Skip to Content

Systems and Scale | Activity 2.3

Activity 2.3: Zooming into Air (30 min)

Target Student Performance

Students describe air at atomic-molecular, microscopic, macroscopic, and large scales, identifying specific molecules in air.

Students “zoom into air,” moving from large scale down to the atomic-molecular scale. They learn about atoms and molecules, and are introduced to air molecules: N2, O2, H2O, and CO2.

Resources You Provide

  • piece of paper (1 per student)

Resources Provided

Recurring Resources


Prepare a computer and a projector to display the PPT.


1. Use the instructional model to show students where they are in the course of the unit.

Show students Slide 2 of the 2.3 Zooming Into Air PPT

Formative assessment takes place in steps 3 and 7 of the activity. When students are asked about whether air has mass, Level 2 students, in particular, may not believe that air has mass or is made of atoms. They probably think of air as insubstantial—not a material like solids or liquids. Some Level 2 students and virtually all Level 3 students say that air has mass and is made of atoms, but they often fail to consider the mass of gases or the atoms and molecules in gases when they explain carbon transforming processes, like combustion or plant growth.

When students are asked questions about atoms in ethanol, most students will confirm that ethanol contains atoms, but many of them will not be able to apply the facts about atoms to the atoms in ethanol. For example, saying that the ethanol is “burned up” or “turned into energy” is in conflict with the first fact: Atoms last forever. When questioned about atoms in flames, students may have difficulty because in a flame we see both materials: glowing gases and white-hot particles of soot, which are made of atoms; and forms of energy, heat and light, which are not made of atoms.

Remember that these questions are particularly difficult and especially challenging for Level 2 students who are just learning to connect atomic models with macroscopic phenomena.


Make sure that students are watching actively by assigning them to identify the systems at one of the four benchmark scales: atomic-molecular, microscopic, macroscopic, or large scale.