question_answer

  Classify each of the following as a physical or a chemical change. Give reasons. (a) Drying of a shirt in the sun. (b) Rising of hot air over a radiator. (c) Burning of kerosene in a lantern. (d) Change in the colour of black tea on adding lemon juice to it. (e) Churning of milk cream to get butter.             [NCERT Exemplar]

Answer:

               (a) It is a physical change because water is converted from its liquid state to gaseous state because of the sun's heat. (b) It is a physical change because water in the radiator is converted from a liquid state to gaseous state. (c) It is a chemical change because combustion of kerosene occurs and new products are formed. (d) It is a chemical change because there is a reaction between the citric acid in the lemon and the compounds of tea resulting in formation of new products. (e) It is a physical change because the cream suspended in the milk is separated by churning.