Study Guide for the Final Exam
Exam Date: Tuesday, May 13, 8:00 – 10:00 AM
This review guide is not all-inclusive. However, it does cover most of the topics and
concepts you can expect to see on the exam.
, a limited number of questions may
be included from the Homework 3 assignment!
1. Properties of Water
- Know the concept of phase change in water (melting, freezing, sublimation,
Phase changes occur as a result of changes in temperature (temperature is a measure of
the speed of motion of atoms and molecules, their kinetic energy.
Phase changes take energy to occur, one calorie is the amount of energy required to raise
the temperature of one gram of liquid water 1°C. The calorie is a unit of heat/kinetic energy.
Melting- phase change from solid to liquid. Must raise the temperature of ice to the
melting point (32°F;0°C) by adding 0.5 calories per gram per degree, this is specific heat of ice.
Freezing- phase change from liquid to solid. In order for water to freeze, it must lose 80
calories per gram of water to its surroundings. In this case energy is being transferred from the
ice to the air, so this warms the air.
Sublimation- ice goes straight to gas state. No liquid
Deposition- gas goes straight to ice state. No liquid
In essence, these processes represent two phase changes in one, and do the
number of calories involved equals the sum the two
590 calories/g + 80 calories/g= 670 cal/g
Know difference between: humidity, relative humidity, and specific humidity.
Relative Humidity- How much vapor the air can hold before condensation occurs. We
can sense relative humidity because we can feel it. RH is based on air temperature because
temperature is a measure of the amount of energy available for evaporation to occur (it
controls the amount of water vapor that can be pumped into the air).
Specific Humidity- The mass of water vapor per mass of air at any specified temperature.
Can be thought of in terms of density because density equals mass/volume.
- Can you do a simple calculation of relative humidity if given values for the actual water
vapor content of air and the maximum water vapor capacity of the air at a given
RH= Actual vapor (g)/capacity or potential vapor (g)
- Can you do a simple calculation of specific humidity if given values for the mass of water
vapor (in grams) in the air and the mass of air (in kilograms) containing that water
vapor at a given temperature?
Specific Humidity = mass of water vapor (g)/ mass of air (kg)
- That sling psychrometer thingy… sounds like what David used to kill Goliath!
Measures relative humidity