Students were given the following sets of items and asked, for each set, to identify which item had greater thermal energy. For which set would this task be most difficult? Explain. Set 1: 5 g of iron at 45°C and 10 g of iron at 45 °C Set 2: 10 g of water at 30°C and 10 g of water at 50°C Set 3: 32 g of copper at 50°C and 32 g of nickel at 50°C