VanCleave's Science Fun

Your Guide to Science Projects, Fun Experiments, and Science Research

ABOUT THE SOUND PICTURE

With mouth wide open, vibrating air coming up the throat from the vocal chords leaving the open mouth and spreading in all directions. Hi, I am Janice VanCleave, author of 50+ best-selling science experiment books for children ages 4 through high school. I taught science for 27 years and now am creating this science website.   My scream was not staged. The picture was to be of two adult cats, which I was holding. A microsecond before the camera snapped, the two cats dug their claws into my skin as they prepared to leap out of my arms. A picture like this is great for making inferences. Kids could make "guesses" as to why I am screaming. They would be drawing on facts from the photo, such as I look like I am in pain or maybe I am just pretending.

Sound Supplies and Sound Investigations

Educational Innovation Sound Supplies A black and yellow logo for Educational Innovations. A place to find fun science supplies.
Home » Atmospheric Pressure

Atmospheric Pressure

By

Atmospheric Pressure

The force of air molecules pushing on a surface

Also called air pressure or barometric pressure.

Air

A mixture of gases containing about 78% nitrogen, 20% oxygen, and 2% other gases including carbon dioxide and water vapor.

Gas molecules are separate from each other and in constant motion.

Words to Know

air
air pressure atmospheric pressure
barometer
density of air
gas molecules
sea level
weight of air



Air pressure is a measurement of combined force of all the gas molecules in air hitting a surface.

At sea level, air is denser than is the air on top of a mountain. This means that if you spread a blanket on the beach, there are more air molecules hitting the blanket than there would be if you spread the blanket on a flat surface on a mountain.

The force of the air molecules striking a surface is generally about the same as the weight of air above the surface. Imagine a 4 in x 6 in index card laying on the beach. A column of air rising above an index card to the Earth’s atmosphere would weight about 353 pounds.

If an equal size card is laying on the ground in Denver, Colorado, the weight of the air column would be about 290 pounds. The difference in the weight is due to :

  • Denver being about 1 mile above sea level. This means that the column of air is 1 mile shorter than the column of air above the beach.
  • The density of the air at higher altitudes is less (fewer air molecules) than at sea level.

Discover for Yourself

With a bit of imagination, kids can better understand how altitude affects atmospheric pressure. Pretend that the floor is at sea level and the ceiling of the room is the end of the atmosphere and above the ceiling is outer space.

1. Use two 4 in x 6 in index cards. Write “Beach” on one card and lay it on the floor.

2. Write Denver, Colorado on the second card and lay it on a chair or other surface above the floor.

3. Ask These Questions:

  • 1. Which is greater?
  • a. The distance from the Beach (card on the floor) to the outer edge of Earth’s atmosphere (ceiling).
  • b. The distance from Denver, Colorado (the card on the chair) to the outer edge of Earth’s atmosphere (ceiling).
  • (Answer: a. The distance from the Beach (card on the floor) to the outer edge of Earth’s atmosphere (ceiling).)
  • 2. Which region has more air above it?
  • a. The beach (card on the floor)
  • b. Denver, Colorado (the card on the chair)
  • (Answer: a. The beach (the card on the floor).
  • 3. Where would the atmospheric pressure be the least?
  • a. Beach (the card on the floor).
  • b. Denver, Colorado (the card on the chair).
  • (Answer: b. Denver, Colorado (the card on the floor.)
7709: A+ Projects in Earth Science: Winning Experiments A+ Projects in Earth Science: Winning Experiments