Matter and Energy
*Enthalpy and Entropy
I. Matter
A. Definition
B. Substances v mixtures
1. Substances
a. elements
b. compounds
2. Mixtures
a. homogeneous
1. solutions
2. alloys
b. heterogeneous
3. Separating Mixtures
a.Various types
C. Physical Properties
1. Extensive
2. Intensive
D. Chemical Properties
E. Chemical v physical change
II. Energy
A. Definition
1. Definitions
2. Chemical Energy in reactions
3. Writing Reactions
B. Exothermic (feel hot)
a. examples
C. Endothermic (feel cold)
a.examples
III. Phases of Matter
A. Phases
1. solid
2. Liquid
3. Gas
B. Phase Changes
1. phases changes (endo and exo)
a. fusion/freezing
b. vaporization/condensation
c. sublimation/deposition
i. I2 demo
ii. CO2 demo
iii. Naphthalene
2. Heating curves
3. Cooling Curves
C. Phase diagrams
1. Triple point curve
2. Critical pt
D. Thermometry
IV. Additional
1. Boiling vs. Evaporation
2.Vapor pressure and 4 liquids
3. Fractional Distillation and petroleum
4. Minerals
I.
Matter
A.
Definition: anything that has mass and takes up space
The known universe is believed to be composed of: Dark Matter and Energy
B.
Pure Substance v Mixture
1.
A PURE SUBSTANCE is a form of matter that has unique composition and
PROPERTIES
a.
Elements:
(1) The simplest form of matter (periodic table)
(2) They CAN NOT be chemically decomposed
(3) Examples: Na, K, Ca, H2, O2, Hf
b. Compounds
(1)
(2)
(3)
2.
2 or more elements chemically combined
Compounds can be chemically decomposed
Examples: NaCl, H2O, NH3, CH4, HF, C6H12O6
Mixture: Two or more substances physically combined, therefore they can be
physically separated
a.
Homogeneous: a mixture that is like throughout
(1)
Solutions: s/l, l/l, g/l but can also include all other phase combinations
(a)
(2)
Examples: NaCl(aq), HCl(aq), CO2(aq), Air (76%N2, 21%O2, 1%CO2)
Alloys: physical combinations of metals "a solution of metals"
(a)
Examples: brass(Cu/Zn), bronze(Cu/Sn), Steel(Fe, 1-2%C), Cast Iron(Fe, 24%C),
Pewter(Sn85-90%/Cu,Sb hardeners)
(b)
Alloys have superior qualities than the parent metals alone. Harder, stronger,
more resistant to corrosion
b.
Heterogeneous: a mixture that is unlike throughout.
(1)
Examples: dirt, tossed salad, Italian dressing, S + Fe filings
Mixtures do NOT have unique properties!!!!!!!!
- brass doesn't have A mp
- soda doesn't have A bp
- air doesn't have A condensation point
c.
Separating Mixtures: There are various means used to separate mixtures. They
include:
(1)
Solubility (dissolving):add or remove or change solvent to increase or decrease
dissolving
Chromatography is a form of separating components of a mixture based on
polarity/solubility.
(2)
Filtration: pass mixture through a filter to separate different sized particles or
dissolved/non-dissolved
(3)
Sorting: pipette, forceps, magnet
(4)
Melting: heat to reach unique melting points
C.
(5)
Freezing: cooling gases or liquids to initiate phase changes.
(6)
Distillation: heat and evaporate part with lowest boiling point
Physical Properties
1.
Extensive: Properties that depend on HOW MUCH "the outside" of a sample you have
a.
2.
Examples:
(1) mass
(2) weight
(3) volume
Intensive: Properties that depend on THE COMPOSITION "the inside" of the sample
a.
examples:
(1)
(2)
(3)
(4)
(5)
(6)
D.
hardness
density
magnetism
color
vapor pressure
melting point and boiling point
Chemical Properties
Definition: Chemical properties of matter describe a materials "potential" to undergo some
chemical change or reaction by virtue of its composition.
E.
Chemical v Physical Change
1.
A chemical change occurs when a new substance IS formed. This is often identified by:
a.
color change
b.
formation of a gas or a precipitate
c.
absorption or release of energy
d.
