G AS L AWS

B OYLE ’ S L AW B ACKGROUND ( FOR N OTES ) Robert Boyle was among the first to note the relationship between pressure and volume of a gas. During his experiments Temperature and amount of gas weren’t allowed to change (they were held constant) A bicycle pump is a good example of Boyle’s law. As the volume of the air trapped in the pump is reduced, its pressure goes up, and air is forced into the tire. P and V are inversely proportional. This means that if pressure goes up, the volume goes down and vice versa! P and 1/V are proportional 1

Relationship As Pressure increase, Volume decreases P ↑ V↓ The Law P 1 V 1 = P 2 V 2 Constants n=number of particles & T=temperature 2 B OYLE ’ S L AW B ACKGROUND ( FOR N OTES )

3 Temperature and # of particles remain constant How does Pressure and Volume of gases relate graphically? Volume Pressure

As the pressure increases Volume decreases Volume decreases

Boyle’s Mathematical Example: P 1 V 1 = P 2 V 2 What if we had a change in conditions? 1

1)determine which variables you have: 2)determine which law is being represented: 2 Boyle’s Mathematical Example:

3) Rearrange the equation for the variable you don’t know 4) Plug in the variables and chug it on a calculator: V 2 = 1.5L Boyle’s Mathematical Example: 3

B OYLE ’ S L AW D EMO I NSTRUCTIONS D EMO 1: C ARTESIAN D IVER Find the 2 Liter soda bottle with soy sauce packet inside it. Squeeze the bottle (hard) until the packet sinks to the bottom of the bottle. Release the pressure and let the packet float back to the top. See if you can suspend the soy packet in the middle of the bottle. Answer the questions in the demo section of your student handout.

B OYLES L AW C ARTESIAN D IVER E XPLANATION The Cartesian Diver works because the pressure you impose on the closed system compresses the air in the bottle (water does not compress), including the air in the diver. The compression of the air makes it more dense because you are forcing the amount of air into a smaller space. In order for your diver to sink, the density of the diver needs to become greater than the density of water. The more dense the air becomes, the further the diver will sink.

B OYLE ’ S L AW D EMO I NSTRUCTIONS D EMO 2: TEXTBOOK VS. SYRINGE Find the wooden blocks (one with shallow hole drilled in it). You will also need a syringe, small clamp, and ring stand. Look at the example apparatus to get your own equipment set up properly. DO NOT REMOVE THE PLUNGER FROM THE BACK OF THE SYRINGE!! Read the volume on the syringe and record it in this demo section of your handout. Add one book to the top block and then record the volume. Repeat this until 5 books have been added. Recording the data as you go. Repeat for a second trial and then calculate the average value and complete the student handout.

C HARLES ’ L AW B ACKGROUND ( FOR N OTES ) Jacques Charles determined the relationship between temperature and volume of a gas. He measured the volume of air at different temperatures, and observed a pattern of behavior which led to his mathematical law. During his experiments pressure of the system and amount of gas were held constant. V and T are directly proportional. This means that if temperature goes up, the volume goes up and vice versa! 1 A hot air balloon is a good example of this. As the air is heated in the balloon (by the flame above the basket) it expands. This increase in volume causes the balloon to expand and become less dense. Since the air in the balloon is now less dense than the air outside the balloon, it floats.

Relationship As Volume increase, Temperature increases V ↑T ↑ The Law V 1 V 2 = T 1 T 2 Constants n=number of particles & P=pressure 2 C HARLES ’ L AW B ACKGROUND ( FOR N OTES )

3 Volume Temperature Pressure, # of particles remain constant Pressure, # of particles remain constant

Volume of balloon at room temperature Volume of balloon at 5°C

Charles's Mathematical Example: What if we had a change in conditions? 1 V 1 V 2 T 1 T 2 = Eg: A gas has a volume of 3.0 L at 127°C. What is its volume at 227 °C?

2 Charles’s Mathematical Example: 1)determine which variables you have: 2)determine which law is being represented:

Charles’s Mathematical Example: 3 3) Plug in the variables: (500K)(3.0L) = V 2 (400K) V 2 = 3.8L 3.0L V 2 400K 500K = = 4) Cross multiply and chug

C HARLES ’ S L AW D EMO I NSTRUCTIONS D EMO 3: P IPETTE IN W ATER B ATH Find the pipette with a bead of water stuck inside the sealed tip. Read and record (on the student handout) the initial volume marked by the water. Place the pipette in the hot water bath and let it sit for 1 minute. Remove the pipette using the tweezers and record the new volume. Repeat this procedure in the ice water bath.

