K – Grade 3 students
Have you ever seen how fire flies glow at night? Or how about the way a glow sticks glows? These are examples of a process called luminescence, where light is being released from something. We can see that a reaction is happening between liquids in a glow stick because the glow stick starts glowing. With fire flies, it is 2 mixtures in their body that react together to attract other fire flies.
Grade 4 – 5 students
At this grade level, students know that all matter is made up of atoms and that the atoms in the reactants rearrange to form products during chemical reactions. They can also identify that a reaction has happened based on the change in appearance of a solution. They should begin to understand the concept that energy is transferable amongst reactions and can be produced during reactions.
Have you ever had glow in the dark stars or paint that you have to leave in the light for a while so they will glow when you turn the lights off? What you are seeing is an example of luminescence, which is the emission of light from a reaction. Your paint or stars are an example of a reaction involving light that causes the paint or stars to glow. Sometimes when a reaction takes place and energy is released, we can observe the energy by seeing light. To create glowing chemicals, the energy that was stored in the different reactants has to be moved around. When energy is being moved around within the reaction, some of it may be released to the surrounding area and we can observe that energy in the form of light.
Middle school students
At this grade level, students can determine if energy is being transferred based on observations and how the energy can be moved around within a reaction. They will also have an understanding of how energy can be measured in the form of light or heat, and should have a brief knowledge of electrons.
Have you ever had glow in the dark stars or paint that you have to leave in the light for a while so they will glow when you turn the lights off? What you are seeing is an example of luminescence, which is the emission of light from a reaction. Your paint or stars are an example of a reaction involving light that causes the paint or stars to glow. Sometimes when a reaction takes place between things like light or chemicals and energy is released, we can observe it by seeing light. When a reaction takes place, electrons within the reaction can be excited, which means they are given energy. This excitement allows the electrons to store up the energy until all of it is gone and then the electrons release the energy and emit light. It’s kind of like going up and down stairs. You need energy to go up and once you run out of stairs you have to go back down. If you were an electron, you would glow when you went back down because you would be releasing your stored up energy
College-level/ scientific description
Luminescence is the process of light emission due to a reaction. In order for something to emit light, it must have electrons that are pushed into an excited state and then allowed to fall back down to the ground state. Forensic scientists use a chemical known as luminol (that is mixed with hydrogen peroxide) to illuminate blood at crime scenes. The hydrogen peroxide reacts with the iron in the blood to produce oxygen. The oxygen then reacts with the luminol in order to create a reaction and produce energy. We use bleach to create the same effect but with more drastic results.
The excess energy is then taken in by electrons in the system to excite them and push them into higher energy levels until the energy is fully consumed. Once the energy is fully consumed, the electrons become unexcited and will fall into lower states and will emit light in the process. The reason we use a bleach instead of hydrogen peroxide and blood is so that we have even more energy going into the system that can be taken up by the electrons.