monday/tuesday - nov. 14-15 catalyst: 1. if i have a water balloon at 270 o k, what temperature is...

Monday/Tuesday - Nov. 14-15

• Catalyst:

1. If I have a water balloon at 270 oK, what temperature is it in oCelcius? Is the water balloon frozen or not? How do you know?

Writing a Materials/Methods Section

Crushing a Can Without Touching It

Justify – TPS

• Why did the can crush when I put it in the ice bath? Make sure to explain your reason!

Today’s Objectives

• SWBAT explain Gay-Lussac’s Law and calculate the temperature and pressure of a gas. 

• SWBAT explain Boyle’s Law and calculate the pressure and volume of a gas.

The Gas Laws

• We can describe how a gas will change based on the volume, pressure, temperature, and moles of the gas.

• The gas laws focus on these properties and how changing one affects the other three.

Pressure and Temperature Relationship

• Gas molecules move quicker the more we heat them up and increase the temperature.

• This means that they will be hitting the sides of the container more often and the pressure will also increase as the temperature increases.

• If we keep volume constant, then pressure and temperature are directly related.

Gay-Lussac’s Law

Gay-Lussac’s Law

Absolute Zero

This is an direct relationship! As one goes up the other goes up!

Using what you Know now, Why did the Soda Can Get Crushed?

Video Explains! http://www.youtube.com/watch?v=RjUCngugF7w&feature=related

Gay-Lussac’s Law

• Gay-Lussac’s Law relates pressure and temperature through a math expression:

Where P represents pressure and T represents temperature. i and f simply mean before and after the reaction.

Steps to Solve Gas Law Problems

• To solve any gas law problem, follow the following steps:

1.Annotate the problem and make sure to identify what is known and what you need to calculate.

2.Determine which gas law you need to use.

3.Convert all temperatures to Kelvin

4.Solve for the variable that is unknown.

Class Example

• An aerosol can containing gas at 101 kPa and 22 oC is heated to 55 oC. Calculate the pressure in the heated can.

Table Talk

• The gas in a balloon begins at 122 oC and 2 atm. If the gas is decreased to 1 atm, then what is the temperature?

Stop and Jot

• You have a gas that is 111 kPa and a temperature of 273 K. What is the new pressure you increase the temperature to 373 K.

Summarize

White Board (Hot-Cheetoh) Races

• With your table, answer the following questions.

• Once you have come up with your answer, put the white board in the air.

• You must show ALL work in order to get a point for your team.

Question 1

1. Determine the pressure change when a constant volume of gas at 1.00 atm is heated from 20.0 °C to 30.0 °C.

Question 2

2. A gas has a pressure of 0.370 atm at 50.0 °C. What is the pressure at 0 °C.

Question 3

3. 30.0 L sample of nitrogen inside a rigid, metal container at 20.0 °C is placed inside an oven whose temperature is 50.0 °C. The pressure inside the container at 20.0 °C was at 3.00 atm. What is the pressure of the nitrogen after its temperature is increased?

Question 4

4, If a gas in a closed container is pressurized from 15.0 atmospheres to 16.0 atmospheres and its original temperature was 25.0 °C, what would the final temperature of the gas be?

Question 5

5. If a gas is cooled from 323.0 K to 273.15 K and the volume is kept constant what final pressure would result if the original pressure was 750.0 mm Hg?

How Are Pressure and Volume Related?

• Play with the syringe at your table

• With your table, hypothesize about how pressure and volume are related.

• Does pressure increase or decrease as volume is decreased?

Boyle’s Law

• If we keep temperature constant, then volume and pressure are inversely related. As one goes up the other goes down

• If the container gets larger the gas molecules are hitting the walls at a less frequent rate. Therefore, by increasing the volume of a container, we are decreasing the pressure that is felt by that container.

• The reverse is true if we decrease the volume of a container.

Boyle’s Law

Graph of Boyle’s Law

This is an inverse relationship! As one goes up the other

goes down!

Boyle’s Law Equation

• Boyle’s Law states that pressure and volume are inversely proportional and they can be described by the equation:

PiVi=PfVf

• Use the same steps that you used for Gay-Lussac’s Law to solve Boyle’s Law.

Class Example

• A given sample of gas occupies 523 mL at 1 atm. The pressure is increased to 2 atm, while the temperature remains the same. What is the new volume of the gas?

Stop and Jot

• A sample of as in a syringe has a volume of 10 mL and a pressure of 6 atm. What is the new volume if the pressure is decreased to 3 atm?

Summarize

Relay Races

Relay Race Questions

1. What does Gay-Lussac’s Law state?

2. If I increase the temperature of a gas in a container at a constant volume, will the pressure increase, decrease or stay the same?

3. If initial pressure is 10 atm and initial temperature is 5 oC and final pressure is 20 atm, then what is the final temperature?

4. What does Boyle’s Law state?

5. If I increase the volume will pressure increase or decrease?

6. I start with a gas that is 5 atm and a volume of 500 mL. If the final volume is 1500 mL, then what is the final pressure?

Work time

Exit Slip

1. If I increase the temperature of a gas at constant volume, then what will happen to the pressure of the gas?

2. If I increase the volume of a gas at constant temperature, then what will happen to the pressure of the gas?

Closing Time

• Extension Activity 4.3 – Gay-Lussac and Boyle’s Law

• Quiz Next Monday/Tuesday!

• Materials and Methods section due Wednesday!