Matter exists in three primary states: solid, liquid, and gas, each with distinct properties. Phase changes occur when matter transitions between stat
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Why does water expand when it freezes while most substances contract?
Water's hydrogen bonds form a crystal structure in ice with more space between molecules than in liquid water. This causes about 9% volume expansion. Most substances contract when freezing because particles pack more densely in solid state.
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What happens to temperature during a phase change?
Temperature remains constant during a phase change because energy goes into breaking or forming intermolecular bonds rather than increasing particle kinetic energy. Once all matter has phase-changed, temperature rises again.
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Can gases be liquefied without lowering temperature?
Yes, by increasing pressure above the critical pressure. However, most practical liquefaction involves cooling. High pressure alone at room temperature cannot liquefy most gases, but extreme pressure can.
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