Today, we know every matter around us is composed of atoms. But this fact was a mystery until the end of the 18^th century when Dalton, an English chemist, proposed his atomic theory. Dalton’s atomic theory was the first scientific atomic theory based on his experiments and examinations of previous scientific works. Modern atomic theory is much different from what Dalton had proposed, but some of the ideas of the theory are still valid. Dalton’s theory provided a foundation for modern chemistry.

The law of reciprocal proportions is also known as the law of equivalent proportions or the law of permanent ratios. It along with the law of definite and multiple proportions is one of the fundamental laws of stoichiometry. The law was proposed by German chemist Jeremias Richter in 1791. The is similar to the law of multiple proportions.

The law of multiple proportions is one of the basic laws studied in chemistry. It along with the law of definite proportions has contributed to the understanding of stoichiometry in early days. The law was proposed by English chemist John Dalton in 1803, who is also known for his law of partial pressures. Dalton published the law in his book New System of Chemical Philosophy (Vol 1).

The law of definite proportions is also known as the law of definite composition or the law of constant composition, or simply Proust’s law. It is one of the basic laws in chemistry and a part of the laws of chemical combinations. In 1794, French chemist Joseph Proust proposed this law. That time the knowledge of chemical compound was not fully evolved, and he was opposed by many well-known chemists of that time. But later they were proven wrong. The law of definite proportions was later extended by John Dalton when Dalton proposed the law of multiple proportions.

The law of conservation of matter is a fundamental law in science. It is also known as the law of conservation of mass. The later is used in physics while the former in chemistry. It is one of the laws of chemical combinations in chemistry. The law has huge applications in chemistry, physics, and engineering. In a closed system, the exchange of matter is restricted across its boundaries. So, there is no matter entering the system or leaving the system. Thus, the flow of matter in and out of the system is zero. These statements are true only for a closed system with no nuclear change. We can apply the law to systems which are subjected to physical and chemical changes, not nuclear changes. This will be better understood as we go through the article.

The ideal gas constant is also known as the universal gas constant or the molar gas constant or simply the gas constant. It is a very important constant in chemistry and physics. It is denoted as R. The dimension of the gas constant is expressed in energy per unit mole per unit temperature. The value of the gas constant in SI unit is 8.314 J mol⁻¹ K⁻¹. The gas constant has the same unit as of entropy and molar heat capacity.

Ideal gas equation is PV = nRT. This equation can easily be derived from the combination of Boyle’s law, Charles’s law, and Avogadro’s law. But here, we will derive the equation from the kinetic theory of gases. The kinetic theory of gases is a very important theory which relates macroscopic quantities like pressure to microscopic quantities like the velocity of gas molecules. This equation is applicable only for ideal gases, but be approximated for real gas under some conditions.

The Ideal gas law is also known as general gas law. As the name states the law is applicable under the ideal conditions, not to real gases. The law correlates the pressure, volume, temperature, and amount of gas. It was first formulated by French physicist Émile Clapeyron in 1834.

The Boltzmann constant is a very important constant in physics and chemistry. The constant relates the average kinetic energy of molecules of a gas with thermodynamic temperature. The Boltzmann constant is denoted as k_B or k. The dimension of the Boltzmann constant is energy per thermodynamic temperature. The SI unit is J K⁻¹, which is the same as of entropy. The value of the Boltzmann constant is 1.380 649 × 10⁻²³ J K⁻¹.

Graham's law of diffusion (or Graham's law of effusion) is a law that expresses the relationship between the rate of diffusion or effusion to molar masses of particles. This empirical law was stated by Scottish chemist Thomas Graham in 1848. He established the relationship through experiments.