Gasses or Gases Chapter 14 The first question

  • Slides: 54
Download presentation
Gasses… or Gases? Chapter 14

Gasses… or Gases? Chapter 14

The first question… • Is it gasses, or gases? – According to the New

The first question… • Is it gasses, or gases? – According to the New York Times (the nation’s most prominent paper) it is gases. – According to the National Post (Canada’s national paper) it is gasses. – According to ESPN (the worldwide leader in sports) it is gasses. • I don’t really care. Which ever one you want to use. I’ll use gasses, I think.

Gasses go “squish” • Gasses are compressible, meaning their volume can decrease when pressure

Gasses go “squish” • Gasses are compressible, meaning their volume can decrease when pressure is applied. • Gasses are compressible because there is so much space between them. – In normal air (1 atm), there is 10 times as much space between particles as each particle takes up. This picture is actually way too dense, but I couldn’t find a better one.

A reminder about pressure… • Pressure is the amount of force in an area.

A reminder about pressure… • Pressure is the amount of force in an area. – Measured in pascals (Pa) or kilopascals (k. Pa = 1000 Pa) • Gas pressure is caused by collisions against a surface, like the side of a container.

What affects pressure? • There are 4 variables used to describe a gas: –

What affects pressure? • There are 4 variables used to describe a gas: – Pressure (P) • Measured in kilopascals (k. Pa) – Amount of gas (n) • Measured in moles (mol. ) – Volume (V) • Measured in liters (L) – Temperature • Measured in kelvin (K) not technically a degree.

Amount of Gas and Pressure • As you add gas, two things can go

Amount of Gas and Pressure • As you add gas, two things can go up: – Either the volume can get higher (container expands) – Or the pressure goes up (more collisions) – Or both… • If you double the particles, the volume or the pressure must double. • This is how you inflate tires, balls, and air mattresses, too.

 • https: //www. youtube. com/watch? v=2 WJVHt. F 8 Gw. I • http:

• https: //www. youtube. com/watch? v=2 WJVHt. F 8 Gw. I • http: //phet. colorado. edu/en/simulation/gasproperties

Containers • Non-flexible containers like SCUBA tanks will have the pressure go up. –

Containers • Non-flexible containers like SCUBA tanks will have the pressure go up. – Volume will not change. • Semi-flexible containers like a beach balls will have volume AND pressure go up. • Flexible containers like bubbles will increase in volume, but not pressure.

Volume and Pressure Demo

Volume and Pressure Demo

Volume and Pressure • When you compress air and make the volume less, the

Volume and Pressure • When you compress air and make the volume less, the pressure goes up. • When volume goes up, pressure goes down. – “Inverse relationship” • Twice the volume, means half the pressure. – P*V = a constant

Let’s try a couple… • How much of a volume do you need to

Let’s try a couple… • How much of a volume do you need to have to increase the pressure 5 times? • How many times more gas do you need to have 3 times more pressure?

Okay, quick reminder… • Pressure and amount of gas are DIRECTLY proportional – When

Okay, quick reminder… • Pressure and amount of gas are DIRECTLY proportional – When one goes up, the other goes up. – P=kn • (k is a constant, depending on volume and temperature) • Pressure and volume are INVERSELY proportional – When one goes up, the other goes down. – PV=k • (k is a constant, depending on temperature and moles)

Temperature and Pressure • As temperature goes up, pressure also goes up – P=Tk

Temperature and Pressure • As temperature goes up, pressure also goes up – P=Tk • k is constant for a certain volume and number of moles • Temperature is always measured in Kelvin (K) !!!! • As particles move faster, they move and bounce more. – Almost everything expands when it gets warmer, anyways.

Temperature and Pressure Demo • For Tuesday

Temperature and Pressure Demo • For Tuesday

If you have a sealed container… • Only 3 things can change: – (Because

If you have a sealed container… • Only 3 things can change: – (Because amount of gas can’t change, since it’s sealed) – Pressure – Volume – Temperature • If you keep one the same, the other two will change together.

