ANSWERS: 3
  • A candle burning. Wax in the candle is combining with oxygen in the air to make carbon dioxide and water vapour. All the others just represent physical state changes.
  • Sugar dissolving is not a chemical reaction because there is no chanege in the reactants. The sugar crystals remain as crystals and are not broken down, neither are the molecules of water. Steam condensing into a liquid does not change the construction of the water molecules either, so it is not a chemical rection. A candle burning is a chemical reaction because it is breaking down the wax (Alkane Hydrocarbons) into Hydrogen and a different form of the wax (Alkene Hydrocarbons). The Hydrogen given off is spotaneously oxidized and forms water vapour. The Carbon in the wick is also spontaneously oxidized to form Carbon Dioxide (idealy) but if this is not a fully combusted reaction then Carbon Monoxide (poisonous) will be produced. Alcohol evaporating does not change the molecules of the alcohol, thus it is not a chemical reaction.
  • I think both sugar dissolve (formation of chemical hydrogen bonds), burning of candle due to charring both r chemical reaction but the other are just physical change in the state of matter

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