SCIENCE
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Melting ice
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A candle burning
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Boiling water
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frost forming inside the freezer
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Detailed explanation-1: -The chemical change is combustion of fuel in presence of oxygen. This leads to the production and emission of carbon dioxide from the flame. 3. The burning of a candle is only a chemical change.
Detailed explanation-2: -Physical Changes: On heating, candle wax gets melted. Since it again turns into solid wax on cooling. So, the melting of wax and vapourisation of melted wax are physical changes. Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light.
Detailed explanation-3: -When a candle burns, wax in the candle melts and is then vaporised as it is drawn up the wick. Melting and vaporisation are physical changes. The wax vapours then burn at the wick to leave behind soot and water vapour, while emitting heat and light. The burning of wax vapours is a chemical change.
Detailed explanation-4: -The burning of a candle is an example of both physical and chemical changes.
Detailed explanation-5: -Burning is a chemical change. This is because, new substances (e.g. ash and carbon dioxide CO2) are formed during burning.