FAA Powerplant Written Practice Test

What happens to oil with high specific gravity compared to one with low specific gravity?

1. It is less viscous

2. It may not absorb heat as quickly

3. It has a greater density

4. It evaporates faster

The correct answer is: It has a greater density

The correct response highlights that oil with high specific gravity exhibits greater density when compared to oil with low specific gravity. Specific gravity is the ratio of the density of a substance to the density of a reference substance, typically water for liquids. Therefore, oils with high specific gravity contain more mass in a given volume compared to those with lower specific gravity. A greater density typically translates to certain physical characteristics in terms of how the oil behaves in various applications. For example, denser oils might settle at the bottom of a mixture more quickly, and they may not flow as easily as less dense oils. Furthermore, oils with high specific gravity may have different thermal properties, affecting their heat retention and transfer capabilities. The other options presented do not accurately describe the relationship between specific gravity and oil properties. For instance, the viscosity of a fluid is influenced by a multitude of factors and does not solely depend on its specific gravity. Similarly, the rate of evaporation is more complex and is influenced by temperature, surface area, and volatility rather than just specific gravity. The suggestion regarding heat absorption capacity is also not strictly tied to specific gravity; it involves additional factors such as thermal conductivity and specific heat capacity of the material.