1. Composition of the atmosphere

2. Composition of the Atmosphere ▪Composition = what something is made of. ▪ “Air” is all around us and it behaves often like a liquid- it flows, moves, and causes things to happen (weather!) ▪Air = mixture of dozens of types of gases.

3. ▪Air has MASS!! This means it can exert a FORCE (push) on you! ▪The air that surrounds the planet is held in place by gravity and is called our atmosphere. ▪Gravity becomes less and less as you move away from Earth. ▪As a result, there are fewer and fewer molecules as you move away from the surface.

4. Air!!! ▪The air around us is 78%: NITROGEN ▪21% of the air around us is: OXYGEN ▪The remaining 1% is a mixture of all other gases: Carbon dioxide, helium, argon, neon, hydrogen…

6. Water Vapor ▪Water is present in gas form in the air we breathe. We call this water vapor. ▪The amount of water vapor in the air is called “humidity” and varies greatly with time and location. ▪Water vapor is an important part of the water cycle and is a driving force in most types of weather.

7. POP QUIZ ▪1. ________ is a mixture of gases. ▪2. ________ is a blanket of gases that surrounds a planet. ▪3. 78% of our atmosphere on Earth is made of what gas? ▪4. 21% of our atmosphere on Earth is made of what gas? ▪5. Humidity refers to the amount of water __________ in the air.