Problem Statement
One litre of crude oil weighs 9.6 N. Calculate its specific weight, density, and specific gravity.
Given Data
- Volume, \(V = 1 \, \text{litre}\)
- Weight, \(W = 9.6 \, \text{N}\)
Solution
1. Convert Volume to SI Units (m³)
The calculations require the volume to be in cubic meters to be consistent with the weight in Newtons.
2. Calculate Specific Weight (γ)
Specific weight is defined as weight per unit volume.
3. Calculate Density (ρ)
Specific weight (\(\gamma\)) is related to density (\(\rho\)) by the formula \(\gamma = \rho g\), where \(g\) is the acceleration due to gravity (\(9.81 \, \text{m/s}^2\)). We can rearrange this to solve for density.
4. Calculate Specific Gravity (s)
Specific gravity is the ratio of the density of the substance to the density of a reference substance, which is water (\(\rho_{water} = 1000 \, \text{kg/m}^3\)).
Specific Weight, \( \gamma = 9600 \, \text{N/m}^3 \)
Density, \( \rho = 978.59 \, \text{kg/m}^3 \)
Specific Gravity, \( s = 0.979 \)
Explanation of Terms
Specific Weight (\(\gamma\)): This represents the force exerted by gravity on a unit volume of a fluid. It depends on both the fluid's density and the local gravitational acceleration.
Density (\(\rho\)): This is an intrinsic property of a substance, representing its mass per unit volume. It tells you how tightly packed the matter is.
Specific Gravity (s): This is a dimensionless ratio that compares the density of a substance to the density of water. It provides a quick way to determine if a substance will sink or float in water.
Physical Meaning
The calculated specific gravity of approximately 0.979 is less than 1. This means that this particular crude oil is less dense than water. If mixed, the oil would float on top of the water.
These properties are fundamental in the petroleum industry for:
- Quality Assessment: The density and specific gravity (often expressed as API gravity) are key indicators of a crude oil's quality and market price.
- Transportation and Storage: Knowing the weight and volume is essential for designing pipelines, pumps, and storage tanks.
- Refining Processes: These properties influence how the crude oil is processed and separated into different products like gasoline and diesel.
