Gases
Properties of Gases According to Kinetic Molecular Theory
1. All gases are made up of tiny particles called molecules.
2. The molecules are small in relation to the distances between them.
3. Gas molecules are in constant state of motion and move in straight lines.
4. Gas molecules are perfectly elastic.
5. The velocity and kinetic energy of the molecules changes with the temperature, with increasing temperatures, and decreasing with decreasing temperatures.
6. The average energy possessed by the particles is the same regardless of the mass.
Gas Laws
1. Boyle’s Law – pressure and volume
V α where α means proportional
PV = K where K is constant
| [ P1V1 = P2V2 ] |
V1 = the volume at pressure 1 P1
V2 = the volume at pressure 2 P2
2. Charles’ Law – Volume and Temperature
“At constant pressure, the volume of a given mass is directly proportional to the absolute temperature.”
*If the absolute temperature is doubled, the volume of gas is doubled.
V α T or V/T = K
| V1/ T1 = V2/T2 |
3. Avogadro’s Law
“The volume of a gas is directly proportional directly related to the number of moles of a gas when the temperature and pressure are not changed.”
V α n
V = Kn
V/N = K
4. Gay Lussac’s Law – Temperature and Pressure
“The pressure of the gas is directly related to its Kelvin temperature.”
*An increase in temperature increases the pressure of a gas and a decrease in temperature decreases the pressure of the gas as long as the volume and number of moles of the gas remains constant.
P α T where V = constant
P = KT
| P/T = K |
5. The Combined Gas Law
“To determine the new volume when both the temperature and pressure are changed, we have to consider how the volume will change as temperature changes when pressure is held constant.”
PV/T= C
| P1V1/T1 = P2V2/T2 |
6. Ideal Gas Law
Boyle’s Law: V α (where n and T constant)
Charles’ Law: V α T (n and P constant)
Avogradro’s Law: V α n (P and T constant)
Combining the three laws, you will get:
V α nT/P
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