Lab 2: Thermal Expansion and Latent Heats

  When start heating up a ring and a ball, the atoms of the ring are going toward inside and outside. Both inside and outside diameters are increase even though outside atoms have more power than inside atoms. For the ball, atoms are going outside to make the ball gets bigger after heating.

  When we started heating the ring, the diameters of the ring changed, so the ball was easily pass through the ring.

  There are four variables to make the bar expand. Also, we found the unit for α.

  There was a bimetallic strip that left side is brass and right side is invar. No matter which side we heat first, it always curve to right because brass has higher coefficient of volume expansion.

  Professor put this bimetallic strip into an ice box. But it curves to left this time because the coefficient of volume expansion.

  This is the linear thermal expansion experiment. The purpose of this experiment is to find out the coefficients of linear expansion of the tube.

  The α we got is 19x10^-6 but true α value is 24x10^-6. There were a lot of uncertainities because ΔL, Lo, r, ΔT and θ are all observed by eyes. So my uncertainty of α is 19x10^-6 ± 5x10^-6 (/°C).

  There were ice in the cup. We put a heater into the cup to heat the ice for five minutes. These are the predicted graph and experimental graph of temperature changing.

  Logger Pro gave us the slope dT/dt is 0.3495 and we knew power is 293W. So we could find out the mass of water and latent heat.

  There was an example problem. We knew heat is 215kj, ice mass is 0.790kg, the temperature of ice is -5℃, we need to found the final temperature. The answer we got is -17.185℃ which is not make sense.

  There was another problem. We know mass of ice is 255g, temperature of ice is -12℃, temperature of water is 22℃, and final temperature is 0℃. We need to found the mass of water.

  One of our group member was blowing the tube to make water raise a certain height. The purpose of this experiment is to find out the pressure. The equation we used to found the pressure is ΔP=ρ(g)y.

  In today's lab, we did a lot of interesting experiments. We figure out the thermal expansion by heating a ring. Also, we heated a rod to calculate the expansion in length. We heated ice to found out the mass of ice and latent heat. And finally, we did a pressure experiment by blowed a tube to make water raise in certain height.