1. Are you feeling the PRESSURE?

2. Gravity exerts a pressure onto the ground Pressure is inversely proportional to surface area Pressure α 1 / surface area

3. Snowshoe Application Increase the surface area and thus decrease the pressure Result? You can walk on the snow without sinking!

5. What other areas of technology can you think of that compensates for changes in pressure? Space travel Flying on an airplane Scuba diving Climbing/living on mountains

6. Gas Pressure Like snowshoeing example, the pressure of a gas is also the force per unit area Force is created by moving molecules as they collide, mainly against the walls of the container

7. Units of Pressure International units of pressure SI unit is the pascal (Pa) –1 Pa = 1N/m 2 –1 kPa = 1000 Pa = 1000N/m 2 (unit used for atmospheric pressure) At Sea Level –Average atmospheric pressure is 101.325 kPa = 1 atm –(Standard ambient pressure  100 kPa)

8. Standard Laboratory Conditions STP : Standard Temperature and Pressure Temperature = 0 º C Pressure = 101.325 kPa (1atm) SATP : Standard Ambient Temperature and Pressure Temperature = 25 º C Pressure = 100 kPa

9. Table 1: SI and Non-SI Units of Gas Pressure Unit NameUnitConversion PascalPa1Pa = 1N/m 2 Atmosphereatm1atm = 101.325 kPa Millimeters of mercury (Hg) mm Hg760 mm Hg = 1 atm = 101.325 kPa Torrtorr1 torr = 1 mm Hg

10. Conversion Practice! Pressure kPaatmmm Hgtorr (a)1.25 (b)98.8 (c)235 (d)2.60 (e)635 0.01239.38 84.60.836635 2631980 31.30.309235 0.975 741

11. Learning Checkpoint Assigned Questions: p. 425 Practice UC # 1, 2, 3