What happens to ice when it is heated from -25°C to 0°C?

• A. The temperature decreases
• B. The temperature remains constant
• C. The temperature increases, then remains constant at melting
• D. The ice vaporizes completely

Answer: (C)

When ice is heated from -25°C to 0°C, the ice undergoes a temperature increase as it absorbs heat. The temperature rises steadily from -25°C until it reaches 0°C. At this point, the ice does not continue to increase in temperature but remains at 0°C during the phase change from solid to liquid - this is known as melting.

During the melting process, the energy being added to the ice is used to break the bonds that hold the water molecules in the solid state, rather than increasing the temperature. This process continues until all the ice has transformed into liquid water, at which point the temperature can again begin to increase if additional heat is supplied.

This is a fundamental principle of thermodynamics and phase changes, illustrating the importance of latent heat, which is the energy required for a substance to change its state without a change in temperature.