CHM 2045C
Chapter 6: Principles of Reactivity: Energy &
Chemical Reactions
Key Terms
0. Calorimeter:
a device used for measuring the heats of chemical reactions.
1. Calorimetry: the experimental determination of the
heats of chemical reactions.
2. Chemical potential energy: the
potential energy associated with chemical bonding.
3. Cold: the absence of heat
4. Electrical energy: the energy of
electrons moving through a conductor.
5. Electrostatic energy: the potential
energy that is associated with the separation of two charges.
6. Endothermic process: a process in which
heat is transferred from the surroundings to the system.
7. Energy: the capacity to do work.
8. Enthalpy: the heat content of a
substance at consistent pressure. We
abbreviate enthalpy by the letter H and changes in enthalpy by ΔH.
9. Exothermic process: a process in which
heat is transferred from the system to the surroundings.
10. First Law of Thermodynamics: another
name for the law of conservation of energy.
11. Gravitational energy: the potential
energy that results from the attraction of any two masses.
12. Heat: the
flow of energy from an object at a higher temperature to an object of lower
temperature
13. Heat of fusion, ΔH fus: the heat
required to convert a solid at the melting point to a liquid,
14. Heat of vaporization, ΔH vap: the heat required to convert a liquid at its boiling point
to a gas.
15. Hess’s law: if a reaction is the sum of
two or more other reactions, ΔH for the overall process is the sum of the ΔH values of
those reactions.
16. Internal energy: for a chemical system,
this is the sum of the potential and kinetic energies of the atoms, molecules,
or ions in the system. We abbreviate
internal energy by the letter E and
change in internal energy by ΔE.
17. Kinetic energy: the energy of motion.
18. Law of conservation of energy: energy
is neither created nor destroyed in ordinary processes.
19. Mechanical energy: the energy of a
moving object at the macroscopic level.
20. Potential energy: energy that results
from an objects position; stored energy.
21. Sound (or Sound Energy): a type of energy
that results from the compressions and expansions of the spaces between
molecules.
22. Specific heat capacity: the quantity of
heat required to raise the temperature of 1 gram of a substance by one Kelvin
unit or one degree Celsius.
23. Standard molar enthalpy of formation, ΔHof , the enthalpy
change for the formation of 1 mole of a compound directly from its component
elements in their standard state.
24. Standard state: for an element or
compound this is the most stable form of the substance in the physical state
that exists at pressure of 1 bar (approximately 1 atmosphere) at a specified
temperature. For a solute, the
concentration is 1 M.
25. State function: a function whose value
is determined only by the state of the system and not by the pathway by which
that state was achieved.
1. Sublimation: the change of state in
which a material changes directly from the solid state to the gaseous state
without passing through the liquid state.
2. Surroundings: everything outside the
system that can exchange energy with the system.
3. System: the object, or collection of
objects, being studied.
4. Temperature: a property that determines the direction of
heat transfer; heat transfers from at a higher temperature to something at a
lower temperature.
5. Thermal energy: heat energy due to the
motion of atoms, molecules, and ions.
6. Thermal equilibrium: the condition at
which two objects are at the same temperature.
7. Thermodynamics: the science of heat and
work.
8. Work: work is done when a force,
F, is applied through a distance,
d.
Mathematically, w = F x d.
Forms of
Energy:
a) Mechanical Energy of Motion
Energy exhibited by objects in
motion.
Example: any moving object.
b) Thermal Energy
Unorganized energy of motion exhibited
by vibrations of atoms and
molecules.
Example: rub hands together.
c) Sound Energy
Organized energy of motion
exhibited by vibrations of atoms and
molecules.
Example: any sound.
d) Electrical Energy
Energy
resulting from the forces between charged particles.
Example: Electrical energy from
a hand-cranked generator lights a
bulb.
e) Magnetic Energy
Energy resulting from the forces
between magnets, causing the
magnets to attract or repel. Example: one magnet floats above
another magnet.
f) Radiant Energy
Energy resulting from the
vibrations of charges, such as radio
waves, microwaves, light rays, and
X-rays.
Example: radiant energy
from a floodlight shining on a solar
cell powers the free play radio.
g) Gravitational Potential Energy
Energy stored in raised objects,
which have the potential to fall.
Examples: water wheel or any
raised object.
h) Strain Potential Energy
Energy stored in stretched or
compressed objects, such as springs.
Examples: music box and wind-up
toys.
i) Electrical
Potential Energy
Energy stored in the separation of
static (not moving) electric
charges.
Example: capacitor
j) Chemical Potential Energy
Energy
available in the chemical bonds between atoms or molecules.
Example: battery
k) Nuclear Energy
Energy available
in the nucleus of atoms that can decay.
Examples: smoke detector, the
Sun