Answers:
High-energy electrons from NADH and FADH2, are passed into and along the  electron transport chain . 
The energy from the electrons moving down the chain is used to move H+ ions across the  inner membrane .
H+ ions build up in the  intermembrane  space, making it  positively  charged and making the matrix negatively charged. 
In the inner membrane, H+ ions move through channels of  ATP synthase .
The ATP synthase uses the energy from the moving ions to combine ADP and phosphate, forming high-energy  ATP .