Air and Atmosphere Overview

Definition of Air & Atmosphere: Air is a mixture of gases; the atmosphere is the layer of

air surrounding Earth. Composition: Nitrogen (78%), Oxygen (21%),

Argon, Carbon Dioxide (0.04%), water vapor, dust. Importance: Oxygen

for breathing/combustion, CO2 for plants (photosynthesis), Ozone layer protects from UV rays, air for flight/sound.

Properties of Air: Invisible, has mass, exerts pressure, compressible (demonstrated

in experiments). Gas Cycle: Respiration (O2 in, CO2 out) and Photosynthesis (CO2 in,

O2 out) maintain balance.