C HARLES ’ S L AW D EMO I NSTRUCTIONS D EMO 4: E GG IN A B OTTLE PUT ON YOUR GOGGLES!! Fill the Erlenmeyer flask with about 15 mL of water and then place it on the hot plate. Turn the hot plate on and watch for the water to begin to boil. While you wait for it to boil, get a hard boiled egg and make sure that it is well coated in oil. As soon as the water begins to boil, turn off the hot plate and CAREFULLY remove the flask using the gloves provided. Place the egg over the opening of the flask. While balancing the egg on top of the flask, set it in the ice water. Use the knife to cut up the egg and rinse out the flask.

C HARLES ’ S L AW E GG E XPLANATION The boiling water in the flask causes the temperature of the gas above it to expand. When the egg is placed over the flask, the gas inside can no longer escape and no additional air is allowed into the flask. Cooling the flask in the ice water causes the volume of the gas to decrease. This creates a partial vacuum inside the flask. This vacuum “pulls” the egg inside the flask.

G AY -L USSAC ’ S L AW B ACKGROUND ( FOR N OTES ) 1 Old man Lussac determined the relationship between temperature and pressure of a gas. He measured the temperature of air at different pressures, and observed a pattern of behavior which led to his mathematical law. During his experiments volume of the system and amount of gas were held constant. P and T are directly proportional. This means that if pressure goes up, the volume goes up and vice versa! Pressure Gauge Pressure Gauge Tire pressure during the winter is a good example of this. As winter approaches it is always a good idea to check your tire pressure. As the air in the tire get colder the pressure decreases. This is also why after a long road trip,when your tires are hot, the pressure goes up.

Relationship As Pressure increase, Temperature increases P ↑T ↑ The Law P 1 P 2 = T 1 T 2 Constants n=number of particles & V = volume 2 G AY -L USSAC ’ S L AW B ACKGROUND ( FOR N OTES )

3 Pressure Temperature Volume, # of particles remain constant Volume, # of particles remain constant

Pressure Gauge Pressure Gauge Car before a trip Let’s get on the road Dude! Pressure Gauge Pressure Gauge Car after a trip WHWE!!

Gay-Lussac’s Mathematical Example: Gay-Lussac’s Mathematical Example: What if we had a change in conditions? 1 P 1 P 2 T 1 T 2 = Eg: A gas has a pressure of 3.0 atm at 127º C. What is its pressure at 227º C?

2 1)determine which variables you have: 2)determine which law is being represented: Gay-Lussac’s Mathematical

3 3) Plug in the variables: 4) Cross multiply and chug 3.0atm P 2 400K 500K = = P 2 = 3.8atm Gay-Lussac’s Mathematical

G AY -L USSAC ’ S L AW D EMO I NSTRUCTIONS D EMO 5: C RUSH THE C AN PUT ON YOUR GOGGLES!! Place about 10 mL of water in a can and then place it on the hot plate. Turn the hot plate to medium. Wait until you see steam coming from the can or you can hear it boiling. Do not let the all of the water in the can evaporate. Once the can is hot, turn off the hot plate. Use the tongs to grab the can and flip it upside down into the cold water.

G AY -L USSAC ’ S L AW D EMO I NSTRUCTIONS D EMO 6: B ALLOONS AND F LASKS Look at the two flasks. One with a balloon inside an another with the balloon outside. First look at the flask with the balloon inside. Pull the balloon out of the flask and then let go. Now take the flask and put it on the hot plate. Second look at the flask with the balloon outside. Push the balloon inside the flask and then let go. Now take this flask and put it in the ice water.

G AY -L USSAC ’ S L AW C OLLAPSING C AN E XPLANATION When the warm air in the can is cooled by putting it in cold water, the gas particles slow down and do not collide as frequently with the inside walls of the can. This decreases the pressure on the inside of the can. The atmospheric pressure is now greater than the pressure inside the can and air cannot move into the can because the opening is submerged. The high pressure outside thus pushes in on the can walls and collapses the can.