Relative Density

Introduction

Different substances have different densities. Some objects float in water while others sink. To compare densities of substances easily, we use the concept of relative density.

Definition

Relative Density is the ratio of the density of a substance to the density of water at 4°C.

Explanation

Relative density compares how dense a substance is with respect to water. It is given by:

Relative Density = Density of Substance / Density of Water

Since both densities are in the same unit, relative density has no unit.

From this concept:

• If relative density > 1 → substance sinks in water
• If relative density < 1 → substance floats on water
• If relative density = 1 → substance remains suspended

Types

1. Relative Density Greater Than 1

• Substance is denser than water
• Object sinks in water

2. Relative Density Less Than 1

• Substance is less dense than water
• Object floats on water

3. Relative Density Equal to 1

• Density is same as water
• Object remains suspended

Importance

• Helps compare densities of different substances
• Useful in determining purity of substances
• Important in fluid mechanics and science experiments

Examples

• Iron has relative density greater than 1, so it sinks
• Wood has relative density less than 1, so it floats
• Oil floats on water due to lower relative density

Important Points

• Relative density is a ratio
• It has no unit
• It compares density with water
• Decides floating or sinking of objects
• Depends on density of substance

Conclusion

Relative density is a simple and useful concept to compare densities of substances. It helps us understand why objects float or sink and plays an important role in science and daily life.