The Gas Laws • Science’s “Laws” – Mathematical predictions (equations) that can’t be broken

The Gas Laws • Science’s “Laws” – Mathematical predictions (equations) that can’t be broken • 3 that relate to pressure, volume, and temperature. • Boyle’s Law – Volume and Pressure • Charles’s Law – Temperature and Volume • Gay-Lussac’s Law – Pressure and Temperature

Balloon in a vacuum demo

Balloon in a vacuum demo

Boyle’s Law • Starting pressure times starting volume equals ending pressure times ending volume

Boyle’s Law • Starting pressure times starting volume equals ending pressure times ending volume – P 1*V 1 = P 2*V 2 • INVERSE! – P 1/P 2 = V 2/V 1 • See how they’re flipped? – INVERSE! » INVERSE!

Okay, let’s try some • P 1*V 1 = P 2*V 2 • I

Okay, let’s try some • P 1*V 1 = P 2*V 2 • I have a container that is 30 m. L, and it is at 1 atm of pressure. I want it to have 6 atm of pressure. How many m. L must my container be?

Okay, let’s try some • P 1*V 1 = P 2*V 2 • I

Okay, let’s try some • P 1*V 1 = P 2*V 2 • I have a container that is 30 m. L, and it is at 1 atm of pressure. I want it to have 6 atm of pressure. How many m. L must my container be? • A tennis ball has about 1. 5 atm in it. It has a volume 58 m. L. When you hit it with a racket, it decreased in volume to 30. m. L. What is the pressure inside the tennis ball when you hit it?

Balloon Demo • Maybe heated can if we have enough time

Balloon Demo • Maybe heated can if we have enough time

Charles’s Law (Or Charles’) • Or Chuck’s Law, I guess. • In a flexible

Charles’s Law (Or Charles’) • Or Chuck’s Law, I guess. • In a flexible enclosed container (like a balloon) as the temperature decreases, the volume will also decrease. – All the temperatures MUST BE in Kelvin!!!! • V 1/T 1 = V 2/T 2 • V 1*T 2 = V 2*T 1 • V 1/V 2 = T 1/T 2 – You only need to know one of these, and you can solve for any of them.

Some Charles’s Law Problems • You have a balloon with a volume of 25.

Some Charles’s Law Problems • You have a balloon with a volume of 25. 0 m. L at 370. K, and you cool it down to 280. K. What is the new volume of the balloon?

Some Charles’s Law Problems • You have a balloon with a volume of 25.

Some Charles’s Law Problems • You have a balloon with a volume of 25. 0 m. L at 370 K, and you cool it down to 280 K. What is the new volume of the balloon? • You have a 300. 0 L drum that you want to collapse to only 30. 0 L. It is currently 25. 0°C. What temperature do you need to get it down to? Answer in Kelvin and °C.

Boyle vs. Charles • Boyle’s: – Pressure and Volume are INVERSE. • Multiplied together

Boyle vs. Charles • Boyle’s: – Pressure and Volume are INVERSE. • Multiplied together • Charles’s: – Temperature and Volume are DIRECT • Divide one by the other • Divide = Direct • B comes before C – Pressure comes before Temperature – BP and CT

 • http: //ed. ted. com/lessons/1207 -1 -a-bennetbrianh 264

• http: //ed. ted. com/lessons/1207 -1 -a-bennetbrianh 264

Gay-Lussac’s Law • When volume is constant (like in a rigid container) the pressure

Gay-Lussac’s Law • When volume is constant (like in a rigid container) the pressure and temperature are directly proportional – When one goes up, the other goes up. • P 1/T 1 = P 2/T 2 – Direct = divide – Temperature STILL must be in Kelvin! KELLLVINNN!

You want a problem? I got your problems right here, buddy. • P 1/T

You want a problem? I got your problems right here, buddy. • P 1/T 1 = P 2/T 2 • You have a SCUBA tank that starts at 1000. k. Pa, and you want it to have 7000. k. Pa inside of it. If you start at 293 K, what temperature must you heat it up to?

