1. Chapter 13
States of Matter

2. Section 13.1: Nature of Gases
Kinetic Theory and a Model for Gases
Kinetic Energy: Energy that an object has because of its motion
Kinetic Theory: All matter consists of tiny particles that are in constant motion
Particles in a gas are usually atoms/molecules.
There are three fundamentals to the kinetic theory applying to gases which we will review one by one.

3. Kinetic Theory: Fundamental # 1
Particles in a gas are considered to be small, hard spheres w/ insignificant volume.
- a lot of empty space between particles
- no attractive/repulsive forces b/w
particles
- Motion of 1 particle is independent
from the motion of other particles
CORRECTION: There are attractive/repulsive forces that exist between particles in a gas. Otherwise there would be no phase changes and gases could not flow.

4. Kinetic Theory: Fundamental #2
Motion of particles in a gas is rapid, constant and random
- a gas will fill the shape of any container
- uncontained gas spreads out with no limit
- gas particles will travel in a straight path until they collide with something else
Why would individuals in Mexico not be able to smell pizza from a shop in Washington D.C? (Oxygen molecules can travel 1700 km/h at 20 degrees Celsius)

5. Kinetic Theory: Fundamental # 3
All Collisions between particles in a gas are perfectly elastic
Elastic Collision
-Total kinetic energy remains constant between 2 molecules.
-No K.E. is lost, only transferred
Example:
Observe and record how Newton’s cradle works.

6. Gas Pressure
Gas Pressure: result of simultaneous collisions of billions of rapidly moving particles in a gas with an object.
In a vacuum, there is no pressure. Why?
Demonstration: Marshmallow peep in a vacuum

7. Layers of the Atmosphere

8. Components of Dry Troposphere Air
Substance
Formula
Percent of All Gas Molecules
Major Components
Nitrogen and Oxygen N2 O2
78%
21%
Minor Components
Argon
Carbon Dioxide Ar
CO2
.93%
.033%
Trace Amounts Ne
NH3 He
CH4
.0018%
.0010%
.0005%
.0002%

9. Atmospheric Pressure What is atmospheric pressure?
Results from the collisions of atoms and molecules in air with objects
Air exerts pressure on earth b/c gravity holds particles in the atmosphere.
As you climb higher up a
mountain, does atmospheric
pressure increase or
decrease? Why?

10. Atmospheric Pressure
How much pressure are you under? Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch). The force on 1,000 square centimeters (a little larger than a square foot) is about a ton!
Why doesn't all that pressure squash me?
Remember that you have air inside your body too, that air balances out the pressure outside so you stay nice and firm and not squishy.

11. Atmospheric Pressure
Why do my ears pop?
. As the number of molecules of air around you decreases, the air pressure decreases. This causes your ears to pop in order to balance the pressure between the outside and inside of your ear.
Why do athletes and trainers often recommend high altitude training as a means to increase exercise endurance?
At higher altitudes, less oxygen results in the heart working harder.

12. Measuring Pressure Barometer: used to measure atmospheric pressure
The SI units of pressure is Pascal (Pa)
other units: Millimeters of Mercury (mm Hg)
atmospheres (atm
1 atm = 760 mm Hg = kPa
Old Mercury Barometer Is Shown to the Left.
Low pressure = Bad Weather
FF High pressure = Good Weather
High pressure generally relates to "nicer" weather, while low pressure often relates to bad weather. This is because these pressure systems have their own general characteristics. One characteristic I like to use while observing weather conditions such as pressure and making forcasts is the rotational direction of these pressure systems. For example, low pressure systems rotate counterclockwise in the northern hemisphere, while high pressure systems rotate clockwise. With low pressure systems, counterclockwise rotation causes converging winds. This means that the winds are coming together. Where are they coming from? Pressure moves from high pressure systems to low pressure systems. Therefore, moving air causes wind. When this air converges (as in a low pressure, counterclockwise system), due to its rotation, the air gets forced downward. In general, when this air is forced to the ground and has nowhere to go, it pushes out and back up around the center of the low pressure system. This upward movement of air causes instability in the atmosphere, which equals clouds, especially when the air being drawn in (converging air) has a different temperature than the air that it is replacing. Warm air below cooler air equals instability and rising thermals (rising hot air). There are many variables left out in this simple explaination, but in general it quickly answers the question. High pressure systems diverge air and therefore are the opposite. One has to remember, however, that these systems can interact in very complicated and unpredictable ways.

13. Converting between Units of Pressure
STP = ( 101.3kPa or 1 atm) Example 1) A pressure gauge records a pressure of 450 kPa. What is the measurement expressed in atmospheres and millimeters of mercury?

14. Outer Space HW: Consider the following…
What would happen if you were in outer space without a space suit?
-Think about…
-atmospheric pressure
-temperature
-gravity

15. Kinetic Energy and Temperature
What’s the difference between Heat and Temperature?
Heat = Energy
Temperature = measurement of heat
When a substance is heated, its particles absorb energy- some is stored as P.E.
The rest of the energy speeds up the particles and increases K.E.
The faster the particles move, the higher the temperature!

16. Average Kinetic Energy
At a given temperature, the kinetic energy for different types of atoms/molecules is averaged. Kelvin temperature is directly proportional to avg K.E of particles in a substance. Ex) Helium gas. 200 K K.E. = 2x 100 K K.E. = x

17. Kinetic Theory
Is it possible for particles to have absolutely no motion?
Absolute Zero is the temperature at which the motion of particles theoretically ceases. ( degrees C)
Absolute Zero has never been produced in a laboratory

18. Section 13.2 The Nature of Liquids
Liquids, like gases
can fill the shape of a container because liquid particles have K.E.
Can flow
Unlike gases, particles in a liquid are
held together by stronger intermolecular forces.
Closer together and more dense

19. Evaporation Vaporization: conversion of a liquid to a gas/vapor
When such a conversion occurs at the surface of a liquid that is not boiling, the process is called evaporation
During evaporation…
-only molecules with enough KE can overcome the intermolecular forces between the molecules and escape from the surface of a liquid

20. When a liquid is heated…
heat adds KE to particles
added energy allows particles to overcome intermolecular forces
Molecules with highest KE escape liquid
Remaining molecules have lower KE
What happens to the temperature of your body when you sweat?
As evaporation occurs, temp decreases
Evaporation is a cooling process

21. Vapor Pressure
Vapor refers to a gas phase at a temperature where the same substance can also exist in the liquid or solid state
Vapor Pressure: is a measure of the force exerted by a gas above a liquid

22. Vapor Pressure + Temp Change
Increased Temp of contained Liquid = Increased Vapor Pressure
When temp increases, more particles vaporize and create greater pressure from colliding with each other and the container.
Manometer: measures the vapor pressure of a liquid
You determine the vapor pressure in mm Hg by measuring the difference between the two levels of mercury.