Unit 4A

Gases in the Atmosphere

Do Now List the gases found in the atmosphere

and percentages.

Do Now Answers:

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.

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.

4.A.2 Graphing Atmospheric Data Suppose it were possible for you to fly

form Earth’s 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

Do Now What caused the can to be crushed in the

last lab?

Take out your lab.

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.

4.A.3 Properties of Gas Lab

Station A: Massing the balloon

Air molecule

.890 g .670 g

Deflated balloon

Inflated balloon

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.

Station BTried 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.

Station C

Beaker of Water

Cup/beaker

What we did: Lowered inverted glass into water…then tilted it.

Beaker of Water

Cup/beaker

Bubbles! Show us presence of gas

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.

Station D

Beaker of H2O

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.

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.

Station EWhat we did:

Filled bottle with two holes in it, with water. Put cap on tightly, removed finger from hole.

holesWhat 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.

Station FWhat 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 increases…if one decreases, the other decreases. Car tires?

4.A.4 Pressure Pressure:

Force applied to an area.

Pressure is directly proportionally to force. Pressure is inversely proportional to area.

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?

International System of Units (SI)

Base Unit: length, mass, etc.

Derived Unit: formed by mathematically combining base units Ex. Newton, Pascals

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

4.A.5. Applications of Pressure Turn to page 311 in your textbook, try #1-

3.

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)

Types of Barometers

Mercury Barometer

Barometer – measure atmospheric pressure

mmHg to measure pressure

Or inches of mercury

Mercury is 13.6x more dense than water. Water Barometer

Conversions Pressure:

1 atm = 760 mm Hg = 101.3 kPa

Homework Pg. 333 # 1-6, 7a &b, 8,

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+NJ+07045

Think – Pair - Share What are the three states of matter?

Briefly explain each.

http://www.harcourtschool.com/activity/states_of_matter/

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)

States of Matter

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/

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?

Kinetic Molecular Theory (KMT) 1. Gases particles are tiny!

Size is negligible compared to the distances between particles

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

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.

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

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.

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

Pressure-Volume Relationship

Boyle’s Law A gas at a constant temperature:

P X V = k

Pressure (P) Volume (V) Constant (k)

*** Handout***

4.A.9. Predicting Gas Behavior: Pressure – Volume Do pg. 319 #1-3