Chapter 3: Airbags

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Chapter 3 Airbags
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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.

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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

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

• The Nylon bag is inside your steering wheel.
• Solid sodium azide (NaN3) 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.

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Problems with this reaction?

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

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Why do we use it?

• It produces the gas very quickly but not so
  quickly that its more of a hazard.
• Reactants are small for storage before they are
  needed.
• The amount of dangerous chemicals is minimal.
• Heat from the reaction is absorbed, in part, by
  the physical components of the airbag system.

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Section 3.1States of Matter
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Solid

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

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Liquid

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

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Gas

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

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Changes in State
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Temperature of state changes

• Freezing point melting point
• Boiling point condensation point

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Whats between the particles?
?
Nothing! There is absolutely nothing between the
particles!