Make Music with Water Glasses

In this science experiment, kids explore sound and pitch by turning glasses of water into musical instruments.

Sound is created through vibrations. The vibrations create waves that travel through the air until they are either received (for example, by your ear) or absorbed.  For example, when someone plucks a guitar string, it causes the string to vibrate.  These vibrations then push through the air, making the molecules in the air bump into one another (like dominoes falling) until the vibration reaches your eardrum and makes it vibrate.

Sound waves themselves are invisible, but you can sometimes feel them, and you can see them when they bump into something solid and make it move, such as a bowl full of rice placed on top of a speaker.  

In this experiment, you create sound waves when you strike the glass.  The sound waves sound the same when the glasses are empty, but when you add water, it changes the size of the sound waves, because many of the sound waves created have to travel through the water before they can reach your ear.  (Think about how it feels to walk through water -- this is how the sound waves feel too!)  This changes the "pitch" of the sound you are hearing.  The more water, the lower the pitch.  The less water, the higher the pitch.