Gas Laws

Properties of Gases Gases take the shape and volume of their container Gases are the most compressible state of matter Gases have much lower densities than liquids and solids

Boyle’s Law Relates pressure and volume of gases At a constant temperature, as volume (V) increases, pressure (P) decreases. P1V1=P2V2

Boyle’s Law The gas in a balloon has a volume of 7.5 L at 100 kPa. In the atmosphere, the gas expands to a volume of 11 L. Assuming a constant temperature, what is the final pressure in the balloon? P1V1=P2V2

Boyle’s Law (100 kPa)(7.5 L) = (11 L) P2 P2 = 68 kPa P1= 100 kPa V1= 7.5 L V2= 11 L P2= ? (100 kPa)(7.5 L) = (11 L) P2 P2 = 68 kPa

Gay-Lussac’s Law Relates the pressure of a gas to temperature If volume remains constant, as the temperature (T) of a gas increases, pressure (P) increases. Temperature measured in Kelvins! (K) P1/T1 = P2/T2 This is why spray cans may explode if heated!

Gay-Lussac’s Law A sample of gas is collected at a temperature of 476 K and a pressure of 46 kPa. The next day, the temperature is 500 K. What is the new pressure?

Charles’s Law Relates temperature of a gas to its volume. At a constant pressure, as the temperature (T) of a gas increases, the volume (V) increases. V1/T1 = V2/T2

Charles’s Law A bottle contains 2.5 L of gas at a temperature of 360 K. If the temperature decreases to 345 K, what is the new volume?

𝑃1𝑉1 𝑇1 = 𝑃2𝑉2 𝑇2 Combined Gas Law Let’s put it all together! We can predict and describe the behavior of gases regarding changes in pressure, temperature, and volume. 𝑃1𝑉1 𝑇1 = 𝑃2𝑉2 𝑇2

Combined Gas Law If I initially have a gas at a pressure of 12 kPa, a volume of 23 liters, and a temperature of 200 K, and then I raise the pressure to 14 kPa and increase the temperature to 300 K, what is the new volume of the gas? 𝑃1𝑉1 𝑇1 = 𝑃2𝑉2 𝑇2 (12 kPa x 23 L)/200 K = (14 kPa x V2)/300 K 276/200 = (14 x V2)/300 82800 = 2800 x V2 V2 = 30 L

Test Review! Kinetic Theory of Matter Law of Conservation of Mass Law of Conservation of Energy Archimedes’ Principle Pascal’s Principle Viscosity Bernoulli’s Principle Boyle’s Law Charles’ Law Gay-Lussac’s Law

Gas Laws Practice Identify the gas law and fill in the missing information. As volume increases, pressure ________. As temperature _________, volume increases. As temperature increases, pressure __________. Identify the gas law, put numbers into the formula, and predict the answer based on your knowledge of the gas laws. A balloon is filled with 35.0 L of helium in the morning when the temperature is 20 K. By noon the temperature has risen to 45 K. What is the new volume of the balloon? If a sample of gas is at a pressure of 5 kPa and a temperature of 50 K, what will be the pressure of the gas if I decrease the temperature to 45 K? A weather balloon has a volume of 35 L at sea level (1.0 kPa). After the balloon is released it rises to where the air pressure is 0.75 kPa. What will the new volume of the weather balloon be?