You want a problem? I got your problems right here, buddy. • P 1/T

You want a problem? I got your problems right here, buddy. • P 1/T 1 = P 2/T 2 • You have a SCUBA tank that starts at 1000 k. Pa, and you want it to have 7000 k. Pa inside of it. If you start at 293 K, what temperature must you heat it up to? • You have a can of propane that is at 300. k. Pa at 15°C. It heats up to 30. °C in the sun. What is the new pressure?

The Combined Gas Law • If you combined these three laws, you can get

The Combined Gas Law • If you combined these three laws, you can get one “mega-law” that includes all 3 (temperature, volume, and pressure) • This allows you to calculate how much of one measurement you have, if you know the other 5! – It also makes it so you don’t really need to know the other 3 equations.

Using the Combined Gas Law • If something stays the same (“constant”) just cancel

Using the Combined Gas Law • If something stays the same (“constant”) just cancel it out from both sides of the equation. • If all 3 (temperature, pressure and volume) change, then use all the variables and solve for the unknown. • Got it?

Okay, let’s try some.

Okay, let’s try some.

Okay, let’s try some. • No.

Okay, let’s try some. • No.

Okay, let’s try some. • Yes.

Okay, let’s try some. • Yes.

Okay, let’s try some. • Fine… Ugh, whatever.

Okay, let’s try some. • Fine… Ugh, whatever.

Okay, let’s try some. • Solve with the Combined Gas Law: • If the

Okay, let’s try some. • Solve with the Combined Gas Law: • If the temperature remains constant, but the pressure increases from 100. k. Pa to 300. k. Pa, how much would the volume decrease to if it started at 230. L?

Okay, let’s try some. • Solve with the Combined Gas Law: • Original measurements:

Okay, let’s try some. • Solve with the Combined Gas Law: • Original measurements: – Pressure: 37. 1 atm – Volume: 22. 5 m. L – Temperature: 250. 0 K • New measurements: – Pressure: ? – Volume: 30. 2 m. L – Temperature: 270. 0 K

How we all feel right now. • http: //www. tagtele. com/videos/voir/24776 • (2: 49)

How we all feel right now. • http: //www. tagtele. com/videos/voir/24776 • (2: 49)

All the gas laws in one. • • P*V (Boyle’s Law) V/T (Charles’s Law)

All the gas laws in one. • • P*V (Boyle’s Law) V/T (Charles’s Law) P/T (Gay-Lussac’s Law) V/n (Avegadro’s Law of Volume 1 mole = 22. 4) – N= moles • Put them all together you get…

What was noticed… • When you calculate PV/n. T, you always got the same

What was noticed… • When you calculate PV/n. T, you always got the same number. – Or very, very close. • THE gas constant (R) !!! – Calculated using moles, k. Pa, Liters, and Kelvin. • So, let’s calculate it, using Mr. V’s (wife’s) SCUBA tanks!

 • 1 person will be the pressure person In each of – Use

• 1 person will be the pressure person In each of – Use the pressure gauge on the tank – Convert psi into k. Pa (1 psi = 6. 895 k. Pa) the groups • 1 person will be moles – Use the scale, with one empty tank and one full tank. The difference is the mass of the air inside. – Use the molar mass (g/mol) of dry air. (28. 97 g/mol. ). – Determine the moles be dividing mass in g by molar mass. • 1 person will be temperature – Only the temperature of the full tank “matters”. – Use the temperature gun, convert to Kelvin. • 1 person will be volume – Get the data from Faber’s e-mail on my website, facebook or twitter feed. Give the volume in Liters. • If someone is missing, combine the bottom 2 jobs.

