making a telephone system from polystyrene cups and string.
2 cups per child, string. Also consider yoghurt pottles, fishing line, sharp pencil or sewing needle
make a hole in the bottom of the cup, attach the string and two children take the telephone - one either side of a door... can you hear your partner.... how does the sound travel??
Speaking into the cup creates sound waves which are converted into vibrations at the bottom of the cup. The vibrations travel along the string and are converted back into sound waves at the other end so your friend can hear what you said. Sound travels through the air but it travels even better through solids such as your cup and string, allowing you to hear sounds that might be too far away when traveling through the air.