Thin Air Challenges: The Air Density Altitude Quiz

If you go higher in altitude, there is less gravity pulling air molecules together. If molecules are less crowded, the air is less dense. Therefore, air density decreases as altitude increases.

If you are at sea level, you have the most air above you. If there is more air above, there is more weight pressing down. Therefore, the molecules at the bottom are squeezed closest together, creating the highest density.

If you go up a mountain, the percentage of oxygen stays at 21%. However, if the air is less dense, there are fewer total molecules in each breath. Therefore, you get less oxygen per breath even though the percentage is the same.

If an object has mass, gravity pulls it toward the center of the Earth. If air is made of gas particles that have mass, then gravity pulls them down. Therefore, gravity is the reason most of our air is packed near the surface.

If altitude increases, air density decreases to a point where there aren't enough oxygen molecules for humans. If we didn't pump air into the cabin, passengers couldn't breathe. Therefore, pressurization mimics sea-level density.

If air is less dense, there are fewer molecules for the ball to crash into. If there are fewer collisions (drag), the ball maintains its speed longer. Therefore, baseballs hit further in high-altitude cities like Denver.

If you go higher, there is less weight (pressure). If there is less weight, the molecules spread out (low density). Therefore, as altitude increases, both pressure and density decrease.

If you take a one-cubic-meter box of air, density is how many molecules are inside. If you pack more molecules in, it becomes denser. Therefore, density is mass per unit of volume.

If you are measuring how high you are above the ocean, you are measuring altitude.

If a balloon rises, the outside air density drops, meaning there are fewer molecules hitting the outside of the balloon. If the inside pressure stays the same, it pushes outward more than the outside pushes in. Therefore, the balloon grows larger.

If gravity pulls air down, the lowest layer will always be the most crowded. Since the Troposphere is the layer touching the Earth's surface, it contains about 80% of the atmosphere's mass. Therefore, it is the densest layer.

If air is cold, molecules move slower and stay closer together. If molecules stay closer together, more fit in the same space. Therefore, cold air has a higher density than warm air.

If gravity were stronger, it would pull air molecules toward the surface with more force. If the pull is stronger, the molecules get squeezed tighter. Therefore, air density at the surface would increase.

If the air is thin (low density), there is a lot of empty space between molecules. If you take a breath, you inhale fewer oxygen molecules than at sea level. Therefore, you need a tank to provide a concentrated supply.

If you move away from the Earth's surface, the molecules spread out.

If you change temperature, altitude, or water vapor content, you change how many molecules fit in a space. Since color doesn't change mass or volume, it does not affect density.

If you add water vapor (H2​O), it replaces heavier Nitrogen (N2​) molecules. Since water molecules weigh less than nitrogen molecules, the overall mass of the air volume drops. Therefore, humid air is actually lighter and less dense than dry air.

If the exosphere is the outermost layer, it is the furthest from Earth's gravity. If gravity is weakest there, molecules are miles apart. Therefore, it has the lowest density.

If you go up, the outside air becomes less dense and exerts less pressure. If the air trapped inside the bag stays the same, it pushes out with more force than the outside air pushes in. Therefore, the bag puffs up.

If the air is less dense, your lungs have to work harder to find the same amount of oxygen. If your muscles get less oxygen, they tire out faster. Therefore, physical exercise feels much more difficult.