A petroleum refinery separates crude oil into fractions and then converts some fractions into higher-value products before shipping them to distributors. A simplified process flow is shown below.
(a) Identify each step (1–4) as involving a physical change, a chemical change, or both. For any step that involves both, briefly separate the sub-processes into physical and chemical portions.
(b) For each step, cite specific evidence available to plant engineers, technicians, or motorists that supports your classification. Your evidence may include temperature data, phase observations, composition analysis, or energy considerations.
(c) Choose one step you classified as a chemical change and write a balanced symbolic or word equation that represents the chemical transformation occurring.
(d) Suppose an engineer proposes operating the fractionating column at 250 °C instead of 400 °C. Predict how this adjustment would affect the type(s) of change occurring in step 1 and justify your answer in terms of intermolecular forces and vapor-liquid equilibrium.