Final answer:
To bring about a phase change in a substance, an increase or decrease in energy is required, typically affecting molecular bonds without changing temperature, known as latent heat. This can be achieved through processes like melting, vaporization, freezing, and condensation. Pressure changes can also induce phase transitions as illustrated in phase diagrams, including the unique triple point.
Step-by-step explanation:
To bring about a phase change, an increase or decrease in energy is typically required. This energy transfer does not result in a change in temperature of the substance during the phase change itself because the energy is used to alter the bonds between particles. For example, melting a solid into a liquid or vaporizing a liquid into a gas requires an input of energy, known as the heat of fusion and the heat of vaporization respectively.
The amount of energy involved depends on the mass of the sample and the strength and number of molecular bonds or force pairs. When energy is added to a substance and is used for breaking intermolecular bonds, the process is endothermic, such as in melting or vaporization. Conversely, when a substance releases energy by forming intermolecular bonds, the process is exothermic, such as in freezing or condensation.
Changes in pressure can also induce phase changes, manipulating the conditions under which a substance will change from one phase to another. A phase diagram illustrates the relationship between pressure and temperature and shows the conditions for phase coexistence. The triple point on a phase diagram is where the three phases of a substance coexist at equilibrium.