carbon dioxide, sugar, etc. The molecules of water and carbon dioxide are represented in Fig. . .
Note that a water molecule comprises two hydrogen atoms and one oxygen atom. Similarly, a molecule of carbon dioxide contains two oxygen atoms combined with one carbon atom. Thus, the atoms of different Fig. .
A depiction of molecules of water and carbon dioxide Water molecule (H O) Carbon dioxide molecule (CO ) Fig. . A representation of atoms and molecules will learn about the measurement of physical properties. .
. Measurement of physical properties Quantitative measurement of properties is reaquired for scientific investigation. Many properties of matter, such as length, area, volume, etc., are quantitative in nature. Any quantitative observation or measurement is represented by a number followed by units in which it is measured.
For example, length of a room can be represented as m; here, is the number and m denotes metre, the unit in which the length is measured. Earlier, two different systems of measurement, i.e., the English System and the Metric System were being used in different parts of the world. The metric system, which originated in France in late eighteenth century, was more convenient as it was based on the decimal system. Late, need of a common standard system was felt by the scientific community.
Such a system was established in and is discussed in detail below. . . The International System of Units (SI) The International System of Units (in French Le Systeme International d’Unités — abbreviated as SI) was established by the th General Conference on Weights and Measures (CGPM from Conference Generale des Poids et Measures ).
The CGPM is an inter- governmental treaty organisation created by a diplomatic treaty known as Metre Convention, which was signed in Paris in . The SI system has seven base units and they are listed in Table . . These units pertain to the seven fundamental scientific quantities.
The other physical quantities, such as speed, volume, density, etc., can be derived from these quantities. Maintaining the National Standards of Measurement The system of units,