'A scientist in a local university has just proposed a new temperature scale called the Xanthine temperature scale. On the Xanthine scale, water boils at -15.0 X and freezes at -80 X. Determine the temperature of 300 K on the Xanthine scale. (5) Estimate the minimum amount of energy, in kJ, required to completely melt 250 g of nickel at room temperature. At sea level, the temperature and pressure of a weather balloon is 30C and 100kPa, respectively. As the balloon reaches a certain height, the pressure decreases to 90 kPa. What is the temperature at this height? State any assumption that you need to make to solve this problem. (6) (5)