CH' 20 GASES

1
CH. 20 GASES GASES FLOW, THEREFORE THEY ARE
FLUIDS. GASES HAVE NO DEFINITE SHAPE OR
VOLUME. GASES IN OUR ATMOSPHERE ARE HELD IN BY
GRAVITY AND ENERGIZED BY THE SUN.
2
DENSITY OF THE ATMOSPHERE DECREASES WITH
ALTITUDE. WE CALL THIS THINNER AIR. CHART P. 291
SHOWS LAYERS OF ATMOSPHERE. THE ATMOSPHERE ABOVE
US PUTS PRESSURE ON US. 1 M3 OF AIR HAS A MASS OF
ABOUT 1.2 KG
3
AN INSTRUMENT USED FOR MEASURING AIR PRESSURE IS
THE BAROMETER. AN ANEROID BAROMETER USES A SPRING
AND LEVER SYSTEM TO SHOW DIFFERENCES IN
PRESSURE. AN ALTIMETER IS A TYPE OF ANEROID
BAROMETER THAT SHOWS DIFFERENCES IN ALTITUDE
4
BOYLES LAW PRESSURE AND VOLUME ARE INVERSELY
PROPORTIONAL. AS ONE GOES UP THE OTHER GOES
DOWN. CUT THE VOLUME IN HALF, AND THE PRESSURE
DOUBLES. BUOYANCY WORKS FOR AIR THE SAME AS IT
WORKS FOR LIQUIDS
5
1 M3 OF AIR HAS A MASS OF 1.2 KG. THEREFORE ITS
WEIGHT IS ABOUT 12 N. 1 M3 OF AIR HAS A
BUOYANCY OF 12 N. ANY OBJECT WITH A DENSITY LESS
THAN AIR WILL RISE. OR ANY OBJECT WITH A MASS
LESS THAN 1.2 KG PER M3 WILL RISE
6
BERNOULLIS PRINCIPLE SAYS THAT WHEN THE SPEED OF
A FLUID INCREASES, THE PRESSURE DROPS. WHEN THE
AIR FLOWS IN A STEADY PATH IT IS CALLED
STREAMLINES. IF THE AIR BECOMES TURBULENT, OR A
CURLY PATH IT IS CALLED AN EDDY.