GAS LAWS Tennis ball example – Would you rather be hit by a tennis ball going 5mph or 100mph?
Let’s review what PRESSURE is… PRESSURE is the force exerted on a given area. Another way to think of pressure… how hard the particles are hitting Tennis ball example
DRAW ON YOUR WHITEBOARD: Two containers - one container is twice as big as the other. Both have the same amount of gas particles (5 particles each). Circle the container with greater pressure.
If you increase the VOLUME of a gas (size of container in previous example), the PRESSURE will decrease. Show what this would look like in the graph below. Pressure Volume
The reverse is also true… As PRESSURE increases, the VOLUME of a gas decreases. (Think about what happened to the bubble when the air pressure was greater than the pressure inside the bottle) Show what this would look like in the graph below. Volume Pressure
BOYLE’S LAW As pressure increases, volume decreases AND As volume increases, pressure decreases (for the same amount of gas at the same temperature)
So what is the relationship between TEMPERATURE and VOLUME of a gas So what is the relationship between TEMPERATURE and VOLUME of a gas? First, let’s look at the relationship between TEMPERATURE and PRESSURE.
Which container has the highest pressure Which container has the highest pressure? (be able to explain your answer) 20 C 10 C
Therefore, as the TEMPERATURE of a gas increases, the PRESSURE of a gas increases. This makes the gas expand, so the VOLUME increases.
CHARLES’S LAW As temperature increases, volume increases (for the same amount of gas at the same pressure)
BOYLE’S LAW: (stop at 1:09) https://www. youtube. com/watch BOYLE’S LAW: (stop at 1:09) https://www.youtube.com/watch?v=Xto88gMmDzw CHARLES’S LAW: https://www.youtube.com/watch?v=XBET-aUiJE8
Exit Ticket Two balloons are filled with equal volumes of air. One balloon is put into a freezer and the other is put into a hot car. 3 hours later… What would you expect to happen? Which gas law does this illustrate? A marshmallow is placed into a syringe. What would happen if you push the plunger? Why? What would happen if you pulled the plunger back out? Why?
#2 - Gas Laws Review & Intro to Atmospheric Pressure Picture A Picture B Write IN WORDS what Picture A shows. What gas law is this? Write IN WORDS what Picture B shows.
What is atmospheric pressure? Why don’t you feel atmospheric pressure? Read pp. 163-164 (Atmospheric Pressure) and answer the questions below. What is atmospheric pressure? Why don’t you feel atmospheric pressure? Why does atmospheric pressure change as you drive up to the top of a mountain? 1. pressure caused by the weight of the atmosphere 2. the fluids inside your body also exert pressure 3. there is less “fluid” being pulled down on you (less atmosphere less pressure)
DID YOU BRING YOUR CAN??? GIRLS: Put your hair up!!! Coke / pepsi cans
What the what??? Mrs. Johnson can use Jedi mind tricks to mysteriously make the eyedropper go up and down. Or can she…? Find out if you finish PART A (Charles’s Law) and have extra time.
Safety / Getting Materials Pull back loose hair Aprons and GOGGLES Get Burners (back of room) Get water in 400 or 600 mL beaker (pretty full) Get 5 mL water in a graduated cylinder Get tongs Clear Desk of all binders and excess stuff, keeping it neatly UNDER DESKS or on the SIDE OF ROOM. (not in aisles)
Lab procedures: 5 mL water (NO MORE in can) Use tongs to hold really close to flame Hold until water is sizzling (boiling in can) Blow flame out Turn over can in cold water To Clean Up: PUT EVERYTHING BACK WHERE IT GOES!!!!!!!! Empty water from cans Put cans in box (back of room) When finished: Begin Part B – Cartesian Diver.
CAN HATERS!!!
SO WHAT ACTUALLY HAPPENED? Coke / pepsi cans
SO WHAT ACTUALLY HAPPENED?
Explain how gases create pressure Explain how gases create pressure. (Hint: think about what the molecules are doing)
Explain why one small tank of highly pressurized helium gas can be used to fill up hundreds of balloons.
Explain why a soda left in a super-hot car on a summer day might explode.
What would happen to the size of a balloon if the pressure around it decreased, like when you drive up to Mt. Ashland?
What would happen to the volume of a can full of hot gas if you cooled it off quickly?
Two gases have temperatures of 50C and 100C Two gases have temperatures of 50C and 100C. They have an equal number of gas particles and are in the same size container. Which would have a greater pressure and why?