Working Under Pressure

Air pressure changes are related to changing weather conditions. In this lab, you

will build and use your own barometer to measure air pressure.

Problem

How can a barometer detect changes in air pressure?

Materials

white glue

pencil

metric ruler

plastic wrap

drinking straw, 12–15 cm long

construction paper strip, 10 cm ´ 25 cm

scissors

tape

wide-mouthed glass jar

rubber band

1.  Cut a square piece of plastic wrap large enough to cover the top of your jar.

2.  Stretch the plastic wrap over the open end of the jar.  Use a rubber band to hold the balloon on the rim of the jar.

3.  Place a small amount of glue on the center of the plastic wrap top.  Attach one end of the straw to the glue.  Allow the other end to extend several cm beyond the edge of the jar.  This is your pointer.  Add a pea-sized piece of modeling clay to the end of the pointer.

4.  Fold a strip of construction paper lengthwise and draw a scale along the edge with marks .5cm apart.   Write “High Pressure” at the top of your scale and “Low Pressure” at the bottom. 

5. Record the date and time on your data table.  Note the level of the straw on the cardboard strip.

6. Check the barometer each day. Record your observations in your data table.

7. Record the weather conditions for each day.

1

Analyze and conclude

1. What change in atmospheric conditions must occur to cause the free end of

the straw to rise? What change must occur for it to fall?

2. According to your observations, what kind of weather is usually associated

with high air pressure? With low air pressure?

3. What effect, if any, would a great temperature change have on

the accuracy of your barometer?

More to Explore

Compare changes in air pressure shown by your barometer with high and low air

pressure readings shown on newspaper weather maps during the same time

period. How do your readings compare with the readings in the newspapers?

Barometric Pressure Data Table