● Phase diagram and phase rule-
❖ Phase Diagram is a type of chart used to show conditions at which thermodynamically distinct phases can occur
at equilibrium
❖ True equilibrium is said to exist in a system when the same state can be realized by approaching from either
direction. Example: ice and water at 1atm. Pressure and at 0oC.
❖ Metastable equilibrium- Water at -5oC can be achieved by careful cooling of water but not by fusion of water.
Emulsions/colloidal systems and glasses are metastable.
❖ Phase: The homogeneous part of a heterogeneous system which is chemically uniform, physically distinct and
mechanically separable
❖ Component: Minimum number of independent chemical constituents required to describe all parts of a system
❖ Degrees of freedom- min no. of independent variables of a system.
1) Chemical reactions or physical changes are classified as exothermic or endothermic.
2) An exothermic process is a chemical reaction or a physical change in which heat is evolved (q is negative);
3) An endothermic process is a chemical reaction or a physical change in which heat is absorbed (q is positive).
4) In the exothermic reaction, the reaction flask initially warms; in the endothermic reaction, the reaction flask
initially cools.
5) Enthalpy (H) is an extensive property of a substance that can be used to obtain the heat absTHERMOCHEMISTRY
● System is the specific part of the universe that is of interest to us. For chemists,
systems usually include substances involved in chemical and physical changes. For example, in an acid-base
neutralization experiment, the system may be a beaker containing 50 mL of HCl to which 50 mL of NaOH is
added.
● The surroundings are the rest of the universe outside the system.
● There are three types of systems.
● An open system can exchange mass and energy,
● usually in the form of heat with its surroundings a closed system, which allows the transfer of energy (heat) but
not mass.
● an isolated system, which does not allow the transfer of either mass or energy.
6) The heat of reaction (at a given temperature) is the value of q required to return a system to the given
temperature at the completion of the reaction.
7) orbed or evolved in a chemical reaction.
8) State function, a property dependent only on the current state of the system,NOT THE PATH.
★ The heat capacity ( C ) of a substance is the amount of heat required to raise the temperature of a given quantity
of the substance by one degree Celsius. Its units are J/°C.
★ The specific heat ( s ) of a substance is the amount of heat required to raise the temperature of one gram of the
substance by one degree Celsius. It has the
★ units J/g . °C.
★ Specific heat is an intensive property whereas heat capacity is an extensive property.
❖ Phase Diagram is a type of chart used to show conditions at which thermodynamically distinct phases can occur
at equilibrium
❖ True equilibrium is said to exist in a system when the same state can be realized by approaching from either
direction. Example: ice and water at 1atm. Pressure and at 0oC.
❖ Metastable equilibrium- Water at -5oC can be achieved by careful cooling of water but not by fusion of water.
Emulsions/colloidal systems and glasses are metastable.
❖ Phase: The homogeneous part of a heterogeneous system which is chemically uniform, physically distinct and
mechanically separable
❖ Component: Minimum number of independent chemical constituents required to describe all parts of a system
❖ Degrees of freedom- min no. of independent variables of a system.
1) Chemical reactions or physical changes are classified as exothermic or endothermic.
2) An exothermic process is a chemical reaction or a physical change in which heat is evolved (q is negative);
3) An endothermic process is a chemical reaction or a physical change in which heat is absorbed (q is positive).
4) In the exothermic reaction, the reaction flask initially warms; in the endothermic reaction, the reaction flask
initially cools.
5) Enthalpy (H) is an extensive property of a substance that can be used to obtain the heat absTHERMOCHEMISTRY
● System is the specific part of the universe that is of interest to us. For chemists,
systems usually include substances involved in chemical and physical changes. For example, in an acid-base
neutralization experiment, the system may be a beaker containing 50 mL of HCl to which 50 mL of NaOH is
added.
● The surroundings are the rest of the universe outside the system.
● There are three types of systems.
● An open system can exchange mass and energy,
● usually in the form of heat with its surroundings a closed system, which allows the transfer of energy (heat) but
not mass.
● an isolated system, which does not allow the transfer of either mass or energy.
6) The heat of reaction (at a given temperature) is the value of q required to return a system to the given
temperature at the completion of the reaction.
7) orbed or evolved in a chemical reaction.
8) State function, a property dependent only on the current state of the system,NOT THE PATH.
★ The heat capacity ( C ) of a substance is the amount of heat required to raise the temperature of a given quantity
of the substance by one degree Celsius. Its units are J/°C.
★ The specific heat ( s ) of a substance is the amount of heat required to raise the temperature of one gram of the
substance by one degree Celsius. It has the
★ units J/g . °C.
★ Specific heat is an intensive property whereas heat capacity is an extensive property.
