Download Find your NEW seats Bellringer: Please complete Ms - Parkway C-2

FIRST- Find your NEW seats
Bellringer:
Grab a chemistry textbook and read
pages 390-395, take 10 bullet notes
HW Due:
Any old homework or labs not turned in before spring break
Agenda Day 8
- Bellringer
(extension of gas law unit)
- Gas Law Unit Tests back
- Notes & Demos on Dalton’s Law &
section 13.2 in textbook
- Prepare for lab next class
HW for next class:
1. Read pages 390-395, take 10 bullet notes and complete
problems 8, 11, 12, 13, & 14
AND
2. With your new lab partner write (or type) up a 1-page
proposal for your “ten-minute lab” to be performed next week
on energy
What questions do you
have from the Gas Law
Unit Test?
Going back to Dalton’s
Law of Partial Pressures
• Remember:
o Ptot = P1 + P2 + P3 + … Pn
o Where n is the total number of gases in the
mixture.
• So what about your objective that states: “How
Dalton’s Law of Partial Pressures applies to gases
collected over water”?
• What does that mean and how is it useful?
• http://www.kentchemistry.com/links/GasLaws/dalton.
htm
Collecting gases over
water
• While helpful there is the unavoidable problem. The gas
saturates with water vapor and now the total pressure
inside the bottle is the sum of two pressures - the gas
itself and the added water vapor.
• WE DO NOT WANT THE WATER VAPOR PRESSURE.
• So we get rid of it by subtraction.
• Pdry gas = Ptotal - Pwater vapor
Pressure of Water Vapor
• This means we must get
the water vapor pressure
from somewhere.
• We get it from a table
because the water vapor
pressure depends only on
the temperature, NOT
how big the container is
or the pressure of the
other gas.
Temp
(oC)
Vapor Pressure Temp
(mmHg)
(oC)
Vapor
Pressure
(mmHg)
-10
2.15
40
55.3
0
4.58
60
149.4
5
6.54
80
355.1
10
9.21
95
634
11
9.84
96
658
12
10.52
97
682
13
11.23
98
707
14
11.99
99
733
15
12.79
100
760
20
17.54
101
788
25
23.76
110
1074.6
30
31.8
120
1489
37
47.07
200
11659
Dalton’s Law of Partial
Pressures as it relates to
collecting a gas over water
directly relates to the lab we
are going to complete next class
Practice Problem
(Remember these problems often times involve the ideal gas law equation
as well)
• A.) If 5.00 X 10-4 moles of Hydrogen gas is formed by
bubbling it up through water, it occupies a volume of
42.35 mL at 22.0 oC. Using the moles of hydrogen
determine the pressure of the dry Hydrogen gas
• B.) What is the total pressure including the water
vapor?
Section 13.2 in text
“A Model for Liquids”
• This section discusses
o Evaporation
o Vapor Pressure
o Boiling Point
• What do any of those terms mean to you?
Evaporation
• Liquids may change to a vapor at temperatures below their
boiling points through the process of evaporation.
Evaporation is a surface phenomenon in which molecules
located near the liquid's edge, escape into the
surroundings as vapor (a gas). On the other hand, boiling is
a process in which molecules anywhere in the liquid escape,
resulting in the formation of vapor bubbles within the
liquid.
• During evaporation, only those molecules with a certain
minimum K.E. can escape from the surface of the liquid and
become a gas.
• How would you predict that process of evaporation to
change when you heat a liquid?
Vapor Pressure
• Definition: is the amount of gas/vapor pressure above a
liquid in a closed system.
• Over time, the number of particles entering the vapor
phase (liquid to gas) increases and some of the particles
condense (gas to liquid) and return to the liquid state.
• Eventually, the number of particles condensing will equal
(=) the number of particles vaporizing.
• Predict: How will vapor pressure change if you increase the
temperature of a closed system (i.e. you increase K.E.)?
Trying to put it all
together
• Boiling points at various altitudes
http://www.youtube.com/watch?v=dx4XOYpj1_k
• Boiling water at room temperature
http://www.youtube.com/watch?feature=player_embed
ded&v=QGSo7zcg_qA#!
So then, what’s Boiling Point?
• When a liquid is heated to a temperature at which
particles throughout the liquid have enough kinetic
energy to vaporize, the liquid begins to boil…but how
will we know what temperature that is?
• A liquid boils when its vapor pressure is equal (=) to
the external pressure
• The normal boiling point is defined as the boiling point
of a liquid at atmospheric (standard) pressure: 1 atm
or 101.3 kPa or 760 torr or 760 mmHg or 14.7 psi
End of: Application of
Dalton’s Law of Partial
Pressures &
Section 13.2 in Textbook
HW for next class:
1. Read pgs 390-395, take 10 bullet notes and complete problems 8,
11, 12, 13, & 14
AND
2. With your new lab partner write (or type) up a 1-page proposal for
your “ten-minute lab” to be performed next week on energy