No, but it is just one word: saltpeter.
No, "epsom salt" is not typically capitalized. It refers to a type of magnesium sulfate mineral compound and is considered a common noun. However, "Epsom" is capitalized because it is derived from the name of a place in England where the salt was originally obtained. In most contexts, you would write it as "epsom salt."
Earth, as in we live on the planet Earth, is supposed to be capitalized. Earth, as in the dirt we walk on, is not supposed to be capitalized.
Usually, yes a phase of the moon is supposed to be capitalized.
No, it shouldn't be capitalized.
No it shouldn't be capitalized.
Yes, America should be capitalized.
no
Yes, "Pterodactyl" is supposed to be capitalized as it is a proper noun referring to a specific genus of pterosaur.
No, but the names of individual languages are capitalized.
Yes, Siamese would be capitalized.
No, "salt" is not capitalized unless it is used at the beginning of a sentence or part of a proper noun.
Yes.