Chapter 3: Airbags

1
Chapter 3 Airbags
2
Introductory Activity

• What makes an effective airbag?
• List criteria necessary to consider an airbag
  effective.
• List characteristics that would be good in an
  airbag
• List characteristics that youd want to avoid in
  an airbag

3
Airbags

• This chapter will introduce the chemistry needed
  to understand how airbags work
• Section 3.1 States of matter
• Section 3.2 Properties of matter
• Section 3.3 Density
• Section 3.4 Changes in matter
• Section 3.5 Gas Behavior
• Section 3.6 Counting Molecules
• Section 3.7 Gas Laws

4
Airbags
Changes
States of Matter
Gas
Properties
Kinetic Molecular Theory
Density
Gas Laws
5
IntroAirbags
6
How do airbags work in your car?

• Nylon bag inside your steering wheel
• Solid sodium azide (NaN3) with is ignited with
  electricity when a crash sets off the trigger
• 2 NaN3 (s) ? 2 Na (s) 3 N2 (g)
• The nitrogen gas fills the airbag

7
Problems with this reaction?

• It produces sodium metal, which reacts with water
  to form hydrogen gas enough heat to ignite that
  hydrogen gas
• Reaction produces heat, so gas is very hot in
  airbag
• NaN3 is very toxic

8
Why do we use it?

• It produces the gas very quickly, but not so
  quick that its more of a hazard
• Reactants are small to store before needed
• Amount of dangerous chemicals is minimal
• Heat from reaction is absorbed, in part, by the
  physical components of the airbag system

9
Section 3.1States of Matter
10
Solid

• Closely packed together particles
• Vibrate in place
• Cant switch places
• Definite shape
• Definite volume

11
Liquid

• Particles more spread out than solid
• Particles are free to move past each other
• Slightly compressible
• Definite volume
• No definite shape take shape of container

12
Gas

• Particles very spread out
• Rapid, random motion
• Highly compressible
• No definite volumethey will fill container
• No definite shapetake shape of container

13
Changes in State
14
Temperature of state changes

• Freezing point melting point
• Boiling point condensation point

15
Whats between the particles?
?
Nothing! There is absolutely nothing between the
particles!
16
Section 3.2Properties of Matter
What properties are useful or not useful in an
airbag?
17
Physical versus Chemical Properties
Chemical Property
Physical Property
Can be observed or tested without changing the
atoms or molecules
In the process of observing or testing, the atoms
or molecules are changed into different
substance(s)
18
Intensive and Extensive Properties
Extensive Property
Intensive Property
Size of the sample doesnt matteryoud say a big
piece and a small piece were the same with
respect to this property
Size of the sample does mattera big piece and a
small piece would be different with respect to
this property
19
Lets Practice
Flammability Boiling point Solubility Malleability
Reactivity with oxygen
Example Are the following properties are
physical or chemical?
20
Lets Practice
Flammability Boiling point Solubility Malleability
Reactivity with oxygen
Chemical Physical Physical Physical Chemical
Example Are the following properties are
physical or chemical?
21
Lets Practice
Mass Volume Color Flammability Texture
Example Are the following properties are
intensive or extensive?
22
Lets Practice
Mass Volume Color Flammability Texture
Extensive Extensive Intensive Intensive Intensive
Example Are the following properties are
intensive or extensive?