Why Does Cutting an Onion Make You Cry?
Description: This phenomenon can be used to illustrate both chemical reactions and the particle nature of matter. Onions gather sulfur from the ground to form large organic compounds. When the cells in an onion are breached (during cutting or eating) they release sulfenic acid which becomes a sulfur containing gas that eventually reaches your eye. Your eyes produce tears to remove the irritant. Students could speculate on how the irritant reaches your eyes and even investigate possible solutions to this problem. This phenomenon was submitted by Brian Babulic.
Web Resource: Science News for Kids - Informational Text Article
Indestructible Coating - Polyurea
Description: In this video a watermelon is covered with a polymer and survives a drop from a large tower. The polymer is formed when two reactants join to make a flexible and durable polymer known as a polyurea. The chemical reaction is exothermic, releasing heat as the reactants combine. This phenomenon could be used in a unit on chemical reactions, extended structures or chemical engineering. The company Line-X uses this polymer to make bed liners for pickup trucks.
Web Resources: Polyurea - Wikipedia, Line-X
Aerogels - World’s Lightest Solids
Description: Aerogels are a group of synthetic materials that are incredibly light and also amazing insulators. They have numerous applications such as insulators in electronics. Aerogels were used as thermal insulators in the Mars Rover and also act to filter space dust. This phenomenon could be used as an application of chemical engineering or as an example of a thermal insulators.
Web Resource: Aerogel - Wikipedia
Reaction in a Bag
Description: This video shows a chemical reaction of sodium bicarbonate (baking soda), calcium chloride (road salt), and an indicator phenol red. The chemicals react to form calcium carbonate, sodium chloride, and carbon dioxide gas. This changes the pH inside the bag resulting in a color change in the phenol red. As much air as possible should be removed from the bag as possible to show the production of the gas. This could be used as an example of chemical reaction that releases energy (exothermic). Since the bag is sealed it could be massed before and after to show the conservation of mass (atoms). This phenomenon was submitted by Brian Babulic.
Web Resources: Reaction in a Bag - Flinn Scientific, American Chemical Society - Explanation
Burning Steel Wool
Description: This is an excellent phenomenon to discuss chemical reactions and the conservation of mass. Steel wool is burned leading to an increase in mass. When doing this in class show the students the burning steel wool to begin with and have them predict the change in mass. Most students believe the mass will either increase or decrease. This phenomenon can be used at the beginning of a unit on chemical reactions and students can investigate their individual models. (e.g. mass comes from fire, oxygen, carbon, etc.)
Web Resources: Combustion of Iron Wool - CFNS Experiment 36
Will It Conduct?
Description: Conductivity is an excellent way to classify material by their observable properties. Conducting material (e.g. metal), non-conducting material (e.g. plastic), and semi-conducting material (e.g. graphite) should all be used. A simple circuit with a lightbulb is used to determine the conductivity of different materials. These properties can be used to determine if a chemical change has occurred by testing before and after substances have been mixed. These properties can also be used in the design of an engineering solution.
Web Resource: Teach Engineering - Conductivity
Slime
Description: Everyone loves slime...especially elementary students. This phenomenon is a great introduction into chemical reactions. The properties of the reactants can be compared to the properties of the products to show that a chemical reaction has occurred. In high school the chemistry of polymers and cross-linking can be explored through slime.
Web Resource: The Science of Slime - American Chemical Society
Elephant Toothpaste
Description: Elephant toothpaste is a dramatic chemistry demonstration that involves the decomposition of concentrated hydrogen peroxide (H2O2) into water and oxygen. Potassium iodide is used as a catalyst to speed up the reaction. Soap is added to trap the escaping oxygen gas and food coloring is often added to the experiment. This phenomenon can be using in elementary science classes to illustrate non-reversible reactions and can be studied in more detail in middle and high school.
Web Resource: Elephant toothpaste - Wikipedia
