Final Answer:
1. The energy change required to change 200 g of water at 273 K is the heat absorbed during the phase transition from ice to water and then heating the water to 273 K.
2. The energy change needed to change 1200 g of steam at 373 K involves cooling the steam to water at 373 K and then further cooling the water to its final temperature.
3. The heat change for a 348 g sample of steam at 373 K includes the heat released during the phase transition from steam to water and then further cooling the water to 373 K.
Step-by-step explanation:
1. For the first question, at 273 K, water is in the liquid phase. The energy change involves the heat absorbed during the phase transition from ice to water (latent heat of fusion) and then heating the water to 273 K (specific heat capacity of water).
2. In the second question, steam at 373 K needs to be cooled to water at 373 K, involving the release of heat during the phase transition (latent heat of vaporization). Then, the water needs to be cooled to its final temperature.
3. The third question involves the heat change for a sample of steam at 373 K. This includes the heat released during the phase transition from steam to water (latent heat of vaporization) and then further cooling the water to 373 K.