Hot Air

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In this activity, learners set up an experiment to investigate the effects of hot air on the path of a laser beam. They observe the wandering position of the laser beam spot on the wall after the light travels through hot air rising from the candle flame. Learners produce a table of observations from both the Cool Air and Hot Air experiments, and answer questions using evidence from their experiment. Apply what learners discover in this experiment to real-life by discussing why stars "twinkle."

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
45 to 60 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 14 - 18

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


Materials List (per group of students)

  • Candle holder (modeling clay, or sticky adhesive putty)
  • Candle (birthday cake size) and matches or lighter
  • Laser pointer
  • Binder clip
  • Graph paper (8.5 x 11 inches with 1/4 inch grid size)
  • Masking tape
  • Cup (8 to 12 inches high) preferably non-flammable
  • Meter stick


  • Earth and Space Science
    • Astronomy
      • Stars and Galaxies
      • Probes, Satellites and Spacecraft
    • Earth Structure
      • Atmosphere
  • Physical Sciences
    • Heat and Thermodynamics
      • Heat and Temperature
    • Light and Optics
      • Lasers
      • Reflection and Refraction
    • Structure and Properties of Matter
      • Volume and Density
  • Engineering and Technology
    • Engineering
      • Aerospace Engineering
  • Life Sciences
    • Human Senses and Perception
      • Vision
      • Perception
  • Mathematics
    • Data Analysis and Probability
      • Data Analysis
      • Data Collection
      • Data Representation
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results


To use this activity, learners need to:

  • see
  • read
  • touch

Learning styles supported:

  • Involves teamwork and communication skills
  • Involves hands-on or lab activities


Components that are part of this resource:

Includes alignment to state and/or national standards:

Includes assesments for student learning:

This resource is part of:

Access Rights:

  • Free access


  • The University of Texas McDonald Observatory


  • All rights reserved, The University of Texas McDonald Observatory, 2011