Matter is anything that has mass and takes up space. Scientists study the measurable characteristics of matter, known as physical properties, to classify and differentiate objects. While matter possesses many properties, three fundamental ones—mass, volume, and density—provide the essential framework for its study.
Mass: The Measure of ‘Stuff’
Mass is a fundamental property representing the amount of matter an object contains. This quantity determines an object’s inertia, which is its resistance to a change in motion. Mass remains constant regardless of the object’s location in the universe.
Mass is frequently confused with weight, but they are distinct concepts. Weight measures the gravitational force exerted on an object’s mass, changing depending on the local gravitational field strength. For example, a person’s mass stays the same on the Moon, but their weight is significantly less due to weaker gravity. Mass is measured using standard units like the kilogram (kg) or gram (g) within the International System of Units (SI).
Volume: Occupying Space
Volume is the measure of the amount of three-dimensional space that an object or substance occupies. It applies to matter in solid, liquid, or gas states. Volume is measured in units derived from length measurements, such as the cubic meter or cubic centimeter.
For liquids and gases, volume is commonly expressed in units like the liter (L) or milliliter (mL). For regularly shaped objects, volume is calculated using a geometric formula based on its dimensions. The volume of irregularly shaped objects is often determined through the displacement method, which involves measuring the change in water level when the object is fully submerged.
Density: The Ratio of Mass and Volume
Density relates an object’s mass to the space it occupies, measuring how tightly matter is packed together. It is defined as the ratio of mass to volume (Density = Mass/Volume). This property is an intensive measure, meaning it remains constant regardless of the amount of substance present.
Because different substances have unique atomic structures, density is a reliable characteristic for identifying pure materials. For example, the density of pure water is approximately one gram per cubic centimeter. This ratio explains why wood, which is less dense than water, floats, while iron, which is denser, sinks. Common units for density include grams per cubic centimeter or kilograms per cubic meter.