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 Pressure is the force created by the collisions of molecules with the walls of a container
Unit Symbol Definition/Relationship Pascal Pa SI pressure unit 1 Pa = 1 newton/meter 2 Millimeter of mm Hg Pressure that supports a 1 mm mercury column of mercury in a barometer Atmosphere atm Average atmospheric pressure at sea level and 0 °C Torr torr 1 torr = 1 mm Hg
Pressure Is caused by the collisions of molecules with the walls of a container is equal to force/unit area Standard Pressure
1 standard atmosphere (atm) 101.3 kPa (kilopascals) 14.7 lbs/in 2 760 mm Hg (millimeters of mercury) 760 torr
Standard Temperature
Standard Temperature equals: 273 Kelvin (273 K) 0 °°°C The Kelvin Scale
Converting between Celsius and Kelvin Gas law problems involving temperature require that the temperature be in KELVINS! Kelvins = °°°C + 273
°C = Kelvins - 273 Converting between Fahrenheit and Celsius Gas law problems involving temperature require that the temperature be in KELVINS!
Either of these: 273 Kelvin (273 K) 0 °°°C
Standard And any one of these: Temperature and 1 atm Pressure 101.3 kPa “STP” 14.7 lbs/in 2 (psi) 760 mm Hg 760 torr