Closed system. If the system is not closed, matter or energy can escape from the system. an example of this is if you react magnesium and hydrochloric acid in a open system. The H₂ gas is going to escape making it look like some of the mass disappeared . in that same reaction some in an open system will also loose heat to the surrounding which will make it look like less heat was produced.
Answer:
As the sun's angle changes, (because of the rotation of the earth) the sun slowly begins to shine more or less sunshine slowly. When sunsets and sunrises occur, the color of the sky changes because the sunshine is starting to fade out or in.
I put it in my own words so you don't have to worry about plagiarism :)
0.92%. student calculated that the amount of NaCl that should form in the lab
