2Introductory 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
3AirbagsThis 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
4Kinetic Molecular Theory AirbagsUse differentWork because of changesChangesStates of MatterTo produceWhich is aGasWith differentPropertiesProperties explained byOne of which isKinetic Molecular TheoryDensityGas LawsExplanation for
6How 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
7Problems 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
8Why 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
10Solid Closely packed together particles Vibrate in place Can’t switch placesDefinite shapeDefinite volume
11Liquid Particles more spread out than solid Particles are free to move past each otherSlightly compressibleDefinite volumeNo definite shape – take shape of container
12Gas Particles very spread out Rapid, random motion Highly compressible No definite volume—they will fill containerNo definite shape—take shape of container
13Changes in State Gas Increasing molecular motion (temperature) Liquid SublimationBoiling orEvaporatingLiquidMeltingDepositionCondensingSolidFreezing
14Temperature of state changes Freezing point = melting pointBoiling point = condensation point
15What’s between the particles? Nothing! There is absolutely nothing between the particles!
16Section 3.2—Properties of Matter What properties are useful or not useful in an airbag?
17Physical 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)
18Intensive 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
19Are the following properties are physical or chemical? Let’s PracticeFlammabilityBoiling pointSolubilityMalleabilityReactivity with oxygenExample:Are the following properties are physical or chemical?
20Are the following properties are physical or chemical? Let’s PracticeFlammabilityBoiling pointSolubilityMalleabilityReactivity with oxygenChemicalPhysicalExample:Are the following properties are physical or chemical?
21Are the following properties are intensive or extensive? Let’s PracticeMassVolumeColorFlammabilityTextureExample:Are the following properties are intensive or extensive?
22Are the following properties are intensive or extensive? Let’s PracticeMassVolumeColorFlammabilityTextureExtensiveIntensiveExample:Are the following properties are intensive or extensive?