Help me solve this please

List four observations that indicate that a chemical reaction may be taking place

The table describes how some substances were formed substance 19 description formed by boiling pure water formed by combining three hydrogen atoms to every nitrogen atom formed by adding 5 g of sugar to 1 l of water formed by compressing carbon under high pressure based on the given descriptions, which substance is most likely a mixture?

Which characteristics can be used to differentiate star systems? check all that apply.