th
nd
 Homework questions/collect (Pg. 432: #1-12)
 2 nd combined gas law example for warm-up
 Sec. 12.2 quiz: “The Gas Laws”
 Lab discussion/write up: “Charles’ Law: The
Effect of Temperature on Volume”
 Gas Laws and Drinking Straw Activity
Lab next time - dress appropriately!

 Questions/Problems?
 Hand In

Additional Example
A gas at STP occupies 28 cm 3 of space. If the pressure changes to 3.8 atm and the temperature increases to
203°C, find the new volume.
 Use the combined gas law: P
1
V
1
T
1
= P
2
V
2
T
2
 P
 V
1
 T
1
1
 P
 T
2
2
= 1.00 atm
= 28.0 cm
= 0°C + 273 = 273 K
= 3.8 atm
3
= 203°C + 273 = 476 K
V
2
= 12.8 cm 3

Sec. 12.2 quiz
“The Gas Laws”
 You may use your book, notes, and a calculator to complete the quiz on your own.
 Question #5 was NOT covered in this section…the answer is (C) Dalton.

Lab: “Charles’ Law: The Effect of
Temperature on Volume”
Background
 According to the kinetic-molecular theory, an increase in temperature will cause the molecules of a gas to move faster and exert more pressure, causing the gas to expand.
 Conversely, as a gas cools, the molecules move more slowly and the gas will contract, or exert less pressure.
 The relationship between the volume of a gas and its temperature is known as Charles’s Law.

Lab: “Charles’ Law: The Effect of
Temperature on Volume”
Title, Purpose and Hypothesis
 You will have to read through the lab to find the purpose of this lab and write your hypothesis statement.

Lab: “Charles’ Law: The Effect of
Temperature on Volume”
Changes to Materials List
 Remember, 1 cm 3 = 1 mL
 You will use a hot plate NOT a bunsen burner.
 Change “thermometer” to “temperature probe”.
 You will need a 100 mL graduated cylinder, NOT a
50 mL.
 Cross out the barometer – we don’t have one. I will look online to find the atmospheric pressure.

Lab: “Charles’ Law: The Effect of
Temperature on Volume”
Procedure
 The procedure for this lab is pretty straightforward and we will follow the directions in the lab handout.
 I have graph paper for you to use to graph your data.

Lab: “Charles’ Law: The Effect of
Temperature on Volume”
Lab Write-up and Reflection Statement
 With a partner of your choice, complete the lab write-up.
 Don’t forget to leave space for the reflection statement.
 Be sure to update your table of contents in your lab folder.
We will be in the lab next time: dress appropriately!

(Answer on the back of your post-lab question sheet)
 Why can we drink through a straw?
 try to explain it without using the word suck in your description

 Fill your cup ½ full of water.
 Put your straw in the cup.
 Place one finger over the straw and lift it out of the water.
 Observe the water in the straw carefully.

 Grab a second straw.
 Put both straws into your mouth.
 Lower one of them into the glass and the other should be outside of the glass.
 Try to drink the water through the straw in the glass

 Tape two straws together end to end and drink from them.
 Continue to add straws until you have a total of 8 straws taped together.
 Try drinking out of your elongated straw vertically and as horizontally as possible.

 Use flexible tubing to make a giant straw on the stairwell.

1. Why does the water stay in the straw in activity #1?
2. Why can’t you drink very well in activity #2 (two straws in your mouth)?
3. Why is there a limit to the height of a straw you can drink from?
4. What is the maximum theoretical height through which you can drink?
Atmospheric pressure = 760 mmHg
Mercury is 13.7 times more dense than water is.