospheric Pressure
What is the atmospheric pressure at sea level?
**Atmospheric Pressure **is pressure exerted against bodies immersed in the atmosphere resulting from the weight of air pressing down from above. It is caused by the weight of the air. At sea level, atmospheric pressure is about 101 kPa.
About how many kilograms of air occupy a classroom that has 200-m² floor area and a 4-m-high ceiling? (Assume a chilly temperature of 10ºC)
The mass of air is 1000kg. The volume of air is areaXheight= 200m²X4m=800³. Each cubic meter of air has a mass of about 1.25kg, so 800m³X1.25kg/m³=1000kg
Why doesn’t the pressure of the atmosphere break windows?
Atmospheric pressure is exerted on both sides of a window, so no net force is exerted on the glass.
What is a Barameter?
A **barameter **is a device used to measure the pressure of the atmosphere.
How do barometers work? Why is a barometer filled with mercury and not water?
Mercury barometers work by measuring air pressure. They are constructed using a long glass tube, with a small reservoir at the bottom full of mercury. When the atmospheric pressure rises, more force is put to bear on the reservoir of mercury, which then forces the mercury to a higher level of the tube. Mercury barometers have millimetre markings along the length of their tubes to enable easy reading of the pressure. Mercury is used because it is more dense. Using water would require a much longer glass tube.
What is **Boyle’s law **
The product of pressure and volume is a constant for a given mass of confined gas regardless of changes in either pressure or volume individually, as as the temperature remains unchanged P1V1=P2V2
What is Archimedes’ Principle?
An object surrounded by air is buoyed up by a force equal to the weight of the air displaced.
