Post on 14-Dec-2015
GAS LAWS2014
http://www.nclark.net/GasLaws
GAS LAWS Charles’ Law (slide 4)
Boyle’s Law (slide 31)
Guy Lusaac’s Law (slide 77)
LeChatelier’s Principle (slide 105)
Ideal Gas Law (slide )
PRESSURE CONVERSIONS
STP means standard temperature and pressure
1 standard atmosphere = 1.000 atm = 760.0 mm Hg = 760.0 torr =101,325 Pa = 14.69 psi
***all of these equal each other!***
Temperature: 0 ˚C or 273 K
CHARLES LAW
CHARLES’S LAW
Volume of a gas increases with temperature. (Gases expand with heat).↑ T = ↑ V ↓ T = ↓ V
*Constant amount of gas at a constant pressure
Jacques Charles proposes Charles's Law. 1787
The formula for the law is:
V1/T1 = V2/T2
Where: V1 is the initial volume T1 is the initial temperature
V2 is the final volume T2 is the final temperature
***temperature MUST be in Kelvin (absolute zero) NOT oC or oF!***
Set up of Demonstration. Blow up two similar balloons so they have the
same circumference. Place balloon in ice water on one side to 500 ml. Place equal balloon in hot water on one side to
500ml. Put small block and weight, or use finger to
depress balloon under water. Sketch/Record difference in volume between the
balloons. How does temperature effect the volume of a
gas? Think about the gas molecules in each balloon.
DEMONSTRATION
- Balloon in hot and coldwater
--What happens??
- Glass bottle with balloon in hot water
Demonstration: Fit a balloon to the top of a glass bottle and place in pan with water. Place on top of heat source and observe.
Demonstration: Fit a balloon to the top of a glass bottle and place in pan with water. Place on top of heat source and observe.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
This law means that when the temperature goes up, the volume of the gas goes up.
When the temperature goes
down, the volume of the gas decreases.
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/gaslaw/charles_law.html
Key Concept ~ When the temperature of a gas is increased, its volume will increase. Students will be micro waving small amounts of popcorn
in a clear bowl. Popcorn pops when the moisture inside boils and expands, bursting the kernel open. Instructions: Place about two tablespoons of popcorn in the clear plastic bowl. Put the top on the bowl and place in the microwave. Close the microwave door and turn the microwave on high. Watch as closely as you can as the popcorn kernels begin to pop, but of course DO NOT OPEN THE DOOR! As soon as the vigorous popping stops, turn off the microwave. Questions: Describe what you see (yeah, I know, but try). What do you think makes the popcorn pop? Put your popcorn in a paper bag and then squirt in some butter if you wish.
Station 2 Microwave Popcorn
Station 9 Super Duster & Office Buster Key Concept ~ When the volume of a gas increases, its
temperature will decrease.
Obtain a can of compressed "air," such as those used to clean electronic equipment. As you depress the nozzle, the gas inside (typically an HFC) responds to the reduced pressure by "boiling" or rapidly turning into a gas. This is an endothermic process so the can gets extremely cold (can even cause frost-bite if you hold it too long.) I like the students to relate this to the phenomenon of water boiling at lower temperatures at high altitudes due to the lower pressure. (Lots of campers know this very well.) The classic Drinking Bird uses a similar concept and makes a good companion to this station. Simply challenge the students to explain the bird's motion. Instructions: Wrap your hand around one of the duster cans. Make sure your palm is in complete contact with the can. Now, depress the nozzle. Questions: What do you feel? Why? Shake the can. What do you notice? Try to explain what happens when you depress the nozzle - See more at: http://www.arborsci.com/cool/chemistry-gas-laws-smorgasborg#sthash.Qy9PndDT.dpuf
When temperatures get colder, you may need to add some more molecules to get the safe PSI for your vehicle.
Copyright © 2010 Ryan P. Murphy
Other Examples Of Charles’ Law
You may notice that your sports equipment doesn’t work well when you go out into your garage in the winter. The air molecules are moving very
slowly so the ball is flat.
Copyright © 2010 Ryan P. Murphy
You may notice that your sports equipment doesn’t work well when you go out into your garage in the winter. The air molecules are moving very
slowly so the ball is flat.
Copyright © 2010 Ryan P. Murphy
A 2.0L sample of air is collected at 298 K and then cooled to 278 K. The pressure is held constant at 1.0 atm.
a. Does the volume increase or decrease?b. Calculate the volume of air at 278 K.
Step One: Write down the information given and check units.
Step Two: Write down the correct formula.
Step Three: Plug the given information into the formula and solve for the unknown variable.
Step Four: Record the two answers.
V1 = 2.0L V2= ?T1 = 298 K T2 = 278 KP1 = 1.0 atm P2 = 1.0 atm
change
same
V1/T1 = V2/T2
V1/T1 = V2/T2
2.0 =
V2
298 278(2.0)(278) = V2 (298)
298 298
a. The volume will decreaseb. V2 = 1.9L
BOYLES LAW
BOYLE’S LAW: Pressure and Volume are inversely proportional.
