Do Now Copy the Frayer model into your notes Definition: The weight of the Earth’s atmosphere pressing down on everything at the surface. Characteristics Non-examples Examples

Announcements Going to cancel the test Homework due on Friday Will have a short quiz on Friday over materials today. Homework due on Friday

Agenda Chemical composition of the atmosphere Voting with our feet Air labs

Chemical composition 78% Nitrogen 21% Oxygen 1% Argon 0.036% other gases

Voting with our feet In a few minutes, we’re all going to be standing up. First, some rules. During this activity there is to be NO talking until I give you permission! Once I give you permission, then your conversation is to remain on task.

Voting with our feet continued In a few minutes we’re going to be standing up and moving around the room. The side of the room closest to my desk will be the agree side. The side of the room with the window will be the disagree. The middle of the room will be the undecided.

Voting with your feet continued After we move, we’ll be discussing in our groups why we think what we think. Questions?

Air has a weight.

Air molecules bounce off each other to create pressure.

Air takes up space.

Our atmosphere was initially composed of 100% oxygen.

Throughout the layers, the chemical composition remains constant.

Air labs You’re going to be working with your partner. You need to stay on task. ONLY ONE OF YOU SHOULD PUT YOUR MOUTHS ON THE BALLOON! You need to fill out the handout as you go.

Air labs: Does air have weight? Our scales don’t work the best, so I weighed it for you. Flat balloon weight: .012 g Inflated balloon weight: .117 g

Air pressure Air pressure, or atmospheric pressure, refers to the weight of the Earth’s atmosphere pressing down on everything at the surface. Air pressure varies slightly over the Earth’s surface, and is responsible for weather.