I know I'm a bit late but just in case you still need some of the answers.
1: Oxygen
2: Change in shape
3: Water breaking down into hydrogen and oxygen
4: I think it's Milk but I might be wrong.
I might be wrong about some of them, sorry it's not much.
A) halogens.
bromine, chlorine and fluorine are found in group 7 of the periodic table. thus they are halogens
(2)<span>less than 750 N.( if the downward acceleration of elevator were g,then answer would be 0 N.)</span>
25g of mass will require 25g of opposite force on the ball from the road and opposition is moving upward to work on the ball