Chapter 3: Airbags. Introductory Activity What makes an effective airbag? List criteria necessary to...
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Transcript of Chapter 3: Airbags. Introductory Activity What makes an effective airbag? List criteria necessary to...
Introductory Activity
What makes an effective airbag?List criteria necessary to consider an
airbag effective. List characteristics that would be good in
an airbagList characteristics that you’d want to
avoid in an airbag
Airbags
This chapter will introduce the chemistry needed to understand how airbags workSection 3.1: States of matterSection 3.2: Properties of matterSection 3.3: DensitySection 3.4: Changes in matterSection 3.5: Gas BehaviorSection 3.6: Counting MoleculesSection 3.7: Gas Laws
Airbags
States of
Matter
States of
Matter
Use different
PropertiesProperties
ChangesChanges
Gas LawsGas LawsDensityDensity
Kinetic Molecular
Theory
Kinetic Molecular
Theory
With different
Work because of changes
One of which is
GasGas
Properties explained by
To produce
Explanation for
Which is a
How do airbags work in your car?
Nylon bag inside your steering wheelSolid 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
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
Why do we use it?
It produces the gas very quickly, but not so quick that it’s 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
Solid
Closely packed together particlesVibrate in placeCan’t switch placesDefinite shapeDefinite volume
Liquid
Particles more spread out than solidParticles are free to move past each otherSlightly compressibleDefinite volumeNo definite shape – take shape of container
Gas
Particles very spread outRapid, random motionHighly compressibleNo definite volume—they will fill containerNo definite shape—take shape of container
Solid
Liquid
GasSublimation
Melting
Boiling or Evaporating
Condensing
Freezing
Deposition
Incr
easi
ng m
olec
ular
mot
ion
(tem
pera
ture
)
Changes in State
Physical versus Chemical Properties
Chemical PropertyPhysical 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)
Intensive and Extensive Properties
Extensive PropertyIntensive Property
Size of the sample doesn’t matter—you’d say a big
piece and a small piece were the
same with respect to this property
Size of the sample does matter—a big piece and a small
piece would be different with
respect to this property
Let’s Practice
Example:Are the
following properties are
physical or chemical?
Flammability
Boiling point
Solubility
Malleability
Reactivity with oxygen
Let’s Practice
Chemical
Physical
Physical
Physical
Chemical
Flammability
Boiling point
Solubility
Malleability
Reactivity with oxygen
Example:Are the
following properties are
physical or chemical?
Let’s Practice
Example:Are the
following properties are intensive or extensive?
Mass
Volume
Color
Flammability
Texture