Questions Are gas particles attracting or repelling each other? Are gas particles traveling randomly or in an ordered manner? Are there small or great distances between gas particles? How are average kinetic energy and temperature related?

Can Crush

The Property of Gases – Kinetic Molecular Theory

Kinetic Molecular Theory of Gases The word kinetic refers to motion. Kinetic energy is the energy an object has because of its motion. Kinetic Molecular Theory (KMT) makes assumptions about: ▫ Size ▫ Motion ▫ Energy of gas particles

Kinetic Molecular Theory Part 1 1.According to the KMT all matter consists of tiny particles that are in constant, random motion They move in a straight line until they collide with other particles or with the walls of the container.

Kinetic Molecular Theory Part 2 2. Gas particles are much smaller than the distances between them. Most of a gas consists of empty space.  Gas consists of small particles that are separated from one another by empty space  Most of the volume of a gas consists of empty space  Because they are so far apart, there are no attractive or repulsive forces between the gas molecules  The motion of one particle is independent of the motion of other particles

Kinetic Molecular Theory Part 3 3.No kinetic energy is lost when gas particles collide with each other or with the walls of the container (elastic collision)  Undergoes elastic collision – no kinetic energy is lost when particles collide.  The total amount of kinetic energy remains constant.

Kinetic Molecular Theory Part 4 4.All gases have the same average kinetic energy at a given temperature  Temperature is a measure of average kinetic energy of particle in a sample of matter.  Kinetic energy and temperature are directly related  The higher the temperature, the greater the kinetic energy  The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance _____ o C = _______Kelvin  There is no temperature lower than 0 Kelvin (Absolute Zero).  Kinetic Energy = ½ mv 2 ; where m = mass and v = velocity

Absolute Zero The greater the atomic and molecular motion, the greater the temperature is of a substance. If all atomic and molecular motion would stop, the temperature would be at absolute zero (0 Kelvin or -273 o C)

Question Time What is kinetic energy? What are the four postulates of the Kinetic Molecular Theory (KMT)? How are kinetic energy and temperature related? How do you convert from o C to Kelvin? What is the lowest possible temperature? What does it mean to be at absolute zero?

Diffusion and Effusion Diffusion – describes the movement of one material through another ▫ Particles diffuse from an area of high concentration to low concentration Effusion – gas escapes through a tiny opening. The heavier the molecule, the slower it will effuse or diffuse

Diffusion and Effusion Diffusion Effusion

What does that look like? DiffusionEffusion

Question Time What is diffusion? What is effusion?

Pressure Pressure is the force per unit area Gas pressure is the force exerted by a gas per unit surface area of an object.  Gas pressure is the result of billions of collisions of billions of gas molecules with an object

Pressure (continued) Atmospheric pressure (air pressure) results from the collisions of air molecules with objects.  The air pressure at higher altitudes is slightly lower than at sea level because the density of the Earth’s atmosphere decreases as elevation increases. Vacuum - Empty space with no particles and no pressure

This plastic bottle was sealed at approximately 14,000 feet (4,300 m) altitude, and was crushed by the increase in atmospheric pressure —at 9,000 feet (2,700 m) and 1,000 feet (300 m)— as it was brought down towards sea level.

Measuring Pressure Barometer – an instrument used to measure atmospheric pressure

Measuring Pressure Manometer – an instrument used to measure gas pressure in a closed container

Question Time What is pressure? What is gas pressure? What is atmospheric pressure? Why is pressure less as you climb a mountain? What is a vacuum? What instrument is used to measure atmospheric pressure? What is a manometer used for?

Units of Pressure and STP Average atmospheric pressure is 1 atm 1atm = 760 torr = 760 mmHg = kPa STP (Standard Temperature and Pressure) ▫ 1 atm and 0 o C or 1 atm and 273 K

Dalton’s Partial Pressure Dalton’s law of partial pressures states that the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture. P total = P 1 + P 2 +P P n

Question Time What is STP? What is equal to 1 atm? What does Dalton’s Law of Partial Pressure state? What is the formula?

Conversion Factors for Pressure 1 atm = 760 torr = 760 mmHg = kPa Convert 2.5 atm into torr, mmHg and kPa

1 atm = 760 torr = 760 mmHg = kPa Convert 215 kPa into atm, mmHg and torr

Dalton’s Law of Partial Pressure P Total = P 1 + P 2 + P 3 + …….. P n A mixture of O 2, CO 2 and N 2 has a total pressure of 0.97 atm. What is the partial pressure of O 2, if the partial pressure of CO 2 is 0.70 atm and the partial pressure of N 2 is 0.12 atm?

P Total = P 1 + P 2 + P 3 + …….. P n There is a mixture of CO 2, O 2 and CO in a container. What is the total pressure if the pressure in atm of O 2 is atm, CO 2 is 235 kPa and CO is 455 torr?