Air, It's Really There

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This lesson focuses on molecular motion in gases. Learners compare the mass of a basketball when it is deflated and after it has been inflated. The inflated ball has the greater mass so learners can conclude that gas is matter because it has mass and takes up space. Then learners consider how heating and cooling affect molecular motion in gases. They dip the mouth of a bottle in detergent solution and observe a bubble growing and shrinking when the bottle is warmed and cooled. Learners will discover that the attractions between gas molecules are so minimal that attractions can’t be used to explain the behavior of gases like they can for liquids and solids.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
45 to 60 minutes

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 11 - 14

Resource Types:
Activity, Demonstration, Experiment/Lab Activity, Lesson/Lesson Plan


Materials List (per group of students)

  • 2 clear plastic cups
  • 8-oz plastic bottle
  • Detergent solution in a cup
  • Hot water (about 50 °C)
  • Cold water
  • Basketball, very deflated
  • Balance that measures in grams
  • Pump
  • Can of compressed gas (available at any office supply store)
  • Goggles


  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
    • Chemistry
    • States of Matter
      • Solids
      • Liquids
      • Gases
    • Structure and Properties of Matter
      • Elementary Particles and Nuclear Physics
      • Mass and Weight
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Sports and Exercise
  • Toys


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves hands-on or lab activities