In thermodynamics, a system is the part of the universe we study, and everything else is the surroundings. Systems can be classified into open, closed, and isolated systems based on how they exchange matter and energy with the surroundings.
1. Open System
- Exchanges both matter and energy with surroundings.
- Example: A boiling pot of water (water vapor escapes = matter, heat leaves = energy).
2. Closed System
- Exchanges only energy, not matter with surroundings.
- The mass inside remains constant, but heat or work can cross the boundary.
- Example: A sealed pressure cooker (heat enters, but no water vapor escapes).
3. Isolated System
- Exchanges neither matter nor energy with surroundings.
- Completely cut off from its environment (ideal case, rarely perfect in reality).
- Example: A thermos flask (approximately isolated, minimizes heat and matter exchange).