What does the law of conversation of mass say? how can you know whether a chemical equation is in accordance with this law?

Excuse ! extra points plus ! super desperate ! the position of an object does not move relative to a reference point. relative to the reference point the object _. a.) is not moving. b.) is moving.

Agas expands from an initial volume of 0.040 m^3 and an initial pressure of 210 kpa to a final volume of 0.065 m^3 while its temperature is kept constant. how much work is done by the system?

Need asap ‼️ 20 pts which gravitational force field diagram is drawn correctly? (answers in pictures below)