Floating Balloons
Phenomenon:
If you let go of a helium balloon, it will rise higher and higher into the sky until it is so high that you can no longer see it.
Student Task:
Construct an explanation based on evidence for what causes a helium balloon to float up into the sky.
Model
Students develop models to describe the molecular structure of gases in the atmosphere.
Investigate
Students plan and carry out an investigation to gather evidence that gases have weight.
Obtain Information
Students read about the forces that cause an object to sink or float.
Analyze Data
Students use the Periodic Table of the Elements to compare the mass of different atoms.
Explanation:
A balloon floats away into the sky because the helium gas (plus the balloon) is lighter than the weight of the air it displaces. The denser air (made mostly of nitrogen and oxygen) pushes the less-dense helium balloon up into the sky.
NGSS Standard:
MS-PS1-1. Develop models to describe the atomic composition of simple molecules and extended structures.
[Clarification Statement: Emphasis is on developing models of molecules that vary in complexity.]
Utah SEEd Standard:
6.2.1 Develop models to show that molecules are made of different kinds, proportions and quantities of atoms.
Recommended Teaching Sequence:
Day 1:
Ask questions to define the components of the system, including the forces acting on the system.
Plan and carry out an investigation to gather evidence that gases have weight (mass).
Day 2:
Analyze data in the Periodic Table of the Elements to compare the relative weights (mass) of different gases.
Develop models to describe the molecular structure of gases in the atmosphere.
Day 3:
Read to obtain information about the forces that cause an object to sink or float in a fluid (air or water).
Construct an explanation based on evidence for what causes a balloon to float up into the sky. Support your explanation with a model of the system.
Formative Assessment:
Use what students have written in their science notebooks as a formative assessment, including their written explanation for the phenomenon and model drawing of the system. Do students understand that matter is made of atoms and molecules that are in constant motion? Do they understand that the behavior of a substance is connected to its atomic composition and molecular structure?
Lesson Contributor:
April Mitchell, Science Coach, Salt Lake City School District