# What Is Mass Measurement?

Mass is a physical quantity measured by weighing. Weighing instruments typically take the effects of g into account, so objects with different shapes and locations can be compared.

We weigh things all the time, for example on a balance. Our weight changes when we are on Earth versus when we are in space, but our mass remains the same.

## Units of Measurement

The SI base unit for mass is the kilogram, kg. The kilogram is also the standard unit for determining density, although there are several other ways to measure density (as well as many non-SI units). It’s important to distinguish between mass and weight. Mass measures how much matter something is made of, while weight is the force that gravity exerts on an object.

The kilogram is one of seven base units that make up the International System of Units, or SI. Other base units include the meter, second and joule. All other physical quantities can be derived from these base units. Strict adherence to the SI convention requires that all measurement results be reported in these units. However, there are some derived SI units that may be used in chemistry. These are listed below. They are based on other physical constants, including Planck’s constant. Derived SI units are not part of the official definition of the kilogram.

## Density

Density is a characteristic physical property of matter that indicates how tightly the mass is packed into a volume of three-dimensional space. The density of solids is measured in kilograms per cubic meter, g/cm3, and the density of liquids is usually reported as grams per millilitre (g/ml) or gram/cubic centimetre, g/cm3.

The symbol most commonly used for density is , but it can also be represented by the Latin letter D. Because density is a derived quantity – it is calculated from measurements of two other quantities – students need to be introduced to the concept with care.

To obtain accurate density measurements, a clean sample is essential, as is controlled temperature and pressure. Getting these conditions right can be challenging, but getting good results will ensure that volume and mass calculations are correct. This will improve the precision of a balance and increase the usefulness of an experiment. In addition to a laboratory balance, hydrometers and pycnometers are used to measure the density of liquids.

## Weight

Mass is all around us, and it can be measured using a balance scale. It is determined by the atomic and molecular makeup of an object. Since every object has different protons, neutrons and electrons, each has a different mass.

The kilogram (kg) is a base unit in the International System of Units, and it is used to measure mass. It was first defined in 1795 as the mass of a cubic decimetre of water at its melting point, but in 1889 it became independent of water, and is now defined as one kilogram of a metal alloy.

Unlike weight, which depends on the gravitational force of the Earth, mass is an intrinsic property that remains unchanged no matter where it is. The term “weight” should be phased out and replaced with “mass,” especially when referring to an object’s inertial properties. Mass is usually measured in kilograms (kg) and grams, while weight is typically measured in ounces or pounds.

## Gravitational Force

Scientists have long used the force of gravity, or G, to measure the masses of objects. They do this by measuring the acceleration of freely falling objects and dividing it by an object’s gravitational mass.

This formula is known as Newton’s law of universal gravitation, or F = ma, and it is the key to understanding both inertial and gravitational mass. The equation tells you how reluctant an object is to be accelerated, and that is directly related to its inertial mass.

The gravitational force is also a crucial factor in the universe, controlling everything from the trajectories of celestial bodies to the formation of stars and galaxies. It’s the force that causes pennies to spiral around a hole in a common donation toy at your favorite chain store. It’s the force that keeps you on Earth, and the force that causes astronauts to feel weightlessness in space. The force of gravity is much stronger on larger masses, which is why you can feel the pull of your own body on Earth but not the pull of the pennies on the toy in your hand.

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