- Slides: 13
Pressure and Temperature William Thomson “Lord Kelvin”
CA Standards Students know the values and meanings of standard temperature and pressure (STP). Students know how to convert between the Celsius and Kelvin temperature scales. Students know there is no temperature lower than 0 Kelvin.
Measuring Pressure The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17 th century. The device was called a “barometer” Baro = weight Meter = measure
An Early Barometer The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.
Pressure q. Is caused by the collisions of molecules with the walls of a container qis equal to force/unit area
Standard Pressure q 1 standard atmosphere (atm) q 101. 3 k. Pa (kilopascals) q 14. 7 lbs/in 2 q 760 mm Hg (millimeters of mercury) q 760 torr
Pressure is the force created by the collisions of molecules with the walls of a container Unit Pascal Symbol Pa Definition/Relationship SI pressure unit 1 Pa = 1 newton/meter 2 Millimeter of mercury mm Hg Pressure that supports a 1 mm column of mercury in a barometer Atmosphere atm Torr torr Average atmospheric pressure at sea level and 0 C 1 torr = 1 mm Hg
The Kelvin Scale
Standard Temperature equals: q 273 Kelvin (273 K) q 0 C
Converting Celsius to Kelvin Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins = C + 273 °C = Kelvins - 273
Either of these: q 273 Kelvin (273 K) q 0 C And any one of these: q 1 atm q 101. 3 k. Pa q 14. 7 lbs/in 2 (psi) q 760 mm Hg q 760 torr Standard Temperature and Pressure “STP”
Standard Molar Volume One mole of a gas at STP has a volume of 22. 4 Liters
Liters 4 22. 4 L 10 23 22. x Mole Atomic Mass 6. 02 L Atoms or molecules Grams Mole Relationships