Do Now Copy the Frayer model into your

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

Announcements • Going to cancel the test ▫ 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.