Thermal ExpansionWhen the temperature of a substance is increased, it's molecules vibrate faster and tend to move furtherapart. With few exceptions all forms of matter solids, liquids and gases expand when they are heated andcontract when cooled this property is known as THERMAL EXPANSION.

ExamplesGAS-Gases when warmed become less dense causing them to rise. When the air near the floor of a roomis warmed, gravity pulls the more dense cooler air from the ceiling down and forces the warm air up.This air circulation is called convection current.LIQUID-Thermometers.SOLID-Expansion joints in bridges for the summer months.

The value for thermal expansion can be found by using the following formula...Linear expansion α occurs in most solids while volume expansion β occurs in liquids and gases.

Linear expansion ΔLLi

= αΔT Volume expansionΔVVi

= βΔT

Where...ΔL=Change in length Li=Initial Length ΔT =Change in Temp α =Coefficient of linear expansionΔV =Change in Volume Vi=Initial Volume β =Coefficient of volume expansion

Some common coefficients...α (unit oC-1) β (unit oC-1)

Aluminum 25 x 10-6 Methanol 1100 x 10-6Iron, steel 12 x 10-6 Gasoline 950 x 10-6Glass(soft) 9 x 10-6 Mercury 180 x 10-6Glass(PYREX) 3 x 10-6 Water 210x 10-6Concrete 12 x 10-6 Air (most Gases) 3400 x 10-6Platinum 9 x 10-6Copper 16 x 10-6Brass 19 x 10-6

Problems1. A piece of aluminum siding is 3.66m long on a cold winter day(-28oC). How much longer is it on avery hot summer day(39oC)?2. A piece of steel is 11.5m long at 22oC. It is heated to 1221oC, close to its melting temperature, howlong will it be?3. What would the change be in length of a 2.0 meter Pyrex stirring rod if it is heated from 23oC to300oC?4. A steel I-Beam used in the construction of a bridge is 9.2 meters long at 20oC. On a hot summer daythe temp goes up to 40oC. What is the beams new length?5. A brass wire is 0.500 m long at 20oC. If heated to 50oC what change in length would occur?6. A gap must be left in steel railroad rails to prevent stress. A 12 m rail is laid at 20oC, what gap shouldbe left so that the rails just touch at 45oC?7. A house has a volume of 500m3 at 20oC. How much air enters or leaves the house if the temperaturefalls to 0 oC? Which way does the air flow?8. In an experiment to determine the coefficient of linear expansion for Aluminum, a 0.50m rod is heatedfrom 20oC to 100oC. The increase in length is found to be 0.0096 mm. What is the experimentalcoefficient that was found for Aluminum?9. A gasoline tank has a capacity of 60 L at 20oC. If the tank is filled to the top, how much gasoline willoverflow if the car is left in the sun all day and the gasoline reaches a temp of 45oC.(ignore the expansionof the tank)

10. A tank truck takes on a load of 45725 L of gasoline in Houston at 32oC. The truck delivers its load inOmaha at -18oC. How many liters does the truck deliver? What happened to the gas?