Define internal energy and explain its components.

Internal energy is the total energy contained within a system, comprising both the kinetic energy of the particles due to their motion and the potential energy associated with the arrangement of the particles.

Exam lens: Write the relationship, substitute values only when needed, and finish by interpreting the result. This question asks: Define internal energy and explain its components. The correct response is Internal energy is the total energy contained within a system, comprising both the kinetic energy of the particles due to their motion and the potential energy associated with the arrangement of the particles., because changes of state are explained by particle energy and arrangement. In Internal energy, the marking point should connect directly to explain why energy transfer can change temperature without changing state. If the question includes values, the working must keep the appropriate unit and operation; if it is an explanation, it must name the relevant particle behaviour or energy change. This item belongs to Internal energy and energy transfers, so avoid answers that switch to a different quantity, confuse heat with temperature, or describe gas pressure without collisions when collisions are the reason. Checkpoint 251 is distinct because it uses this exact question context and the exam lens rather than a generic particle-model sentence.