Question

What does the first law of thermodynamics say?

Answer 1

A thermodynamic system is a part of matter with a defined boundary. The system boundary can be fixed or flexible, and it can be real or imaginary. Thermodynamics is the portion of physics that is related to the movement of heat between one body to another. It also consists of energy-related studies.
There are fourth laws of thermodynamics: zeroth law, first law, second law, and third law.

Complete step by step solution:
According to the first law of thermodynamics, energy cannot be produced or destroyed. This is the Law of Conservation of Energy. Energy can only be converted from the body to body.
Let, the change in the internal energy $\left( E \right)$ of a system is, the total heat $\left( Q \right)$ that flows across its boundaries and the work $\left( W \right)$ done on the system by the surroundings.
According to the first law of thermodynamics:
$\Delta E = Q - W$
According to this law, two types of processes, heat, and work, can cause a change in a system's internal energy. Because both can be measured and quantified, each change in a system's energy must be accompanied by a comparable change in the energy of the environment outside the system.
Energy can neither be created nor destroyed. When heat enters a system or the environment exerts a force on it, the internal energy rises, and the heat and work done become positive. Heat flows out of the system or work done by the system (on the surroundings will deplete internal energy, causing $\left( Q \right)$ and $\left( W \right)$ to be negative.

Note: Thermodynamics is related to various systems, such as:
Separated System - A system that is isolated from its surroundings is unable to exchange both energy and mass. The universe is thought to be a self-contained system.
Closed System - The flow of energy occurs across the closed system's boundary, but the transfer of mass does not. Closed systems consist of refrigerators and gas compression in piston-cylinder assemblies.
Open System - Mass and energy can both be moved between the system and its surroundings in an open system. An open system is a steam turbine, for example.