CLASS 7 · LEARNING KNOWLEDGE

Density and Floating – Basic Principles

How it works

Density is a material property and indicates how much mass is contained in a certain volume of a substance. It is given in kilograms per cubic meter (kg/m³) or also in grams per cubic centimeter (g/cm³). Density is calculated using the formula density = mass / volume. Whether an object floats, sinks, or remains suspended in a liquid depends on how its average density compares with the density of the liquid: If the density of the object is smaller than that of the liquid, it floats. If it is greater, it sinks. If it is equal, it remains suspended in the liquid. Water has a density of about 1000 kg/m³.

Note
The density of an object is calculated as mass divided by volume. An object floats in a liquid if its density is smaller than that of the liquid. If its density is greater, it sinks. If it is equal, it remains suspended.

An example

A wooden block has a mass of 200 g and a volume of 400 cm³. Will it float in water?

The density of the wooden block is 200 g / 400 cm³ = 0.5 g/cm³ = 500 kg/m³. Since the density of water is 1000 kg/m³ and the wooden block has a lower density, it floats.

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Own explanation and own practice exercises by AmyMath. Subject reference framework: Physics. The topic assignment may vary by federal state.