Energy of Systems

[Sofia Ban]

Lavelle mentioned that there were 3 ways of changing the energy of a system, but can someone explain a little bit more about each?

[205007651]

The first way is to add or remove the amount of substance in a system. This can only be used for an open system.
The second way is to heat or cool the system, which can be used for a closed system.
The third way is do either do work on the system or let the system do the work on the surroundings. This is also for a closed system.

[Wilson 2E]

Why does changing the amount of substance effect internal energy? Is it due to a change in enthalpy?

[Jessica Katzman 4F]

Adding or removing substance in a system changes the energy of an open system, changing the temperature of a closed system will change its energy, and doing work on the system/letting the system do work on the environment changes the energy of a closed system

[805307623]

Internal energy is an extensive property, so internal energy depends on the size of the system (amount of substance it contains).