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Kinetic Theory and Gases. Kinetic Theory. Explains how temperature and pressure affect the motion of molecules. http://exploration.grc.nasa.gov/education/rocket/Images/state.gif. Hydraulics. http://library.thinkquest.org/C007574/media/brake1.gif.

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kinetic theory
Kinetic Theory

Explains how temperature and pressure affect the motion of molecules

http://exploration.grc.nasa.gov/education/rocket/Images/state.gif

hydraulics
Hydraulics

http://library.thinkquest.org/C007574/media/brake1.gif

http://csumc.wisc.edu/cmct/ParkStreetCT/locations/idealbodyshop/car.jpg

http://www.hydraulic-equipment-manufacturers.com/gifs/hydraulic-lift.jpg

ke kinetic energy
KE—Kinetic Energy

Energy of motion

Depends on:

  • Mass
  • Velocity
pe potential energy
PE—Potential Energy

Stored Energy

  • Gravitational Potential Energy

Energy due to height above earth

2) Chemical Potential Energy

Energy stored in bonds of batteries, food, gasoline, etc.

ideal gases
Ideal Gases

Particles are point masses—they have no volume

Particles have no mutual attraction to each other

Behavior of ideal gases is a model for how real gases behave

Ideal Gas calculations are simple and the results are close to those for real gases

three assumptions of kinetic theory
Three Assumptions of Kinetic Theory
  • All matter is made of particles

2) Particles are in constant motion

  • All collisions are perfectly elastic

(molecules do not lose energy in collisions)

oxygen gas
Oxygen Gas
  • At 25oC,

average speed = 443 m/s (1000 mph)

  • Between collisions, an oxygen molecule travels 314 times its diameter
  • There are 4.5 billion collisions each second
pressure
Pressure

Air Pressure:

the weight of air over an area

Standard Pressure:

average normal

air pressure at sea level

= 760 mmHg = 1 atm

= 14.7 lbs/in2 = 101.3 kPa

what causes gas pressure
What Causes Gas Pressure?

number and intensity of collisions

-- speed of particles (temperature)

-- concentration of particles

-- mass / size of particles

barometer

760mm

Barometer

Used to measure air pressure

The weight of a column of mercury is balanced by the weight of the air

http://umpgal.gsfc.nasa.gov/www_root/homepage/uars-science/UARS_brochure/JPEGs/barometer.jpg

evangelista torricelli
Evangelista Torricelli

http://www.forestry-suppliers.com/images/200/5491_w2.jpg

how is pressure related to altitude

chips

chips

chips

chips

http://www.met.utah.edu/jhorel/html/mesonet/lessons/pres_mtn.gif

http://www.visionlearning.com/library/modules/mid107/Image/VLObject-2362-031023021035.gif

How is Pressure related to Altitude?
boiling

Pvap

Pvap

P atm

P atm

P atm

Pvap

t = 0 min

t = 5 min

BOILING!

t = 1 min

Boiling

Pvap= Patm

boiling16
Boiling
  • The boiling point of water in Oregon is usually about ____________
  • Is Oregon above or below sea level?

(~974 feet above sea level)

Record High : 815 mmHg

Record Low: 656 mmHg

<100oC

try these
Try These

101.3

760

1 atm = ________ mmHg = ________ kPa

2.1 atm = _____mmHg 0.8 atm =_____mmHg

798 mmHg = _____atm 684 mmHg =_____atm

750 mmHg = _____kPa 790 mmHg =_____kPa

1596

608

1.05

0.9

105.3

99.97

demonstrations
Demonstrations

Crush the can

Vacuum pump (shaving cream, marshmallow, balloon)

Tube with cap

Flask with index card

Gas can

Air pressure – mat, glass square, well plate, soda suction

Mustard container

Balloon in Flask

Fire Syringe

Syringe/Martian Popping Thing

Bernoulli bag/ball in funnell

Hero’s Fountain

temperature

100 K

273 K

500 K

273 K

# of molecules

Kinetic Energy

Temperature

Average Kinetic Energy of particles in a substance (depends on the speed and mass of particles)

100 K

500 K

temperature scales
Temperature Scales

http://www.rain.org/~mkummel/stumpers/08oct99a.gif

Water Boils

Kelvin:

