This is College Physics Answers with Shaun Dychko. This question is slightly confusing because example [14.1] doesn't talk anything about ice, it just talks about water heating from 20.0 degrees Celsius up to 80.0 degrees Celsius in a pan on a stove. But anyway, we can still answer the question because this temperature change does indicate that the H 2 O is in the liquid state. Since these 20.0 degrees Celsius— and we assume this is in atmospheric pressure by the way that means that this 20.0 degrees Celsius is above the melting point of water— and so this change in temperature indicates that the phase must be liquid because the temperature can't change until the phase change is complete. So... as the ice in its crystal form is transitioning into liquid form, these bonds have to be broken before temperature change can occur and so the fact that temperature change is occurring, in an interval of temperature that is above the melting point that must mean that the substance is liquid.