Mass and volume are fundamental physical properties used to describe matter. Though distinct, they are often confused. This article clarifies these properties and their relationship.
Understanding Mass
Mass is a measure of the amount of matter contained within an object. Unlike weight, which changes with gravitational pull, an object’s mass remains constant regardless of its location.
Scientists measure mass using a balance. The standard international (SI) unit for mass is the kilogram (kg). Other common units include grams (g) and milligrams (mg). For instance, a typical apple might have a mass of approximately 150 grams, while an adult human’s mass could be around 70 kilograms.
Understanding Volume
Volume describes the amount of three-dimensional space that an object occupies. Its measurement varies depending on the matter’s state and shape.
For liquids, volume is commonly measured using containers with markings. For regularly shaped solid objects, volume can be calculated using geometric formulas. The volume of irregularly shaped solids can be determined through the water displacement method, where the object is submerged in water, and the change in water level indicates its volume. The SI unit for volume is the cubic meter (m³), but liters (L), milliliters (mL), and cubic centimeters (cm³) are also widely used, especially for smaller quantities. A standard soda can, for example, typically holds about 355 milliliters.
Distinguishing Mass and Volume
Mass and volume are not the same; they describe different aspects of an object. Mass quantifies the amount of matter within an object, whereas volume quantifies the space that object occupies. One is about the substance itself, while the other is about its spatial extent.
This distinction becomes clear with contrasting examples. Imagine a large, deflated balloon compared to a small, heavy rock. The balloon, when inflated, might occupy a large volume of space, but it has very little mass. In contrast, a small rock, like a piece of lead, occupies a small volume but possesses a significant amount of mass. Another common illustration involves a kilogram of feathers and a kilogram of lead; both have the same mass, but the feathers would occupy a much larger volume than the lead.
The Connection: Density
While mass and volume are different, they are intrinsically linked through the concept of density. Density is a property that describes how much mass is packed into a given amount of volume. It tells us how concentrated the matter is within an object.
The relationship between mass and volume is expressed by the formula: Density = Mass / Volume. This means that if you know an object’s mass and its volume, you can calculate its density. Density helps explain why some objects float and others sink. For instance, a piece of wood floats on water because wood is less dense than water; a given volume of wood contains less mass than the same volume of water. Conversely, a metal coin sinks because it is denser than water, meaning it has more mass packed into the same amount of space.