Unit #1

Activity 1
Up, Up and Away: Building a Hot Air Balloon

Activity Overview

The question of how a hot air balloon works sets the context for making the connection between the micro and macro scale worlds.

In this activity students investigate the question: "How does a hot air balloon work?" Students begin by building small hot air balloons and then launching them. Students then discuss how they think a hot air balloon floats. Finally, students are introduced to the use of models as a tool for understanding.

Learning Objectives

Students will:

• Construct and launch a hot air balloon.
• Propose hypotheses and make critical comments about each others' ideas.
• Define, in the simplest terms, what a model is.

Conceptual Prologue

Macro-Micro Connection

In this unit students will be exploring the basic characteristics of how atoms behave and how the behavior of invisibly small atoms (microscale) can explain what is observed with the eyes (macroscale). To draw students into a study of the abstract concept of invisible atoms, the hot air balloon is used. Throughout the unit the curriculum will refer back to how what was learned can further extend understanding of why the hot air balloon flies. In this activity, students will begin their journey to the micro world by observing the macro behavior of a hot air balloon, and developing hypotheses about how it works.

Science Concepts

In this activity students build hot air balloons and are asked to consider how they might work. To really understand how they work, students need to understand the nature of the atomic scale world. Specifically, a full explanation would eventually require that they understand that all substances are made of atoms and molecules, that these particles move randomly, that the temperature of atoms and molecules are directly related to their kinetic energy which is the energy of motion related to mass and velocity, and that pressure is due to the repeated impacts of molecules. Throughout this module, as students learn more of these concepts, we will return to the idea of the hot air balloon to obtain a deeper understanding of how it works.

Naive Conceptions

Many issues may come up during the discussion of how the hot air balloon works. The point of this activity is to get students thinking, not to correct all of their naive science conceptions in this one lesson. As this is the intro to the curriculum this activity serves as a way to determine what students understand. It would be good to note what kinds of naive conceptions come up during the discussion of the hot air balloon, so that these can be addressed with the appropriate activities later in the unit.

Some possible naive conceptions that may come up include:

• Air is not matter.

Air is matter. Anything that has mass is considered to be matter.

• All gasses are the same substance - air.

Different gasses consist of different atoms or molecules. Even air is a mixture of several different molecules.

• Matter is continuous.

Matter is particulate, consisting of atoms and molecules with empty space between them.

• Hot things expand because the molecules or atoms get bigger when they are hot.

Hot things expand because the distance between their atoms or molecules expands.

• Heating something makes it lighter.

Heating only speeds up the motion of the atoms or molecules; it does not affect their mass.

• The word "model" doesn't have any scientific meaning.

Model, in scientific terms, can mean several things. In this activity the term model is used most loosely to refer to an idea or theory of how something works. A more useful idea of a model which will be explored in later activities is something which based on certain rules can make predictions about various phenomena, like behavior of gasses, the weather, and the economy. Students may hear the word "model" and think: fashion, a good example, a small replica, etc.

Activity Design and Execution

Major Science Concepts:	• None
Assumed Previous Knowledge:	• None
Time:	• 50 minutes to build and launch the balloons • 20 minutes for the discussion
Materials:	OPTION A: for each group: • Scissors • Ruler • Pencil • 2 sheets of tissue paper (51 cm x 60 cm) • Glue stick • 4 paper clips • Bunsen burner for the entire class: • Fire Extinguisher (just in case) OPTION B: for each group: • Scissors • Ruler • Pencil • 9 sheets of tissue paper (51 cm x 60 cm) • Glue stick • 1 sheet of construction paper for the entire class: • hot air popcorn popper (~1440 watts) Option C: for each group: • A dry cleaning bag • Cellophane tape • 10 Paper clips for the whole class: • Hair dryer or hot air popcorn popper (~1440 watts)
Advanced Preparation: (if any)	• If option C is chosen below have students bring in dry cleaning bags the thinner the better. • Have students bring in a three ring binder and some lined paper to go in this binder. This will be the notebook in which they will keep all of their notes, assignments, worksheets, lab results, etc.

Investigative Question: How does a hot air balloon work?

Give the Prepost test

1. Explain to students that they will build a hot air balloon and try to come up with some explanation for how it works.
2. Have the students build a hot air balloon based on one of the three options below:
   1. Have groups of 2-3 students build a small hot air balloon out of tissue paper that will be launched using a Bunsen burner. PDF file of small balloon plans.
   2. Have 2-4 students each build a larger hot air balloon out of tissue paper that will be launched with a hot air popcorn popper. PDF file of large balloon plans. (Used with permission from the Science Learning Network as OMSI.)
   3. Have 2-3 students each build a hot air balloon from dry cleaning bags that will be launched with a hair dryer (or hot air popcorn popper). HTML page of plastic balloon plans.
3. After students launch their balloons, ask them “How does a hot air balloon float?” This will help us determine how students are currently thinking about the problem and what previous knowledge they have about heat, gasses, and why things float. The goal of this discussion is not to answer this question but to bring up questions which can be addressed with other activities later on. The discussion should be very open, encouraging students to comment upon each other's explanations.
4. When the class seems to have settled upon 2-3 different explanations, talk to the students about the concept of modeling. Tell them that each explanation could be called a different model of what is happening. Further explain that modeling can take many forms, and that we will use lots of different models in our quest to understand how a hot air balloon flies.

Assessment

Have students write several things in their notebooks:

1. Define in their own words what a model is.
2. Write down the 2 or 3 models that the class came up with to explain how a hot air balloon works. Provide diagrams where necessary.
   

Extensions • If there is time at the end of the module, it would be nice to close with the construction of a larger scale hot air balloon. This could be done with tissue paper or plastic bags. • A mathematically advanced class could actually determine the temperature at which a balloon will begin to float.

Additional Resources • The definitive list of ballooning links.