When energy flows out of a system, it must all flow into the surroundings. When energy flows out of a system, ΔEsystem is negative. When energy flows into the surroundings, ΔEsurroundings is positive. Energy is exchanged between the system and surroundings through heat and work.

Going through a phase. Adding or removing energy from matter causes a physical change as matter moves from one state to another. For example, adding thermal energy (heat) to liquid water causes it to become steam or vapor (a gas). And removing energy from liquid water causes it to become ice (a solid).

Consequently: 1) When energy (heat or work) flow out of the system, the system decreases in its amount. This is assigned a negative sign and is called exothermic. 2) When energy (heat or work) flows into the system, the system increases its energy amount.

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. The levels in the food chain are producers, primary consumers, higher-level consumers, and finally decomposers. These levels are used to describe ecosystem structure and dynamics.

The Second Law of Thermodynamics states that “in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state.” This is also commonly referred to as entropy. In the process of energy transfer, some energy will dissipate as heat.

The factors that affect an object’s gravitational potential energy are its height relative to some reference point, its mass, and the strength of the gravitational field it is in.

Kinetic energy is the energy an object has because of its motion. If we want to accelerate an object, then we must apply a force. Applying a force requires us to do work. After work has been done, energy has been transferred to the object, and the object will be moving with a new constant speed.