A cup contains 50g of boiling water (100°C), into which a 5g ice cube (0°C) is dropped. Which of the following is true about the final temperature of the water in the cup after the ice cube melts and the temperature reaches equilibrium? Assume the temperature immediately drops below 100°C so that none of the water boils away into the air: all 55g of liquid remain in the end of the cup after the experiment. Also, assume that we can ignore heat lost to the environment and imagine the cup is perfectly insulated. The final temperature must be warmer than 90.9°C. The final temperature must be exactly 90.9°C (at least to 3 significant figures precision). The final temperature must be cooler than 90.9°C.

A cup contains 50g of boiling water (100°C), into which a 5g ice cube (0°C) is dropped. Which of the following is true about the final temperature of the water in the cup after the ice cube melts and the temperature reaches equilibrium? Assume the temperature immediately drops below 100°C so that none of the water boils away into the air: all 55g of liquid remain in the end of the cup after the experiment. Also, assume that we can ignore heat lost to the environment and imagine the cup is perfectly insulated. The final temperature must be warmer than 90.9°C. The final temperature must be exactly 90.9°C (at least to 3 significant figures precision). The final temperature must be cooler than 90.9°C.