Final answer:
In the phase diagram for water, number 1 represents a solid, number 2 represents the phase change melting, and number 3 represents the phase change boiling.
Step-by-step explanation:
In the phase diagram for water, the solid phase is represented by number 1. The phase change melting, where a solid changes to a liquid, is represented by number 2. The phase change boiling, where a liquid changes to a gas, is represented by number 3.
In a temperature-vs.-time diagram for water, the solid phase is indicated by a constant temperature line before reaching 0°C, melting is shown at the plateau at 0°C, and boiling is represented by the plateau at 100°C under 1 atm pressure.
To understand the various phases of water as represented in a temperature-vs.-time diagram or a phase diagram, we can look at a typical graph that shows the states of matter (solid, liquid, gas) and the phase transitions (melting, freezing, boiling, condensation). In a temperature-vs.-time plot, the phase where the substance is a solid is represented by the portion of the graph where the temperature remains constant while time increases until it reaches the melting point. The phase change of melting is illustrated by a plateau, where the temperature does not change as the solid turns into a liquid. This is usually at 0°C for water under normal atmospheric pressure.
The phase change boiling is shown as another plateau at the boiling point of the substance, which is 100°C for water at 1 atmosphere of pressure. This is the phase transition from liquid to gas. In the phase diagram for water, the solid phase is represented by number 1. The phase change melting, where a solid changes to a liquid, is represented by number 2. The phase change boiling, where a liquid changes to a gas, is represented by number 3.