A manometer is a device that measures pressure, typically using vertical or inclined tubes of mercury or water that rise or fall in response to changes in pressure. An open tube manometer measures gas pressure in a container. A barometer is a type of manometer that measures air pressure for predicting changes in the weather. You can make your own functioning manometer and barometer using easy-to-find materials.
Draw a line across the width of the poster board at 6 inches from one end and 18 inches from the same end. Lightly score the lines using the scissors, and fold on the lines to make a three-sided stand. Secure the ends with tape.
Place the ruler vertically in the centre of one side of the stand, about 2 inches from the bottom. Tape the ruler in place. Fill the cup with water, and add about 20 drops of food colouring. Stir until the colouring is uniform. Add more if you wish. Cut off and discard the neck of the balloon.
Push the small end of the funnel into one end of the 48-inch piece of aquarium tubing. Use the modelling clay to seal the connection. Bend the remaining end of the aquarium tubing into a U-shape starting on the right side of the ruler, going down around the bottom of the ruler and up the other side. Tape in place as you go.
Pour the water slowly into the funnel until there is about 18 inches in the tubing. Do not let it spill out the other end of the tubing. Tap the tubing lightly to release air bubbles from the water. Stretch the remainder of the balloon over the wide end of the funnel.
Measure changes in the height of the water level in the side of the tubing with the open end. Rising pressure will cause the water level to rise, and falling pressure will cause the water level to fall.
Stand the ruler in the glass, next to the side. Tape the ruler in place near the top of the glass. Place the 12-inch piece of aquarium tubing next to one side of the ruler, about 1/2 inch from the bottom of the glass. Tape the tubing to the ruler near the top of the glass.
Fill the glass halfway with water. Add 10 or more drops of food colouring and stir. Using the tubing like a straw, pull water halfway up the tube and stick your tongue in the open end of the tube to hold the water in place. Quickly remove your tongue and push modelling clay into the opening of the tubing.
Record the beginning water level. Observe the barometer every day and mark changes. You will see the level rising and falling with the air pressure. Rising levels mean a high pressure area is coming and bringing clearing or fair weather. Falling levels mean a low pressure area is approaching and bringing clouds and precipitation. Compare your forecasts to the TV meteorologist's predictions.