Air- She's so heavy!

Learning Goals:
1. Students will apply their understanding of an arm balance to create and manipulate a balanced state and an unbalanced state.
2. Through manipulation of the balance and the balloons, students will discover that adding air to one balloon makes it heavier than the deflated balloon, concluding that air has mass.

Key Concepts:
1. Two items weighing the same will hang perfectly horizontal on an equal arm balance.
2. Moving a fulcrum can adjust the balancing point, or center of mass for a system.
3. A lower arm of an equal arm balance means that an object is heavier.
4. Adding air to a balloon makes it heavier than the same deflated balloon.

Vocabulary Words:
1. Equal Arm Balance
2. Fulcrum
3. Center of Mass
4. Air

This lesson is an introductory lesson for air. Early in the year, we study balance and weighing as a science kit. In an attempt to link science content areas and show interconnectedness, I am spring-boarding a new unit off previous knowledge and experience. Students will review and explore the equal arm balance while trying to answer the question, "How can you make one arm lower and one arm higher?". Students will think of many ways to accomplish this that are NOT specific, but that it okay! You can acknowledge the successful ideas and pose new questions that will ultimately take you towards the discovery that blowing air in a balloon will lower that arm on the equal arm balance.

BACKGROUND
Students have the background from the balancing and weighing unit, which includes an understanding of an arm balance and application of basic vocabulary.
GETTING SET UP
Each group of 3 of 4 will get straws, paperclips, and balloons. Please note that all of the balloons have to be the same.
TEACHER INTRO
"Who remembers working with an equal arm balance and mobiles in our last science unit? In your group please draw me a picture of an equal arm balance."

As students share their drawings such questions may come up:
1. Is the weight on each side equal?
2. What would happen if you moved the fulcrum?
"Excellent! Now that we all remember about making mobiles you are going to have a mobile challenge today! You are going to make a mobile (or equal arm balance, they can be interchangeable) using straws and paperclips. You will also get two balloons. Your challenge is to build a mobile that balances the two balloons."
Walk around during this time and see if students can successfully build a mobile that will balance the two same balloons. Share and discuss the solutions that the students come up with.
"Great! Now you have a new challenge. Make one arm on the equal arm balance lower than the other!"
Possible Solutions:
1. Move the fulcrum. "Good thinking! Can you keep the fulcrum in the same spot and make one arm dip down?
2. Adding paper clips to a balloon. "Awesome! Now, without adding paper clips can you make one arm dip down?"
Hopefully the students will discover blowing air into one balloon. (Hint: "Is there something you can do to the balloon to make it dip down?)
Once the students have discovered this, it is time to take them through a discussion that air has mass!
"Why do you think blowing in the balloon made that side dip down? Taking what we know about equal arm balances, what must that mean about the inflated balloon?

The process of building an equal arm balance is a great assessment tool to see which students have retained the previously taught information. It is also a great opportunity for group work as well as creative problem solving and inquiry. Most students may assume that adding air to a balloon would make it float up and be the higher arm. It may take awhile for the students to comprehend that air actually has weight. It is a great beginning point for discussing other properties of air found in future lessons.

Assessment will be derived from teacher observation and whole group sharing and presenting the ideas.

2. II. A. 2. The student will classify a substance as a solid, liquid or gas.