What do you think, can water bend a straw? What about other clear liquids?
In this super simple science experiments, kids will learn about light, refraction, and why a straw appears to be bent when submerged in a glass of liquid. You’ll find printable instructions, a video demonstration, and a helpful explanation of how this experiment works, below.
- Empty Glass
- Plastic Straw
Step 1 – Start with some observations about the straw. Is there anything unusual about the straw? Make sure the kids notice that is it perfectly straight. Next, place the straw in the empty glass. Make a few more observations and point out that the straw is still straight.
Helpful tip: Use a large plastic straw from a water bottle to see the results more clearly.
Step 2 – Next, pour water into the glass until it is nearly full. Now make a few more observations. What is different about the straw? Make sure to look directly at the side of the glass at the straw. What do you see?
Step 3 – You will notice that near the top of the water line the straw appears to bend. Remove the straw from the water. Is it still bent? Do you know what caused the straw to appear to be bent? Find out the answer in the how does this experiment work section below.
When you add the water to the glass, the straw appears to bend, but once you remove the straw you see it isn’t really bent at all. This is because the straw is not bending, but the light around the straw is bending due to refraction. Light refracts as it passes from one medium to the next because it travels at different speeds through those mediums. Light travels fastest through air, a little slower through water, and even slower through glass.
Refraction is the bending of light as it passes from one medium into another (ie. air to water, water to air).
We need light in order to see. When we look at the straw outside of the glass of water, the light coming from the straw travels through the air straight to your eye. As you look at the straw in the glass of water, the light coming from the straw to your eye bends as it passes through three different mediums (water, glass, and air). As the light passes from one medium to the next, it changes speed and bends.
Other Ideas to Try
Try this experiment with liquids other than water. Liquids to try would be light corn syrup, rubbing alcohol, or clear Gatorade. Does the liquid you use affect how much the straw appears to bend?
I hope you enjoyed the experiment. Here are some printable instructions: