Today, you are going to be learning about chemiluminescence. Wait, what?! Let’s back up. Have you ever seen a firefly? As you know, fireflies are one of the unique creatures that glows in the dark. The reaction that fireflies use to glow is called bioluminescence. Fireflies, among other bioluminescent organisms, mostly use their glowing abilities to attract mates.
1. What are the different kinds of light?
2. Does all light produce heat?
3. How do glow sticks emit light?
Now that you know the background behind light sticks, let’s experiment!
YOU WILL NEED:
• Three glow sticks (same size and color)
• Three tall glasses
• A dark room
Here’s what to do!
1. Take your glow sticks out of the package. Make observations, feel them, and take notes about their appearance.
2. Bend one of the glow sticks. You should hear a snap. What happens after you bend it? It should have started to glow! Feel the glow stick--has the temperature changed? Take notes about the glow stick after you bent it.
3. Bend the other two glow sticks. Wait one minute to make sure all three are glowing at the same intensity. You can move on to the next two steps while you are waiting.
4. Fill one tall glass with ice water.
5. Ask an adult to help you fill the second tall glass with hot water. Make sure it’s not TOO hot! You will be placing a glow stick in the water and don’t want to melt the plastic. 50 degrees C /120 degrees F is an appropriate temperature.
6. Place one glow stick in the glass of ice water and one glow stick in the glass of hot water. Place the third glow stick in a glass of room temperature water between the other two. This will allow you to easily compare the intensity of the glow. Start the timer.
8. Observe each glow stick. What is happening to them? Are they all giving off the same amount of light? How long did it take for the light intensity to change?
9. You should have seen the glow stick in the ice water grow dimmer and the glow stick in the hot water glow brighter. Why do you think this happened?
10. Now, switch them! Place the glow stick that was in the hot water into the ice water, and place the glow stick that was in the ice water into the hot water. Set the timer.
11. How long did it take for the glow sticks to return to a “normal” glow? How long did it take for the sticks to get brighter/dimmer than the room temperature glow stick?
12. Remove all three glow sticks from the glasses and set them on a table. Set the timer. How long does it take for them to return to a normal (room temperature) glow?
ANALYZE: Explain how temperature affected the glow of the light sticks.
So why did the cold water cause the glow stick to become dimmer and the hot water cause the glow stick to become brighter? Chemical reactions occur slower at lower temperatures and faster at higher temperatures. When you put a glow stick in cold water, the chemical reaction slows down but will last for a longer period of time. When you put a glow stick in hot water, the reaction speeds up but will be over quicker. How can you test this out? Try putting one glow stick in the freezer and one in hot water to compare how long each lasts!