Examples:
1. the burning of paper
2. magnesium bubbling in hydrochloric acid
3. the rusting of an iron hammer
4. the corrosion of a battery terminal
2.
A physical change occurs when there is a change in the:
a.
size
b.
shape
c.
phase of a material
Note. A new substance is NOT formed!!!
d.
Examples:
1. the melting of solder
2. dissolving sugar in water
3. boiling water
4. drawing copper into wire
II.
Energy
A.
Definitions:
1.
Definitions
Energy - a quantity that can manipulate matter. It comes in many forms and
can be converted from one form or another but never destroyed. (Law of
conservation of energy)
a. Kinetic- energy of motion
ex. heat, mechanical, sound, light
b. Potential- stored energy
ex. chemical, gravitational
2.
Energy is involved in EVERY chemical and physical reaction. In chemical
reactions energy goes both in and out during the breaking and making of
bonds. The energy absorbed and released is never equal. Overall if more
energy goes in the reaction is considered ENDOTHERMIC, if more energy
is released it is considered EXOTHERMIC!
3.
Writing Reactions
aA (s) + bB(l) --> cC(aq) + dD(g) + energy
EXOTHERMIC
or
aA (s) + bB(s) + energy --> cC(aq) + dD(g)
ENDOTHERMIC
B.
Exothermic -reactions that release energy
(out) (heat)
ex.1 NaC2H3O2(aq) --> NaC2H3O2(s) + heat
ex.2 H2(g) + O2(g) --> H2O(l) + heat
These reactions feel HOT because energy is be
released from the reaction to its environment.
Are the above reactions physical or chemical changes?
C.
Endothermic -reactions that absorb energy
(in)
(heat)
ex.1 Ba(OH)2(s) + NH4SCN(s) + heat -->
Ba(SCN)2(aq) + NH3(g) + H2O(l)
ex.2 KNO3(s) + heat --> K+(aq) + NO3-(aq)
These reactions feel COLD because energy is be
absorbed into the reaction from its environment.
III. Phases of Matter
A.
Phases
1.
Phase Changes
a.
b.
B.
Heating and Cooling Curves (link to Mr. Kent's heating curve)
1.
Heating Curves (water)
1. There are many conclusions that can be made from observing
the heating curve of a substance. Some of them are:
a. melting/freezing point
b. boiling/condensation point
c. heat of fusion
d. heat of vaporization
e. specific heat
2.
Cooling Curves
C.
Phase Change Diagrams
1.
2.
Terminology:
a. triple point- the temperature and pressure at which a substance exists on all three phases
in equilibrium
b. critical point - the temp and pressure above which there is no boundary between gas and
liquid phases, they become one supercritical fluid.
interesting fact: CO2 process of decaffeination of coffee
This process is technically known as supercritical fluid extraction. Pre-steamed beans are
soaked in a bath of supercritical carbon dioxide at a pressure of 73 to 300 atmospheres.
After a thorough soaking for around ten hours, the pressure is reduced, allowing the CO2
to evaporate, or the pressurized CO2 is run through either water or charcoal filters to
remove the caffeine. The carbon dioxide is then used on another batch of beans.[6] This
liquid works better than water because it is kept in supercritical state near the transition
from liquid to gas, combining favorable diffusivity properties of the gas with increased
density of a liquid. This process has the advantage that it avoids the use of potentially
harmful substances.
IV. Energy Calculations
A.
Energy in a chemical reaction is generally released as heat when bonds are formed. Likewise
energy is necessarily absorbed when breaking bonds.
1.
Changing temperature:
formula: Q=mc(delta)T
2.
Changing Phase:
a.
fusion/ freezing
formula: Q=mHf
b.
vaporization/ condensation
formula: Q=mHv
B.
C.
Vocabulary
1.
Heat - A type of energy, flows into or out of EVERY rxn
2.
Specific Heat - Amount of heat required to change 1 gram of any substance 1oC (or K)
3.
Heat of Fusion - Amount of heat required to melt 1 gram of any substance
4.
Heat of Vaporization - Amount of heat required to vaporize 1 gram of any substance
5.
Temperature - The measurement of average particle motion (avg KE)
6.
Joule - The unit for heat
Heat in the Reference Tables
1.
Table I in the reference tables gives examples of several different types of heat in reactions.