CHEM 1110 Chapter Notes - Chapter 5: Coffee Cup, Kinetic Energy, State Function
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CHEM 1110: Principles of Chemistry 1 – Chapter 5 Reading Notes
Thermodynamics – the study of energy and its transformations
Thermochemistry – the relationship between chemical reactions and energy
changes involving heat
Energy – the capacity to do work or transfer heat
Work – the energy used to cause an object to move against a forces
Heat – the energy used to cause the temperature of an object to increase
Kinetic energy: Ek = .5mv2
Potential energy – energy in virtue of its position
Electrostatic potential energy arises from the interactions between charged
particles: Eel = (kQ1Q2)/d
SI unit for energy is the Joule ( 1 J = 1 kg * m2/s2
Calorie – amount of energy required to raise the temperature of water 1 degree C
o1 cal = 4.184 J
o1 Calorie (C) = 1000 cal = 1kcal
System is made of reactants and products
Open system: matter and energy can be exchanged with surroundings
Isolated system: nothing can be exchanged with its surroundings
First law of thermodynamics – energy cannot be created nor destroyed
Internal energy (E) – sum of all the kinetic and potential energies of the
component so fa system
oChange in internal energy ∆E = Efinal – Einitial
Positive ∆E means system has gained energy from its surroundings
A system may exchange energy with its surrounding as heat or as work
When heat is added to a system or work is done on a system its internal energy
increases
o∆E = q + w (q is heat; w is work)
Endothermic: when a process absorbs heat
Exothermic: when heat leaves a system
State function: a value of the system that is determined by specifying the
system’s condition ex. Internal energy
oThe value of a state function depends only on the present state of the
system, not the path it took to reach that state
Enthalpy relates to heat flow
oH = E + PV (pressure = p; v = volume)
Internal energy, pressure, and volume are all state functions
Pressure-volume work (P-V work) – the work involved in the
expansion/compression of gases
oW = -P∆V
oPressure is either positive or 0
oThe negative w is because the system does work on its surroundings
oPositive w means work is done on the system by its surroundings
Change in enthalpy: ∆H = ∆(E+PV) ∆H = ∆E + P∆V which is the same as ∆H =
(qp+w)-w) = qp
oQp is saying the process occurred at constant pressure
oThe change in enthalpy= the heat qp gained/lost at constant pressure