Post on 02-Mar-2015
September 25, 2011
Unit II - Matter and Energy
The two driving forces in chemistry are Enthalpy (heat) and Entropy (randomness).
Almost everything in nature wants to be in the lowest energy(enthalpy) state possible but the highest randomness (entropy).
ex. cars rust, rocks erodes, acorns fall down, fire burns, hail scatters
The one exception?????
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1. Matter -anything that has mass and takesup space
2. Energy -a quantity that can manipulate matter. It comes in many forms and
can be converted from one form or another but never destroyed.
a. Kinetic- energy of motionex. heat, mechanical, sound, light
b. Potential- stored energyex. chemical, gravitational
Energy is involved in EVERY reaction. It either goes in (endothermic)or comes out (exothermic)!!
I- Definitions:
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3. Physical Properties - a. Extensive: any property that
depends on the AMOUNT of matter
- mass - weight - volume
b. Intensive: any property that depends on the COMPOSITION of matter
- hardness - color - density- mp - bp - magnetism- odor - phase - conductivity
4. Chemical Properties - the degree to which something reacts with other substances
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Physical changeAny change in size, shape or phase
ex. crushing rockmelting iceboiling waterdissolving saltcutting gemsVS.
Any change in which a new substance is formed.
Includes one or more of the following:1. energy absorption or release2. color change3. gas evolved4. precipitate formed
5. Chemical change
ex. rusting of ironcombustion of alcoholelectrolysis of water
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6. Energy in Reactions
A) Endo thermic -reactions that absorb energy (in) (heat)
ex.1 Ba(OH)2(s) + NH
4SCN(s) + heat -->
Ba(SCN)2(aq) + NH
3(g) + H
2O(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.
Are the above reactions physical or chemical changes?
September 25, 2011
Energy in Reactions(cont'd)
B) Exothermic -reactions that release energy (out) (heat)
ex.1 NaC2H
3O
2(aq) --> NaC
2H
3O
2(s) + heat
ex.2 H2(g) + O
2(g) --> H
2O(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?
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II. Substances vs. Mixtures
1.Substances: Any material having its own unique composition and properties.
A. Elements- building blocks of matter1. can not be chemically decomposed2. 90 naturally occurringex. O2, H2, Al, Hg, Hf, W
B. Compounds (molecules)- two or more elements chemically combined.
1. can be chemically separated2. different ratios = different propertiesex. H2O, NH3, CH4, HF, NaCl, MgF2
Homogeneous
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2.Mixtures: two or more substances PHYSICALLY combined.
A. Heterogeneous- unlike throughout (nonuniform composition)
examples: dirt, sand and salt, S and Fe filings
B. Homogeneous- like throughout (uniform composition)
a. Solutions- X mixed with liquids (solute/solvent)1. s/l NaCl(aq)2. l/l coffee, lemonade, HCl(aq)3. g/l H2CO3(aq), O2(aq)
b. Alloys- mixtures of metalsexamples: brass, bronze, steel, pewter, nitinol
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
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3.
· Freezing: cooling gases or liquids to initiate phase changes
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4. Representative Particles-Categorize the following using the terms: element, compound and mixture
1. 2. 3.
4. 5. 6.
7. 8. 9.
A
A
A
A
A
A
A
AA
AA A
A
A A
B
B
BBB
BB
BBB
B
B
B
B
B
B
B
B
B
B
B
B B
B
B
B
B
A
B
B
A
A
A
AA
A A
AA
AA
A
AA
A
AA
A
Z
Z ZA
A
AA
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3. Heating and Cooling CurvesA. 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
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Heating Curves Cont'd
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B. Cooling Curves
c.p. / b.p.
f.p. / m.p.
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4. Phase Diagrams
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IV. Energy CalculationsEnergy 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 T
2. Changing Phase:A) fusion/ freezingformula: Q=mHf
B)vaporization/ condensationformula: Q=mHv
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Heat
Specific Heat
Heat of Fusion
Heat of Vaporization
Temperature
Joule
3. A type of energy, flowsinto or out of EVERY rxn
1. Amount of heat required to vaporize 1 gram of any substance
4. Amount of heat requiredto melt 1 gram of anysubstance
2. The unit for heat
5. The measurement of average particle motion (avg KE)
6. Amount of heat requiredto change 1 gram of anysubstance 1oC (or K)
3. Heat Vocabulary
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4. Heat in the Reference Tables:Table I in the reference tables gives examples of several different types of heat in reactions.
Heats of Reaction at 101.3 kPa and 298 KReaction H (kJ)*
CH4(g) + 2O2(g) CO2(g) + 2H2O(l) –890.4C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(l) –2219.22C8H18(!) + 25O2(g) 16CO2(g) + 18H2O(l) –109432CH3OH(!) + 3O2(g) 2CO2(g) + 4H2O(l) –1452C2H5OH(!) + 3O2(g) 2CO2(g) + 3H2O(l) –1367C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(l) –28042CO(g) + O2(g) 2CO2(g) –566.0C(s) + O2(g) CO2(g) –393.54Al(s) + 3O2(g) 2Al2O3(s) –3351N2(g) + O2(g) 2NO(g) +182.6N2(g) + 2O2(g) 2NO2(g) +66.42H2(g) + O2(g) 2H2O(g) –483.62H2(g) + O2(g) 2H2O(l) –571.6N2 (g) + 3H2(g) 2NH3(g) –91.82C(s) + 3H2(g) C2H6(g) –84.02C(s) + 2H2(g) C2H4(g) +52.42C(s) + H2(g) C2H2(g) +227.4H2(g) + I2(g) 2HI(g) +53.0KNO3(s) H2O K+(aq) + NO3–(aq) +34.89NaOH(s) H2O Na+(aq) + OH–(aq) –44.51NH4Cl(s) H2O NH4+(aq) + Cl–(aq) +14.78NH4NO3(s) H2O NH4+(aq) + NO3–(aq) +25.69NaCl(s) H2O Na+(aq) + Cl–(aq) +3.88LiBr(s) H2O Li+(aq) + Br–(aq) –48.83H+(aq) + OH–(aq) H2O(!) –55.8*Minus sign indicates an exothermic reaction.
Heat of Reaction
Heat ofFormation
Heat ofSolution