Pressure and Temperature William Thomson Lord Kelvin CA

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 gas molecules hitting the walls of a container. So, the pressure exerted by a gas depends on how many times the gas hits the walls and how fast the gas hits the walls. q. Is equal to force/unit area

Standard Pressure q 1 standard atmosphere q 101. 3 k. Pa (kilopascals) q 760 torr or q 760 mm Hg (millimeters (atm) or or of mercury)

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

Temperature is the average kinetic energy of the particles of a substance. Standard Temperature equals: q 273 Kelvin (273 K) or 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”