# Gas Laws Chapter 14 in your book.

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Gas Laws Chapter 14 in your book

Gas Laws Unit ESSENTIAL QUESTIONS OBJECTIVES How do gases respond to changes in pressure, volume, and temperature? Why do you suppose we study ideal gases? Why is the ideal gas law useful even though ideal gases do not exist? Describe three factors that affect gas pressure Explain the relationship and calculate problems between p, v, and t of a gas Relate the total pressure to the partial pressures of gases contained in a mixture Use Graham’s diffusion rate to calculate the rate of diffusion of given gases.

Chemcatalyst: ___.___ Write down 4 properties of gases:
Give me 2 examples of gases:

Pressure Conversions 1 atm = 101.3 kPa = 760 mmHg (torr)
How can we write these as conversion factors?

Do you know why torr and mmHg are the same?
Evangelista Torricelli invented the first barometer using mercury! Torr is in honor of his work with pressure and measuring it!

Pressure Conversions Write what you are given with its units
Write the conversion factor next a. Be sure to make sure you’re units cancel out! Multiply the top and multiply the bottom… then divide Check SigFigs and units!!!

Let’s try this one together:
If you have 99.6 kPa, how many atm would that be?

Try this one on your own:
How many mmHg are in atm?

WWLKD? What would Lord Kelvin do? With Temperature…

Temperature Conversions
For gas laws, we will be using KELVINS The Kelvin scale is only positive! Absolute Zero = 0 K K = oC + 273 oC = K - 273

Let’s try these: How many kelvins are equal to 21.0 oC?

Volume Conversions 1000 mL = 1L How many liters are in 545 mL?

Standard Temperature and Pressure
STP Standard Temperature and Pressure Temperature: 0oC Pressure: 1.00 atm

Chemcatalyst:___.___ How many atmospheres are equivalent to 450 kPa?
Show work and units! Try your best on Sig Figs! 

Peeps Demonstration/Video

Pressure & Volume What happened to the peep’s volume when the air was sucked out? What happened to the pressure as the air was being sucked out? What happened to the peep’s volume when air was let back in?

Fill in the blanks: As the pressure _______________, the volume _______________. This is an ________ or ________ relationship.

Boyle’s Law PV =K P1V1 = P2V2 P= Pressure (atm, Kpa, Pa, mmHg (torr))
K is a constant; so we can say the initial and final conditions are equal As P increases, V decreases; As P decreases, V increases P1V1 = P2V2 P= Pressure (atm, Kpa, Pa, mmHg (torr)) V= Volume (mL or L)

Let’s try this one together:
5.00 L of a gas is at 1.08 atm. What pressure is obtained when the volume is 10.0 L?

Try this one on your own:
2.50 L of a gas was at an unknown pressure. However, at standard pressure, its volume was measured to be 8.00 L. What was the unknown pressure? (x) (2.50 L) = (1.00 atm) (8.00 L) X = 3.20 atm

Boyle’s Law Practice In small groups, no more than 3 complete problems in your packet on page 1 Must show work on a separate sheet of paper What ever you do not finish is homework Good Luck 

Chemcatalyst:__.___ If a balloon has 30.0L of gas at kPa, what is the volume, if the pressure is decreased to kPa? Show all work with units and try your best with Sig figs!

Liquid Nitrogen & balloons
Video! What happen to the balloon in liquid nitrogen and after the liquid nitrogen? What two factors were affected in this video?

Charles’ Law V/T =K V= Volume (mL or L) T= Temperature (K)
K is a constant; so we can say the initial and final conditions are equal As V increases, T increases; As V decreases, T decreases V= Volume (mL or L) T= Temperature (K)

Let’s do this one together!
A balloon is inflated at 24oC and has a volume of L. What is the volume when the balloon is heated to 58oC?

Try this one on your own:
If a sample gas occupies 6.80L at 325oC, what will the temperature be if the volume decreases to L?

Charles’ Law Practice In pairs complete 1-3 in your packet on page 2
Show work on a separate sheet of paper You will have 10 minutes to complete these 3 problems!

AXE Can Video What will happen to the AXE can when it is placed in a bon fire? How to fix a ping pong ball with chemistry?!

