Candy Conflagration

Chemistry, Biology:	Combustion, Energy Density
Grade Range:	Elementary School, Middle School, High School
Format:	Stage

This demonstration is an exciting way to show the parts needed for a combustion reaction. There is a lot of possible information to include in this demonstration, making it versatile in the age ranges it can be used with.

Materials

• Test Tubes
• Ring Stand with Ring Clamp
• Blowtorch
• Scoopula
• Sodium Chlorate or Potassium PerChlorate salt
• Small Candies (Nerds, Sour Patch Kids, Gummy Bears, etc.)

Safety Precautions

Please read the Fire Safety section of the Demonstration Safety page before performing this demonstration. Sodium Chlorate MSDS, Potassium Chlorate MSDS

This demonstration requires: Goggles, Heat Gloves

Demonstration

1. Using the scoopula, scoop some of the salt into the test tube. fill the test tube no more than a quarter inch with the salt; too much salt and the demonstration won't work as well. Aim the test tube perpendicular to the audience. If you aren't at least 10 feet away from the audience, a blast shield is required.
2. Place some of the candy onto the scoopula, making sure that it is in small enough pieces to fit into the test tube. Set nearby.
3. Ask the audience to name the three things needed for a fire. After you get the answers, explain the purpose of the blowtorch (Heat), candy (Fuel) and salt (Oxygen).
4. Put on the goggles and heat gloves, and start heating the salt with the blowtorch. As you heat the salt, be sure to move the flame of the blowtorch around. If you keep it on one spot for too long, it may melt the glass!
5. When you see that most of the salt is melted, ask the students for a countdown starting at 5. As they countdown, pick up the scoopula, and when they reach one pour the candy into the test tube.
   • If the reaction does not start immediately, continue to heat the test tube until it starts.
6. After it finishes, let the test tube cool for a few minutes, then remove it while still wearing the hot gloves. It can be thrown away.

Why This Works

Short Explanation

Chemistry

Combustion Reactions are common reactions where we see heat as a result of the reaction. In order to have a combustion reaction, we need to have a fuel source, an Oxygen source, and a heat source. The fuel source, in this case, is the candy that we add to the test tube. Candy has a lot of sugar in it, and sugars contain a lot of energy in them. Our Oxygen source is the salt that we added at the beginning. Sodium Chlorate and Potassium PerChlorate both have a lot of extra Oxygen stored in them. This extra Oxygen is released when we heat the salt up and melt it. The blowtorch was the heat source, and by providing enough heat for the salt to melt, we can then add in the candy and watch it burn! As it burned, you should see a color to the flame in the test tube. The color is there because of the salt! Sodium gives off an orange flame when heated, and Potassium gives off a purple flame.

Biology

For a combustion reaction you need three things: a heat source, like the blowtorch, an Oxygen source, and a fuel source. The (Per)Chlorate salt was our oxygen source, since it had a lot of extra oxygen stored in it which we released by heating it. The candy that we added was our fuel source for this reaction. Candy has a lot of sugar in it, and that sugar has a lot of energy stored inside of it. The small amount of candy added to the tube would have contained about five Calories of energy in it. We use a capital C on Calories, however, because it actually stands for kilocalories. In other words, our five Calories is actually five thousand calories! Our bodies can use this energy, however, so that we can walk, talk, think and experience the world around us!

Full Explanation

Chemistry

We are looking at a classic combustion reaction: By using a heat source, a fuel and an Oxygen source, we are able to generate a flame. The Oxygen source we use, however, will determine the color of the flame during the reaction.

Sodim Chlorate:	2 NaClO3 + Heat ->	2 NaCl (Orange) + 3 O2
Potassium PerChlorate:	1 KClO4 + Heat ->	1 KCl (Purple) + 2 O2

At the start of the demonstration, we heat the Oxygen source in order to get it to break down and release the Oxygen contained within it. Since the sources we used were (Per)Chlorate salts, they contained a lot of it, and so the decomposition of the salts will generate a large amount of Oxygen. It is important that, during this step, we make sure to not heat the salt too long. If we do, then they will completely separate before we drop the candy in, and by that point much of the Oxygen will be gone from our test tube, resulting in a failed demonstration.

When the reaction itself takes place, we see a classic combustion reaction between the sugar (Glucose) in the candy and the Oxygen:

Candy Conflagration:

C6H12O6 + 2 O2 ->

4 C + 2 CO2 + 6 H2O + Heat

We get four products from this reaction, of which we only see two of them: the Carbon and the heat released. The Carbon we see left behind in the test tube, and we also see part of it in the smoke that comes out of the reaction. The heat we very clearly see coming out of the test tube as a flame, which is colored based on the salt that we added at the beginning. Elements have different wavelengths of light that they give off when heated. Metal, including the alkali metals, give very distinct colors when they are heated, which makes it easy to identify what metal is being burned. This method of identifying elements is known as Wave Chromatography.

It is worth noting that this reaction is not what we would call a "clean" combustion reaction. A Clean combustion is when you have a reaction that only has three products: CO₂, H₂O and Heat. Although this reaction could have the necessary things to be clean, There is a limiting factor: How much free Oxygen there is to bond with. Since we have it within a test tube, there is only a small amount of space for the reaction to take place. Because of this, the Oxygen released from the salt as it is being heated is, for the most part, escaping from the tube. This loss of available Oxygen means that, by the time we drop the candy in, there isn't as much Oxygen left for it to react with, and therefore some of the carbon has to be left behind as a product, Which we see inside the test tube and released as smoke.

Additional Information

• This demonstration pairs well with the Burning Salts and the Methanol Cannon.
• This demonstration is a part of the Chemistry Show