Here's a breakdown:

* Density is the mass of a substance per unit volume.

* Reference substance is usually water at 4°C.

Therefore, specific gravity tells you how much denser or less dense a substance is compared to water.

For example:

* If a substance has a specific gravity of 2, it means it is twice as dense as water.

* If a substance has a specific gravity of 0.5, it means it is half as dense as water.

Key points to remember:

* Specific gravity is a dimensionless quantity, meaning it has no units.

* It's a useful measure for comparing the densities of liquids and solids.

* It's affected by temperature and pressure.

Applications of specific gravity:

* Industry: To control the quality of products like milk, honey, and chemicals.

* Mining: To determine the purity of ores.

* Medicine: To measure the concentration of urine and blood.

* Hydrometry: To determine the density of liquids, like water in a river or ocean.