Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 1 Some Forms of Energy - Solar...
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Transcript of Thermochemistry General Chemistry I CHM 111 Dr Erdal OnurhanSlide 1 Some Forms of Energy - Solar...
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 1
Some Forms of Energy
- Solar Energy, part of radiant energy. Solar energy comes from the Sun and is the primary source of Earth’s energy. - Thermal Energy is due to random motion of atoms and molecules. It is generally calculated from temperature measurements. Temperature is not a measure of thermal energy itself. - Chemical Energy is stored within the structural units of chemical substances. When a chemical reaction takes place, chemical energy is released, stored, or converted to other forms of energy. - Potential Energy is the energy due to the position of an object. Chemical energy can be considered to be a form of potential energy, since it is associated with the positions of atoms in the molecules. - Kinetic Energy is the energy produced by a moving object.
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 2
System-Boundary-Surroundings
ImaginaryBoundary Im
aginary
BoundaryIm
agin
ary
Bou
ndar
y
ImaginaryBoundary
The boundary might be imaginary, as in this case, or real, as in other cases.
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 3
Three Types of Systems
Open: energy anmass can beexchanged
Closed: onlyenergy can beexchanged
Isolated: nothing is exchanged
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 4
An Example to State Functions – Distance vs. Displacement
A
B
There are many routes between A and B. The distance covered by the coloured routes is different from one another. The displacement, however, is the same for all routes, AB.
Displacement is a state function, whereas distance is not.
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 5
Another Example of a State Function- Volume
A I1
I2 B
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 6
The First Law of Thermodynamics
System
Surroundings Universe
Energy Out
It is obvious that, energy lost by the system is absorbed by the surroundings. Since the Universe comprises both the system and the surroundings, energy is conserved in the process.
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 7
Sign Convention for Work and Heat
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 8
Expansion of a Gas in a Cylinder
Initial State Final State
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 9
Bomb Calorimeter
The thermometer is used to determine t of the reaction. qcal is calculated from
cal calq C t
Thermochemistry
General Chemistry I CHM 111 Dr Erdal Onurhan Slide 10
An Open Calorimeter
The thermometer is used to determine t of the reaction. q is calculated from
q ms T