Which of the following best describes an open system in the context of the classification of matter?

• A. A system that can exchange only energy, but not matter, with its surroundings.
• B. A system that cannot exchange either matter or energy with its surroundings.
• C. A system that can exchange both matter and energy with its surroundings.
• D. A system that contains only pure substances and no mixtures.

Answer: (C)

Verified step by step guidance

1. Understand the concept of a system in chemistry: A system is the part of the universe we focus on, while everything else is the surroundings.
2. Recall the classification of systems based on exchange with surroundings: Closed systems exchange energy but not matter; isolated systems exchange neither energy nor matter; open systems exchange both energy and matter.
3. Analyze each option in the problem: The first option describes a closed system, the second an isolated system, the third an open system, and the fourth is unrelated to system classification.
4. Identify that an open system allows both matter and energy to pass between the system and its surroundings, which matches the third option.
5. Conclude that the best description of an open system is 'A system that can exchange both matter and energy with its surroundings.'