Chapter 11

Chapter 11.2

THE GAS LAWS

Background Terminology

Gas Pressure is simply a collision of gas particles with an object. (Pressure is force per unit area)

A vacuum is created (or exists) when there are no (or very few) collisions of gas particles.

Barometers are instruments used to measure atmospheric pressure. Because the particles in air move in every direction, they exert pressure in all directions. This pressure is atmospheric pressure or air pressure.

Air pressure differs at different points on earth because gravity is greater at the surface of the earth. Therefore, air pressure is less at higher altitudes than it is at sea level.

A manometer is an instrument used to measure gas pressure in a closed container.

Units of Pressure

The SI unit of pressure is Pascal (Pa). Pressure can also be reported in the following units:

kilopascal (kPa), millimeters of mercury (mmHg), atmospheres (atm), and Torr

You should know these values and their conversions: 101.3 kPa = 1 atm = 760 Torr = 760 mmHg

Examples: 3.3 atm = ____2_5__0_8___ mmHg

564 kPa = ____5_._5_7___ atm

745 mmHg = ____7_4__5___ Torr

212 Torr = ___0_.2__7_9___ atm

Standard Temperature and Pressure (STP)

Scientists have agreed upon standard gas conditions of temperature and pressure of a gas. These values are:

Temp: 0?C

Pressure: 1 atm

Temperature conversion: All values of temperature in relation to gas laws; must be converted to Kelvin.

K = ?C + 273

Examples: 25?C = ____2_9_8_____K 313 K = ____4_0_____ ?C

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