Exam 2 Lecture 2 Thermodynamic Flashcards
What determines how much internal energy a system has?
- Chemical identity Chemical identity
- • Sample size
- • Temperature
- • Pressure
- • Physical state (s, l, g)
State function definition
• A function or property whose value depends only on the present state of the system, not the path used to arrive at that condition
Examples of state functions
– Age – Weight – Location – Elevation
If the system returns to its original conditions, then for a state function of that system…
the overall change is zero
Delta state=initial state-final state=0
1
C. because you can burn a variable amount of calories depending on the nature of your workout
Explain why location is a state function
2
Explain why elevation is a state function
3
Internal energy of a nonreacting system is a state function Internal energy of ________
a nonreacting system is a state function
The energy change that occurs during a chemical reaction is______
Delta E: a state function
What does delta E equal?
4
What does q mean 4
5 heat
what does w mean 4
5 work
Example of electron flow with no conservation of energy
6 undamned waterfall (energy converted to sound and heat)
Why is q not a state function?
Contributions of q and w can vary depending on how you set the experiment up (pressure or no pressure)
why is w not a state function?
Contributions of q and w can vary depending on how you set the experiment up (pressure or no pressure)
Example of electron flow with conservation of energy
7 hydroelectric power
Potential energy has proportionate relationships to
8
Kinetic energy has proportionate relationships to
8
Chemical potential energy:
stored in bonds
– Thermal energy:
kinetic energy of molecules
– Heat: is ___ energy
radiant
Work is ___
some form of movement
——> +energy
Delta E = -energy
+energy—–>
Delta E= +energy
________is necessary for work to occur in a chemical reaction
A difference in pressure
Describe Delta E in changes in energy and q and w
9
Define Enthalpy in terms of p and q
10 In enthalpy, no work is performed
If enthalpy is negative
11
If enthalpy is positive
11
ΔH depends on the _______ of reactants and products
physical states
13
14
How to determine ΔH experimentally
calorimetry
How to determine ΔH experimentally
calorimetry
heat Capacity formula
15
Specific heat formula
16
By __________,________, ________, you can determine ΔH for the reaction
the mass of the water, the temperature change, and the specific heat of the surroundings (water)
Steps to determine ΔH experimentally
17
1 calorie is the same as
the specific heat of water
define bomb calorimeter
Volume change is minimized:
a device for determining heats of combustion by igniting a sample in a high pressure of oxygen in a sealed vessel and measuring the resulting rise in temperature: used for measuring the calorific value of foods.
If no work is performed, then ΔH=
ΔE
If there is gas generation or gas consumption, then ΔH doesn’t =
ΔE
Model why physical state is important to energy used in a reaction
