The Behavior of Gases, Chapter 14

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The Behavior of Gases,
Chapter 14 (Unit 1)
Mr. Samaniego
Lawndale High School
California Standards
Gases and Their Properties
4. The kinetic molecular theory describes the motion
of atoms and molecules and explains the
properties of gases. As a basis for understanding
this concept:
a. Students know the random motion of molecules
and their collisions with a surface create the
observable pressure on that surface.
c. Students know how to apply the gas laws to
relations between the pressure, temperature, and
volume of any amount of an ideal gas or any
mixture of ideal gases.
Thinking Map
Draw a Circle Map on Gases.
Gases
Phases of Matter
Direct and Inverse Relationships
As more people watch football, less
watch tv shows.
Inverse
More people listen to an artist as they
become more popular.
Direct
The more money you make, the more
money you spend.
Direct
Inverse vs. Direct
Which relationship is direct or inverse?
Volume vs. Temperature
3.0
Volume (L)
3.0
Direct
2.0
1.0
0.0
Direct
2.0
1.0
0.0
0
200
400
600
Temperature (K)
800
1000
0
200
Pressure vs. Volume
Pressure (kPa)
Pressure (atm)
Pressure vs.
Temperature
300
250
200
150
100
50
0
Inverse
0.0
0.5
1.0
1.5
2.0
Volume (L)
2.5
3.0
400
600
Temperature (K)
800
1000
The Gas Laws
Boyle’s Law
Charles’Law
P1V1  P2V 2
V1
T