Absolute temperature scale

Cannot have a negative

Kelvin temperature

0 K = Absolute Zero

Water

Freezes

oC + 273 = K

practice problems
Practice Problems
  • Convert to Kelvin

23oC = _____ K

-11oC = _____ K

32 oF = _____ K

  • Convert to Celsius

315 K = _____ oC

277 K = _____ oC

212 oF = _____ oC

296

262

273

42

4

100

slide22
STP
  • Standard Temperature and Pressure

0oC

1 atm

diffusion
Diffusion
  • What is diffusion

The random movement of particles through a medium

5 factors that affect the diffusion rate of gases
5 Factors that Affect the Diffusion Rate of Gases
  • Mass of Particles

↑ mass, ↓ rate of diffusion

  • Concentration of Particles

↑ conc, ↑ rate of diffusion

  • Temperature

↑ temp, ↑ rate of diffusion

  • Air Pressure

↑ Pair, ↓ rate of diffusion

  • Presence of Another Gas

Another gas, ↓ rate of diffusion

compare the relative rate of diffusion of h 2 n 2

=

=

3.74

Compare the relative rate of diffusion of H2 & N2

=

H2 diffuses 3.74 times faster (further) than N2

lab 40

VNH3

36.5

VNH3

MHCl

=

=

17

MNH3

VHCl

VHCl

Lab 40

What is the relative rate of diffusion of NH3 to HCl?

1 m

NH3

HCl

NH3(g) + HCl (g)  NH4Cl (s)

= 1.5 times faster/further

boyle s law
The pressure of a gas is inversely proportional to its volume

(when temperature is constant)

P X V = k (constant)

P1 V1 = P2 V2

Initial Final

USE COMMON UNITS FOR P AND V!!!

(both atm, kPa; or both L, ml, cm3)

V

P

Boyle’s Law

Robert Boyle

1627-1691

try this

V1

P1

?V2

P2

Try This
  • You have 1000 ml of gas at 754 mmHg. Find the volume at standard pressure.

P1 V1 = P2 V2

(754 mmHg)(1000ml) = (760 mmHg)V2

760 mmHg 760 mmHg

V2 = 992.1 ml

dalton s law

Partial

Dalton’s Law

Total pressure = sum of partial pressures

Ptotal = dPgas 1 + dPgas 2 + dPgas 3 + …

Pair = dPN2 + dPO2 + dPH2O etc.

gases collected over water

Pair

Ptotal

Pressure of

“dry gas”

Air Pressure

Use Periodic Table

Gases collected over water

over water

Gases collected contain water vapor

H2O + O2

lower bottle until water levels are equal

Ptotal = dPH2O + dPgas

slide33

H2O Vapor

Gas

Pressure of

“dry gas”

From Periodic Table

750 mmHg

Ptotal

= PH2O + dPgas

Pair

vapor pressure chart on pt
Vapor Pressure Chart on PT

dPH2O changes with water temp

Ex: A sample of H2 is collected

at 25oC and the pressure is 775 mmHg. What is the pressure of the “dry gas”?

over water

example 2

V1

Pvap— Periodic Table

Ptotal

?V2

Example 2

80 ml of gas are collected

at 22oC. The air pressure was 758 mmHg. Find the volume of dry gas at standard pressure.

over water

P2

P1

charles law

=

KELVIN

Charles’ Law

The volume of a gas is directly proportional to the absolute temperature (Kelvin) if the pressure is held constant

V

T (K)

apparently oil tank rail cars are cleaned by scouring them with steam
Apparently, oil tank rail cars are cleaned by scouring them with steam.

Unfortunately, someone shut the hatch too soon...

try this 1
Try This #1

If you had 100 ml of a dry gas at 30oC, what volume would it occupy at 60oC?

V2 = 109.9 ml

try this 2
Try This #2

350 ml of gas at 0oC is compressed to 100 ml. What is the new temperature?

open vs closed containers
Open Container

Increase Temp?

# collisions?

Pressure?

Volume?

Closed Container

Increase Temp?

# collisions?

Pressure?

Volume?

Open vs Closed Containers
guess the gas law

V

8)

9) Ptotal = dPgas1 + dPgas2

10) Inverse Proportion

11) Direct Proportion

12)

13) “collected over water”

14) balloon in ice

15) compressed syringe

T

Guess the Gas Law
  • An eqn with V and T
  • An eqn with P and V
  • “find the pressure of the dry gas”
  • Uses vapor pressure of water
  • PV = k

P

V