↓ volume = ↑ pressure↑ volume = ↓ pressure
1662, Robert Boyle
Very Important! Record in Journal.
Activity! Syringes
Activity! Syringes
Depress plunger on the syringe.
Activity! Syringes Depress plunger on the syringe. Cover hole with finger.
Activity! Syringes Depress plunger on the syringe. Cover hole with finger. Try and pull handle (gently please).
Why is it difficult?Keep thumb on opening.
Activity! Syringes Depress plunger on the syringe. Cover hole with finger. Try and pull handle (gently please).
Why is it difficult?Keep thumb on opening.
Activity! Syringes Answer: It was difficult because your
finger created a sealed vacuum and prevented air from entering the chamber.
Keep thumb on opening.
Activity! Syringes Answer: It was difficult because your
finger created a sealed vacuum and prevented air from entering the chamber. Atmospheric pressure is 1 kilogram per square centimeter at sea level. Keep thumb on
opening.
Activity! Syringes (Opposite)
Activity! Syringes (Opposite) Fill syringe.
Activity! Syringes (Opposite) Fill syringe. Cover hole with finger.
Activity! Syringes (Opposite) Fill syringe. Cover hole with finger. Try and push handle (gently please).
Activity! Syringes (Opposite) Fill syringe. Cover hole with finger. Try and push handle (gently please).
How does this represent Boyles Law?
Activity! Syringes (Opposite) How does this represent Boyles Law?
Activity! Syringes (Opposite) How does this represent Boyles Law? Answer: As you depress the plunger,
you increase pressure and the volume of the gas is decreased.
Activity! Syringes (Opposite) How does this represent Boyles Law? Answer: As you depress the plunger,
you increase pressure and the volume of the gas is decreased.
Please determine how many milliliters you were able to compress the gas inside using the numbers on the syringe.
Activity! Syringes (Opposite) How does this represent Boyles Law? Answer: As you depress the plunger, you
increase pressure and the volume of the gas is decreased.
Please determine how many milliliters you were able to compress the gas inside using the numbers on the syringe.
Answer: You should be able to compress the gas to about 50% of it’s starting volume by hand and then it gets difficult.
“Can’t wait to eat my yogurt.”
As you inhale, your diaphragm flattens out allowing your chest to expand and allows more air to flow into your lungs.
As you inhale, your diaphragm flattens out allowing your chest to expand and allows more air to flow into your lungs. Air pressure decrease, air then rushes
into your lungs.
As you exhale, your diaphragm relaxes to a normal state. Space in chest decreases.
As you exhale, your diaphragm relaxes to a normal state. Space in chest decreases. Air pressure increases, air then rushes
out of your lungs.
Which is a inhale, and which is a exhale?
A B
Which is a inhale, and which is a exhale?
A B
Which is a inhale, and which is a exhale?
InhaleA B
Which is a inhale, and which is a exhale?
InhaleA B
Which is a inhale, and which is a exhale?
Inhale ExhaleA B
Which is a inhale, and which is a exhale?
A BA B
Which is a inhale, and which is a exhale?
A BA B
Which is a inhale, and which is a exhale?
InhaleA BA B
Which is a inhale, and which is a exhale?
InhaleA BA B
Which is a inhale, and which is a exhale?
Inhale ExhaleA BA B
Cartesian Diver to Display Boyle's Law One 2-liter bottle (clear) One small glass dropper Water
Once you've managed to gather these supplies, it would be advised to find a handyman or somebody skilled in construction/engineering to assist in deciphering the following steps:
Fill the 2 liter bottle between 2/3 and 3/4 full of water. Take your eyedropper, the "diver" and fill it with just enough water so that the top of
the dropper is just buoyant enough to tread the water. Apply the lid to the 2 liter bottle. It must be airtight! Squeeze the bottle. Observe.
If you have successfully followed the instructions, good for you. Your Cartesian diver should dive to the bottom as you squeeze the bottle. That's Boyle's law in action!
When you squeeze inward, you are reducing the volume of the bottle. As we know, this reduction in volume increases the pressure of all of the gas, including what is contained in your eyedropper.
This increase in pressure pushes against the water, forcing more water up into the eyedropper. As you can see, this additional water decreases the diver's buoyancy, causing it to "dive" to the bottom. Stop squeezing the bottle and everything returns to normal, allowing your diver to ascend back to the water's surface. You would be keen to let go slowly, so your diver doesn't ascend too quickly. Wouldn't want it getting the bends!
The Bends (Decompression Sickness) – Bubbles form in blood if you rise to quickly because of the rapid decrease in pressure.
