Matter is the fundamental substance that makes up everything in the universe, defined simply as anything that has substance and occupies space. Every unique substance, from the air we breathe to the metals used in construction, possesses a distinct set of characteristics that allow scientists to describe and differentiate it from all others. These measurable characteristics are known as properties, and they provide a standardized way to understand how a material behaves and what it is composed of. By examining these properties, which fall into different categories based on how they are measured and what they describe, we can categorize and identify every type of material. This discussion will explore seven of the most fundamental properties used in science to characterize matter.
Extensive Properties: Mass and Volume
Some characteristics of a substance are directly linked to the amount of material being observed. These characteristics, which change proportionally with the size of the sample, are referred to as extensive properties. The first of these is mass, which represents the total amount of matter contained within an object, typically measured in grams or kilograms in the International System of Units (SI). Mass is an inherent measure of a body’s inertia, or its resistance to a change in motion, and it remains constant regardless of the object’s location.
Weight is the measure of the gravitational force acting on that mass, meaning it would change if you moved the object to the moon. The second extensive property is volume, which quantifies the three-dimensional space that the substance occupies. Volume is measured in units like cubic meters (m³) or liters for liquids.
Because both mass and volume depend on the sample size, they are not useful for identifying an unknown substance. For example, a small piece of gold and a large piece of gold will have different values for both their mass and their volume. While these properties are necessary to describe how much matter is present, they cannot distinguish gold from silver.
Intensive Properties Used for Identification
Unlike mass and volume, other properties remain constant regardless of how much material is present, making them highly valuable for identification. These are known as intensive properties, which are inherent to the composition of the substance itself. The most foundational of these is density, which is the ratio of a substance’s mass to its volume.
Density provides a unique, defining value for a pure substance because increasing the mass of the sample also increases the volume proportionally, keeping the ratio constant. For instance, gold always has a density of approximately 19.3 grams per cubic centimeter, whether you have a tiny flake or a massive ingot. If a scientist measures an unknown solid and calculates a density that matches this value, the material is highly likely to be gold.
Two other important intensive properties relate to the transformation between states of matter. The melting point is the specific temperature at which a solid substance transitions into a liquid state. For pure water, this point is consistently 0 degrees Celsius at standard atmospheric pressure.
The boiling point is the precise temperature at which a liquid turns into a gas. Water’s boiling point is a fixed 100 degrees Celsius under standard conditions, regardless of whether a beaker holds a milliliter or a liter of water. The consistency of these transition temperatures provides reliable data for distinguishing one substance from another, as every pure compound has its own signature melting and boiling temperature.
Composition and Transformation: Chemical Properties and State
The final two fundamental properties describe the physical form of a substance and its potential to change its identity. The state or phase of matter refers to the physical form a substance takes under specific conditions of temperature and pressure. On Earth, matter is commonly observed in three states: solid, liquid, and gas.
In a solid, atoms are packed tightly in a fixed arrangement, giving the material a definite shape and volume. Liquid particles are close together but move freely past one another, allowing the substance to take the shape of its container while maintaining a constant volume. Gas particles are widely separated and move rapidly, causing the substance to expand and fill the entire volume of its container. A change in state, such as ice melting into water, is a physical transformation because the substance’s chemical composition (H₂O) remains the same.
The seventh property is chemical reactivity, which describes a substance’s ability to undergo a change in composition and form a new substance. These chemical properties can only be observed when the substance is interacting with another material or undergoing a chemical change. Examples include flammability, which is the potential to burn, or the tendency of a metal like iron to combine with oxygen to form rust. Observing a substance’s chemical reactivity helps to characterize the material, as it reveals how the material will behave in the presence of other chemicals.