HSC: Chemistry Chapter no 4: Chemical Thermodynamics
CHAPTER 4 : CHEMICAL THERMODYNAMICS 4.1 Introduction Summary • Many physical and chemical changes involve energy. Examples: Ice melts into water. Water changes into steam. Carbon burns to form carbon dioxide. In all these changes, energy is either absorbed or released. Energy can change from one form into another. Examples: Dry cell: Chemical Energy → Electrical Energy Electroplating: Electrical Energy → Chemical Energy Hydroelectric dam: Potential Energy → Kinetic Energy → Electrical Energy What is Thermodynamics? Thermodynamics is the branch of chemistry that studies: • Heat changes • Work done • Energy changes during physical and chemical processes. It only tells us how much energy changes. It does NOT tell: • How fast the reaction occurs. • The mechanism (steps) of the reaction. 4.2 Terms Used in Thermodynamics 4.2.1 System and Surroundings System The part of the universe chosen for study is called the system. Example: Gas inside a cyl...