JAMB 2025 Physics · Question 86

If the specific gravity of a liquid is 0.76, calculate its density((ρw\rho_w = 1000Kgm−3^{-3})

Options

  1. A.760Kgm−3^{-3}
  2. B.76Kgm−3^{-3}
  3. C.7.6Kgm−3^{-3}
  4. D.7600Kgm−3^{-3}

Answer: A. 760Kgm−3^{-3}

Explanation written with AI and checked against the answer key

1. Analyze the question

You are asked to find the density of a liquid given its specific gravity (also known as relative density) and the density of water.

2. Explain the concept

Specific Gravity (Relative Density) is a dimensionless quantity defined as the ratio of the density of a substance to the density of a reference substance (usually water).

The formula is:

Specific Gravity=Density of substanceDensity of water\text{Specific Gravity} = \frac{\text{Density of substance}}{\text{Density of water}}

To find the density of the substance, we rearrange the formula:

Density of substance=Specific Gravity×Density of water\text{Density of substance} = \text{Specific Gravity} \times \text{Density of water}
3. Show the solution
  • Given: • Specific Gravity = 0.76 • Density of water (ρw\rho_w) = 1000 kgm⁻³
  • Calculation: $Density of liquid=0.76×1000 kgm−3\text{Density of liquid} = 0.76 \times 1000 \text{ kgm}^{-3}$ $Density of liquid=760 kgm−3\text{Density of liquid} = 760 \text{ kgm}^{-3}$
4. Identify the answer

Comparing our result to the given options: A. 760 kgm⁻³ B. 76 kgm⁻³ C. 7.6 kgm⁻³ D. 7600 kgm⁻³

The correct option is A.

5. Tip

When dealing with specific gravity, remember that it is just a multiplier. If you are converting from specific gravity to density in SI units (kgm⁻³), simply multiply by 1000. If you are converting to CGS units (gcm⁻³), the specific gravity value is numerically equal to the density (e.g., 0.76 gcm⁻³). This is a quick way to verify your work during the exam!

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