Basic properties – numerical value of the specific gravity of water For engineering calculations, the specific gravity (relative density) of pure water is conventionally taken as:

Introduction:
Specific gravity, also called relative density, is a dimensionless ratio comparing the density of a substance to that of a reference fluid (for liquids, typically water at standard conditions). The question asks for the conventional value used for water itself.

Given Data / Assumptions:

• Reference temperature near 4°C for exact unity or room temperature for approximate unity.
• Reference fluid for liquids is water unless stated otherwise.
• Dimensionless ratio SG = rho_substance / rho_water.

Concept / Approach:

By definition, when the substance is water and the reference is water, the ratio is unity. Although water density varies slightly with temperature and pressure, for most engineering problems SG(water) is taken as 1. This simplifies conversions between mass density and specific gravity in tabulations and calculations.

Step-by-Step Solution:

Verification / Alternative check:

At 4°C, water density is approximately 1000 kg/m^3 by definition in SI, making SG precisely 1. At 20°C, density is about 998 kg/m^3; SG is still effectively 1 for routine work.

Why Other Options Are Wrong:

0.001 / 0.01 / 0.1 / 10: These values correspond to unrealistic relative densities for water under normal conditions.

Common Pitfalls:

Confusing specific gravity with specific weight or mass fraction. Specific gravity is unitless and compares densities directly.

Final Answer:

1