Describe the differences between various states of matter

Ch. 10 Physical Characteristics of Gases 10.1 Kinetic Molecular Theory

The Kinetic Molecular Theory based on the idea that particles are constantly moving can be applied to solid, liquid, or gas provides a model of ideal gas behavior so only an approximation

Gases consist of tiny particles that are very far apart most volume is empty space-low density allows gases to be easily compressed All collisions between particles and container walls are elastic there is no net loss of energy when particles collide total kinetic energy stays constant even though it can be transferred between particles

Particles are in continuous, rapid, random motion since they are moving, they have KE KE overcomes their attractive forces No forces of attraction or repulsion like billiard balls bounce apart immediately

Average kinetic energy depends on temperature KE increases as temperature increases KE = ½mv2 where m = mass of particle where v = velocity of particle so at the same T, lighter particles have higher speeds than heavier ones velocity and temperature are directly proportional

Real vs. Ideal Gases ideal gas is defined by the KMT most gases behave close to the ideal when high temperature – so they have enough KE to overcome attractive forces low pressure – so they are very spread out Gases with little attraction are more ideal (monatomic gases)

Ch. 10 Physical Characteristics of Gases 10.2 Pressure

Pressure P : force per unit area on a surface Newton – SI unit for force (1 kg*m/s2) why would shoes with smaller diameter heel not be allowed on gym floor? As surface area decreases, pressure increases Pressure exerted by a gas depends on volume temperature number of molecules

Measuring Pressure barometer instrument used to measure atmospheric pressure first one created by Torricelli in early 1600s glass tube filled with mercury is inverted in a dish mercury flows out of the tube until pressure of the Hg inside the tube is equal to the atmospheric pressure on the Hg in the dish

Measuring Pressure manometer: measures pressure of gas in a container gas has less pressure than atmosphere if the Hg is closer to chamber gas has more pressure than atmosphere if the Hg is further from chamber

Units of Pressure millimeters of mercury (mmHg) torr (torr) from mercury barometer torr (torr) from Toricelli inventing barometer atmosphere of pressure (atm) Pascal (Pa) = 1N/m2 (SI unit) named after French scientist 1 atm = 760 mmHg = 760 torr = 101.325 kPa

Practice Conversions Convert 0.927 atm to mmHg torr kPa

Practice Conversions Convert 148.6 kPa to atm mmHg torr

The pressure of a gas is measured as 49 torr The pressure of a gas is measured as 49 torr. Convert this pressure to atmospheres, kiloPascals, and mmHg.

Pressure Conversions The pressure of a gas is measured as 49 torr. Represent this pressure in atmospheres, Pascals, and mmHg.

Ch. 10: Physical Properties of Gases 10.3 Gas Laws: Relationships between volume, temperature, pressure, and amount of gas.

Boyle’s Law: P and V as one increases, the other decreases inversely proportional pressure is caused by moving molecules hitting container walls If V is decreased and the # of molecules stays constant, there will be more molecules hitting the walls per unit

Boyle’s Law: P and V Boyle’s Law: the V of fixed mass of gas varies inversely with P at a constant T. PV = k k is a constant for a certain sample of gas that depends on the mass of gas and T What kind of graph is V vs. P? If we have a set of new conditions for the same sample of gas, they will have same k so:

Boyle’s Law

Boyle’s Law: P and V Discovered by Irish chemist, Robert Boyle Used a J-shaped tube to experiment with varying pressures in multistory home and effects on volume of enclosed gas

Example: Boyle’s Law Consider a 1.53-L sample of gaseous SO2 at a pressure of 5.6 x 103 Pa. If the pressure is changed to 1.5 x 104 Pa at constant temperature, what will be the new volume of the gas?

