Expansion and ContractionREVIEW

Expansion and Contraction

• As the average energy of particles increases, the spaces between the particles increases. They expand (increase their volume) as the temperature increases. As the average energy of particles decreases, the spaces between the particles decreases. They contract (decrease their volume) as the temperature decreases.

Steel Bridges

• Have expansion joints.

Railroad Rails

Concrete roads

• Have expansion joints built in.

Sidewalks

• Sidewalks are built with expansion joints to try and avoid the cracking that may occur.

• Sometimes a sidewalk will develop a crack even with expansion joints. Do you know what happens to the size of the cracks in the winter and summer?

Cars

• Cars have engines with many working parts. The parts are engineered to be a little loose when cold so that when the engine becomes warm the parts do not expand to be to tight.

Post Quiz

1. Molecules are in constant motion.

True

False

Post Quiz

2. Molecules get farther apart because

a. Energy is added

b. Energy is taken away

c. Molecules can’t get farther apart

d. Molecules are taken away from the substance.

Insulators and Conductors

Objective: Describe insulators and conductors. Identify materials that are good insulators and conductors.

• Insulators are materials that do not allow heat to move easily through them.

What are Insulators?

Using your booklet, name materials that are insulators.

What do Insulators help do?

What are Conductors?

• Conductors are materials that allow heat to move easily through them.

Examples of Conductors

• Metal

• Glass

• Paper

Who’s Hungry???

To eat you must….• Decide which material I need to cook with.

Do I need to cook with an Insulator or a Conductor?

• Insulator- does not allow heat to travel through it easily.

• Conductor- does allow heat to travel through it easily.

And the Answer Is…

Conductor!!!