Objectives To learn about atmospheric pressure and how barometers work To learn the units of pressure To understand how the pressure and volume of a gas are related To do calculations involving Boyle’s Law To learn about absolute zero To understand how the volume and temperature of a gas are related To do calculations involving Charles’s Law To understand how the volume and number of moles of a gas are related To do calculations involving Avogadro’s Law

A. Pressure Measuring Pressure Barometer – device that measures atmospheric pressure Invented by Evangelista Torricelli in 1643

A. Pressure Atmospheric Pressure Changing weather conditions

A. Pressure Atmospheric Pressure Changing altitude

A. Pressure Units of Pressure 1 standard atmosphere = 1.000 atm = 760.0 mm Hg = 760.0 torr = 101,325 Pa

A. Pressure Units of Pressure A manometer measures the pressure of a gas in a container.

B. Pressure and Volume: Boyle’s Law Robert Boyle’s experiment

B. Pressure and Volume: Boyle’s Law

B. Pressure and Volume: Boyle’s Law Graphing Boyle’s results

B. Pressure and Volume: Boyle’s Law This graph has the shape of half of a hyperbola with an equation PV = k Volume and pressure are inversely proportional. If one increases the other decreases.

B. Pressure and Volume: Boyle’s Law Another way of stating Boyle’s Law is P1V1 = P2V2 (constant temperature and amount of gas)

C. Volume and Temperature: Charles’s Law Graphing data for several gases

C. Volume and Temperature: Charles’s Law It is easier to write an equation for the relationship if the lines intersect the origin of the graph. Use absolute zero for the temperature

C. Volume and Temperature: Charles’s Law These graphs are lines with an equation V = bT (where T is in kelvins) Volume and temperature are directly proportional. If one increases the other increases. Another way of stating Charles’s Law is V1 = V2 T1 T2 (constant pressure and amount of gas)

D. Volume and Moles: Avogadro’s Law

D. Volume and Moles: Avogadro’s Law Volume and moles are directly proportional. If one increases the other increases. V = an constant temperature and pressure Another way of stating Avogadro’s Law is V1 = V2 n1 n2 (constant temperature and pressure)

Objectives To understand the ideal gas law and use it in calculations To understand the relationship between the partial and total pressure of a gas mixture To do calculations involving Dalton’s law of partial pressures To understand the molar volume of an ideal gas To learn the definition of STP To do stoichiometry calculations using the ideal gas law

A. The Ideal Gas Law Boyle’s Law V = k (at constant T and n) P Charles’s Law V = bT (at constant P and n) Avogadro’s Law V = an (at constant T and P) We can combine these equations to get

A. The Ideal Gas Law Rearranging the equation gives the ideal gas law PV = nRT R = 0.08206 L atm mol K

B. Dalton’s Law of Partial Pressures What happens to the pressure of a gas as we mix different gases in the container?

B. Dalton’s Law of Partial Pressures For a mixtures of gases in a container, the total pressure exerted is the sum of the partial pressures of the gases present. Ptotal = P1 + P2 + P3

B. Dalton’s Law of Partial Pressures The pressure of the gas is affected by the number of particles. The pressure is independent of the nature of the particles.

B. Dalton’s Law of Partial Pressures Two crucial things we learn from this are: The volume of the individual particles is not very important. The forces among the particles must not be very important.

B. Dalton’s Law of Partial Pressures Collecting a gas over water Total pressure is the pressure of the gas + the vapor pressure of the water.

B. Dalton’s Law of Partial Pressures Collecting a gas over water How can we find the pressure of the gas collected alone?

C. Gas Stoichiometry Molar Volume Standard temperature and pressure (STP) 0oC and 1 atm For one mole of a gas at STP Molar volume of an ideal gas at STP 22.4 L

Objectives To understand the relationship between laws and models (theories) To understand the postulates of the kinetic molecular theory To understand temperature To learn how the kinetic molecular theory explains the gas laws To describe the properties of real gases

A. Laws and Models: A Review

A. Laws and Models: A Review A model can never be proved absolutely true. A model is an approximation and is destined to be modified.

B. The Kinetic Molecular Theory of Gases

C. The Implications of the Kinetic Molecular Theory Meaning of temperature – Kelvin temperature is directly proportional to the average kinetic energy of the gas particles Relationship between Pressure and Temperature – gas pressure increases as the temperature increases because the particles speed up Relationship between Volume and Temperature – volume of a gas increases with temperature because the particles speed up

D. Real Gases Gases do not behave ideally under conditions of high pressure and low temperature. Why?

D. Real Gases At high pressure the volume is decreased Molecule volumes become important Attractions become important