The metric system provides a single coherent set of units that can be used to measure all quantities. This includes mass.

A pineapple or a baseball bat have different types of matter, but they both have the same amount of mass. Mass is also a fundamental property of matter that determines many other properties, such as gravitational attraction and resistance to acceleration.

## Definition

Kids are naturally inquisitive, and teaching them about mass at a young age is an excellent way to help them effortlessly grasp more complicated concepts like physics later on. Mass is the amount of matter in an object, and it depends only on the type of atoms that make up the object, as well as how many atoms are there.

Weight, on the other hand, is the force of gravity on an object. If you are 40 kilograms on Earth, you would weigh 88 pounds, but on the moon or Jupiter (or in space), your weight would be zero since there is no gravity on these planets. The same applies to vehicles and objects that are in orbit or travelling at high speeds. To measure an object’s weight, a balance-type weighing scale is used and the object’s conventional mass is measured by being compared against a stainless steel mass standard. This method is unaffected by the gravitational acceleration of the Earth.

## Units of Mass

Mass is the amount of matter an object contains. An object with more mass will be harder to move or stop than an object with less mass. This is because an object with more mass has greater inertia.

A kilogram is the standard unit of mass in the SI system. It was defined in 1875 as the mass of a certain cylinder of platinum-iridium kept in France, called the International Prototype Kilogram, or kg. The kilogram is one of 7 SI base units.

Scientists at NIST are working to develop a definition of the kilogram based on an invariant of nature, such as the Planck constant or the Avogadro constant, rather than a physical object. A new definition would allow the kilogram to be available worldwide at any time. This would make it easier to compare the masses of different particles or objects. For now, the standard kilogram remains a fixed reference, and its value can be determined experimentally using a moving-coil watt balance.

## Measurement Methods

Mass is measured using a variety of different tools depending on the level of accuracy required. One of the simplest is the balance scale, which works on the principle that an object’s mass changes when standard weights are added or removed until a state of equilibrium is achieved. This method is used extensively in laboratories and industry, although it can be subject to environmental influences such as vibrations or drafts.

More accurate mass measurements can be made using mass spectrometers that measure the distribution of mass error samples (see Figure 2). This is done by plotting the frequency (histogram) of these data. The precision of the distribution can be assessed by comparing it to the theoretical value s = standard deviation of the sample. It can also be compared to other methods of measurement by testing for statistically distinguishable mean values or examining their scatter. A typical error magnitude for a sample is s = 0.0030 Da, with an associated uncertainty of 0.001 Da.

## Conclusions

Weighing objects to measure their mass is commonplace in the lab, and students may be familiar with using an old-fashioned balance like this one. When an object’s weight is compared to that of a stainless steel standard, its conventional mass—that is, its true or actual mass minus an unknown degree of buoyancy—can be determined. This method works just as well in space and other places with no gravity as it does on Earth.

Another measurement of matter is its volume, which is simply how much space an object takes up. By measuring and graphing the results, students can see that if a solid changes state (melting or dissolving), or if substances react to form new substances as products, the total mass of the materials does not change. This is a direct result of the principle that states that matter always retains its own intrinsic property of matterness, or inertia. It is an important distinction to make because it relates to an object’s resistance to acceleration.

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