Relative Humidity
Relative humidity, abbreviated RH, equals the actual vapor density divided by saturation vapor density then multiplied by one hundred. The actual vapor density is how much water vapor is actually in the air. The saturation vapor density is when the air is saturated with water vapor. When the actual amount equals the saturation amount you have one hundred percent relative humidity. 
The following list compares the amount of water vapor in air at one hundred percent relative humidity across a range of temperatures from minus twenty degrees through fifty degrees. Use this list to answer the questions below.
At minus twenty degrees there is one gram of water vapor in the air at 100% relative humidity. 
At minus fifteen degrees there is two grams of water vapor in the air at 100% relative humidity.
At minus ten degrees there is three grams of water vapor in the air at 100% relative humidity.
At minus five degrees there is four grams of water vapor in the air at 100% relative humidity.
At zero degrees there is five grams of water vapor in the air at 100% relative humidity.
At five degrees there is seven grams of water vapor in the air at 100% relative humidity.
At ten degrees there is eight grams of water vapor in the air at 100% relative humidity.
At fifteen degrees there is ten grams of water vapor in the air at 100% relative humidity.
At twenty degrees there is fifteen grams of water vapor in the air at 100% relative humidity.
At twenty five degrees there is twenty grams of water vapor in the air at 100% relative humidity.
At thirty degrees there is twenty eight grams of water vapor in the air at 100% relative humidity.
At thirty five degrees there is thirty seven grams of water vapor in the air at 100% relative humidity.
At forty degrees there is fifty grams of water vapor in the air at 100% relative humidity.
At forty five degrees there is seventy grams of water vapor in the air at 100% relative humidity.
At fifty degrees there is ninety five grams of water vapor in the air at 100% relative humidity.

Questions

1. How much water can exist in a cubic meter of air at 25¼C?
2. How much water vapor can exist in the same volume of air at 15¼C?
3. Explain the difference in answers in questions 1 and 2.
4. If the relative humidity of the air in question #1 were 50%, how much vapor would exist?
5. If you wanted to increase the relative humidity of the room would you increase of decrease its temperature? Explain your answer.
6. At 20¼C what is the RH of three cubic meters of air if there exists only 30.0 g of water vapor in that air?
7. If that same air (3m3 with 30.0g of water) is cooled to 5¼C what will happen to the air and water vapor that exists in it?