This is thermodynamics,a very peculiar topic in CHEMISTRY..The universe is composed of the system and the surrounding..The system can be any object[an engine or chemical cell] or quantity of matter selected for study which then becomes the surrounding..the system of interests in thermodynamics is finite and its said to attain a state of thermodynamic equilibrium when it shows no further tendency to change its properties with time..this shows why TIME is not a thermodynamic variable..The contact between a system and a surrounding depends on the nature of the system..The engine in the above bracket will have both thermal and mechanical contact while the cell will be the chemical contact..the surrounding which respond to such changes to occur in a system constitutes a big avenue for heat and work..The imaginary envelope which encloses a system and separates it from the surrounding is called the BOUNDARY and has the properties which serves either to isolate the system from the surrounding or provide for interaction in a specific way between the system and the surroundings...An ISOLATED system can exchange matter nor energy with the surrounding,if the exchange of matter and energy is allowed,the system is said to be OPEN and if the exchange of ENERGY ONLY is allowed,the system is said to be CLOSED and its mass remains constant..HEAT AND WORK are the forms by which energy can be transferred through the walls of a system...This is just the way the world is,human beings are like the system,anything you do affects the people around you and your surroundings.All i just have to say is NEVER CROSS YOUR BOUNDARY...