The International System of Units or in short SI (in French Le Systeme International d’Unités) is the currently accepted system of measurement. It originated from France. The SI was established in 1960 by the 11 CGPM (General Conference on Weights and Measures or Conférence Générale des Poids et Mesures in French). The SI system is the updated version of the metric system. It is presently accepted worldwide; though, certain countries like the USA still follows traditional English units. The SI system includes the seven base units, names of 22 derived units, and a set of prefixes.

Everything around us, in the earth, and beyond earth is matter. Matter consists of atoms. Every type of atom is associated with an element. There are 118 elements known to us, and they are arranged in the modern periodic table. This article mentions some of the most abundant elements in different systems.

There are two ways in which we can classify properties of matter. Based on how properties are determined, they can be classified into two categories: physical properties and chemical properties. Based on the dependence of properties on the amount of a substance, we can classify them into intensive properties and extensive properties. The figure below explains the same.

Matter is anything which has mass and occupies space. Examples of matter are books, phones, laptops, water, juices, coffee, air, Earth, Moon, Sun, and anything which is composed of atoms. Based on physical characteristics, we can classify matter into two main categories: pure substances and mixtures. Mixtures can further divide into homogeneous and heterogeneous mixtures and pure substances into elements and compounds.

Matter is anything that possesses mass and occupies space. In other words, one which you can weigh and measure volume is matter. Matter includes everything which satisfies the above two conditions: mass and volume.

There are four classical or fundamental states of matter, viz. solid, liquid, gas, and plasma. The latter among the four is not common in comparison to the rest three.

Chemistry is a very important branch of science. Chemistry is the study of science that deals with constituents of matter like atoms molecules, ions etc.; and its properties, structure, behaviour, and interactions among them. Since everything is made up of atoms and molecules, we can see the chemistry all around us. Today, chemistry has grown into a very diverse field. There is a significant overlap between chemistry and other branches of science, for example, biochemistry (chemistry and biology), physical chemistry (chemistry and physics), medicinal chemistry (medicine and chemistry), chemical engineering (chemistry and engineering) etc.

Hydrostatic pressure is the pressure exerted by a fluid at hydrostatic equilibrium on the contact surface due to gravity. If a fluid is confined in a container, the pressure on the bottom and on the walls of the container is due to hydrostatic pressure.

Standard ambient temperature is 25 ℃ or 298.15 K or 77 ℉.

Standard pressure is 1 bar or 100.000 kPa or 750.06 mmHg (or torr) or 14.504 psi.

Normal temperature is 20 ℃ or 293.15 K or 68 ℉.

Normal pressure is 1 atm or 101.325 kPa or 760 mmHg (or torr) or 14.6959 psi.