Mass is the quantity that an object has, a property that determines heaviness. Different objects with the same amount of matter can have very different weights.

A balance is the most common instrument used to measure mass. Other measurement techniques include versions of mass spectrometry that detect the resonant vibrational frequencies of molecules.

## Units of Measurement

Various units of measurement are used to quantify physical quantities, such as length, mass, and volume. The metric system is the world’s most commonly used measure of length and other quantities, but some countries still use customary units for certain measurements. Unit conversion is easier within the metric system because of its regular 10-base and standard prefixes that increase or decrease by powers of 10 at a time.

For example, a milligram is one thousandth of a gram, and a dekaliter is 10 times larger than a liter. The meter is the basic metric unit for measuring length, while kilograms are the base units for mass and capacity.

The kilogram was originally defined as the mass of a cubic decimeter of water, but it was redefined in the metric system in 1875 to include the current value of Planck’s constant. The new definition is based on the International Prototype Kilogram, a plum-sized platinum and iridium cylinder kept at NIST.

## Prefixes

Prefixes allow for a simpler way to express how much bigger or smaller a measurement is than its base unit. There are four common metric, or SI, prefixes: milli (m), kilo (k), deci (d) and centi (c). Prefixes are abbreviated as lowercase letters except for the word kilogram, which contains the letter g.

Scientists and governments from around the world recently voted to add four new prefixes to the existing system, allowing for measurements that go up to yottagrams (24 zeroes) and zettabytes for huge quantities of digital data. This was done to meet the needs of industries and scientists that need to deal with massive amounts of information. The metric system is important for keeping data consistent and accurate, building confidence in science and the ability to make informed decisions. This is especially true when it comes to the smallest measurements, such as those used in chemistry, microbiology and computer science. Those measurements are used to create very tiny chips that then find their way into other types of technology.

## Metric System

The metric system is used around the world and is an important part of science. It is also known as the International System of Units, or SI for short.

The basic units of the metric system are the meter (m-tr), centimeter, liter and kilogram. The meter is the base unit for length, centiliter for volume and the kilogram for mass.

Each metric unit is 10 times larger than the previous one, and its name can be derived from the prefix it begins with or from the base it uses. For example, a kilo means a thousand grams; a ton is a million kilograms.

To help students better understand the metric system, consider introducing it into curriculum across multiple disciplines. For instance, incorporating metric measurements into art, language arts, social studies and vocational technologies can emulate real-world applications and provide opportunities for students to build their understanding of how the SI works outside of math and science classes.

## Conversions

There are several systems of measurement that include units for properties such as length, volume and weight. Most countries use the metric system, although some continue to use a mixture of units, such as feet for distance and pounds for mass. Changing from one set of units to another requires conversions, which express the same property in a different form.

A conversion factor is a number used to change the value of a unit of measure, such as multiplying or dividing. For example, to convert from kilograms to grams, divide the weight by 1000.

Various books provide conversion factors and algorithms, and the available resources vary widely in terms of how many units are covered, how accurate the conversion factors are and the methods that are presented. For example, Wildi [wildi] presents a series of directed acyclic graphs; each node is a unit and the arcs between them are labeled with conversion factors. The user traverses the graph, converting from one unit to another along the way by multiplying (or dividing if moving against the direction of the graph arrows). This method is not as convenient as using a table of metric conversions.