🔍 Key Concepts

• Thermal expansion of liquids when heated • How a liquid’s measured size (amount of space it occupies) changes with temperature • Difference between properties that describe how much liquid you have vs. how the liquid behaves (thickness, density, etc.)

💭 Think About

• When you heat fuel oil in a closed tank, what exactly is getting ‘bigger’—is it its behavior (like thickness or ability to conduct heat) or the amount of space it takes up? • Which property, if increased, would directly mean the fuel occupies more space even though the mass (amount of fuel) is the same? • Consider which choice is already defined by how much space a substance occupies per unit of mass, versus something that changes the liquid’s flow or heat transfer.

✅ Before You Answer

• Make sure you can define viscosity (thickness/flow), conductivity (heat transfer ability), and specific gravity (density relative to water). • Ask: which property would a tank sounding or ullage reading respond to when the fuel is heated—i.e., which one directly changes the space filled in the tank? • Verify which option represents the actual size/extent of the liquid in three dimensions, not just how it flows or how dense it is.