Burning Issues

Source Institutions

Add to list Go to activity
Activity link broken? See if it's at the internet archive
Learners use a candle to investigate the products of combustion. When a glass rod is held over a lit candle, the candle flame deposits carbon on the rod. Then the candle and a drop of pH indicator are covered by a glass jar. Water vapor condenses on the sides of the jar, and carbon dioxide gas reacts with the water in the indicator to form carbonic acid. The candle goes out, and the indicator changes colors to show the presence of an acid. The combustion reaction of a candle is similar to the burning of wood or gas. Combustion reactions are responsible for some types of environmental pollution, including smog. Use this activity to introduce learners to combustion as well as greenhouse gases and global warming. For safety reasons, this activity works best as a demonstration for younger audiences.

Quick Guide

Preparation Time:
10 to 30 minutes

Learning Time:
5 to 10 minutes

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

Age Range:
Ages 11 - adult

Resource Types:
Activity, Demonstration, Experiment/Lab Activity


Materials List (per group of students)

  • One votive candle (keep 3 on hand)
  • One petri dish
  • Two 4-inch glass rods
  • Two caps from small dropper bottles
  • One 30-ml dropper bottle
  • Bromthymol blue
  • One large glass jar with a neck small enough to fit inside the petri dish cover
  • One butane lighter or box of matches
  • Paper towels
  • Two plastic beakers


  • Earth and Space Science
    • Earth Structure
      • Atmosphere
  • Physical Sciences
    • Chemistry
      • Chemical Reactions
      • Acids and Bases

Informal Categories

  • Nature and Environment


To use this activity, learners need to:

  • see
  • see color
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


Components that are part of this resource:

This resource is part of:

Access Rights:

  • Free access



Funding Source:

  • National Science Foundation