Unit 4A

1
Unit 4A

• Gases in the Atmosphere

2
Do Now

• List the gases found in the atmosphere and
  percentages.

3
Do Now Answers
4
4.A.1. Structure of the Atmosphere

• A. Atmosphere layer of gases that surround Earth
  
• 1. Troposphere closest to earth
• 2. Stratosphere
• 3. Mesosphere
• 4. Thermosphere outermost layer

Figure 4.1 Just how thin is the atmosphere that
surrounds us? Looking up from Earth, the skies
can seem endless.
5
B. Troposphere

• 1. Gases mix continuously
• 2. Components have not changed for thousand of
  years (except CO2)
• 3. Humidity Levels of H2O in the air
• Ranges form 1-5

Figure 4.2 Analysis of gases trapped in glacial
ice show the composition of the air has not
changed much since ancient times.
6
4.A.2 Graphing Atmospheric Data

• Suppose it were possible for you to fly form
  Earths surface up into the farthest regions of
  the atmosphere. What would you encounter as you
  traveled 5, 10 or 50km away from Earth?
• Turn to page 304
• Do problems 1-6

7
Do Now

• What caused the can to be crushed in the last
  lab?
• Take out your lab.

8
Answer Do Now

• When the can is put in the cold water upside
  down, the hot gas water molecule are very rapidly
  cooled. Some of the gas molecules are condensed
  back to the liquid water, so there are less gas
  molecules present.
• Cold water also cools the remaining gas
  molecules, which makes the molecules slow down,
  then there are fewer collisions with the walls of
  the can, which in turn causes less pressure
  inside of the can. The air pressure on the
  outside of the can is stronger. This causes the
  can to crush.

9
4.A.3 Properties of Gas Lab
10
Station A Massing the balloon
Air molecule
Inflated balloon
Deflated balloon
.890 g
.670 g
What did this station show?
Air has weight your balanced showed a difference
in mass meaning air has mass even though it is
invisible and we think of it as being weightless.
11
Station B
Tried to blow up a balloon in a bottle.
Balloon
arrows show pressure collisions against the
sides of bottle and the sides of the balloon.
What did this station show?
Air has pressure and exerts pressure on both
sides of the balloon. The balloon can be blown up
a little bit.gases can compress.
12
Station C
What we did Lowered inverted glass into
waterthen tilted it.
Bubbles! Show us presence of gas
Cup/beaker
Cup/beaker
Beaker of Water
Beaker of Water
What did this station show?
Air occupies space Since the water did not enter
the glass until tilted, air molecules take up
space (they are a part of matter)when the glass
is tilted, air escapes and rises showing that it
is less dense than water.
13
Station D
Test tube of water
What we did Filled test tube with water, put
plastic on opening, inverted, put in beaker, move
up and down keeping mouth of test tube immersed
in water.
Beaker of H2O
What happened
The water remained in the test tube regardless of
how high or low the test tube was.
What does this mean?
Air molecules are exerting an equal pressure on
the water in the beaker compared to the pressure
of the water caused by gravity.
14
Station E
What we did Filled bottle with two holes in it,
with water. Put cap on tightly, removed finger
from hole.
holes
What happened?
When both holes are unblocked, water flows
through one of them, when one of the holes is
blocked, the water stops coming out the other
hole.
What we learned
Air exerts pressure in all directions- the
external pressure of the atmosphere prevents
water from coming out.
15
Station F
What we did Two balloons of same size. Submerge
one into a cold water bath and the other into a
hot water bath. Take them out and compare.
What happened
Cold balloon- gets smaller, Warm balloon- gets
bigger
What this shows us
Temperature and volume are directly related. If
one increases the other increasesif one
decreases, the other decreases. Car tires?
16
4.A.4 Pressure

• Pressure
• Force applied to an area.
• Pressure is directly proportionally to force.
• Pressure is inversely proportional to area.

17
Something to think about.

• If someone were to accidentally step on your
  foot, which shoes would you prefer the person
  wore?
• Explain your choice in terms of the concept of
  pressure.
• How about a high heel?

