West Valley High School General Chemistry Mr. Mata Chapter 11A Gases West Valley High School General Chemistry Mr. Mata

Standard 4d Students will know how to calculate gas laws using pressure, temperature, and volume.

Essential Question How are the Boyle’s gas law and Charles’ gas law used to relate pressure, volume, temperature?

The Atmosphere The atmosphere is the thin layer of gases that surround the earth. Air is composed of a mixture of gases: 78 % Nitrogen, N2 21 % Oxygen, O2 0.1 % Argon, Ar 365 ppm CO2 0 - 4 % water, H2O

Physical Properties of Gases No definite shape or volume: expand to fill container, take shape of container. Compressible increase pressure, decrease volume. Low Density air at room temperature and pressure: 0.00117 g/cm3. Exert uniform pressure on walls of container. Mix spontaneously and completely. Diffusion (high conc.  low conc.)

Pressure Pressure = force exerted per unit area. P = F/A Atmospheric Pressure = force exerted by earth’s atmosphere. Atmospheric Pressure is measured with a barometer. Aneroid Barometer

Measuring Pressure The first device for measuring atmospheric pressure was developed by Evangelista Torricelli. during the 17th century. The device was called a “barometer”. Baro = “weight” Meter = “measure” Mercury Barometer

Pressure Units mm of mercury (mm Hg) 1 mm Hg = 1 torr 760 mm Hg = 760 torr = 1 atm 1 atm is 1 atmosphere of pressure, (aka: standard pressure).

Robert Boyle (1627-1691) Born into an aristocratic Irish family. Became interested in medicine, astronomy, chemistry.  Avid hot air balloonist.

Boyle’s Law As pressure of gas increases, volume decreases: This is an inverse proportion: as one increases the other decreases P1V1 = P2V2

Boyle’s Law Graph Insert figure 12.9

Boyle’s Law Problem #1 A gas has a volume of 5 L at 2 atm pressure and the pressure is increased to 4 atm. Calculate the new volume. P1V1 = P2V2 -> V2 = P1V1 P2 V2 = (2 atm) (5 L) = 2.5 L 4 atm

Boyle’s Law Problem #2 A gas has a pressure of 6.5 atm and a volume of 20 L. Calculate the new pressure if the volume is increased to 80 L. P1V1 = P2V2 -> P2 = P1V1 V2 P2 = (6.5 atm) (20 L) = 1.6 atm 80 L

Jaques Charles (1746-1823) French Physicist. Conducted the first scientific balloon flight in 1783.

CHARLES’ LAW Volume is directly proportional to temperature Volume & temperature both increase or both decrease together V1 = V2 T1 T2

Charles’s Law Graph Insert figure 12.11

Charles’s Problem #1 A certain gas in a closed container has a volume of 0.567 mL at a temperature of 25oC. If there is no change in pressure, calculate the volume at - 25oC. First Convert Temperatures to Kelvin. K = oC + 273 T1 = 25 + 273 = 298 K T2 = -25 + 273 = 248 K

Charles’s Problem #1 (continued) T1 = 298 K T2 = 248 K V1 = 0.567 mL V2 = ? V1 = V2 -> V2 = V1 T2 T1 T2 T1 V2 = (0.567 mL) (248 K) = 0.47 mL 298 K

Charles’s Problem #2 A certain gas in a closed container has a volume of 25 mL at a temperature of 23oC. What volume will it occupy at 250 C? First Convert Temperatures to Kelvin. K = oC + 273 T1 = 23 + 273 = 296 K T2 = 250 + 273 = 523 K

Charles’s Problem #2 (continued) T1 = 296 K T2 = 523 K V1 = 25 mL V2 = ? V1 = V2 -> V2 = V1 T2 T1 T2 T1 V2 = (25 mL) (523 K) = 44.2 mL 296 K

Chapter 11A SUTW Prompt Describe how pressure, volume, and temperature are related in Boyle and Charles’ gas laws. Complete an 8 -10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. Due Date: Tomorrow (start of class).