No,Law of constant composition is valid only for compounds made from the specified isotopes of the element.
No, one example would be wüstite. Please see the link.
True: Ionic compounds are composed of anions and cations False: They are composed of nonmetallic elements.
TRUE
Yes, it is.
No, this composition is variable.
The composition varies considerably by producer and country. Some countries may require the addition of iodine compounds, for instance; others may not. Please see the link.
Yes, after the Law of definite proportions; but now it is clear that this law is not applicable to all known chemical compounds.
They can be reversed by physical changes...
true
Definite chemical composition is when a mineral is made of the same material throughout. Basically when a mineral is only made of one material all the way through, not part iron in one part and then gold in the rest.
properties of compounds are different than elements
No, homeostasis means 'maintaining a constant internal environment.' What you are thinking of is photosynthesis.