Accurate mass measurements are crucial for scientific research, industrial processes, and everyday tasks. In recent years, advances in mass measurement technology have increased the sensitivity and precision of instruments.
The kilogram is a standard unit of mass. Learn about the history of this important metric and its applications. Also, discover what the difference is between mass and weight.
What is mass?
Mass is the property of matter that determines its resistance to change in motion (change of acceleration) when a force acts on it. It also determines the strength of gravitational interaction with other bodies. Different atoms and particles, theoretically with the same amount of matter, have different masses. The SI unit of mass is the kilogram.
Until the time of Newton, mass was measured on balance scales using Hooke’s law and the fact that an object’s weight is proportional to its inertial mass and inversely proportional to its acceleration. This led to the equivalence of weight and inertia, which can be written as F = ma.
The difference between weight and mass is that weight depends on the gravitational pull of the Earth, and thus varies from place to place. Mass, on the other hand, is not affected by gravity and remains constant wherever you are in the universe. This is why space astronauts “weigh” less when they get further away from the Earth.
What is the SI unit of mass?
The SI unit of mass is the kilogram, abbreviated kg. The kilogram is one of seven base units (time, metre, ampere, kelvin, mole, candela) of the International System of Units (SI).
The kilogram was defined by reference to a physical artefact, the international prototype, until its redefinition in 2019. The new definition for the kilogram is based on a fundamental constant rather than an object.
This change allows secondary standard weights to be derived from the SI base units and also makes the kilogram compatible with the speed of light and the Planck constant.
A consistent and accurate measurement system is necessary to ensure that our everyday measurements remain comparable around the world. This is important for the credibility of scientific research, environmental monitoring, medical diagnostics and many other activities. The SI system is essential for our confidence in data about climate change, pollution and health. This is why the BIPM and its member organisations are working to make sure that all countries will soon have the same rules for writing and presenting measurements.
What is the unit of weight?
In the United States customary system, weight is measured in units called ounces (oz) and pounds (lb). In common parlance, the term weight may also be used to refer to mass. However, this usage should be phased out and the word mass should be used whenever possible.
The kilogram is the SI unit of mass. The gram and its multiples and submultiples are derived units that form part of the SI. Other derived units of mass include the dyne (SI unit of force) and the kilogram-force.
The pound is not an SI unit of mass, but the International Prototype Kilogram kept at NIST in Washington DC is used as a standard for weighing other objects. The pound is still commonly used in the US to measure weight, although the terms pound-mass and pound-force are often preferred. You can use conversion factors to convert from one customary unit of weight to another, and you will need to do this sometimes in order to solve problems involving weight.
What is the unit of volume?
Volume is the amount of three-dimensional space occupied by an object or enclosed by a surface. It is usually measured in cubic units based on the SI or metric system. In chemistry, the unit of volume most commonly used is the liter (L), although milliliters (mL) are also often used because most laboratory experiments involve liquid mixtures and suspensions.
Other units of volume include the cubic foot (ft3) and the cubic meter (m3), both of which are used to measure large objects or spaces. A cubic meter is equivalent to a cube with sides one meter long—think of a swimming pool!
In science, the most common method for measuring mass is by using a balance. The unknown mass of an object is placed on a scale together with a known mass, and the difference in weight between the two is the result of the gravitational pull exerted by the earth at that specific location. The force exerted on an object can also be measured by its acceleration, which is equal to its mass multiplied by the cosine of its velocity.