2 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
3 AirbagsThis 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
4 Kinetic Molecular Theory AirbagsUse differentWork because of changesChangesStates of MatterTo produceWhich is aGasWith differentPropertiesProperties explained byOne of which isKinetic Molecular TheoryDensityGas LawsExplanation for
6 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 trigger2 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 gasReaction produces heat, so gas is very hot in airbagNaN3 is very toxic
8 Why do we use it?It produces the gas very quickly, but not so quick that it’s more of a hazardReactants are small to store before neededAmount of dangerous chemicals is minimalHeat from reaction is absorbed, in part, by the physical components of the airbag system
10 Solid Closely packed together particles Vibrate in place Can’t switch placesDefinite shapeDefinite volume
11 Liquid Particles more spread out than solid Particles are free to move past each otherSlightly compressibleDefinite volumeNo definite shape – take shape of container
12 Gas Particles very spread out Rapid, random motion Highly compressible No definite volume—they will fill containerNo definite shape—take shape of container
13 Changes in State Gas Increasing molecular motion (temperature) Liquid SublimationBoiling orEvaporatingLiquidMeltingDepositionCondensingSolidFreezing
14 Temperature of state changes Freezing point = melting pointBoiling point = condensation point
15 What’s between the particles? Nothing! There is absolutely nothing between the particles!
16 Section 3.2—Properties of Matter What properties are useful or not useful in an airbag?
17 Physical versus Chemical Properties Physical PropertyChemical PropertyCan be observed or tested without changing the atoms or moleculesIn the process of observing or testing, the atoms or molecules are changed into different substance(s)
18 Intensive and Extensive Properties Intensive PropertyExtensive PropertySize of the sample doesn’t matter—you’d say a big piece and a small piece were the same with respect to this propertySize of the sample does matter—a big piece and a small piece would be different with respect to this property
19 Are the following properties are physical or chemical? Let’s PracticeFlammabilityBoiling pointSolubilityMalleabilityReactivity with oxygenExample:Are the following properties are physical or chemical?
20 Are the following properties are physical or chemical? Let’s PracticeFlammabilityBoiling pointSolubilityMalleabilityReactivity with oxygenChemicalPhysicalExample:Are the following properties are physical or chemical?
21 Are the following properties are intensive or extensive? Let’s PracticeMassVolumeColorFlammabilityTextureExample:Are the following properties are intensive or extensive?
22 Are the following properties are intensive or extensive? Let’s PracticeMassVolumeColorFlammabilityTextureExtensiveIntensiveExample:Are the following properties are intensive or extensive?