Cup Phone

📞 What is it about?

Connect two cups with a string and talk to each other from a distance. Discover together how sound travels through solid materials in this classic science experiment.

👶 Recommended age: 3–7 years
⏱ Estimated time: Less than 1 hour
💪 Energy level: Medium
💰 Approximate cost: Low

🛒 Materials needed

• 2 plastic or cardboard cups
• Sturdy string or thin rope
• A needle or toothpick to make the hole
• A paperclip or toothpick to hold the string inside

🛒 Science experiment kit for kids

🏠 Home alternatives

Don't have all the materials? No problem.

• Instead of plastic cups → use empty clean aluminum cans — they transmit sound even better.
• Instead of string → use a shoelace or thick yarn.
• Everything you need is probably already at home.

📋 Step-by-step instructions

1. Make a small hole in the bottom of each cup with the toothpick or needle.
2. Thread the string through the hole in each cup and tie it to a paperclip or toothpick so it doesn't slip out.
3. Stretch the string between the two cups until it is taut — it must not be loose.
4. One person speaks softly into their cup while the other listens through theirs.
5. Experiment with different string lengths and materials.

💡 Extra ideas

• Try string made of different materials — wool, rope, yarn — and compare which one carries sound the best.
• Try bending the string to see if the sound bends with it.
• Explain to your child that the string vibrates when you speak and those vibrations travel to the other cup — just like headphones work.

🎥 Example video

Watch tutorial