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Finding the Carbon in Sugar

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.

Session 1: The Burning Candle

In this activity, students will learn about combustion and energy by sealing a burning candle in a jar and by burning white sugar. They will observe, measure, predict, record observations, infer and draw conclusions based on their investigations. Students will discover that burning (combustion) is a chemical reaction that 1) takes place when a fuel combines rapidly with oxygen and 2) produces substances such as CO2 and water.  

  1. Direct students’ attention to the materials you have gathered (a large beaker, candle, matches, and wet paper towels). Light the candle and ask, What is happening to the candle? After students answer that it is burning, ask, Are we seeing a physical change in the candle, or a chemical change? Remind students that chemical changes produce substances different from the ones that were originally present. Chemical changes also usually produce or consume energy. 

  2. Prompt students to predict what might happen if the candle is covered with the beaker. After students have made their predictions, place the lighted candle on the wet towels and cover it with the beaker. Fold the edges of the towels around the lip of the container to create a seal. Have students observe what happens to the candle. The flame will grow progressively smaller until it finally extinguishes (this usually takes less than a minute). 

  3. Ask students, What happened to the candle? Did it run out of material to burn? Do you think it ran out of something else? Help students understand that the candle used up all the oxygen trapped within the beaker. Lift the beaker slowly and have students observe the other substances present: smoke and condensed water vapor on the sides of the glass. Let them examine the candlewick. Ask, What can we see or feel that was produced by the burning candle? (heat, water, smoke, charred wick) What did the candle use as fuel while it was burning? (melted wax and the wick as fuel, oxygen gas from air)


Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932


Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education