Physical and Chemical Changes

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A physical change is a temporary change in which no new substance is formed and the chemical composition remains the same. Only physical properties like colour, state, shape, or size may change.

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A chemical change is a permanent change in which new substance(s) are formed. The new substance has properties that are completely different from the original substance. A chemical change is also call…

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Melting of ice is a physical change because only the state changes from solid to liquid. No new substance is formed, and water can freeze back into ice again.

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Burning of paper forms a new substance called ash. The original paper cannot be obtained back easily, so the change is permanent and irreversible. This is a chemical change.

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Sugar first melts, then turns reddish brown, and finally becomes black. A black residue called charcoal is formed, along with carbon dioxide and water vapour. This is a chemical change. Candle wax _h…

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Charcoal is a form of carbon, an element. It is black, not sweet, and has properties completely different from sugar.

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Rust forms. Rusting is a chemical process in which iron reacts with oxygen in presence of moisture to produce a reddish brown substance called rust. Iron(s) + Oxygen(g) + Water(l) → Rust(s) Rust is…

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Rusting forms a new substance with properties different from iron. Rust is not magnetic, and iron cannot be obtained back from rust by simple methods. So rusting is permanent and irreversible.