Yes, specific gravity depends on temperature.
Specific gravity is defined as the ratio of the density of a substance to the density of a reference substance, typically water for liquids and solids. Density itself changes with temperature; most substances expand when heated and contract when cooled, altering their volume and thus their density (mass per unit volume). Since specific gravity is a ratio of densities, and densities change with temperature, the specific gravity value will also change with temperature.
According to the provided reference, "Specific gravity varies with temperature and pressure." This means that for an accurate specific gravity measurement, the temperature and pressure conditions under which the substance and the reference substance (like water) are measured must be considered.
Why Temperature Affects Specific Gravity
- Density Changes: Temperature directly impacts the density of most materials. As temperature increases, molecules typically move faster and spread further apart, causing the material to expand and its density to decrease.
- Ratio: Specific gravity is a ratio of the substance's density to the reference density. If the substance's density changes with temperature, the specific gravity ratio will also change unless the reference density changes in exactly the same proportion (which is usually not the case).
Practical Implications
Because specific gravity varies with temperature, measurements must be handled carefully:
- Consistent Conditions: To compare specific gravity values accurately, both the substance being measured and the reference substance (like water) should be at the same temperature and pressure.
- Standard Conditions: Often, specific gravity values are reported relative to standard conditions (e.g., 20°C or 25°C).
- Correction Factors: If measurements are taken at different temperatures, correction factors are often used to adjust the value to a standard reference temperature and pressure.
For example, the specific gravity of a liquid measured at 30°C will be slightly different than if measured at 20°C, even if it's the same liquid. This is crucial in various fields, such as chemistry, physics, and engineering, where precise material properties are necessary.
Understanding this dependency is vital for accurate measurements and comparisons of specific gravity across different conditions.
