Chapter 13
States of Matter - Solid
- Liquid
- Gas
- '
- Barometer- a common instrument to measure air pressure
- Pressure conversion
- 1 atm= 760 mm Hg
- 1 atm= 760 torr
- 1 atm = 14.7 psi
- 1 atm= 101,325 Pa
- Atmospheric pressure results from the mass of the air being pulled toward the center of the earth by gravity.
- What is the pressure in atm if the pressure was measured 28 psi?
- What is the pressure in atm if the pressure was measured 28 psi?
Boyle's Law- The Irish scientist Robert Boyle( 1627-1691) was one of the first scientist to carefully study gases.
- Using a J-shape tube closed at one end. He saw that there was a relationship between pressure and volume
- Pressure and volume are inversely proportional. If one doubles, the other decreases by one-half.
PV = PV
Problem
- What happens to the pressure of a tire when you add air in to the tire?
When the number of the air molecule in the tire is increased, the pressure is increased.
- A 1.5 L sample of Freon-12 had a pressure of 56 torr. If the pressure is changed to 150 torr, what is the new volume if the temperature is constant?
Charles' Law - - The French physicist Jacques Charles( 1746- 1823) showed that the volume of a given amount of gas at constant pressure will increase with the temperature of the gas.
- Temperature is proportional to volume.
- As temperature increase volume increase.
- As temperature decrease volume decreases.
Combined Gas Law - - Assumption:Number of moles constant
- - This law combines both Boyle’s law and Charles’s Law
Avogadro's Law
- - the number of moles is proportional to volume.
- - As number of moles increase volume increase.
- - As number of moles decrease volume decreases.
- Ideal Gas Law
- PV=nRT
- R= universal gas constant
- 0.08206 L*atm/(mol *K)
- - ideal gas law was derived from the observation of boyle’s, Charles’s and Avrogadro’s.
- - Assumption: the gas must be ideal.
- Kinetic molecular theory of gases is a relatively simple model that attempts to explain the behavior of an ideal gas.
- 1. Gases consist of tiny particles (atoms or molecules)
- 2. These particles are so small, compared with the distances between them, that the volume(size) of the individual particles can be assumed to be zero.
- 3. the particles are in constant random motion, colliding with the walls of the container. These collision with the walls cause the pressure exerted by the gas.
- 4. The particles are assumed not to attract or to repel each other
- 5. The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the gas
- Dalton's Law
- Many important gases contain a mixture of components.
- John Dalton was one of the first scientist to studied mixtures of gases
- His observation became Dalton’s law of partial pressures.
- For a mixture of gases in a container, the total pressure exerted is the sum of the partial pressures of the gases present.
Links!