Final answer:
The metal cube will stay in a solid state after adding 3000J of energy because its final temperature of 12°C is substantially below its melting point of 450°C, and far from its boiling point of 1530°C.
Step-by-step explanation:
To determine the state of matter the metal cube will be in after adding 3000J of energy, we need to look at the melting point and boiling point of the metal. Since the melting point of the metal is 450°C and the boiling point is 1530°C, and the thermal equilibrium after heating is only 12°C, we can conclude that the metal cube will remain in the solid state. The heat energy added is not sufficient to increase the cube's temperature to its melting point. Taking the example of water, as heat is added to ice, its temperature increases until it reaches the melting point, here 0°C for water, before it can transition to a liquid state. Similarly, the metal cube's temperature must reach at least 450°C to start melting. Since the cube only warms up to 12°C, which is far below its melting point, it does not undergo a phase change and remains solid.