premise: a guitar is a kind of musical instrument sent2: as matter vibrates harder / faster , the volume of the sound produced will increase sent3: a string is a kind of object made from matter sent4: as a string of a musical instrument is plucked harder , the pitch produced will not change sent5: as a string of a musical instrument is plucked harder , the string will vibrate harder / faster.
hypothesis: the mass of substance will stay the same during thermal expansion caused by increasing heat