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Which kind of system lets energy move in and out but keeps all its matter inside?
AAn open system
BAn empty system
CA closed system
DA perfect system
Answer & Solution
Correct answer: C. A closed system
1. A beaker of water left uncovered loses water vapour to the room, so matter escapes.
2. The same beaker with a glass cover still heats and cools, but the vapour condenses and falls back.
3. A system that exchanges only energy, never matter, is a closed system.
4. Reactions can reach equilibrium only in a closed system, because nothing is allowed to leave.
_Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 8: Chemical equilibrium_
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