A physical change occurs when something is altered. Such as cutting a piece of paper or chopping a piece of wood into pieces. Melting ice, breaking glass, evaporating liquids are go through a physical change.
Physical changes occur when substances are mixed but don't chemically react.
Answer:
the answer is b
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It is difficult to prove the law of conservation of mass when a gas is produced because the gas molecules move quickly into the outside space and away
