Science Assessment

A person is going for a walk in the evening. To make sure that she can be seen walking when it gets dark, she wears a glow stick around her neck. The glow stick can be used as a light source when she bends the stick. Although the stick is sealed, bending the stick allows two chemicals to come in contact and react with each other. During the chemical reaction, light is given off by the glow stick.

When the reaction stops, light is no longer given off. What happens to the mass of the glow stick after the chemical reaction occurs? Explain.

1. The mass will decrease because there are fewer atoms inside of the glow stick after the reaction. Some of the atoms were turned into energy that is given off in the form of light.
2. The mass will increase because there are more atoms inside of the glow stick after the reaction. Some energy from the light was turned into atoms.
3. The mass will stay the same because the number of each type of atom inside the glow stick did not change. Some of the atoms separated from one another and then connected in different ways to form different molecules.
4. The mass will stay the same because the total number of atoms inside of the glow stick did not change. Some of the atoms changed into different atoms that form different molecules.