Obi wan hears the destruction of a planet and all of its people through 'the force'. these sounds are only in his head and are not carried through space, since space has no through which sound could transmit.

a community that experiences major changes undergoes progress

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds