1	California Chemistry Standard 4: Gases
2	The Kinetic-Molecular Theory
3	The Kinetic-Molecular Theory
4	Ideal Gases
5	Ideal Gases
6	Ideal Gases
7	California Chemistry Standard C4b:
8	Properties of Gases
9	Properties of Gases
10	Properties of Gases
11	Properties of Gases
12	California Chemistry Standard C4a:
13	Pressure
14	Pressure
15	Collisions cause Pressure The pressure of a gas is caused by the collision of molecules against the sides of the container.
16	Low Pressure vs. High Pressure inside a System The number of collisions of gas molecules against the wall of the container determines the pressure in the container. Notice the difference in the number of collisions. Figure (a) would have a lower pressure than Figure (b).
17	Pressure Applications
18	Measuring Pressure
19	Measuring Pressure
20	Pressure Units
21	Know how to do pressure conversions!
22	California Chemistry Standard C4d:
23	Standard Temperature and Pressure
24	California Chemistry Standard C4c:
25	The Gas Laws – Boyle’s Law
26	The Gas Laws – Boyle’s Law
27	Know how to calculate Boyle’s Law problems!
28	California Chemistry Standard C4f:
29	The Kelvin Temperature Scale
30	Convert:
31	Charles’s Law
32	Know how to do Charles’s Law Problems:
33	Gay-Lussac’s Law
34	Gay-Lussac’s Law Problems:
35	The Combined Gas Law
36	Combined Gas Law Problem:
37	Volume-Mass Relationships of gases
38	Calculating volume, moles, & mass
39	The Ideal Gas Law
40	Ideal Gas Law Problem:
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43	Pressure Practice Convert the following: 145 mm Hg into bars 450 psi into kPa 900 mm Hg into torrs 4580 Pa into kPa 5. 25 psi into atm 6. 150 atm into Pa 109 kPa into atm 76.9 mm Hg into bars 98.6 torr into kPa 3 atm into kPa
44	Answers 0.19 bars 3102.4 kPa 900 torr 4.58 kPa 1.7 at5m 15199108.32 Pa 0.10 bars 13.14 kPa 303.98 kPa 1.08 atm
45	Robert Boyle Robert Boyle, an Irish chemist (1627-1691), performed the first quantitative experiments on gases used a j-shaped tube to study the relationship between the pressure of the trapped gas and its volume.
46	Boyle’s Law Boyle’s Law states that at constant temperature the volume of a fixed amount of gas is inversely proportional to its pressure. Boyle’s Law: P₁V₁ = P₂V₂
47	Boyle Proves Changes in Pressure cause Changes in Volume As the pressure in a closed system (like a piston) decreases, the volume of the gas inside the system increases. The pressure in the system decreases exponentially. Proving an indirect relationship.
48	Example: Sulfur dioxide (SO₂), a gas, that plays a central role in the formation of acid rain, is found in the exhaust of automobiles and power plants. 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 a constant temperature, what will be the new volume of the gas?
49	Solution: P₁V₁= P₂V₂ P₁= 5.6 x 10³ Pa P₂= 1.5 x 10⁴ Pa V₁= 1.53 L V₂= ? Rearrange the formula to isolate V₂. P₁V_{1 =}(5.6X 10³ Pa)(1.53 L) = O.57 L P₂(1.5 X 10⁴ Pa)
50	Does Boyle’s law really work? Since Boyle’s experiments (only three centuries of technological advances!) we have found that his law only holds precisely at very low pressures. We describe a gas that strictly follows Boyle’s law an “ideal gas”.
51	Jacques Charles In the century following Boyle, a French physicist, Jacques Charles (1746-1823), was the first person to fill a balloon with hydrogen gas and who made the first solo balloon flight.
52	Charles’s Law Charles’s Law states that at constant pressure the volume of a fixed amount of gas is directly proportional to its absolute temperature.
53	Volume vs. Temperature: Charles’ Law Notice the linear relationship. This relationship between temperature and volume describes a “direct relationship”. This means when temperature increases, so does the volume.
54	The importance of 0 Kelvin At temperatures below 0 K, the extrapolated volume of gases would be negative. The fact that a gas can’t have a negative volume tells us 0 K has a special significance. Absolute temperature is measured in Kelvins. At 0 K, all motion of any atom or bond ceases, therefore producing no energy. Temperatures of approximately 0.000001K have been produced in laboratories, but 0 K has never been reached.
55	Example: A sample of a gas at 15°C and 1 atm has a volume of 2.58 L. What volume will the gas occupy at 38°C and 1 atm? (NOTE: The pressure did not change. So you do not need to worry about it!)
56	Solution: V₁ = V₂Don’t forget to convert °C to K T₁ T₂ V₁= 2.58L V₂=? T₁ = 15°C=288K T₂ = 38°C=311K Rearrange to solve for V₂. V₁T₂₌(2.58L)(311K) = 2.79 L T₁ (288K)
57	The Combined Gas Law The combined gas law was derived from Boyle’s and Charles’s work. A direct relationship was observed. As temperature increased, volume increased. As volume increased pressure increased. This resulted in a combined formula to calculate changes observed in a gas due to changes in either temperature, pressure or volume.
58	Combined Gas Law Equation By combining the equation for Boyle’s Law and Charles’s Law. We derive the Combined Gas Law Equation where:
59	Example: A sample of a gas at 15°C and 2.0 atm has a volume of 2 mL. What volume will the gas occupy at 38°C and 1 atm?
60	Solution P₁V₁ = P₂ V₂ Don’t forget to convert Temperatures! T₁ T₂ P₁= 2 atm P₂= 1 atm V₁=2 mL V₂=? T₁=15°C=288K T₂=38°C=311K Rearrange to solve for V₂! V₂= P₁V₁T₂ = (2 atm)(2 mL)(311K) = 4.32 mL T₁P₂(288K)(1 atm)
61	Summary: Boyle’s Law – Inverse relationship when PV¯ and if P¯V Charles’s Law -- Direct relationship When VT and if V¯T¯
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65	Gas Laws Chapters 10 & 11 Pressure—chemical, physical and conversions Boyle’s Law Charles’s Law Combined Gas Law
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67	Chemical Properties Produce Gases Chemists harness chemical properties to produce a desired gas through chemical reactions. Such as the reaction of zinc and hydrochloric acid.
68	Physical Properties of Gases Gases are: compressible and they assume the shape and volume of any container. infinitely soluble in one another.