Chemistry ch. 9 vocabs

system (sys.)

part of the universe that is our focus

surroundings (surr.)

everything else (around the sys.)

universe

system + surroundings

what are the types of systems in thermochemistry?

1. isolated system

2. closed system

3. open system

what occurs in terms of matter and energy in a isolated system?

nothing, b/c the sys. is isolated, there’s no additional exchange in matter or energy w/ the surroundings

what occurs in terms of matter and energy in a closed system?

there’s a exchange of energy w/ the surroundings; there’s no exchange with matter b/c the system is closed therefore we (surrounding) cannot add or take out any matter from the system.

what occurs in terms of matter and energy in a open system?

both an exchange of matter and energy w/ the surrounding

Energy

capacity to do work(w) or to produce heat(q)

what unit is Energy in?

units of Joules(J)

what are the different broad types of energy?

1. potential

2. kinetic

what is potential energy?

energy of position

What are the subunit energies in potential energy?

1. gravitational

2. chemical

What increases potential energy?

if w is done to change the position of an object in a field, then its potential E increases

what are some examples that would increase potential energy?

your body in the earth’s gravitational field; when you climb a flight of stairs you DO WORK, and your potential energy increases

What decreases potential energy?

if NO w is done to change the position of an object, the potential energy of the object decreases

what are some examples of decrease in potential energy?

(in chemistry) when two oppositely charged materials come together d/t attractive forces, the potential energy decreases (b/c the bond is from attractive that occurred naturally)

what is kinetic energy?

the energy an object possesses d/t its motion

What are the subunit energies in kinetic energy

1. thermal

2. mechanical

3. electrical

what increases KE?

1. increase in mass (kg)

2. increase in speed (velocity; v²)

3. increase in temperature

4. falling/descending

what decreases KE

1. decrease in mass (kg)

2. decrease in speed (v²)

3. decrease in temperature

4. moving upward (going against gravity loses speed → KE decreases → doing work to move up → KE converts to potential energy

work (w)

force acting over distance

heat (q)

energy transfer b/w two objects b/c of a difference in temperature

heat capacity

energy required for a certain change in temperature

specific heat capacity (Csp)

energy required to heat ONE GRAM of a substance by 1˚C (or 1K)

molar heat capacity (Cn)

energy required to raise the temperature of ONE MOLE of a substance by one degree

internal energy (U)

1. total of all energy present in a substance

2. sum of kinetic (q) and potential (w) energies of all the “particles” in the system

First Law of Thermodynamics

1. energy of the universe is constant

2. energy can be transferred within the universe, but it is neither created nor destroyed

3. energy is conserved

4. ∆U = q + w

heat of reaction (Hrxn)

heat exchanged b/w sys and sure during a chemical rxn

what types of heats of reaction are there in thermochemistry

1. endothermic rxn

2. exothermic rxn

what are ways to determine heats of reaction?

Calorimetry

1. bomb calorimeter

2. coffee cup

what’s held constant for a bomb calorimetry?

Volume

what’s held constant for a coffee cup calorimetry?

Pressure

state function

property of the system that only depends on its present state

what are some simplified examples of state function?

two lines labeled, X and Y are drawn on Mt.K to show that both route has the SAME change in elevation (state function, b/c it doesn’t matter what path you take, you’ll have traveled the same elevation); but they have very DIFFERENT distances traveled (not state function; depends on the path)

Hess’ Law

1. ∆H is the same whether a run takes place in one step or in a series of steps (as long as initial and final states are the same)

standard states

states that aa substance is at standard conditions (p=1 atm; T is usually. specified as 25˚C)

spontaneous process

occurs w/o outside intervention

non-spontaneous

requires outside intervention (typically spontaneous in reverse direction

Entropy (S)

a measure of molecular disorder, randomness, or energy dispersal within a system

Second Law of Termodynamics

in any spontaneous process, there is always an increase in the disorder (entropy) of the universe

reversible rxn

takes place I a infinite number of infinitesimally small steps; sys Is at eq. at each step

irreversible rxn

processes carried out in finite time, all real processes are irreversible, no eq

Third Law of Thermodynamics

the entropy of a pure, perfect crystal at 0K is zero

• if S=0, then W=1

Gibbs Free Energy

energy ‘free’ (available) to do useful work