Mass is all around you, even the oxygen you breathe. It is important to understand that mass and weight are two different physical properties.
The easiest way to measure mass is with a balance. A balance works by comparing the object to another known mass. The result is the mass of the object.
What is mass?
Mass is a physical property of matter. It is a measure of how much matter is in an object and it determines the resistance of that matter to acceleration. For this reason, a heavier object will resist a change in velocity or direction with greater force than a lighter one.
The mass of an object is also determined by its atomic and molecular makeup. All objects, including the planets and their moons, contain atoms and therefore have mass. In order to properly measure the mass of an object, it must be placed on a scale that takes gravity into account. This is why a balance is used for measuring mass.
As a result of Einstein’s special theory of relativity, mass underwent a major revision. It was shown that mass and energy are interchangeable, that matter can convert to energy and vice versa, and that an object’s mass will increase at speeds at which it approaches the speed of light.
How is mass measured?
The physical property of matter that is most closely associated with its density is mass. Many common measurement instruments use mass for their measurements, including balances used in laboratories for weighing substances. While mass and weight are often confused, they are two distinct concepts.
While scientists measure objects using various methods, they use the SI base unit kilogram to represent a kilogram of mass. This standard is calibrated against a number of platinum-iridium prototype kilograms held by the International Bureau of Weights and Measures (BIPM). The BIPM distributes these replicas to national metrology institutes around the world, which then serve as their national standards for measuring mass.
When teaching children about mass, it can be helpful to start by comparing the size of different objects, such as a pen and a bottle of water. It is also a good idea to introduce them to basic gravity by having them hold the same object in different environments, like on the Moon. This will help them understand that while objects may feel differently in different environments, their mass remains the same.
Does mass depend on gravity?
Until the time of Newton what we now refer to as mass was actually called weight. In fact, until the early 20th century many a spring scale was calibrated to measure both the inertial mass of an object and its gravitational weight.
Gravity depends on the fact that matter has a tendency to gravitate toward itself and other matter. This is because the more massive an object is, the stronger its gravitational force will be.
The gravitational force between two objects varies with the masses of the objects and inversely with the square of the distance between them. This is the law of universal gravitation, and it is why objects with equal masses always attract each other.
The reason that different atoms or particles, even with the same amount of matter, have different masses is because of the differences in their internal energy. This is also why you would weigh more on Earth than on the Moon.
Does mass measure weight?
Many people use the terms mass and weight interchangeably, but they are different quantities. Mass is the amount of matter in a body and has the measuring unit kilogram (kg) in the International System of Units. Weight is the force of gravity acting on an object and has the unit pound-force (or avoirdupois pound in the US customary units).
A measure of an object’s resistance to acceleration, weight depends on the strength of the gravitational field (or g) at the location where it is measured and can vary from place to place. Mass, on the other hand, is an intrinsic property of matter and doesn’t change no matter where you are.
Instruments that can accurately measure mass include a triple beam balance and an inertial balance. However, many digital balances and spring scales that you would see at a supermarket actually measure apparent weight rather than mass. The only instruments that really measure mass are those that can be accelerated in a controlled way such as an inertial balance or frequency shift technology.