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3 An immersion heater of power 250 W is placed in a beaker of crushed ice which has a specific latent heat of fusion of 334 000 J kg-1. (a) Calculate the mass of ice per second being melted by the heater initially. (2) (b) Give one significant source of uncertainty in this experiment. Explain how it would have affected the mass of ice being melted each second. (2) (Total for Question 3 = 4 marks)