To find density from relative density, you need to multiply the relative density by the density of the reference substance. This is because relative density is the ratio of a substance's density to the density of a reference substance, as explained in the reference material.
Here's a breakdown of the process:
Understanding Relative Density
-
Relative density (also called specific gravity): This is a dimensionless quantity that compares the density of a substance to the density of a reference substance.
- The reference substance is usually water for liquids and solids (density of approximately 1000 kg/m³ or 1 g/cm³).
- For gases, the reference substance is often air.
-
Calculation: Relative density is calculated by dividing the density of the sample by the density of the reference substance. So, the formula looks like this:
Relative Density = Density of Substance / Density of Reference Substance
Finding Density from Relative Density
To rearrange this formula to find the density of a substance when you know its relative density and the density of the reference material, the formula becomes:
Density of Substance = Relative Density x Density of Reference Substance
Here’s how you would use the formula:
- Identify the Relative Density: You'll need to know the relative density of the substance you're interested in.
- Determine the Reference Substance: Identify the reference material used to determine the relative density, usually water or air.
- Find the Density of the Reference Substance: You must know the density of the reference substance. As mentioned earlier, water is often used, with a density of approximately 1000 kg/m³ or 1 g/cm³. For other references, like air, look up the appropriate density value for your conditions (temperature and pressure).
- Apply the Formula: Multiply the relative density by the density of the reference substance. This gives you the density of the substance.
Example
Let's say we have a material with a relative density of 2.5, using water as a reference material.
- Relative Density = 2.5
- Density of water (reference) = 1000 kg/m³
- Density of the material = 2.5 x 1000 kg/m³ = 2500 kg/m³
Practical Insights
- Units: Make sure the units of the reference density and the resulting density are consistent.
- Temperature: The density of many substances is temperature-dependent, including the reference density. Be sure that your density value for the reference material is at the same temperature as when the relative density was determined.
- Applications: Understanding how to find density from relative density is important in various fields, including material science, engineering, and even cooking, where relative density might influence how ingredients layer in recipes.
