🔍 Key Concepts

• Fuel oil heater operation and what happens when fuel is overheated • How impurities and contaminants in fuel behave at high temperature • Difference between chemical contaminants (like metals) and thermal effects (like coking or carbonizing)

💭 Think About

• Think about what physical change makes carbon separate from the fuel and stick to hot metal surfaces. • Which of these choices would directly cause the fuel to "cook" or break down on the heater surfaces rather than just pass through? • Are any of the options more about corrosion or chemical contamination than about actual carbon deposits forming on hot surfaces?

✅ Before You Answer

• Identify which option is directly related to temperature in the heater, not just fuel composition. • Ask whether zinc strips would logically produce carbon deposits or a different type of problem (like corrosion protection). • Consider whether metallic contaminants in fuel would form soft carbon on heater surfaces, or a different kind of hard, ash-like deposit.