I just took a test in school today. What question was I asked?

Question I was asked: An atom consists of a nucleus surrounded by

I just took a test in school today. What question was I asked?

Question I was asked: Which is the best example of a pure substance?

I just took a test in school today. What question was I asked?

Question I was asked:
If 1 kg of the compound toluene melts at -95C, then 500 g of toluene will