Barometers are great tools to teach students about air pressure. This science experiment uses everyday household objects, and can be done very easily at school, or assigned as a home project.
Students learn best when they are given hands-on projects. They can 'study' a barometer, but will truly understand how a barometer works if they can assemble and use one of their own.
Gather together the following items:
- Glass Jar
- Straw or Plastic tubing
- Chewed piece of gum
- Flat Surface
- Paper and a Pencil
- Tap water
- Permanent Marker
Assembling the Barometer
Follow the steps below to make your barometer:
- Set your glass jar on a flat surface such as a table or school desk.
Place your ruler inside the jar with the numbers facing you. The 1 inch mark should be toward the bottom of the jar with the numbers increasing as they go out of the jar. Use your tape to tape the ruler in place. Tape the ruler near the top so the tape doesn't come off in the water.
- Place your straw or plastic tubing next to the ruler. Make sure that the straw does not touch the bottom of the jar like the ruler does. Have it start at the 1/2 inch mark.
- Tape the straw to the ruler or to the jar right next to the ruler. Make sure your straw doesn't cover up any numbers. You will need to be able to read those.
- Fill your jar up halfway with some tap water. The number the water comes to on your ruler will depend on the size jar you used.
- Chew your piece of gum if you haven't already, and get ready to use it. This is the tricky part of the experiment.
- You need to suck some of the water up in the straw, but don't suck it up all the way to the top. When you do this you are going to need to be able to quickly plug up your end of the straw with the gum. It may take several tries to get it right.
- Mark the line where your water is in the straw on your ruler. Do this with a permanent marker so that if the water rises, it won't wash away your mark.
Now you have assembled the barometer and are ready to start using it to measure air pressure.
Predicting the Weather
You will use the paper and pencil in the materials list to keep track of the water level. You are going to note if the water level rises or decreases, and will be predicting the weather based on what the water level is doing.
If the water level rises you can assume that the air pressure is increasing which brings about fair weather. That is weather that is clear.
When the water level decreases you can assume that the air pressure is decreasing which brings about clouds and precipitation (rain).
Chart the water level a couple times a day, over a several day period, to ensure you will record changing weather patterns.
NOTE: This experiment is best done in an area that has a pretty constant climate and temperature. You will get more accurate results this way.
Students should share in groups or in front of the class any findings that they have made. Students could also be asked to give a written report, instead of an oral report. The important thing is to make sure each child understands what happens when the air pressure increases and what happens when the air pressure decreases. The child should understand that the barometer is the instrument used to measure these increases and decreases, and that the barometer helps scientists predict the weather.