Lesson 12.1

Gases

Density

• density pepsi vs diet pepsi 3.5 min

• volume of a marble

• density animation

What are the main physical properties of gases?

• Gases assume the volume and shape of the container.

• Gases are most compressible of states of matter.

• Gases will mix evenly and completely when confined to same container.

• Gases have much lower densities than liquids and solids.

List the Gases

Periodic Table in back of textbook

Why diatomic?

Noble Gases

• Single atoms

• Complete outer valance shell

• Octet rule is satisfied

Kinetic Molecular Theory

• Gases have similar physical properties

• Little variation in behavior

• Kinetic = Greek word “to move”

Particles in motion

• Particles are small– Lots of empty space– No significant attraction or repulsion forces

• Constant random motion

Kinetic Energy = ½ mv2

• Molecules travel in a straight line

• Hit a wall or another molecule then Energy is transferred – no energy is lost

• m is mass

• v is velocity (speed and direction)

Compression and Expansion

Diffusion and Effusion

• Diffusion – smell cooking throughout the house

• Effusion – gas escapes from a small hole

different rates depends on size

• Smaller particles travel faster

Diffusion Ratio

NH3 or HCl

Back to molar mass!

NH3 36.5 g/mol and HCl 17.0 g/mol

molarmassB

molarmassA

RateB

RateA

47.10.17

5.36

HCl

NH3

Find Diffusion Ratio

N2 and Ne CO and CO2

1light

heavy

18.12.20

0.28

Ne

N2

1heavy

light

798.044

28

CO

CO

2

Pressure

Think about it

Walk on deep snow with boots, snow shoes, skis.

Which sink the most? Why?

Pressure = force / unit of area

The pressure in car or bicycle tires is measured in pounds per square inches.

Car tires

26-30 lb/sq.in.

Bicycle tires

40-60/sq.in.

Who will wear out the carpet first?

125 lbs woman wearing high heels?

Or, same woman wearing flats? Why?

Barometer or Manometer

• Instruments that measure pressure

Units of Measure

29.92

1.0

101.325

1013.25

Dalton’s Law Partial Pressure

Ptotal = P1 + P2 + P3 + . . . + Pn

O2 + CO2 + N2

PCO2 = 0.70 PN2

= 0.12 Ptotal = 0.97 atm

Find PO2 = 0.97 – 0.70 – 0.12 = 0.15 atm

Textbook page 409 # 4,5,6

p. 409 # 4,5,6

4. PH2 = 161 mmHg

5. Ptotal = 13.78 kPa

6. PCO2 = 10.2 kPa

Explain how a person can break a board, like in Karate?