BG 1108 General Chemistry (Lecture Summary)

Chapter 6 (Semester 2/2012)

Thermochemistry

6.1 The Nature of Energy and Types of Energy

6.2 Energy Changes in Chemical Reactions

6.3 Introduction to Thermodynamics

6.5 Calorimetry

6.1 Energy…capacity to do work

Radiant Energy Thermal Energy Chemical Energy Potential Energy

-Solar Energy -Random Motionof atoms molecules

-Stored within the structural units of chemical substances

-Available by virtue of an object’s position

Heat…..Transfer of thermal energy b/w two bodies that are different temperatures

Thermochemistry……..Study of heat change in chemical reactions

System …. Specific part of the universe that is of interest to us

Surroundings…..Rest of universe outside the system

6.2 Energy Changes and Chemical reactions.

3 types of system

Open Closed Isolated

-can exchange mass and energy

-Allows transfer of energy (heat) But not mass

-Does not allow transfer of either mass or energy

2 types of processes

Endothermic Exothermic

Heat is absorbed from the surroundings

Heat is released to the surroundings

6.3 Introduction to Thermodynamics.Thermodynamics..means scientific study of the interconversion of heat and other kinds of energy.

State of a system....defined by values of all relevant macroscopic properties (composition,energy,temperature, pressure,and volume)

State functions......Properties that are determined by the state of the system, regardless of how that condition was achieved. (Energy,Pressure,Volume and Temperature)

Specific heat(s),and Heat Capacity (C)

C = m s Specific Heat ( J/(g *oC) )

Mass of substance (g)

Heat Capacity J/ oC

Heat Change q = mst

q = c t

t = tfinal - tinitial

6.5 Calorimetry

Calorimetry

Constant -Volume Constant- Pressure

-no heat or mass is lost to the surroundings

q system = 0

q system = q cal + q rxn

q cal = - q rxn

q cal = C cal t

-Pressure is constant ..

Heat change q rxn = enthalpy change H

enthalpy change H = HEAT CHANGE MEASURED AT CONSTANT PRESSURE

C cal = heat capacity of the calorimeter