a) Calculate the temperature change of the beer due to heat released by the condensation process. The heat capacity of the glass may be neglected. The glass contains 200 ml of beer, and one gram of water is condensing (heat capacity of water (beer): 1 cal per gram per °C, phase change from vapor to liquid releases 539 cal/g).
b) What assumptions are we making in the above calculation?
2) (8 points) Particularly during cold winter days, we experience very dry air in our appartments.
a) Can you explain this phenomenon?
b) Many of us are probably using humidifiers in order to make the air more comfortable. Consider a room of the size of 150 square feet that is 9 ft high. The temperature of the room is 20°C, relative humidity initially 30%. Assuming that there is no exchange of air between the room and the rest of the appartment, how much water do you have to evaporate in order to increase the relative humidity to 60%? Use the vapor pressure curve for H2O (fig) to determine what the approximate water vapor pressure difference is between 30% and 60% relative humidity. Then convert this pressure difference into a quantity of H2O knowing that 1 mbar of H2O vapor pressure is equivalent to 0.74g of water/m3 at 20°C.
3) (12 points) On the National Climate Data Center webpage find the weather station that is closest to your place of birth (or another station of interest) that has at least 50 years of record of preciptation. Look for one station (best by state) and then select the 'total monthly precipitation' dataset (TPCP). I recommend the comma delimited file format. You then have to enter your e-mail address (might have to have an .edu extension, so use your CU/BC address & you may have to login through an .edu domainin order to not being charged for the data) and you'll receive a link to the data set by e-mail.
a) Download the data and import them into EXCEL. Determine minimum, maximum, average and standard deviation of the data using the equivalent EXCEL functions (MIN, MAX,AVERAGE,STDEV). Note that precipitation is measured in hundreds of inch, i.e. 1000 = 10 inches. The last column has annual values - but you might have to sum up teh monthly precipitation values.
b) Make a histogram of the precipitation data
(see example below), print it out and hand it in.
c) Determine the amount of annual precipitation that is
exceeded every 20 years (probability 0.05) and that precipitation falls
short of every 100
years (probability 0.01).
