Fluorescent Liquids

Chemistry, Biology:	Fluorescence
Grade Range:	Elementary School, Middle School
Format:	Hands-on

This demonstration will be fun for students to come and look at, since it uses a black light and is all about making things glow!

Materials

• Fluorescent Liquids Box
• Q&A Cards for Liquids
• Black Light
• Black Cloth

Safety Precautions

Please read the Liquid Chemical section of the Demonstration Safety page before performing this demonstration.

Demonstration

1. Lay out the black cloth on the table, and set the fluorescent liquids box underneath to use as a backdrop. Set out the eight bottles in the color order provided in the Why This Works section. Place the black light either between the bottles and the box or on top of the box. Turn on the black light. Set the Q&A cards in front of their respective bottles. If you'd like, you can also set out the wooden frame with the five smaller bottles, but keep it aside and don't allow students to handle it.
2. As students come up, ask them to try and identify the liquids inside of each bottle, and after each guess they can look at the Q&A card for the respective bottle. Some of the liquids they won't recognize, but most of them they will!
3. After students make guesses, you can turn off the black light to show what colors the solutions are normally. What causes them to change color? Why do they glow?

Why This Works

Fluorescence is when something can absorb high energy light, and then releases lower energy light. Black lights give out violet light, which has a lot of energy to it. Fluorescent materials, such as these liquids, can absorb the violet light, which gives them a lot of energy. The extra energy they give out as light, but the light they give out will have less energy, and will be closer to red on the color scale. The term fluorescence comes from the element Fluorine, which glows brightly under a black light.

Fluorescence is quite common, and it is useful in many research fields. Some animals and plants can glow under black light, and this is called Biofluorescence. Geologists can identify some rocks and minerals based on what color they glow under a black light. Fluorescence has a lot of practical applications as well. Fluorescent lights use fluorescence with the elements or chemicals inside of them to create light. Most white products, such as plastics, paper and clothing, will glow because of white fluorescing agents that are added to them. Almost all safety clothing can fluoresce as well, so it is easier to spot when light shines on it.

Vials

Color	Chemical/Compound
Red	Rhodamine B
Orange	Rhodamine 6G
Green	Fluorescein
Blue	Quinine Sulfate
Indigo	Primuline

Bottles

Color	Chemical/Compound	Additional Info
Red	Resazurin (Redox Indicator)	Higher concentrations will give dark red and purple fluorescence.
Pink	Toilet Bowl Cleaner	This bowl cleaner glows because it uses Phosphoric Acid.
Yellow	Fluorescein	Higher concentrations will give green fluorescence.
Green	Vegetable Oil	Vegetable oil fluoresces partly due to extra chlorophyll in it.
Teal	Honey (in Water)	Honey only weakly fluoresces, which is why beehives don't glow.
Blue	Laundry Soap	Laundry soap has fluorescent compounds added to help clothing look brighter.
Light Blue	Tonic Water	Tonic Water glows because of the Quinine Sulfate added to it.
Indigo/Violet	Salt Water (Concentrated)	Salt only weakly fluoresces, which is why the ocean doesn't glow.

Additional Information

• This demonstration pairs well with the Glowing Bubbles demonstration
• Some of our other demonstrations will fluoresce as well! Try using the following with this demonstration:
  • Balloon On A Stick
  • Banana DNA
  • Box of Rocks
  • Density Rainbow
  • Oobleck
  • Radioactivity
  • Shaking Solution