Combustion/Pollution

Students will realize that air pollution is not always seen, and that all things that burn create some sort of air pollution. Through subsequent lessons, the effects of this pollution can be explored.

This is a great inquiry/observation that can be used to generate questions about the chemical and physical changes that are taking place during the process of burning. I use this in my 4th grade science unit on air pollution. It can be done with a small or large group. Total time is about 30 minutes. You will need small candles (tea type) and small Pyrex dishes. I use this simple observation to introduce the impact of pollution on our bodies. Seeing the actual byproducts created by a burning candle has quite an impact on the students.

Start the lesson by asking students what the words combustion and pollution mean to them. Make a list of terms the students give you. At the end of this discussion the students should understand that combustion requires fuel, oxygen, and a heat source. Students are then divided into groups as small as 2 or as large as 6 or 8. Each group is given a small candle to observe. Students are instructed to write down, in as much detail as possible, what they observe about a burning candle. After about 5 minutes make a list of the students' observations.
Ask the students what heat source caused combustion to occur (the match or lighter), what is the fuel being consumed (the wax), what else is necessary to maintain combustion (oxygen or air). Then ask the students if the candles are polluting the air. Most students will agree that you cannot see anything coming off of the burning candle. To show visually the carbon and other byproducts being produced by the burning candle, hold the bottom of a Pyrex dish over the flame, letting the flame lick the bottom of the bowl slightly. You will see a buildup of soot rather quickly. Give the students another five minutes to look, touch, and smell what they see on the bottom of the bowl. They should then describe this on paper. Discuss what this substance is and when it is not being collected on the bowl where does it go?

Because this lesson involves fire and burning matches and candles you will need to discuss safety concerns with the students prior to the lesson. I light all the candles, but I have let the students put the Pyrex bowls over the flame. To extinguish the flame have the students put the bowl over the top of the candle. A whole new series of observations and questions can be generated from this.

I have all students list their observations. I also use a simple graphic organizer to see if the students are making a cause and effect connection.

Science
3.1.1.2.4 Construct reasonable explanations based on evidence collected from observations or experiments.
4.2.3.2.1 Identify several ways to generate heat energy.