Chapter 6: Thermochemistry- Part 1 Flashcards
What is energy?
The ability to transfer heat
The ability to do work
Work
Symbol: W
W=(force)x(distance)
Major Types of Energy?
PE and KE
Potential Energy
-It is associated with position
-No one equation for calculating PE
Kinetic Energy
-Associated with motion
-Formula KE=1/2mv^2
-M(mass) express in kg
V(velocity) express in m s-1
Problem: What is the kinetic Energy in kg m^2 s^-2, of a baseball (145.5g) moving at 144.841 km hr^-1?
145.5g=0.1455kg
(144.841km hr-1)(1000m/1km)(1hr/3600sec)=40.23m/s
KE=1/2(0.1455kg)(40.23m/s)^2
117.8 kg m^2 s^-2
Heat (thermal energy)
-Energy usually associated with temperature changes…
-Also associated with molecular/atomic motion
Other forms of energy?
~Electrical
~Solar
~Nuclear
~Geothermal
~Chemical
Law of Conservation of Energy contain?
1st law of thermodynamics
Systems
Surroundings
Enthalpy
What is system?
Limited portion of the world that we are interested in.
What is surroundings?
Everything else e.g. the universe
Energy movement is defined in terms of the system and surroundings.
Exothermic processes
Endothermic processes
Exothermic processes
Energy moving from the system to the surroundings.
Endothermic processes
Energy moving from the surroundings to the system.
What is the state function?
A property that is dependent only on the current condition and is independent of how it arrived at that condition.
E.g. altitude, temperature
What is the 1st Law of thermodynamics?
States that energy is neither created nor destroyed can only be shifted from one form to another.
What is a energy for a system, E total made of?
It is made up of microscopic kinetics and potential energy as well as microscopic kinetic and potential energy components.
E total formula
Etotal= KE+ PE + U
Where KE
Macroscopic Kinetic Energy Components
Where PE is
macroscopic potential energy components
Where U
Internal energy (microscopic components)
Measuring E total directly is very difficult (e.g. impossible in most cases), so we look at changes is energy rather than absolute energies
DeltaE=E final-E start
DeltaE= products -E reatants
System formula
U system= q + w
What does q means?
Heat component
What does w means?
Work component
Information in q= “+”
Heat is imported into the systems e.g., an endothermic process
Information q= “-“
Heat is exported from the system, e.g., and exothermic process
Information w= “+”
If the surroundings does work on the systems (imports work)
Information w= “-“
If the system does work o the surroundings (exports work)
Heat Capacity
A) the amount of heat (ENERGY) needed to change thee temperature of an object by 1C or 1K.
B) used most often with objects. Heat capacity is dependent on sample size.
C) heat capacity= energy J/Delta temp (c or K)
Problem: An alumimun part took 161 J of energy to raise its temperature from 22.3 C to 28.9C. What is the heat capacity of the aluminum part?
161 J/28.9-22.3
=24.4 J C^-1
What is specific heat capacity, Cp?
A) It is the amount of heat to change the temp of a given mass of material by 1C or 1K
B) Cp= energy J / (mass)(temp) or q / mass temp)
C) Problem: How much heat is needed to raise the temp of 11.65g of copper from 22.10 C to45.06C? (For Cu Cp= 0.384 J g^-1 C^-1)
0.384 J q^-1 C^-1= ?q / (11.65g)(22.96C)
- q=(0.384 J g^-1 C-1)(11.65g) (22.96C)
=103 J
What is molar heat capacity?
A) It is the amount of heat need to change the temp of a mole of material by 1C or 1K
B) mola heat capacity= energy J / 1 mole temp or q/ J T
C) molar heat capacity = (specific heat capacity) (molar mass)
D) problem: What is the molar heat capacity of Copper?
Molar heat capacity= (0.384 J g^-1 C^-1) (63.55 g mole^-1)
=24.4 J mole^-1 C^-1
