Physical Quantities and their Measurements in Chemistry

A physical quantity is the property of a material or the system that can 

be quantified by measurement. It can be presented as a value, which is the multiplication of a numerical value and a unit. It possesses at least two properties. 

• A numerical or number magnitude.
• The unit in which it is calculated. 

Some of the physical quantities must be more fundamental than others. The most significant material total amounts can be stated only in the method used to measure them. The units in which these quantities are measured are thus called fundamental units. 

It covers an essential part of chemistry and helps us deal with crucial measurements we come across in our day-to-day life.

• The International System of Units : SI

The International System of Units we use daily is the modern or the present version of the metric system. This system is also called by the abbreviation SI, a short form of the whole. It is a coherent system in which there are seven independent base units. SI system has base units for:

• Length
• Mass
• Time
• Temperature
• Electric Current
• Light Intensity
• Amount of Substance

By stating base units for these seven dimensions, SI units can be used simply for mechanics and thermodynamics and chemistry, calculations in electrical measurements, and many more other areas. The definitions of the base units are:

• Length 

Length is the measure of one single dimension, whereas when it comes to the area, it measures two dimensions, and volume measures three dimensions.

Measurement has been critical in human life since they started occupying land and trading with neighbours for their livelihood.

This means the length of an object differs depending on the observer’s speed. The SI unit of length is metre (m). 

• Mass

The mass of an object is defined as its fundamental property. It is the numerical measure of its inertia. It can also be defined as the measure of the amount of matter present in a particular item. Mass is an absolute quantity. The mass of an object determines its acceleration in the presence of an applied force. Any object on the Moon would weigh significantly less than Earth because of the lower gravity, although it would still have the same mass. The SI unit of mass is kilogram (kg). 

• Time

Time is the straight sequence of existence and events in apparently irreversible succession from the past to the present into the future. It is a component quantity of different measurements used to sequence events. Distance and time are intimately related, and the time needed for light to travel a specific length is the same for all observers. The SI unit of time is seconds (s)

• Temperature 

In simple words, it can be said that it is the physical quantity that indicates how hot or cold an object is. It is the manifestation of thermal energy present in all matter around us, which is the heat source when a body is in touch with another colder or hotter than the usual body.

The lowest theoretical temperature ever measured is absolute zero, at which no more thermal energy can be extracted from anybody.

The Celsius scale is used for common temperature measurements in our everyday life in most of the world.

There are different kinds of temperature scales. It may be easy to classify them as empirically and theoretically based. 

• Electric current 

Electric current is defined as a stream of charged particles moving through an electrical conductor or space. It is calculated as the net rate of the movement of electric charge through a surface or into a control volume. The SI unit of electric current is the ampere or amp. An ampere is defined as the flow of electric charge across a surface at the rate of one coulomb per second.

In metals where the charge carriers, that is, the electrons, are negative, conventional current is taken in the opposite direction. In conductors where charge is positive, conventional current is in the same direction as the charge carriers.

• Light Intensity  

Light intensity or light output is calculated to understand if a particular light source provides sufficient light for an intended application. Illuminance is the metric used to find the light intensity in a space. 

Lumens (lm) are the unit of measurement that we use to quantify the quality of visible light the human eye can see. The luminous flux of a particular light source is calculated in lumens.

The human eye can only see the source of light in the visible spectrum and has different sensitivities to light of different wavelengths within the spectrum.

• Amount of Substance 

The amount of substance that we need to find  in a presented sample of matter that may be stated as the quantity or number of discrete atomic scale size particles present in it divided by the Avogadro constant. In the reality of atomistic view, the whole amount of substance present is simply the total number of particles that constitute the entire substance.

The amount of substance that we have dealt with earlier is commonly referred to as the chemical amount. The amount of substance is also a convenient theory in thermodynamics. This quantity should not be mixed up with the mass concentration, which is the mass of the substance. 

The amount of substance is also called the material quantity, and it is also a dimensionless expression of the total number of particles present in a sample. The particles referred to here are usually atoms, but they can be protons, neutrons, electrons, or some more fundamental particles such as quarks.

Conclusion 

Performance measurement plays an important role in creating public value through effective strategic management. The work done in developing and improving performance measurement systems includes philosophical and normative as well as scientific and cognitive issues.

Units are the essential standards for expressing and comparing the measurement of physical quantities. All units we come across can be expressed as combinations of four fundamental units. In modern life, measurement plays a very necessary role. A physical measurement could be stated as the act of deriving quantitative information about a physical object or action by comparison with a reference.