To convert relative density, you use the following methods based on the relationship between relative density, substance density, and water density:
Understanding Relative Density (R.D.)
Relative density, also known as specific gravity, is a dimensionless quantity that compares the density of a substance to the density of a reference material, usually water. It is a useful measure because it indicates whether a substance will float or sink in water.
Calculating Relative Density
The primary way to convert or utilize relative density is through these calculations:
1. Calculating Relative Density from Density
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Formula: Relative Density (R.D.) = Density of substance / Density of water
- This means you divide the density of the substance by the density of water to get the relative density.
2. Calculating Substance Density from Relative Density
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Formula: Density of substance = Relative Density (R.D.) * Density of water
- This means you multiply the relative density of the substance by the density of water to get the substance's density.
Key Considerations
- Density of Water: The density of water is approximately 1000 kg/m³ or 1 g/cm³ at 4°C. This value is often used for calculations unless specified differently.
- Units: Relative density is a ratio and therefore does not have units. The density of the substance and water must have the same units when calculating relative density. When calculating substance density from relative density, the units of water density will determine the unit of the result.
Example: Iron
Using information from the reference:
- The reference states that if the Relative Density of iron is 8.5, you can find iron's density by multiplying the relative density (8.5) by the density of water.
- Density of Iron = 8.5 * 1000 kg/m³ (assuming water density of 1000 kg/m³)
- Density of Iron = 8500 kg/m³
Summary
| Conversion | Formula | Description |
|---|---|---|
| R.D. from Density | Relative Density = Density of substance / Density of water | Divide the density of the substance by the density of water. |
| Density from R.D. | Density of substance = Relative Density * Density of water | Multiply the relative density by the density of water. |
