Final answer:
A scientist develops a model of a phase change, such as gas to liquid, by studying the behavior and properties of the substances involved. They observe the conditions under which the phase change occurs and collect data. Based on this data, they create a model that explains the process of phase change and predicts how it will occur under different conditions.
Step-by-step explanation:
A scientist develops a model of a phase change, such as gas to liquid, by studying the behavior and properties of the substances involved. They observe the conditions under which the phase change occurs and collect data. Based on this data, they create a model that explains the process of phase change and predicts how it will occur under different conditions. For example, in the case of gas to liquid, a scientist may study the changes in pressure and temperature that cause the gas molecules to come closer together and form a liquid.