Mass and energy are conserved options:
A) only in physical changes.
B) always in physical changes and sometimes in chemical changes.
C) only in chemical changes.
D) in chemical changes and physical change

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.

window cleaner is ammonia dissolved in water. this is an example of a