Final answer:
The amount of nickel to be added to copper to attain certain liquidus and solidus temperatures is dictated by the phase diagram for copper-nickel alloys, which is not provided. Additional data are required to make the computation.
Step-by-step explanation:
The question posed by the student cannot be directly answered using the provided reference information alone because the liquidus and solidus temperatures of copper-nickel alloys depend on the specific composition of the two metals in the alloy, which requires information from a copper-nickel binary phase diagram not provided here. To determine how many kilograms of nickel must be added to a certain mass of copper to yield specific liquidus or solidus temperatures, one would typically refer to a copper-nickel phase diagram that outlines the temperature and composition relationships at which alloys of these two metals are fully liquid (liquidus) or begin to solidify (solidus).
Without the phase diagram or an explicit empirical relationship provided, it is not possible to calculate the exact amounts of nickel required to achieve the specified temperatures of 1200℃ and 1300℃. Thus, to respond accurately, we'd need additional data regarding the phase behavior of the copper-nickel system.