Gases Behaviors of Gases

Gases… Assume the SHAPE and VOLUME of the container it occupies. Are easily compressed Lots of free space between particles. Flow easily Particles can move past one another. (No attraction between particles)

3 Measurable Properties of Gases Volume The amount of space a substance takes up Temperature Measure of average energy of motion of gas particles Pressure Force of the outward push

Gas Laws 1. Boyle’s Law 2. Gay-Lussac’s Law Relationship between pressure and volume 2. Gay-Lussac’s Law Relationship between pressure and temperature

Boyle’s Law Pressure increases  Volume decreases Pressure decreases  volume increases Variables are inversely proportional (as one goes up the other goes down)

What does this graph show us? The inversely proportional relationship between pressure and volume.

Boyle’s Law Equation P1 V1 = P2 V2 Where, P = pressure (atm or equivalent) V = volume (L or ml)

Example Problem V1= 2L P1= 3 atm P2= .5 atm V2=?

Gay Lussac’s Law Temp. increases  pressure increases Temp. decreases  pressure decreases Variables are directly proportional (both increase or decrease together)

Gay Lussac’s Law Equation P1 P2 ___ = ___ T1 T2 Where, P = pressure (atm, kPa, Torr) T = temperature (K)

Example Problem P1= 2 atm T1= 200K P2= 4 atm T1= ?

Charles’ Law Temp. increases  volume increases Temp. decreases  volume decreases Variables are directly proportional (both increase or decrease together)

Charles’ Law Equation V1/T1= V2/T2 V= Volume (mL or L) T= Temperature (K)

Example Problem V1= 100 mL T1= 100K V2= 200 mL T2= ?

Crush Soda Can Experiment Place one tablespoon of water into an empty soda can. Heat the can on a hot plate to boil the water. What is happening to the air inside the can? Steam is created from the boiling water and expands inside of the can. The inside of the can was filled with air (gas) and water (liquid) and the liquid was heated until it changed states into a gas. The gas created (water vapor) pushed the original air outside of the can as the water vapor expanded to fill the space within the can.

Crush Soda Can Experiment Use tongs to lift the can off of the hot plate and turn it upside down. Quickly, plunge the can mouth side down into a beaker of cold water. What happened to the gas inside the can? When the can was placed into the cold water, the gas (water vapor), quickly condensed and turned back into water. The pressure that was being exerted on the walls of the can was removed when the gas turned back into a liquid. This experiment shows Gay Lussac’s Law in action. How? When the temperature was decreased, the pressure also decreased. The decrease in pressure caused the can to implode.

So what does that mean? The pressure exerted on the sides inside the soda can at about room temperature is 3.39 atm. That is equal to about 8 pounds of pressure on 1 square centimeter. That is a lot of pressure! Food for thought: It takes about 8 pounds of pressure to rip off a human ear.