1. 13.4 NOTES Pressure

2. A.4 Pressure
Pressure- force over area that force is applied on
Less area with same force = greater pressure
Measured in pascals (Pa), which is the SI unit for pressure
These are very small, so kilopascals, or kPa, are used, which are times greater in size than Pa

3. International System of Units
International standard for the metric system
 Base units
Express fundamental physical quantities of the modernized metric system
Length, mass, time, temperature, quantitiy (mole), electric current, luminous intensity
 Derived units
Made of 2+ base units
Area, volume, pressure

5. A.6 Atmospheric Pressure
Pressure the atmosphere exerts on the Earth’s surface
Standard atmospheric pressure is equal to 1 atmosphere, which is abbreviated atm.
1 atm = kPa = 760 mmHg

6. Barometer- device for measuring atmospheric pressure

7. Datlon’s Law of partial pressure – total pressure of a mixture of gasses is equal to the sum of the individual pressures of all gasses  present
Ptotal = P1 + P2 + P3 + ……

8. Ptot = PO2 + PH2O 49.2 kPa = PO2 + 23.4 kPa PO2 = 25.8 kPa
Example: Oxygen gases is collected over water. If the total pressure of the system is equal to 49.2 kPa, and the pressure of the water vapor is kPa, what is the pressure of the oxygen gas?
Ptot = PO2 + PH2O
49.2 kPa = PO kPa
PO2 = 25.8 kPa

9. A.7 Atoms and Molecules in Motion
Review solids, liquids, and gases are held together by intermolecular forces
These forces are strongest in solids and weakest in gases

10. Kinetic molecular theory
Explains gas behavior
Gases consist of tiny particles in constant random motion
Molecules bang against each other and the walls of the container in elastic collisions (energy is conserved)
As temperature increases, KE and velocity increase (KE = 1/2mv2)
At the same temp, all gases have the same KE.