Gap Band Essay examples
Band Gap of LEDs
By Mohammad Reza Farham
Chemistry 222 Thursday 08.02.2012
Lab Partner: Thanh Nguyen …show more content…
15. A student has claimed that when a material is cooled, a substance usually contracts because the bonds between the atoms get shorter. Using only data directly from this experiment, either support or refute this student’s claim. Supported. When the material is cooled, the Eg increased. Increasing Eg may result from a shorter bond distance (greater orbital overlap). The data supports, but does not prove this claim.
16. A different student has claimed that when a material is cooled, the resistance of a metal should effectively increase, because the electrons must be moving slower due to the low temperature. Using only data directly from this experiment, either support or refute this student’s claim. Refuted. The data shows that metals decrease their resistance when cooled.
17. Suggest a hypothesis that would explain your answer to Question 16.
Most likely, there is less scattering of electrons by the metal atoms at cool temps because they don’t vibrate as much on their lattice positions.
18. Based only on the data from Experiment 4, state a claim about the relationship between the conductivity (ease of electron flow) of a semiconductor in the light compared to in the dark. Be sure to explicitly show (or reference) the data used to suggest your claim. Data Conductivity of a