Matter and Energy Notes

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