Chapter 3: Airbags

How Do Airbags Work?

How do airbags work in your car? A nylon bag is placed inside the 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.

Problems with this reaction? It produces sodium metal, which can reacts with water to form hydrogen gas. There is enough heat produced in a crash that the hydrogen gas could ignite. The sodium azide reaction produces heat, so the N2 gas is very hot in the airbag. NaN3 itself is very toxic.

Why do we use it? This reaction produces the gas very quickly, but not so quick to be a hazard to people. Reactants are small and easy to store before needed. The amount of sodium azide used is minimal. Much of the heat from the reaction is absorbed by the physical components of the airbag system – the insulated air bag or steering column, for example.

Section 3.1—States of Matter Objectives distinguish between states of matter explain the characteristics of different states of matter explain changes in states of matter

Solids Particles are closely packed together in a solid. They vibrate in place but cannot change position. Solids have a definite shape. Solids have a definite volume.

Liquids The particles are more spread out than in a solid. The particles are free to move past each other. Liquids can be compressed slightly. Liquids have a definite volume. They do not have a definite shape – they take the shape of their container.

Gases Gas particles are very far apart. They move rapidly in a random motion. Gases are highly compressible. Gases do not have a definite volume—they will spread out and fill their container. Gases do not have a definite shape—they take the shape of their container.

Changes in State Gas Increasing kinetic energy (temperature) Liquid Sublimation Boiling or Evaporating Liquid Melting Deposition Condensing Solid Freezing

Heating Curve

Temperature of state changes Heating Curves can be read from left to right AND from right to left. That means, Freezing point = melting point Boiling point = condensation point

Heating Curve

Heating Curve for Water