1. …it’s a gas!
Air

2. What do you know about gases?
Have mass and take up space (matter)
Have faster moving molecules than
solids & liquids
Expand to fill the container they're in
Molecules spaced far apart (no bonds)
No fixed volume or shape.
Can be compressed
 molecules can be smooshed together

3. What are Gases Made of?
Argon Atom
Ar Oxygen Molecules
H2O
O2
18P
22N

4. Temperature
SI Temperature
Fahrenheit
Celsius
Kelvin
A thermometer measures the
speed at which the molecules
of a substance are moving
Thermometer Reading Practice
F shows 2 degrees per line
C shows 1 degree per line

5. Evaporation Lab
What substance is the thermometer reading right
now?
Read all directions on your Data Sheet
Write out a hypothesis
Perform the experiment
Write a conclusion

6. Changing States takes Energy
How does sweat cool down your body?
Heat is absorbed by water molecules to excite them to the point
they can break free and become a gas (water vapor)
The particles
move faster
and slide
past each
other.
The particles
are close
together and
vibrate in a
fixed position.
The particles are
far apart and
move very quickly
and randomly.
evaporatingmelting

7. How Heat Affects Molecules
Heat = energy that is being transferred

8. Evaporation Lab
Evaporation [liquid  gas] takes energy (heat)
energy always travels from hot to cold
 from high energy to low energy
when the liquid evaporates, it absorbs some energy
from the air molecules and thermometer bulb
molecules that are touching it
the alcohol in the thermometer contracts as it cools,
lowering the temperature reading
Temperature measures the speed at which the
molecules of a substance are moving

9. Molecules move faster when heated
Molecules move farther apart when heated
When trapped in a container, heated molecules will
collide more with the sides of the container and with
each other, increasing the pressure inside
Balloon & Bottle Experiment

11. Equilibrium
Balance between opposing forces
When two substances of different temperatures come
into contact, heat flows from high to low until a
middle temperature is reached

12. Composition of Earth’s Air
78% Nitrogen
N2 molecules
21% Oxygen
O2 molecules
.04 % Carbon Dioxide
CO2 molecules
.9% Argon
Ar atoms
Water Vapor
Dust, pollen, pollutants

13. Are the amounts important?
78% Nitrogen
Inert (chemically unreactive)
21 % Oxygen
Produced by plants
Essential for animal life
 O2 required for combustion (burning)
 forest fires, engines & cellular respiration
 Higher concentrations in the atmosphere would result in
accelerated combustion rates (brighter, hotter, faster burning)
 more forest fires from lightning
 increased cellular processes (metabolic rates, blood pressure, etc.)
 Lower concentrations would soon asphyxiate all animal life

14. .9% Argon
Inert (chemically unreactive)
.04% Carbon Dioxide
Created by combustion
 forest fires burning, factories, car engines, animals breathing
Essential for plant life
Provides warmth (Greenhouse gas)
 CO2 prevents radiation of infrared light (traps heat)
Too much in atmosphere could cause overheating (global
warming)
Too little in atmosphere would strangle/kill all the plant life

15. Density
Measures the amount of matter within a specific
volume
total mass of atoms occupying a particular space
how close together the atoms are packed
SI base units = g/cm3
or g/ml

16. Pressure
the force of one object pushing on another
Pop can experiment
Candle in jar with water
Ping pong ball bottle
Cartesian Diver
pressure = force
area

17. Pressure
Atmospheric pressure

18. Measuring Atmospheric Pressure
Barometer
inches of mercury
SI unit pascal = N/m2

20. Humidity
A measurement of moisture
(water vapor) content of air
Water vapor is water in it's
gaseous form - it's still H2O
Water molecules mix with
other gasses in the atmosphere
 They fit in between the other gas
molecules in the air
At higher temperatures, the air
can hold more water
 Why? (more space, faster
molecules)

21. Relative Humidity
The amount of moisture in the air compared to what
the air can "hold" at that temperature.
Displayed as a percent:

22. Dew Point
When the air can't "hold" all the moisture it currently
has, then it condenses as dew.
Usually happens as air containing water vapor cools.