Copyright © 2010 Ryan P. Murphy
The Bends (Decompression Sickness) – Bubbles form in blood if you rise to quickly because of the rapid decrease in pressure. A diver must save time to travel to
surface slowly so body can adjust.
Copyright © 2010 Ryan P. Murphy
BOYLE’S LAW
Inverse ↑ P : ↓ V
Formula: P1V1 = P2V2
* a constant amount of gas
* constant temperature
This works because, if the volume of a container is increased, there is a greater area in which the particles of gas inside the container can move. Since the particles have more space, there is less force exerted on the walls of the container by the particles and therefore, less pressure.
What pressure is required to compress 196.0 liters of air at 1.00 atmosphere into a cylinder whose volume is 26.0 liters?
Step One: Write down the information given and check units.
P1 = 1 atm V1 = 196 L, P2 = ? V2 = 26 L
Step Two: Write down the correct formula.
P1V1 = P2V2Step Three: Plug the given information into the formula and solve for the unknown variable.
(1 atm) (196 L) = (P2) (26 L)P2 = 7.5 atm
Freon-12 was a widely used refrigerant but has been replaced by other refrigerants that do not lead to the breakdown of the ozone layer. Consider a 1.5 L sample of Freon-12 gas at a pressure of 56 torr. If the pressure is changed to 150 torr at a constant temperature….
a. Will the volume of gas increase or decrease?b. What will be the new volume of the gas?
Step One: Write down the information given and check units.
Step Two: Write down the correct formula.
Step Three: Plug the given information into the formula and solve for the unknown variable.
Step Four: Record the two answers.
V1 = 1.5 L V2= ?P1 = 56 torr P2 = 150 torr
P1V1 = P2V2
P1V1 = P2V2
(56)(1.5) = (150)(V2)150 150 a. The volume of gas will
decreaseb. V2 = 0.56 L
GUY- LUSAAC’S
LAW
GUY LUSAAC’S LAW
French chemist Joseph Louis Guy-Lussac in 1802
= the pressure of a fixed mass and fixed volume of a gas is directly proportional to the gas's temperature
↑ temperature = ↑ pressure↓ temperature = ↓ pressure
P/T=kWhere: P is the pressure of the gasT is the temperature of the gas (in kelvins)k is a constant
When comparing two substances:
P1/T1=P2/T2
As pressure increases, temperature increases.
Copyright © 2010 Ryan P. Murphy
As pressure increases, temperature increases.
As pressure decreases, temperature decreases.
Copyright © 2010 Ryan P. Murphy
+
+
This photoshop job might look “Funny”.
Caution! Graphic Images of burns / the dangers of pressure and temperature.
The consequences of severe burns and explosions are not “funny”.
Copyright © 2010 Ryan P. Murphy
BOILING WATER AT ROOM TEMPERATURE
↑ pressure =↑
temperature
Describe what should happen?
What does happen?
EXAMPLE:Five grams of octane (C8H18) and enough oxygen to burn it are in an automobile cylinder compressed to 20 atm at 28°C. The mixture explodes and heats the cylinder to 150°C. What is the pressure in the (same sized) cylinder after the explosion?P1 = 20 atm T1 = 301K,P2 = ?T2 = 423 K
P1 / T1 = P2 / T2
(20)/(301) = (P2)/(423)
P2 = 28.4 atm
EXAMPLE 2A 20 L cylinder containing 6 atm of gas at 27 °C. What would the pressure of the gas be if the gas was heated to 77 °C?
P1 = T1 = P2 = T2 =
P1 / T1 = P2 / T2
EXAMPLE 2A 20 L cylinder containing 6 atm of gas at 27 °C. What would the pressure of the gas be if the gas was heated to 77 °C?
P1 = 6 atm T1 = 27 +273 = 300KP2 = ??T2 = 77+273 = 350K
P1 / T1 = P2 / T2
EXAMPLE 2A 20 L cylinder containing 6 atm of gas at 27 °C. What would the pressure of the gas be if the gas was heated to 77 °C?
P1 = 6 atm T1 = 27 +273 = 300KP2 = ??T2 = 77+273 = 350K
P1 / T1 = P2 / T2
(6 atm) x (350K) = (P2)(300K)
P2 = 7atm
PRESSURE CONVERSIONS
STP means standard temperature and pressure
1 standard atmosphere = 1.000 atm = 760.0 mm Hg = 760.0 torr =101,325 Pa = 14.69 psi
***all of these equal each other!***
Temperature: 0 ˚C or 273 K
LE CHATELIER’S
PRINCIPLEIf a stress is applied to a system at equilibrium, the position of the equilibrium will shift to reduce the stress.
3 TYPES OF STRESS:
1. Change amount of reactants and/or products
2. Change Pressure1. Only affects gases2. b/c partial pressures ( and concentrations)
change, a new equilibrium must be reached
3. System will move in direction that has least moles of gas
3. Change in Temperature