Matter

Oh my god, read the book. How much harder can it be to read the answers from the source that the teacher is going to use to grade the test, than it is to ask a forum full of potentially crazy and possibly ignorant people who you don't know. How are you even going to know if the answer you get her is correct? Sheesh.

why not wait til the last minute possible?

I assume you're discussing the conservation of mass/energy?

I do not know your subject of study, but truly closed systems are very rare and usually contrived... The very act of measurment is one likely to change what is being measured according to the uncertainty principal, for example, and imo, the very fact that a system is closed is likely to reduce change to be measured since energy in the system would run out if it were not replenished from ouside...Looking at the earth as we tend to, as a closed system, we might conclude that we are burning through our hydrocarbons at an alarming rate which also has the effect of changing our climate to the point of disaster... However, the fixing of carbon goes on at a rate at least four times faster our current usage every day, week, and year through photosynthesis... Looking at even the earth as a closed system gives a false perspective since everything is related and the boundaries are fluid...