Theory of Gases -- Their Properties and Behavior The study of gas behavior (~1660’s) lead to many of today’s modern theories of atomic behavior The underpinnings of gas behavior provides insight into the physical properties of matter Where in the world does He come from? He is an inert, unreactive atom. It floats to the outer reaches of our atmosphere
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Theory of Gases -- Their Properties and Behavior
The study of gas behavior (~1660’s) lead to many of
today’s modern theories of atomic behavior
The underpinnings of gas behavior provides insight into the physical properties of matter
Where in the world does He come from?
He is an inert, unreactive atom.
It floats to the outer reaches of our atmosphere
The “Three” States of Matter
Ordered Compressible Homogeneous Gases NO YES YES Solids YES NO YES/NO
Liquids NO NO YES
Critical Concepts of Gas Behavior
• About 0.1 % volume of gas is taken up by molecules. There is mostly empty space. In a liquid, there is only 70% empty space.
• Little interaction between neighboring gas molecules/atoms.
• Gases exert a pressure via collisions
Does our atmosphere, which is a ball of gas, exert a pressure?
With the assistance of gravity…YES.
A 1 meter diameter swath of air from ground level to outer space weighs in at 10,300 Kg
or 4,680 lbs.
1 atm = 760 mmHg = 101,325 Pascals (Pa)
The IDEAL GAS LAW
P is pressure;
V is volume;
n = moles of gas
R = constant, either 0.082058 (Lit·atm)/(mole·K) or 8.314472 (J/mole·K)
T is Temperature in Kelvin
We can use the IDEAL GAS equation to derive other gas
laws (this is the reverse of how it was ‘put together’)
Boyle’s law: P1V1 = P2V2 Temp & n held constant
Charles’ Law: 2
2
1
1
TV
TV
= Pressure & n held constant
Avagadro’s Law: 2
2
1
1
nV
nV
= Temp & Pressure constant
Gay-Lussac’s law anybody?
PV = nRT
Let’s consider Boyle’s Law, Temperature and n are held constant
So, we know that PV = nRT
In this case, T, R, and n are constants…
…this requires, nRT = Constant
PV = constant
P1V1 (for state 1) = P2V2 (for state 2) = PxVx =
constant
…as in previous slide,
Boyle’s law: P1V1 = P2V2 Temp & n are held constant
… Derivation of Charles’ Law, P & n are held constant