Charles’ Law: V and T if P is constant, gases expand when heated when T increases, gas molecules move faster and collide with the walls more often and with greater force to keep the P constant, the V must increase

Charles’ Law: V and T Problem: if we use Celsius, we could end up with negative values from calculations in gas laws for volumes we need a T system with no negative values: Kelvin Temperature Scale starts at -273.15 ° C = absolute zero = 0 K lowest possible temperature balloon going into liquid nitrogen

Charles’ Law: V and T Charles’ Law: the V of fixed mass of gas at constant P varies directly with Kelvin T. V = kT k is a constant for a certain sample of gas that depends on the mass of gas and P What kind of graph is V vs. T? If we have a set of new conditions for the same sample of gas, they will have same k so:

Charles’ Law discovered by French physicist, Jacques Charles in 1787 first person to fill balloon with hydrogen gas and make solo balloon flight

Example: Charles’ Law & Temp. A sample of gas at 15°C and 1 atm has a volume of 2.58 L. What volume will this gas occupy at 38°C and 1 atm?

A weather balloon is released at a pressure of 744 mmHg with a volume of 12 L. What will the volume be at a pressure of 704 torr?

Ch. 10: Physical Properties of Gases 10.3 Gas Laws: Relationships between volume, temperature, pressure, and amount of gas.

Gay-Lussac’s Law: P and T Remember: P is the result of collisions of molecules with container walls Force and frequency of collisions depends on average KE KE depends on T If the T increases, collisions occur more often and with higher force so the P must increase

Gay-Lussac’s Law: P and T Gay-Lussac’s Law: the P of fixed mass of gas at constant V varies directly with Kelvin T. P = kT k is a constant for a certain sample of gas that depends on the mass of gas and V What kind of graph is P vs. T? If we have a set of new conditions for the same sample of gas, they will have same k so:

Gay-Lussac’s Law discovered in 1802 by Joseph Gay-Lussac

Example: Gay-Lussac’s Law The gas in an aerosol can is at a pressure of 3.00 atm at 25°C. Directions on the can warn the user not to keep the can in a place where temperature exceeds 52°C. What would the gas pressure be in the can at 52°C?

How to Remember which law goes with each pair of variables: Boyle’s P V T Gay-Lussac’s Charles’

Ch. 10 Physical Characteristics of Gases 10.3b Combined Gas Law

Combined Gas Law a gas often changes in T, P, and V all at once the other gas laws can be combined into one law Combined Gas Law- relationship between P, V, and T of a fixed amount of gas

Example: Combined Gas Law A Helium-filled balloon has volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.°C?

Example A balloon containing 5.5 L of air at 25C and 755 torr is put at the bottom of the ocean. The new temperature is 4 C and the new volume is 2300 mL. What is the new pressure?

Ch. 10 Physical Characteristics of Gases 10.4 Dalton’s Law of Partial Pressure

Dalton’s Law of Partial Pressure John Dalton responsible for atomic theory also studied gas mixtures the P of gas mixture is the sum of the individual pressures of each gas alone the P that each gas exerts in the mixture is independent of the P that are exerted by other gases

Dalton’s Law of Partial Pressure the total P of a mixture of gases is equal to the sum of partial P of component gases, no matter how many different gases PT = P1 + P2 + P3 + … Partial Pressure- P of each gas in mixture

Why? the particles of each gas in a mixture have an equal chance to hit the walls so each gas exerts P independent of that exerted by other gases total P is result of the total # of collisions per unit of wall area

Water Displacement gas produced is less dense than water so it replaces the water in the bottle gas collected is not pure because it contains vapor from the water PT = Pgas + Pwater set for a certain T equal to atmospheric pressure

Example Oxygen gas from decomposition of KClO3 was collected by water displacement. The barometric pressure and the temperature during the experiment were 731.0 torr and 20.0°C respectively. If the partial pressure of water vapor is 17.5 torr at 20.0°C. What was the partial pressure of oxygen collected? PT = PO2 + PH2O 731.0 torr = PO2 + 17.5 PO2 = 713.5 torr

Example Find the partial pressure by 2 gases (A and B) mixed if the overall pressure is 790 mmHg. The percent by volume is A: 20% and B: 80%. PT = PA + PB = 790 mmHg A: 0.20 x 790 = 158 mmHg B: 0.80 x 790 = 632 mmHg