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The Fizzy Candle - University of Manitoba - baking soda and vinegar facts

The Fizzing Candle

1 Materials Required:

• Candles
• Fire safe container (E.G.: beaker, tin can, or small pie plate)
• Lighter or matches
• Baking soda
• Water
• Vinegar
• 2 small beakers or other such containers for pouring liquids

2 Safety Considerations:

• If doing this activity in table groups, remind students to be safe with the fire and to only use lighter or matches to light the candle!
• This activity can also be done as a teacher led demonstration for an unruly class.

3 Curricular Content:

This experiment lines up with the Manitoba Middle Years Specific Learning Outcome of:
It states that students will:
Investigate to determine how characteristics and properties of substances may change
when they interact with one another.

4 Lesson Procedure:

This lesson will use the P.O.E. model of instruction with the students explaining their predictions on paper.

1) In advance, take out all supplies the students will need when they arrive. At each station
o 1 candle
o 1 fire safe container
2) When class begins, have 1 student from each group place 50 ml baking soda in their container and return the container to the centre of the table.
3) Have second student get 30 ml vinegar in a small beaker and place it on the table.
4) Have third student get 15 ml water in a small beaker and place it on the table.
5) When all students are back at their seats, remind them about fire safety as you hand out the matches.
At this point, ask students to pull out a piece of paper and a pen or pencil. They will use this to write down their predictions.
6) Ask students to write what they predict will happen when they add water to the baking soda.
7) Ask the students to write what they predict will happen when they add vinegar to the baking soda.
8) Once the students have completed their predictions, have one member of each group carefully light the candle.
9) Have another student pour the water carefully into the baking soda without pouring any on the candle.

Observation: Did what they predict happen?
At this point, nothing fantastic should happen. The water will just be absorbed into the baking soda to make a paste.
10) Have another student carefully pour the vinegar into the baking soda.
Observation: Did what they predict happen? Did anything happen?
At this point a couple of things should happen:
• The addition of the vinegar should cause the baking soda to begin to fizz.
• The candle should go out.

This activity will likely cause disequilibrium in students. While some students
may predict that the addition of vinegar to baking soda will cause the fizz, many
would not expect the candle to go out as a result. To bring the students back to
a place of equilibrium, we must explain what is happening and why.

What is happening in this activity is a multi-step reaction:
A) Acetic Acid (the sour in the vinegar) reacts with the sodium bicarbonate (the baking soda) to form carbonic acid.
B) Carbonic acid is unstable and immediately falls apart into the gas carbon dioxide and water. (A decomposition reaction.)
The bubbles (or fizz) are a result of the reaction that comes from the carbon dioxide escaping the solution that remains.
Carbon dioxide is more dense (heavier) than oxygen (which the candle needs to remain lit) therefore the oxygen is forced upwards away from the candle. The flame is extinguished because the carbon dioxide forces the oxygen away and basically suffocates the candle.
What is left in the container is a dilute solution of sodium acetate in water.

5 What if…?

It is very easy to change the variables in this activity to experiment further. The students can either research or predict other materials that will react to form carbon dioxide and test them to see whether or not they extinguish the candle
Some ideas include:
o Warm water with yeast and sugar
o Diet Coke and Mentos
o Diet Coke and rock salt
Students could also change other variables in the activity such as:
o The size of the container
o The height of the candle
o Subtract the water initially added to the baking soda

6 Concluding Questions for Students:

1) What was used to perform this experiment?
What did you see?

2) Why did nothing happen when the water was added yet the “fizz” formed when the vinegar was added?

3) Why is this considered a decomposition reaction?

4) Can you think of any other substances which when added together form a paste (like the baking soda and water) or a gas (like the baking soda and vinegar)?

5) Explain why the candle was extinguished.

7 References:

Koballa, T.R. The motivational power of science discrepant events. Retrieved 27 September
2008, from http://bcramond.myweb.uga.edu/home/DiscrepantEvents.htm

Steve Spangler Science. Mentos geyser: Diet Coke eruption. Retrieved 10 October 2008, from

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