Presentation on theme: "Chapter 3: Airbags. Introductory Activity What makes an effective airbag? List criteria necessary to consider an airbag effective. List characteristics."— Presentation transcript:
Chapter 3: Airbags
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 you’d want to avoid in an airbag
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
Airbags States of Matter Use different Properties Changes Gas Laws Density Kinetic Molecular Theory With different Work because of changes One of which is Gas Properties explained by To produce Explanation for Which is a
How do airbags work in your car? Nylon bag inside your steering wheel Solid sodium azide (NaN 3 ) with is ignited with electricity when a crash sets off the trigger 2 NaN 3 (s) 2 Na (s) + 3 N 2 (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 NaN 3 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
Section 3.1—States of Matter
Solid Closely packed together particles Vibrate in place Can’t switch places Definite shape Definite volume
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
Gas Particles very spread out Rapid, random motion Highly compressible No definite volume—they will fill container No definite shape—take shape of container
Solid Liquid Gas Sublimation Melting Boiling or Evaporating Condensing Freezing Deposition Increasing molecular motion (temperature) Changes in State
Temperature of state changes Freezing point = melting point Boiling point = condensation point
What’s between the particles? ? Nothing! There is absolutely nothing between the particles!
Section 3.2—Properties of Matter What properties are useful or not useful in an airbag?
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 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
Let’s Practice Extensive Intensive Mass Volume Color Flammability Texture Example: Are the following properties are intensive or extensive?