It has been suggested that drinking ice-cold water at 0° C can help weight loss because the body uses stored energy in the form of fat to warm the water up to body temperature of 37° C. 0.5 kg of fat stores about 1.6 x 108 J of energy. a) Calculate the mass of ice-cold water that a person would need to drink in order to lose 0.5 kg of fat. Specific thermal capacity, c = 4200 J kg-1 K-1 mass = ............................. kg (2 Marks) b) Give a reason why it is not sensible to drink ice-cold water in order to lose weight. (1 Mark) (Marks available: 3) A can of drinking chocolate contains a chemical heating pack that releases 3.5 x 104 J of energy into drink when activated. Calculate the final temperature of the drink assuming no energy is lost to the can or surroundings. mass of drink = 0.21 kg specific thermal capacity of drink = 4200 J kg-1 K-1 initial temperature of drink = 20° C final temperature of drink = ........................... ° C (Marks available: 3) Answer Answer outline and marking scheme for question: a) M = Q/C.Δ θ = 1.6 x 108 / a 200 x 37 (1 Mark) = 1030 kg (1 Mark) (1000 kg to 2 sf is acceptable) (2 Marks) b) e. g. lower body temperature, you can't just do it (approx twenty times body mass), too much fluid absorbed. (1 Mark) (Marks available: 3) Δ θ = Q/ mc = 3.5 x 104 / 0.21 x 4200 (1 Mark) = 40° C (39.7° C) (1 Mark) Final temperature = 40 + 20 = 60° C (1 Mark) (59.7° C) (Marks available: 3)