Combustion (Belen Santiago)
Title: Sugar Snake Combustion
Principle(s) Investigated:
Standards: MS-PS1-1 Develop models to describe the atomic composition of simple molecules and extended structures
Materials:
-Sugar
-Baking Soda
-Sand
-Lighter Fluid
-Lighter
Procedure: There are other ways to do this
Mix 4 tablespoons of sugar with 1 tablespoon of baking soda
About 1 pound of sand, make a mount
Drench the sand in lighter fluid
Put the mixture of sand and baking soda in the center of the sand
Light of the sand
Student prior knowledge: Molecules, chemical reactions
Explanation:
The carbon sugar snake is the product of chemical reactions that are all dependent on heat.
The first of these reactions occurs when sugar combusts (burns) in the presence of oxygen. This produces carbon dioxide gas and water vapor (also a gas), which pushes more of the sugar/baking soda mixture upwards. Some of this additional sugar heats up but doesn’t have access to any oxygen, so instead of burning, it undergoes thermal decomposition, producing solid carbon and more water vapor. This solid carbon now gives the snake some shape, and also gives the snake its black color. Lastly, the baking soda also decomposes in the heat, producing solid sodium carbonate, and carbon dioxide gas and water vapor. Altogether, these reactions produce both the solid components of the snake (carbon and sodium carbonate) and hot gases (CO2 and water vapor) that expand and inflate the snake up and out of the sand bowl.
The sand in this experiment doesn’t chemically react with anything in the growing snake. Instead, it evenly distributes the heat from the burning lighter fluid to the sugar and the baking soda, ensuring a slow, steady burn and the growth of a long carbon sugar snake.
Questions & Answers:
Why do we add baking soda (NaHCO3) to the sugar?
Baking soda decomposes when heated to release carbon dioxide (CO2):
2NaHCO3 → Na2CO3 + H2O + CO2
Baking soda is added to bread dough to make it rise, and it is the same for this experiment. The carbon dioxide and water vapor that is given off make the snake light and airy, which allows the snake to grow.
What is this "snake" made of?
The "snake" consists of mainly carbon that comes from the heated sugar, but which was not burnt in the flame. The carbon is what makes the "snake" black. There is also Na2CO3 sodium carbonate in the snake, which results from the decomposition of the baking soda when heated.
What chemical reactions occur in the process of formation of the "snake"?
The three main reactions in this process are:
- Combustion of sugar to give carbon dioxide and water vapor:
С12H22O11 + 12O2 → 12CO2 + 11H2O
- Thermal decomposition of sugar to give carbon and water vapor:
С12H22O11 → 12C + 11H2O
- Thermal decomposition of baking soda to give sodium carbonate, carbon dioxide, and water vapor:
2NaHCO3 → Na2CO3 + CO2 + H2O
Applications to Everyday Life:
Sugars are important building blocks in plants. Plants produce simple sugars from water and carbon dioxide during photosynthesis. Simple sugars can be linked together to form small molecules, such as sucrose, or to form long chains. Starch and cellulose are examples of long-chain sugars that are made up of simple sugars, also known as polysaccharides. Plants use sugars as building materials and for nutrient storage.
The longer the sugar molecule, the more difficult it is for our bodies to digest it. Therefore we tend to love sweet things, which contain short, simple sugars. But your body was not designed to eat many simple sugars, and in nature they are rare.
Photographs:
Videos: Sugar Snake