In this chapter we learn about the importance of chemistry; then nature of matter; properties of matter and their measurement which include internal system of units, mass, weight, volume, density, temperature. Then we discuss about the uncertainty in measurement which teaches about scientific notation, significant figures and dimensional analysis. Then we know about some laws of chemical combinations (Law of Conservation of mass, Law of definite proportions, Law of Multiple Proportions, Gay Lussac’s law of Gaseous Volumes, Avogadro Law), Dalton’s Atomic Theory. Then we discuss about atomic and molecular masses; mole concept and molar masses. Finally we discuss about percentage composition and stoichiometry and stoichiometric calculations(limiting reagent, ,mass percent, mole fraction, molarity, molality)