Which process requires more energy: melting 10 kg of water ice or melting 10 kg of dry ice?

The correct choice is based on the energy required to change the phase of substances, which is measured by their enthalpy of fusion and sublimation.

When melting ice at 0°C, the substance undergoes a phase transition from solid (ice) to liquid (water) and requires energy known as the heat of fusion. For water ice, the heat of fusion is approximately 334 kJ/kg. Therefore, melting 10 kg of water ice would require:

10 kg × 334 kJ/kg = 3340 kJ.

On the other hand, dry ice (solid carbon dioxide) sublimates directly into gas without passing through a liquid phase. The amount of energy required for this transition is quantified by its enthalpy of sublimation, which is around 570 kJ/kg. To convert 10 kg of dry ice from solid to gas requires:

10 kg × 570 kJ/kg = 5700 kJ.

Comparatively, if you were to consider melting 20 kg of dry ice, the required energy would be double the amount for 10 kg. This would amount to:

20 kg × 570 kJ/kg = 11400 kJ.

Thus, while melting 10 kg of dry ice requires