Expansion and Expansion and ContractionContraction

Expansion and ContractionExpansion and Contraction

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

Expansion and Contraction in Expansion and Contraction in SolidsSolids

SolidsSolids can become longer or shorter can become longer or shorter depending on the temperature depending on the temperature (average energy of the particles).(average energy of the particles).

Expansion and Contraction in Expansion and Contraction in LiquidsLiquids

When the particles in a When the particles in a liquidliquid are are heated, their average energy heated, their average energy increases and they need more increases and they need more room, so they expand.room, so they expand.When the particles in a lWhen the particles in a liquidiquid are are cooled, the volume decreases, or cooled, the volume decreases, or contracts, because the particles contracts, because the particles need less room.need less room.This is demonstrated by the This is demonstrated by the liquidliquid used in a thermometer. As the used in a thermometer. As the liquidliquid expands and contracts, it expands and contracts, it moves up and down the inside moves up and down the inside tubing ( the tubing ( the bore bore ) of the ) of the thermometer.thermometer.

Expansion and Contraction in Expansion and Contraction in GasesGases

When the particles in a gas are When the particles in a gas are heated, their average energy heated, their average energy increases and they need more room, increases and they need more room, so they expand.so they expand.

When the particles in a gas are When the particles in a gas are cooled, the volume decreases, or cooled, the volume decreases, or contracts, because the particles need contracts, because the particles need less room.less room.

Under extremely high temperature Under extremely high temperature conditions (like the temperatures conditions (like the temperatures inside the Sun, particles can be split inside the Sun, particles can be split into what makes them up (electrons into what makes them up (electrons and ions). This creates a fourth state and ions). This creates a fourth state of matter called of matter called plasmaplasma..

Pre QuizPre Quiz If you were to carefully measure the width If you were to carefully measure the width

of cracks in the sidewalk at many different of cracks in the sidewalk at many different times during a two-year period, which times during a two-year period, which would you expect to find?would you expect to find?a. The cracks would remain the same size a. The cracks would remain the same size throughout the time.throughout the time.b. The cracks would be wider during b. The cracks would be wider during winter than during the summer.winter than during the summer.c. The cracks would be wider during the c. The cracks would be wider during the summer than during the winter.summer than during the winter.d. The cracks would continue to widen as d. The cracks would continue to widen as time passes.time passes.

Pre QuizPre Quiz A railroad track was built with all of the rails A railroad track was built with all of the rails

fitting tightly together, touching each other end-fitting tightly together, touching each other end-to-end. Six months later, the track was ruined to-end. Six months later, the track was ruined when the rails expanded and buckled. What may when the rails expanded and buckled. What may have caused the rails to expand?have caused the rails to expand?a. As the weather got warmer, the particles in a. As the weather got warmer, the particles in the rails moved more slowly.the rails moved more slowly.b. As the weather got colder, the particles in the b. As the weather got colder, the particles in the rails moved more slowly.rails moved more slowly.c. As the weather got warmer, the particles in c. As the weather got warmer, the particles in the rails moved faster.the rails moved faster.d. As the weather got colder, the iron in the rails d. As the weather got colder, the iron in the rails froze.froze.

Pre QuizPre Quiz

One of the best ways to weaken the One of the best ways to weaken the bonds holding particles together is bybonds holding particles together is by

a. heat a. heat

b. grindingb. grinding

c. movement c. movement

d. pressured. pressure

Pre QuizPre Quiz A metal lid was very tightly screwed onto a glass A metal lid was very tightly screwed onto a glass

jar. To get the jar open, Kelly held the lid under jar. To get the jar open, Kelly held the lid under hot water. Why was Kelly able to remove the lid?hot water. Why was Kelly able to remove the lid?a. Metal particles move more rapidly when a. Metal particles move more rapidly when heated so the particles moved further apart, and heated so the particles moved further apart, and the lid became looser.the lid became looser.b. Metal particles move less rapidly when heated b. Metal particles move less rapidly when heated so the particles moved closer together, and the so the particles moved closer together, and the lid became looser.lid became looser.c. The metal particles did not move. The water c. The metal particles did not move. The water loosened the lid.loosened the lid.d. The metal particles melted because the water d. The metal particles melted because the water was so hot.was so hot.

Pre QuizPre Quiz The teacher heats the steel ball over a Bunsen The teacher heats the steel ball over a Bunsen

burner and then tries to put the steel ball through burner and then tries to put the steel ball through a ring that it fit through when it was cold. Based a ring that it fit through when it was cold. Based on what you know about the relationship between on what you know about the relationship between temperature and motion of particles, choose the temperature and motion of particles, choose the best explanation for this experiment.best explanation for this experiment.a. The steel ball will fit because it was heated, a. The steel ball will fit because it was heated, causing the molecules to contract.causing the molecules to contract.b. The steel ball will not fit because it was b. The steel ball will not fit because it was heated, causing the molecules to expand.heated, causing the molecules to expand.c. The steel ball will fit because it was cooled, c. The steel ball will fit because it was cooled, causing molecules to expand.causing molecules to expand.d. The steel ball will not fit because it was d. The steel ball will not fit because it was cooled, causing the molecules to contract.cooled, causing the molecules to contract.

Pre QuizPre Quiz

The Golden Gate Bridge is a The Golden Gate Bridge is a suspension bridge constructed with suspension bridge constructed with steel and concrete. Measurements steel and concrete. Measurements are taken daily on various joints are taken daily on various joints along the surface of the bridge. At 7 along the surface of the bridge. At 7 a.m., joint 1 has a measurement a.m., joint 1 has a measurement reading of 13 cm. At 3 p.m., the reading of 13 cm. At 3 p.m., the same joint has a reading of 6 cm. same joint has a reading of 6 cm. Give a reasonable explanation to Give a reasonable explanation to explain this occurrence.explain this occurrence.

Steel Bridges Steel Bridges

Have expansion joints. Have expansion joints.

Bridge Expansion Joint ExampleBridge Expansion Joint Example

Railroad Tracks Railroad Tracks

Have gaps at each joint.Have gaps at each joint.

Railroad RailsRailroad Rails

Concrete roads Concrete roads

Have expansion joints built in. Have expansion joints built in.

Concrete RoadsConcrete Roads

Concrete RoadsConcrete Roads

Sidewalks Sidewalks

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

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

SidewalksSidewalks

CarsCars

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

Post QuizPost Quiz

1.1. Molecules are in constant motion.Molecules are in constant motion.

TrueTrue

FalseFalse

Post QuizPost Quiz

2.2. Molecules get farther apart becauseMolecules get farther apart because

a. Energy is addeda. Energy is added

b. Energy is taken awayb. Energy is taken away

c. Molecules can’t get farther apartc. Molecules can’t get farther apart

d. Molecules are taken away from d. Molecules are taken away from the substance. the substance.