Q1-Complete the blanks? 1- At very high altitudes, normally reactive species such as atomic oxygen, O, persist for long periods of time because ...............................

7. A body of unknown temperature is placed in a refrigerator at a constant temperature of 0 °F. If after 20 minutes the temperature of the body is 40 °F and after 40 minutes the temperature of the body is 20 ° F, find the initial temperature of the body. (use Newton's Law of Cooling/Warming) 8. A radioactive substance is known to decay at a rate proportional to the amount present. If initially there is 50 milligrams of the substance present and after two hours it is observed that the substance has lost 10% of its original mass, Find the time at which the material has decayed to one half of its initial mass.

1.The Effect of Temperature on Conductivity of Superconductors2. How are conductance and electrical resistance characterized? What is the physical phenomenon that distinguishes conductors, semiconductors, insulators, and superconductors? In metals, how is conductivity affected by defects, temperature, and deformation?5. In semiconductors, how is conductivityaffected by impurities (doping) and temperature?6. Phosphorous is added to high purity silicon to produce a1023 ?3 charges carrier concentration at room temperature. What is this type of material, n or p?7. Calculate the conductivity of this material at room temperature, assuming that the mobilities of electrons andof the gaps are the same as for the intrinsic material?e = 0.14 and ?h = 0.048 ?/ V s.? = 2240(Ω − ?)-1. P why?

5. Calculate the mean, RMS, and most probable speeds for: 1) hydrogen molecule at temperatures of 100 K, 1000 K and 10,000 K and 2) xenon atom at temperatures of l100 K, 1000 K and 10,000 K. Assume the velocity distribution is a Maxwell-Boltzmann distribution for both.

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1. The enthalpy of argon at room temperature and pressure obeys the relation below. Where n is the amount of substance. What is the heat capacity of argon at constant pressure? 5 H = nRT + const. 2