5. which quantities must be conserved in all chemical reactions?

A force of attraction that holds atom together 
When atoms react they form a chemical bond which is defined as a force of attraction that holds atom together. A force of attraction is defined as a kind of force that draws two or more objects together regardless of distance. There are two major categories of forces of attraction, one is intramolecular and intermolecular. Intramolecular forces is the presence of forces in atoms internally. While intermolecular is the force by which the force that is existent in two or more elements. 

the answer is true.

this statement is true.

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.