Chapter 6:†† Principles of Reactivity: Energy & Chemical Reactions
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.†††††† Hessís 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
Example: rub hands together.
c) Sound Energy
Organized energy of motion exhibited by vibrations of atoms and
†Example: any sound.
d) Electrical Energy
Energy resulting from the forces between charged particles.
Example: Electrical energy from a hand-cranked generator lights a
e) Magnetic Energy
Energy resulting from the forces between magnets, causing the
magnets to attract or repel. Example: one magnet floats above
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
j) Chemical Potential Energy
Energy available in the chemical bonds between atoms or molecules.
k) Nuclear Energy
Energy available in the nucleus of atoms that can decay.
Examples: smoke detector, the Sun