Ilooked and looked in my packet all about physical and chemical changes. i can't find the answer to this question. me?

One could argue that photosynthesis is the most important chemical reaction of all, since it makes energy from solar energy. Plants are are at the bottom of most food chains, and you get O2 as a side product, which a lot of organisms rely on for respiration and for other chemical reactions. 

I hope this helps. I'm not sure if the "passage" has any additional information since you didn't attach it.

If you open the bottle of perfume then nothing but the smell will come out of it and yes it is a type of gas smell because it’s say it in english so i can understand better and you

The mass has escaped into a gas which you can not see so the law stays true.