It has been a HUMID week in Fargo, North Dakota! What does humidity mean? Humidity is the amount of moisture that is in the air. When it's humid out, it makes a hot day feel even hotter. Have you ever gotten out of a hot shower and seen steam on your mirror? It sure feels muggy if you have the door closed without the fan running! Why is it that humid air makes it feel warmer?
Test it out:
1. Stand in your bathroom with the door closed. Bring a thermometer in and check the temperature.
2. Turn the shower on hot and leave the thermometer in the bathroom. Shut the door and leave the bathroom for about three minutes.
3. Come back and check it out. What do you notice about the mirror? Does the air feel different? Check the thermometer for any temperature changes.
You probably noticed that the bathroom felt much warmer after the hot shower had been running for a while!
Option 1: Analyze the weather
YOU WILL NEED:
- Internet to check weather.
1. Check the weather each day for two weeks. Record the high, the low, the humidity, and the "feels like."
2. Analyze your results.
Questions to think about:
* Was the humidity typically higher on hotter days or cooler days?
* Did the humidity affect the "feels like" temperature?
* Did the humidity have a larger affect on hotter days or cooler days?
Option 2: Create your own psychrometer
How do you measure humidity? In this activity, you get to create your own humidity-measuring tool called a psychrometer. Another name for the psychrometer is a wet and dry bulb thermometer. This is because a psychrometer is made of two thermometers: one with wet material wrapped around the bulb and the other with the bulb kept dry. See the picture below for reference.
YOU WILL NEED:
* Two identical thermometers
* Gauze or cotton balls
* Rubber band
* Board or sturdy piece of cardboard
* Thick string or wire
Here's what to do!
1. Place both thermometers outside right next to each other for 15 minutes. Check to make sure that they both say the same temperature. This will ensure that they both work identically.
2. Wrap gauze or cotton balls around the bulb of one of the thermometers and secure it with the rubber band. Dip the gauze-wrapped bulb in water.
3. Tape both thermometers to a sturdy piece of cardboard. They should be parallel to each other with both bulbs hanging off the end of the board. Make sure they are very secure!
4. Punch a hole in the end of the cardboard opposite the bulbs. Tie a string through the hole, about a foot long. Make sure the string is tightly knotted.
5. Now for the fun part! Go outside in an open space and START SWINGING! Hold on tight to the string and swing the psychrometer around for 2 minutes. The swinging will help the water surrounding the wet bulb evaporate quickly.
6. Stop swinging every 30 seconds and check the temperatures. Eventually, the wet bulb temperature will quit lowering and level off. Once the wet bulb temperature has leveled off, record the temperature for the both the dry bulb and the wet bulb.
7. Now to find the relative humidity, you subtract the wet bulb temperature from the dry bulb temperature.
Dry bulb = 22 degrees Celsius
Wet Bulb = 17 degrees Celsius
22 - 17 = 5
Temperature difference = 5
8. Now that you have the difference, you consult the psychometric chart to find the relative humidity. The video below contains the psychometric chart and provides an example of how to calculate relative humidity based on your findings.
Image and Video Credits, in order of appearance:
Draper, John William. 1861. Psychrometer, “A textbook on chemistry”. Uploaded from Wikimedia Commons on 6/19/2016. https://commons.wikimedia.org/wiki/File:Psychrometer1861.png. Public Domain Image.
Rafalik, Christopher. “Calculating Relative Humidity using Sling Psychrometer” Published 11/15/2013. Accessed 6/19/2016. https://www.youtube.com/watch?v=14Q3-VtVDAI.