Video 10-1 Kinetic Molecular Theory Properties of Gases Deviations from Ideal Gas Behavior

Chapter 10 PHYSICAL CHARACTERISTICS OF GASES

I. Kinetic-Molecular Theory based on the idea that particles of matter are always in motion ideal gas : gas that perfectly fits all assumptions of the kinetic molecular theory –DOES NOT EXIST

I. Kinetic-Molecular Theory Gases: consist of large numbers of tiny particles that are far apart relative to their size (very small). collisions between particles and particles and container walls are elastic collisions (no net loss of kinetic energy)

I. Kinetic-Molecular Theory Gases: particles are in continuous, rapid, random motion. no attractive or repulsive forces exist between particles

I. Kinetic-Molecular Theory Gases: average kinetic energy (KE) of gas particles is directly proportional to the TEMPERATURE of the gas KE = ½ mv 2

I. Kinetic-Molecular Theory Gases: THE PARTICLES OF ALL SUBSTANCES AT THE SAME TEMPERATURE HAVE THE SAME AVERAGE KINETIC ENERGY!

II. Properties of Gases Expansion: gases have no definite shape or volume will always fill any container in which they are enclosed Fluidity: will flow

II. Properties of Gases Low Density: about 1/1000 the density of its liquid state Compressibility: particles can be forced closer together condensation may occur (depends on T & P)

II. Properties of Gases Diffusion: spontaneous mixing of gases (move from higher concentrations to lower concentrations) depends on speed, diameter, and attractive forces of particles

II. Properties of Gases Effusion: gas particles move through a tiny opening depends on velocity of particles

III. Deviations of Real Gases from Ideal Behavior Many gases behave like ideal gases at high temperature low pressures Gases deviate greatly from ideal behavior at low temperatures high pressures

Video 10-2 Pressure and Units Gas Laws

IV. Gas Pressure Pressure: force per unit area on a surface P = F/a

IV. Gas Pressure Gases: the pressure of the gas will be directly related to the FORCE of the gas particles colliding with the sides of the container it will be INDIRECTLY proportional to the area of the container (sides)

IV. Gas Pressure To INCREASE force or DECREASE area (increase P) increase T decrease V add more gas particles

IV. Gas Pressure ** Gases move from areas of high pressure to low pressure continuously and spontaneously. There is no such thing as “suction”.

IV. Gas Pressure Ex. Drinking Straw

IV. Gas Pressure Ex. Vacuum Cleaner

IV. Gas Pressure Measuring Pressure: barometers: measure atmospheric pressure manometer: measures pressure in a closed container

IV. Gas Pressure Measuring Pressure: barometers:

IV. Gas Pressure Measuring Pressure: manometers:

IV. Gas Pressure Measuring Pressure: manometers:

IV. Gas Pressure Measuring Pressure: manometers:

IV. Gas Pressure Units of Pressure: mm Hg atmospheres (atm) torr kilopascals (kPa)

IV. Gas Pressure Units of Pressure: 1 atm = 760 mm Hg = 760 torr = kPa

IV. Gas Pressure Standard Temperature and Pressure (STP): 0 o C (273.15K) and 1 atmosphere CONVERT ALL TEMPERATURES TO KELVIN

V. Gas Laws relate T, V, P, and moles of gas mathematically

V. Gas Laws Boyle’s Law for a fixed quantity of gas at CONSTANT T, Pressure varies INVERSELY with Volume. P 1 V 1 = P 2 V 2 = k

V. Gas Laws Charles’ Law for a fixed quantity of gas at CONSTANT P, Volume varies DIRECTLY with Temperature ( IN KELVIN ). V 1 / T 1 = V 2 / T 2 = k V 1 T 2 = V 2 T 1 = k

V. Gas Laws Charles’ Law How do you keep P constant? Use an Expandable Container Ex. Balloon

V. Gas Laws Gay-Lussac’s Law for a fixed quantity of gas at CONSTANT V, Pressure varies DIRECTLY with Temperature ( IN KELVIN ). P 1 / T 1 = P 2 / T 2 = k P 1 T 2 = P 2 T 1 = k

V. Gas Laws Gay-Lussac’s Law How do you keep V constant? Use a sealed container with Rigid sides

V. Gas Laws Combined Gas Law for a fixed quantity of gas, Pressure and Temperature ( IN KELVIN ) vary directly and indirectly with Volume. P 1 V 1 / T 1 = P 2 V 2 / T 2 = k P 1 V 1 T 2 = P 2 V 2 T 1

V. Gas Laws Dalton’s Law of Partial Pressures partial pressure: pressure of each gas in a mixture of gases The total pressure of a mixture of gases is equal to the sum of the partial pressures of each gas

V. Gas Laws Dalton’s Law of Partial Pressures P T = P 1 + P 2 + P Each gas does NOT know that the other one exists Adding another gas to the mixture ONLY changes the TOTAL pressure, not the pressure of any other gases in the mixture

V. Gas Laws Collecting Gases by Water Displacement:

V. Gas Laws Collecting Gases by Water Displacement: if a gas is bubbled into an inverted container full of water, the gas will move to the top and push out water. However, the gas in the container is a MIXTURE of the displacing gas and WATER VAPOR. Thus,

V. Gas Laws Collecting Gases by Water Displacement: P T = P gas + P H2O P H2O varies with T (Table A-8 in back of book)