18
International System of Units (SI)

• Base Unit length, mass, etc.
• Derived Unit formed by mathematically combining
  base units
• Ex. Newton, Pascals

19
SI Units Cont.

• Force Newton (kg m/s2) N
• Area m2
• Pressure Pascal (N/m2) Pa

1 Newton downward force holding a bar of
soap 1 Pascal downward pressure of butter on
a slice of bread
20
4.A.5. Applications of Pressure

• Turn to page 311 in your textbook, try 1-3.

21
4.A.6. Atmospheric Pressure

• A typical day at sea level, the force is 100,000
  N per square meter
• 100,000 N/m2 100,000 Pa 100kPa
• 1 atm
• Earth pressure at sea level 1 atmosphere (atm)
  14.7 lb/in2 29.9 in Hg 76 cm 760 mm
  101.3 kilopascals (kPa)

22
Types of Barometers
Mercury Barometer
23
Barometer measure atmospheric pressure

• mmHg to measure pressure
• Or inches of mercury

Water Barometer
Mercury is 13.6x more dense than water.
24
Conversions

• Pressure
• 1 atm 760 mm Hg 101.3 kPa

25
Homework

• Pg. 333 1-6, 7a b, 8,

26
Do Now

• Take out your homework.
• If you had 100 Pa of pressure over a 2.5m by .25m
  area, how much force must have been applied?
• http//www.weather.com/weather/right-now/Montville
  NJ07045

27
Think Pair - Share

• What are the three states of matter?
• Briefly explain each.
• http//www.harcourtschool.com/activity/states_of_m
  atter/

28
4.A.7. Atoms Molecules in Motion

• A. States of Matter
• i. Solids definite shape, definite volume,
  rigid, particles close together (vibrate)
• ii. Liquids- no definite shape, definite volume,
  flows, particles close, but can move past each
  other
• iii. Gases- no definite shape, no definite
  volume, weak intermolecular forces between
  particles (let them move far apart from each
  other)

29
States of Matter
30
Motion of Gas Particles

• 1. move in a straight line
• 2. change direction only after a collision
• 3. speed depends on kinetic energy (depends on
  the mass and velocity)
• http//www.falstad.com/gas/

31
Kinetic Energy of molecules

• Remember Kinetic Energy is energy of motion
• Kinetic energy depends on mass and velocity
  (speed)
• 1. Which has greater kinetic energy a pingpong
  ball or softball traveling at the same speed?
• 2. Why does a car do less damage when it taps the
  wall of the parking garage rather than hitting
  another parked car at 50 mph?

32
Kinetic Molecular Theory (KMT)

• 1. Gases particles are tiny!
• Size is negligible compared to the distances
  between particles

33
Kinetic Molecular Theory (KMT)

• 2. Particles are in constant, random motion
• Collide with each other, objects, and the
  container
• Gas pressure is caused by these collisions

34
Kinetic Molecular Theory (KMT)

• 3. Collisions are elastic
• Although individual gas particles may gain or
  lose kinetic energy, there is no gain or loss of
  TOTAL kinetic energy from the collisions.

35
Kinetic Molecular Theory (KMT)

• 4. Average kinetic energy of the molecules is
  constant and depends on temperature
• Individual particles may range
• Different gases at the same temperature have the
  EQUAL average kinetic energy
• As gas temperature increases, the average
  velocity and kinetic energy increases

36
4.A.8 Pressure-Volume Behavior of Gases

• Gas can be compressed more easily than liquid
• The more pressure applied to a gas, the less
  volume it will occupy.

37

• If the volume was reduced in half, then the
  pressure would be double.
• If the volume was reduced to ¼ than the pressure
  would be 4 times greater.
• Inverse Relationship

38
Pressure-Volume Relationship
39
Boyles Law

• A gas at a constant temperature
• P X V k
• Pressure (P)
• Volume (V)
• Constant (k)
• Handout

40
4.A.9. Predicting Gas Behavior

• Pressure Volume
• Do pg. 319 1-3