ok-here goes nothin'
Measures 1 and 2 begin the expository section of the piece with the opening motive. in the next two measures the left hand mimics exactly what the right hand has done. Measures 3-4 of the right hand are in the left hand measures 5-6. This opening theme of the invention is very fugal. The PAC in F Major at measure 17 and the first beat of 18 marks the end of this opening expositional theme.
The second section is from measures 18-37 and uses the scalar passages to modulate to what sounds like a minor. there is a PAC in a minor at measure 37. in this section the melody has been passed from the left hand to the right hand while the other plays an accompaniment (an obnoxiously long trill).
The third section, which seems like a recapitulation ends on a PAC in d minor. There is a cadence at measure 48 and then what seems like a cadential extension for the next four measures to end on another PAC in d minor.
the song seems to be in a rounded binary form. nice, short, to the point...this is what i like to see.