Final answer:
The claim about gypsum strength not changing much as excess water evaporates is false, as the material gets stronger when it dries. In a different context related to phase change, a salted ice cube can indeed be lifted by a thread attached to it due to refreezing.
Step-by-step explanation:
The statement that the strength of gypsum does not change much between final set and when excess water has been completely evaporated from the cast is False. The strength of the gypsum cast increases significantly as it dries because the evaporation of excess water allows gypsum crystals to grow closer together, making the set material harder and stronger. However, for the second part of the student's question related to the phase change and latent heat, it is True that adding salt to an ice cube can cause the thread to stick to the cube, allowing you to lift the ice cube by the thread. This is because the salt lowers the freezing point of water, causing the ice to melt. However, the freezing point is quickly reached again, and the water refreezes around the thread, effectively 'gluing' the thread to the ice cube.