Year 5 – 6 | Making UV Visible: Glowing Water

Protecting My Skin full resource download  |  Concept 2: Heat and UV from the sun: What’s the difference? download

Background

This lesson provides students with the opportunity to further explore ultraviolet (UV) radiation. It can be used as a follow on
or extension lesson to lesson 4. This experiment simulates what UV light would look like using a bottle of tonic water and a
highlighter pen.

Key messages

• Ultraviolet light interacts differently with matter for a number of reasons:
  – Some pigments selectively absorb UV so they may appear white in the visible but dark in the UV. The pigments
  usually dissipate the UV energy as heat, though the breaking of bonds can also occur
  – Fluorescent molecules absorb UV light and re-radiate that energy as visible light. This makes them look dark in
  the UV but glowing under black light
• Tonic water and highlighters glow under black light because they contain fluorescent chemicals. It contains phosphors
  that turns UV light (light we can’t see) into visible light (light we can see). These chemicals absorb light and then release
  it back
• In this case they absorb highly energetic invisible UV light and release less energetic but visible light. The water is
  transparent, so it is easy to colour with these glowing chemicals. The glowing water can be reused again and again and
  will never lose its glow.

Resources

• The World in UV
• Science questions website
• Science kids’ website
• Dark room to conduct experiment
• Tonic water
• Yellow highlighter
• Clear glass or container
• Black light or UV light

Instructions

1. Make predictions about the scientific investigation and answer the following question
   – What will happen when we place UV light on a glass of tonic water with highlighter dye in a dark room? Record predictions in exercise book.
2. Remove the back of a highlighter and pour some tonic water into the glass or container.
3. Take the ink-soaked felt out of the pen and soak it in the container of tonic water for an hour or so. Squeeze the felt
   until almost all the ink has been transferred to the tonic water.
4. Place the container in a dark room.
5. Place the black light (long wave ultraviolet light) near the glass of tonic water and turn on the switch. The water will
   glow an eerie green.
6. Prompt discussion and ask key questions. Simple explanation: The dye from the highlighters placed in the tonic water
   contain phosphors that turn UV light (light we can’t see) into visible light (light we can see).
7. Explore and explain: Students communicate their ideas, explanations and processes using scientific representations in a
   variety of ways, including multi-modal texts.
8. Students present their findings to the class.

Key questions

• What will happen when we place UV light on a glass of tonic water with highlighter dye in a dark room?
• What do you see? Why do you think this is happening?
• How can we incorporate and use the SunSmart Global UV app into our daily routines?