Final answer:
To predict the final temperature of a metal at 80°C when placed in water at 20°C, with both having the same mass, the hypothesis based on thermal equilibrium could be that the final temperature will be midway between the two initial temperatures, assuming similar specific heat capacities.
Step-by-step explanation:
To predict the temperature of a metal at 80°C after it is placed in a container of room-temperature water at 20°C, with the assumption that both the mass of water and metal are the same, we could use the concept of thermal equilibrium. According to the principle of conservation of energy, the heat lost by the hot metal will be equal to the heat gained by the cooler water until they reach the same temperature. This is simplified because we are assuming the mass of the metal and water are the same.
A reasonable hypothesis could be: 'If a metal at 80°C is placed in an equal mass of water at 20°C, the final temperature of the metal will be lower than 80°C and higher than 20°C.' Specifically, if the specific heat capacities of the metal and water are similar, one might predict the final temperature to be approximately the average of the two initial temperatures, in this case, around 50°C.