How to organize… • All the moles people meet at the periodic table of

How to organize… • All the moles people meet at the periodic table of the elements. (Find the molar mass using a portable electronic or the periodic table). • All of the volume people, get together near the door, and find out the answer from the internet. Phone? Computer? i. Pad? • All of the Pressure people, meet near the safety shower. • All the Temperature people meet in the middle of the room. • AT THE END, GET BACK TOGETHER, AND CALCULATE “R” = PV/n. T

 • PV=n. RT The Ideal Gas Law – But can be written to

• PV=n. RT The Ideal Gas Law – But can be written to solve for any of them. – For example: T = PV/n. R, V= n. RT/P • P 1 V 1 = P 2 V 2 n 1 RT 1 n 2 RT 2 – The R’s are the same, so they cancel out, and you end up with P 1 V 1/n 1 T 1= P 2 V 2/n 2 V 2 • Remember units are important now: – Pressure in k. Pa – Temperature in K – Volume in L – Amount in moles – R is 8. 31

Ideal Gas Problems! • PV=n. RT • How much pressure would you have, if

Ideal Gas Problems! • PV=n. RT • How much pressure would you have, if you have a 4. 00 L container at 275 K that is holding 3. 75 moles?

Ideal Gas Problems! • PV=n. RT • How much pressure would you have, if

Ideal Gas Problems! • PV=n. RT • How much pressure would you have, if you have a 4. 00 L container at 275 K that is holding 3. 75 moles? • How many moles would you need, to fill a 750 m. L container, with a pressure of 3. 00 atm, at 22°C?

Ideal gasses vs. real gasses • Most gasses act the same as ideal gasses.

Ideal gasses vs. real gasses • Most gasses act the same as ideal gasses. – Except at: • Low temperatures • High pressures – So, we can use the ideal gas laws at all times, except for when temperatures are really low or pressure is really high. • Basically, all the time.

Partial Pressures in Gas Mixes • Almost no gasses are pure, and instead are

Partial Pressures in Gas Mixes • Almost no gasses are pure, and instead are mixes of two or more types of particles. – Ex) There is mostly nitrogen in air, but it is also oxygen, carbon dioxide, argon, and more. • Each gas exerts a pressure on its own, called a partial pressure. • The gas pressure is a total of all the partial pressures in a gas. – “Dalton’s Law of Partial Pressure”

Dalton’s Law Problems • What is the total pressure if the partial pressure of

Dalton’s Law Problems • What is the total pressure if the partial pressure of oxygen is 32. 1 k. Pa, nitrogen is 106. 4 k. Pa, and argon is 12. 2 k. Pa?

Dalton’s Law Problems • What is the total pressure if the partial pressure of

Dalton’s Law Problems • What is the total pressure if the partial pressure of oxygen is 32. 1 k. Pa, nitrogen is 106. 4 k. Pa, and argon is 12. 2 k. Pa? • If you have 1 atm of air, and you know that 81. 1 k. Pa is nitrogen, and 18. 3 k. Pa is oxygen what is the amount of air in k. Pa and atm that is NOT nitrogen or oxygen?

How Gasses Move • Diffusion – Gasses move from areas of high concentrations to

How Gasses Move • Diffusion – Gasses move from areas of high concentrations to lower concentrations. • Atoms move away from similar atoms. • Effusion – Gasses move through small holes.

 • http: //www. youtube. com/watch? v=H 7 Qs. Ds 8 ZRMI • http:

• http: //www. youtube. com/watch? v=H 7 Qs. Ds 8 ZRMI • http: //www. youtube. com/watch? v=0 u. BK 7 Vx. T 00 E

Graham’s Law of Effusion • The rate of effusion of a gas is inversely

Graham’s Law of Effusion • The rate of effusion of a gas is inversely proportional to the square root of the mass of the gas. – If we know the molar masses of two gasses, we can compare their effusion rates. • Notice how the v and m are SWITCHED!!!

Graham’s Law Problems! • How many times faster does hydrogen gas move than nitrogen

Graham’s Law Problems! • How many times faster does hydrogen gas move than nitrogen gas?

Graham’s Law Problems! • How many times faster does hydrogen gas move than nitrogen

Graham’s Law Problems! • How many times faster does hydrogen gas move than nitrogen gas? • How many times faster does oxygen gas move compared to Krypton gas?