Steam can be as harmful as boiling water

Chemcatalyst: __.__ What’s happening in this video?

Gay-Lussac’s Law P/T =K P= Pressure (Kpa, atm, or mmHg (torr)
K is a constant; so we can say the initial and final conditions are equal As P increases, T increases; As P decreases, T decreases P= Pressure (Kpa, atm, or mmHg (torr) T= Temperature (K)

Let’s try this one together!
An aerosol can has a pressure of 103 kPa at 25oC, if the can reaches a temperature of 928oC within a fire, what is the new pressure?

Try this one on your own:
The pressure in a car tire is 198 kPa at 27oC. After a long drive, the pressure is 225 kPa. What is the temperature in the tire? T2 = 340 K

Mini lab Egg in a bottle

Chemcatalyst: ___.___ Write down the 3 gas laws and their equations
Write each relationship too (Ie: pressure does this when volume does this) A given sample of air has a volume of 6.00 L at 101 kPa, what volume would it occupy at 25.0 kPa?

Let’s combine them What do each one of these equations have in common?
Do the places where P, V, T switch or change?

Combined Gas Law Red- Boyle’s Law Blue- Charles’ Law
Green- Gay-Lussac’s Law Orange- the COMBINED Gas Law How many “knowns” will you have to have?

Combined gas Laws The volume of a gas-filled baggie is 30.0 L at 313 K and 153 kPa, what would the volume be at STP?

Combined gas law worksheet
Work on Page 3’s chart on the combined gas law in pairs or threes!

Prepare for Quiz on: - Pressure conversions - Named Gas Laws - Combined Gas Laws **Can use given sheet with formulas! 

Chemcatalyst: ____.____
What does it mean for something to be ideal?

Ideal Gases The named gas laws had P, T, and V, but what about moles and mass? Does gas have mass?

IDEAL GAS LAW Moles and Gases
Chemist needed an equation with mass or moles! Introducing the…. (drum role) IDEAL GAS LAW

PV = nRT Ideal Gas Law P= Pressure ( MUST be in atm or kPa)
V= volume (MUST be in LITERS!) n= Number of moles (mols) R= Gas constant For Atm = For kPa = 8.314 T= Temperature (MUST be in KELVIN (K))

Let’s do this one together:
At 34oC, the pressure inside a nitrogen-filled tennis ball with a volume of L is 212 kPa. How many moles of nitrogen are in the tennis ball?

Try this one on your own:
When the temperature of a hollow sphere containing 685 L of helium is held at 621 K, the pressure is 1890 kPa. How many moles of helium are in this sphere?

Ideal Gas Law Practice Work in small groups (2-3 people) and complete the back page in your packet #’s 1-3 Complete on a separate sheet of paper, show all work You have 10 minutes to complete!!!

Molar Mass Reminder: Calculate the molar mass for: CaCO3 Mg(NO3)2
g/mol g/mol

Ideal Gas Law with mass! A steel cylinder that has a volume of 20.0L with nitrogen gas inside has a pressure of 200. kPa and 28oC, how many grams is that nitrogen (N2)? WOOHOO WE DID IT!

Ideal Gas Law Try the mass problems on the ideal gas law worksheet, page 4

Chemcatalyst ___.___ How do we smell things across the room?

Diffusion Tendency for molecules to move towards areas of lower concentration until uniform throughout Move from high concentration to lower ones

Did you know? Dif in latin means “apart”

Effusion The process in which a gas escapes through a small hole
The flow of a gas

Grahams Effusion Equation
the rate of effusion of gases at the same temperature and pressure are inversely related to the square root of their molar masses. Rate of A = √mmB Rate of B √mmA

Did you know? In Latin the prefix eff, means exit
Effusion that gas is exiting through a small hole or one concentrated area!

Try this together: How much faster does helium (He) effuse than nitrogen (N2) at the same temperature?

Try these on your own: Calculate the rate of effusion between oxygen (O2) and carbon dioxide (CO2)

Reach question: If an unknown gas diffuses 5 times faster than Argon, what is the molar mass of the unknown gas?