13.2 Thermal Expansion of Solids and Liquids

The bridges in New Zealand have thermal expansion joints that allow them to change their length.

The density of the hot air is smaller than the density of the surrounding air because of the higher volume of air.

Natural heat transfer occurs in all liquids and gases.
Solids undergo thermal expansion.
Railroad tracks and bridges have expansion joints that allow them to expand and contract with temperature changes.

Thermal expansion is related to temperature change.

A bimetallic strip will bend if the temperature goes up.
It depends on the material.
The expansion of alcohol is greater than the expansion of the glass in a thermometer.

An increase in temperature means an increase in the energy of individual atoms.

In a solid, unlike in a gas, the atoms are tightly packed together, but their energy in the form of small, rapid vibrations pushes neighboring atoms apart from each other.
This neighbor-to-neighbor pushing results in a slightly greater distance, on average, between neighbors, and adds up to a larger size for the whole body.
Under ordinary conditions, there is no preferred direction, and an increase in temperature will increase the solid's size by a certain fraction.

The length is proportional to the change in length.

The values of the coefficients of linear expansion are listed in Table 13.2.

The size of a kelvin and degree Celsius are the same and can be expressed in units of kelvins or degrees Celsius.

The values for liquids and gases are close to each other.

The Golden Gate Bridge's main span is 1275 m long.

The bridge is exposed to different temperatures.
The bridge is made of steel.

The change in length can be calculated using the equation for linear thermal expansion.

Use the coefficients of linear expansion for steel and note the change in temperature.

Plug all of the known values into the equation.

The change in length is observable even though it is not large.

The expansion at each joint is small because it is spread over many joints.

Their areas and volumes increase with the temperature.

The holes get bigger with the temperature.
If you cut a hole in a metal plate, the remaining material will expand the same way it would if the plug was still in place.
The hole must get bigger as the plug gets bigger.

The hole gets slightly larger if the ring of neighbors gets slightly larger.

As temperature increases, objects expand in all directions.

The original boundaries of the objects are shown with solid lines, while the expanded boundaries are shown with dashed lines.
The area of a plug increases.

The change in volume is very close.

The values in Table 13.2 are almost exactly the same.

objects will expand with temperature The exception to this rule is water.

When the temperature is greater than, water expands with it.

The water is dense.

The freezing of water in a pond is the most striking effect of this phenomenon.

The denser the water is, the more it will sink to the bottom.
A layer of warmer water near the surface is then cooled.
The pond has a uniform temperature.
The water is less dense if the temperature drops below the surface layer.
The pond's surface can freeze over.
The ice on top of liquid water insulates against winter's harsh exterior air temperatures.
The characteristic of water is that fish and other aquatic life can survive under ice.
Circulation of water in the pond is necessary for the health of the body of water.

The thermal expansion is very small.

The maximum density is less than the density at and less than that at.

The thermal expansion of materials can have interesting effects on the gas station.

There is a dripping of gasoline from a freshly filled tank on a hot day.
The temperature of the ground under the gas station is cooler than the air temperature above.
The steel tank cools when it is filled with gasoline.
Both gasoline and steel tanks expand as they warm to air temperature, but gasoline expands more than steel, and so it may overflow.

Problems can be caused when interpreting the gasoline gauge by the difference in expansion.

In the summer, the amount of gasoline left in the tank is less than in the winter.
When the "add fuel" light goes on, the gasoline volume is the same as it is in the winter, but there is less mass because the gasoline has expanded.
If you're used to getting another 40 miles on "empty" in the winter, you'll run out more quickly in the summer.

In the summer you can't drive as many miles as you can in the winter because the gas expands more than the tank.

If your 60.0-L steel gasoline tank is full, both the tank and the gasoline have a temperature of.

The amount of spilled gasoline is the difference in the volume changes of the tank and gasoline.

The change in volume of the gasoline and of the tank can be calculated using the equation for volume expansion.

We can combine them into a single equation.

It is significant for a 60.0-L tank.

The effect is striking because of the rapid expansion of gasoline and steel.

The rate of change in thermal properties is discussed.

If you try to cap the tank tightly, you will find that it leaks, either around the cap or by bursting the tank.

Both liquids and solid objects resist being compressed with large forces, and tight constriction of the expanding gas is equivalent to compressing it.
The air gaps in these containers allow them to expand and contract without stressing them.

When gasoline expands, it can cause a tank to explode.

When two parts are joined together by heating one in manufacturing, then slipping the other over, it can be useful.
The expansion of ice when it freezes can explain the weathering of rocks and pavement.

The bulk modulus for gasoline is.

The original volume of gasoline is shown here.

The pressure is much more than a gasoline tank can handle.

The forces and pressures created by thermal stress are comparable to those in the example above.

Railroad tracks and roads can collapse on hot days if they don't have enough expansion joints.
If there is insufficient slack on the power lines, they will snap in the cold weather.
If the pans are cooled quickly or unevenly, they will crack.

Nuclear reactor pressure vessels are threatened by overly rapid cooling and several have been cooled faster than desirable.

When food is frozen, it affects the taste of the food.
The damage is highlighted by the repeated thaw and freezing.
The oceans can be affected.
The thermal expansion of sea water is one of the reasons for the rise in sea level.

Most implants need to be replaced over time because metal does not bond with bone.

Researchers are trying to find a metal coating that will allow metal-to-bone bonding.
One challenge is to find a coating that has the same expansion coefficients as metal.
The thermal stresses during the manufacturing process can lead to cracks at the coatingmetal interface if the expansion coefficients are too different.

There is thermal stress in the mouth.

There is a difference between tooth enamel and dental filling.
It can hurt to eat ice cream or have a hot drink.
There could be cracks in the filling.

Two blocks, A and B, are made of the same material.

Blocks A and B have the same dimensions.

The volume of Block B is four times that of Block A.

The change in volume of Block B should be four times the change in volume of Block A.

The change in the cross-sectional area of Block B is twice that of Block A.

The change in the height of Block B is twice as big as the change in the height of Block A.