Linear Thermal Expansion Demo:

Linear Thermal Expansion Demo:

Thermal expansion is the tendency of matter to change in volume in response to a change in temperature through heat transfer.
At first Prof. Mason showed us a metal ring and a ball that did not fit through the ring.
Prof. Mason heated the metal ring and showed how the diameter of the ring increased. The metal expanded and the ring got thinner as the diameter increased. The ball now fit through the ring. The metal ring underwent thermal expansion.

Next, Prof. Mason showed us a two sided metal rod. One side was coated with brass and the other invar. As the invar side is heated, it curls towards the invar side. When the entire rod is cooled and placed in ice, the rod uncurls from the invar side and eventually bends slightly towards the brass. Invar has a much smaller coefficient of thermal expansion than brass. This explains the reaction to hot and cold exposure to the rod.

 Below is a 1.0m rod attached to tube that provides steam through the rod as well as a rotary sensor and temperature gauge. 

We used the rotary sensor to determine the angle in radians on logger pro, which is later used to find the angular displacement.    

From this measurement, we calculated the angular displacement and the coefficient of linear expansion. For volumetric expansion, the coefficient is 3 times that of the linear expansion.

The uncertainty was calculated through propagation.

Here, a calorimeter is used to measure the change in temperature over time as an immersion heater is heating up ice water. The time lapse is 300s as shown on the graph. 

 We can clearly see that the graph displays a linear fit equation. The graph is temperature vs time for the calorimeter activity above.

These calculations are for the Latent Fusion of Ice and the Latent Vaporization of Water during the previous activity. Since we already knew the amount of power exerted from the immersion heater, the initial temps of the ice water, and the initial mass of the water and ice, we could calculate the for the latent fusion and vaporization values as well as the specific heat of water.

The uncertainty for the power of the immersion heater is as shown below.

The comparison between true values and experimental values for the calculations made are displayed below.

 The following is a heat exchange problem for the calorimeter activity. The change in phases from ice to water and water to steam must be calculated properly. The proper formula is displayed below. The proper Lv and Lf must be used as well. Since the final state of the mixture is ice & water, the final temp is 0.0 degrees Celsius.

The following activity asks us to apply air pressure through a straw that has water inside. The change in height of the water due to pressure changes we made are used in further calculations to determine the pressure we applied. 

In the above videos, air was blown into the tubing at a low pressure and a higher pressure. 
As more air is blown into the tubing, the rate of flow of water will increase and pressure inside of the tube will increase as well. The volume remains constant. 

The derivation of the pressure formula used is shown below. Also displayed in the use of density and volume when making calculations simpler. 

 The below photo shows the calculations made and formulas used to find the pressure inside of the tube. The density of water was used with the pressure formula of force per area unit to find the pressure. We used the change in height as the difference between the height at higher pressure and the height at lower pressure.

Summary:

• Thermal expansion is the tendency of matter to change in volume in response to a change in temperature through heat transfer.
• For thermal expansion problems, we can use the angular displacement as the coefficient of linear expansion and 3 times that of the linear expansion for the coefficient of the volumetric expansion.
• When heat energy is added to a mixture of ice and water at a continuous rate, the graph of temperature change vs time is linear.
• The heat of the surroundings is still equal to the negative of the heat system in these circumstances.
• Latent heat of fusion is the energy required to change a gram of a substance from a solid to liquid state without changing its temperature.
• Latent heat of vaporization is the enthalpy change required to transform a given quantity of a substance from a liquid into gas at a given pressure.
• For pressure problems, we can use the density of water and and the change in height to determine the pressure applied.