Chapter 2 Flashcards
Potential energy/Chemical energy –
Definition: Energy stored within the structural units of chemical substances.
Comes from bond formation between particles of matter
Functions of PE
Energy that holds atoms together, such as when the nucleus of one atom
attracts an electron of another atom (e.g., the C-C bond in ethane) (intramolecular bond).
Energy from two molecules (e.g., methanol and methanol, or methanol and acetone) forming an intermolecular bond.
Kinetic energy
Definition: Energy that results from motion
E = 1⁄2mv^2
Kinetic energy consists of translational, rotational and vibrational motion.
Relationship of KE and PE
At height, the book has high PE and no KE. As the book drops the potential energy decreases, and the kinetic energy increases. When the book hits the
ground it converts its kinetic energy into thermal energy.
Laws of Conservation of Energy
- The energy of the universe is constant.
- Energy cannot be created or destroyed.
- When energy of one form disappears, the same amount of energy must appear in another form(s)
Precision
Reproducibility. Closeness of the individual values to the average value.
Systematic error
error that tends to be either too high or too low.
Does not tend to average itself out
Accuracy
Correctness. Closeness of the average value to the correct value.
Random error
Error that has equal probability of being too high or too low.
Tends to average itself out
System
That part of the universe we are studying (e.g., methane reacting with oxygen in a
cylinder)
Unit of energy
Joule
Named after the English physicist James
Joule. It is the amount of kinetic energy possessed by a 2-kg mass moving at a
speed of 1m/s.
Ek = 1/2mv^2
1 cal = 4.184
Surroundings
The rest of the universe
∆U = q + w
change of internal energy of the system = heat absorbed by the system plus work done on the system.
Heat “q”
- quantity of energy transferred between a system and its surroundings
- It is positive if the system absorbs heat from the surroundings;
- it is negative if the system releases heat to the surroundings (i.e., if the surroundings
absorbs heat from the system)
Work
- Done when a force moves through a distance
- is positive if the system is compressed by the surroundings;
- is negative if the system is expanded by the surroundings (i.e., if the surroundings
is compressed by the system)