1
Gay-Lussac’s Law

Combined Gas Law

Ideal Gas Law
V2
T2
P1
T

1
P2

T2
P1V1
T

1
P2V 2
T2
PV  nRT
Temperature
There are three common units
temperature is measured in:
Celsius
___________
(oC), Fahrenheit
(oF), and _________
Kelvin (K)
Temperature
The important temperature unit
in describing Gas behavior is
Kelvin
___________
(K).
Conversion:
273
Kelvin = Celsius + _____
Pressure
There are five common units pressure
is measured in:
kilopascals
____________ (kPa),
______________
(atm), mm of
atmospheres
mercury (mm Hg), Torr (Torr), and
pounds/inch2 (lbs/in2)
Conversion Factors
101.325 kPa = 760
760 Torr = _______
14.7 lbs/in2
1 atm = _______
___ mm Hg = ____
Amount
There are some common unit amounts
is measured in :
moles
________(mol),
particles, atoms, etc.
The variable n is used for # of moles
The conversion is:
6.02x1023
1 mol = ____________
(anything)
Volume
There are three common units volume
is measure in:
liters
milliliters
_________
(L), _____________
(mL),
cubic centimeters
______
_____________(cm3)
Conversion Factors
1,000 mL= _______
1,000 cm3
1 L= ______
Gas Constant, R
There are different ways of expressing
constant R in solving gas
the gas _________
problems. It only depends on the
units
_______
being used. As long as the
units match, the right value is being
used.
R = 8.31 L*kPa/(mol*K) = 0.0821 L*atm/(mol*K)
LOGIC with Volume/Pressure
increases then the
• If temperature __________,
volume will _________.
increase
increases then the pressure
• If volume __________,
decrease
will __________.
LOGIC with Pressure
increases
• If temperature __________, then the
increase
pressure will _________.
STP: Standard Temperature and Pressure,
T = 0 oC
P = 1 atm = 101.325 kPa = 760 Torr
Strategies in Problem Solving:
Gas Problems
Strategies in Problem Solving:
Gas Problems
Identify
known/
uknown
values
must
include
proper
units!!!
Conversions
use
LOGIC
(You can
do it!)
must
have unit
agreement
Calculator
multiply
across
top
divide
across
bottom
Poster Design
•
•
•
•
Choose 1 Gas Law
Name it and show the formula
Include 1 drawing
Describe what happens: “If temperature
increases…”
• 5 points
Warm-up (2-8-12/2-9-12)
Copy problems and answers into notebook:
1.
What do the following items measure?
a) P pressure
b) V volume
c) n Amount (in moles)
d) R Gas constant
e) T temperature
2.
Which temperature unit must be used in Gas Law calculations?
Kelvin
3.
How do you convert degrees Celsius to Kelvin?
Add 273 (to Celsius)
Benchmark Reflection
Warm-up (2-9-12/2-10-12)
Copy problems and answers into notebook:
1.
What happens to the volume if the pressure increases?
It decreases
2.
What happens to the pressure if the temperature decreases?
It decreases
3.
What happens to the temperature if the volume decreases?
It decreases
Describe #’s 1-3 as “Direct” or “Inverse” relationships.
1. inverse
2. direct
3. direct
5. List the units that apply to each of the following:
a) Pressure
b) volume
c) temperature
4.
atmospheres, kPa
liters
Kelvin
Warm-up (2-13-12/2-14-12)
Copy problems and answers into notebook:
1.
What is the standard temperature (see p. 300)?
I. 0 K
a) I only
II. 0 oC
b) II only
III. 273 K
c) III only
d) II and III
2. Which Centigrade (Celsius) temperature is the same as 298 K?
a) 250C
b) 2120C
c) 5210C
d) 5960C
3. The pressure exerted by a gas is due to
a) the chemical nature of the container;
b) the color of the gas;
c) the height of the container above sea level;
d) the diameter of the gas molecules;
e) the collisions of the gas molecules with the walls of the container.
e) 10580C
Pressure
• What is pressure created by?
The random collision of molecules and
their collisions with a surface. (Standard 4a)
Boyle’s Law
1. A gas has a volume of 12.5 L at 450. kPa
pressure. What pressure is needed to
change the volume of the gas to 6.25 L?
Boyle’s Law
2. A gas has a volume of 284 mL while at
101.325 kPa. What new volume will it
have if the new pressure is 25.3 kPa?
Boyle’s Law
3. An unknown pressure is maintained while
a gas has a volume of 468 mL. If it
expands to 702 mL while the gas has a
new pressure of 1.80 atm, what was the
original pressure?
Boyle’s Law
4. A gas at 203 kPa pressure and unknown
volume changes to 24.5 L while under the
new pressure of 305 kPa. What was the
original volume?
Boyle’s Law
4b. A gas at 502 kPa pressure and
unknown volume changes to 355 L while
under the new pressure of 1,500 kPa.
What was the original volume?
Charles's Law
5. A gas has a volume of 91 mL at a
temperature of 910C. This gas is kept at
constant pressure but its temperature is
reduced to 00C. What should the new
volume be? (remember to use Kelvin)
Charles's Law
6. Calculate the original temperature that 350. mL
of oxygen has, if it occupies 525 mL, while the
temperature is 301 K.
Charles's Law
7. Gas in a tire takes up 12.5 L of space at 22.0oC.
What new temperature in Kelvin should it have if
the new volume is 37.5 L?
Gay-Lussac’s Law
8. The air in a car has a pressure of 1.00 atm while
the car is at 20.0oC. If the air pressure does not
escape from the car, what new pressure would it
have if it heated to 352oC?
Gay-Lussac’s Law
9. The air in a sealed container has a pressure of
1.00 atm while at 32.0oC. What new temperature
would it have if the pressure went up to 3.00
atm?
Combined Gas Law
10. An air bubble occupies a space of 1.52 mL
while at a depth in the ocean where there is 2.50
atm of pressure and a temperature of 15.3 oC.
Find the volume of the bubble just before it
reaches the surface, with a pressure of 1.00
atm and a temperature of 25.0 oC.
Boyle’s Law
11. A scuba diver at 20.0 m experiences a pressure of 2.50
atm. The diver inflates her lungs to 1.8 L and holds her
breath as she heads to the surface her lungs are at a
constant temperature. What would the volume of her
lungs expand to as she breaks the surface where the
pressure is 1.00 atm?
Combined Gas Law
12. A balloon is inflated to 1.00 L at 1.00
atm, 27°C. The balloon rises to an altitude
of 10,000 meters where the temperature is
1590 K and the pressure is 0.500 atm.
What is the new volume of the balloon?
Combined Gas Law
13. A balloon is inflated to 3.25 L at 1.00
atm, with an unknown temperature. The
balloon rises to an altitude of 10,000
meters where the temperature is 1,380 K
and the pressure is 0.409 atm and a
volume of 13.5 L. What is the original
temperature of the balloon?
Clearing Fractions
Dalton’s Law
Dalton’s Law of Partial Pressures: at
constant volume and temperature, the
total pressure exerted by a mixture of
gases is equal to the sum of the partial
pressures of the component gases.
Ptotal = P1 + P2 + P3 + …
Practice
Determine the total pressure exerted by the
following gases: 23.4 kPa of oxygen, 14.8
kPa of nitrogen, and 28.3 kPa of carbon
dioxide.
Follow-up Assignment
• Chapter 14, Behavior of Gases
p. 439: 39-54, and 59 [Don’t write
questions, just answers.]

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