Unit I: Matter & Energy

Textbook Chapters 1,2,11 & 12

What is Chemistry?Concerned with the properties of chemicals and the changes chemicals can undergo

Physical vs. Chemical Changes

• Physical Change change in appearance but the substance itself is not changed.

• Chemical Change produces new substances with different properties.

• Aka Chemical Reaction

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H2O (l) H2O (s)

H2O + ½O2 H2O2

Paper Demo

Evidence of a Chemical Change/Reaction

1. Evolution of a Gas

2. Formation of a Precipitate

3. Release or Absorption of Energy

4. Color Change in the Reaction System

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Properties of Matter• Physical property

– Can be recognized without changing the substance to anything else.

– Examples: color, odor, density, melting pt.

• Chemical property– Describes how a substance reacts to form a

new substance.– Examples: stable, reactive, flammable, inert

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Common States (Phases) of Matter

• Solid

• Liquid

• Gas

• Plasma

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Solids• Particles close together• Particles vibrate but do not move• Strong attractive forces between particles• Crystalline structure (regular geometric pattern) • Definite shape• Definite volume• Lowest PE

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Liquids

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•Particles still close together.

•Particles vibrate and rotate allowing for movement.

•Weaker attractive forces between particles

•No regular pattern of particles

•Take shape of container

•Definite Volume

Gases

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•Particles are very far apart and move all over.

•Particles vibrate, rotate and translate (move from place to place).

•Weakest attractive forces between particles.

•Take shape and volume of container.

•Greatest disorder

•Highest PE

Phase Changes• Types of Physical Change• Melting• Freezing (Solidification)• Vaporization (Boiling)• Condensation• Sublimation• Deposition

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Sublimation of Iodine

{Change in Position of Particles (PE)}

•Triple point•At this temperature and pressure, substance can exist as a solid, liquid or gas.

•Under higher pressure, harder for a solid to melt or a liquid to boil.•Under lower pressure, melting and boiling points lower (easier to change).

Exception is water: increasing pressure, lowers freezing/melting point (think ice skating).

Endothermic vs. Exothermic• Endothermic

– Heat energy is absorbed.– Chemical Bonds broken in chemical rxn.

– 6 kcal + H2 + I2 2HI

• Exothermic– Excess heat is given off (released).– Chemical Bonds formed in chemical rxn.

– CaO(s) + H2O(l) Ca(OH)2(s) + 986 kJ/mol

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Demo• Is this reaction exothermic or endothermic?

• Ba(OH)2.8H2O + 2NH4NO3+ 170kj/mol Ba(NO3)2 + 2NH3 + 10 H2O

Heating Curves• Endothermic or exothermic?

• Be able to label all phases, phase changes, changes in temperature, PE and KE.

Animated Heat Curve

Cooling Curves• Endothermic or

exothermic?

• Be able to label all phases, phase changes, changes in temperature, PE and KE.

2 Factors Affecting Phase of a Material

• Temperature

• Pressure

Image taken from http://invsee.asu.edu/srinivas/liquidmod/states.html on 8/11/11.

n.f.p.= solid-liquid equilibrium point

n.b.p.= liquid-gas equilibrium point

Vapor Pressure• Evaporation

• LG that takes place at the surface of the liquid and occurs at all temp’s.

• From evaporation, vaporization & boiling, the gas (vapor) produced exerts a pressure called vapor pressure.

• ↑Temp of liquid, ↑vapor pressure• Each substance has its own vapor pressure at

differing temperatures.• Ref Table H

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Vp animation

Boiling Point• Liquid will boil at temperature at which vapor

pressure = pressure on liquid.• Point of equilibrium between gas and liquid

• If vapor pressure = 1 atm (std pressure) then called the normal boiling point.

• Ref Table H

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Low pressure lowers b.p. demo

7 Diatomics• Di = 2

• Atomic = atoms

• 7 elements that exist in nature as paired atoms in a molecule.

•To identify them, go to PT start with element #7 and make the shape of a #7 • N2,O2,F2,Cl2,Br2,I2

•Missing one? Whose #1?

• H2

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Temperature vs. Heat• Which one has more heat, a pot of boiling water

or the Arctic Ocean?• Describe the temperature and heat of a 4th of

July sparkler.

SparklersSparklers

Temperature• Measure of the

average kinetic energy (KE) of the particles of a substance.

• Instrument• thermometer

• Units• Fahrenheit (o F)• Celsius (o C)• Kelvin (K) (SI Unit)

• Ref Table T

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Δ of 1oC= Δ of 1K

Temperature AnimationAnimated Temp Movie

Heat• Energy transferred

between objects that are at different temperatures.

• Energy always flows from source to sink.

• Instrument• calorimeter

• Units• Calories• Joules (SI Unit)

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Source ↑(Temp)

Sink ↓(Temp)

Specific Heat• Amount of heat energy required to raise the

temperature of 1 gram of a material 1oC

• What is the specific heat capacity of water?• Ref Table B

4.18 J/goC or 4.18 J/gK

• Equal to 1 calorie/goC

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ESCI connection metals vs. water

Boiling water in a paper cup

Using a bomb calorimeter to determine calories of an almond (4min)

3 Heat Formulas (Ref Table T)

• Q=mHf

• Q=mHv

• Q=mcΔT

• Try examples!

• Ref Table B

Animated Heating CurveEm Cee Delta Tee video

Energy Conversion• Energy

– Ability to do work or transfer heat

• Law of Conservation of Energy

• Energy can not be created nor destroyed, just converted from one form to another.

• 2 Types of Energy• Kinetic and Potential

• Forms of Energy• Kinetic (motion, electrical,

sound, radiant, thermal)• Potential (chemical,

nuclear, gravitational, stored mechanical)

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Classifying Matter• Matter

– Anything that has mass and volume.

• Should remember terms mass, weight, volume and density (Ref Table T) from esci. [Text 1-2]

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Elements• Substances that can not be broken down into

simpler substances by chemical means.• Each element is composed of one type of atom.

Examples:

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Review diatomics. allotropes

Compounds• 2 or more different elements chemically

combined in a definite ratio• Can be decomposed chemically into elements.

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Pure Substances• A sample of matter that has definite chemical

and physical properties.• All samples of a single pure substance are

identical in their properties.• Examples:

– elements & – compounds

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Mixtures• 2 or more substances physically combined with

no definite proportions.• In a mixture, each substance retains its own

properties.• Homogeneous or Heterogeneous

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Heterogeneous Mixtures• Physical combination of substances that are

NOT uniform in composition throughout.

• Examples: sand & water, tossed salad, milk

Milk under a microscope

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Homogeneous Mixtures• Physical combination of substances that

are uniform in composition and properties throughout.

• Examples: salt & water, all solutions and alloys

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Separating Mixtures• Because mixtures are not chemically

combined, they can be separated physically.

• Such as….– Filtration– Centrifugation– Chromatography– Magnetism– Distillation Image taken from

http://library.thinkquest.org/11430/research/images/filtration.gif on 8/11/11.

Image taken from http://images.tutorvista.com/content/chemistry-concepts/magnetic-separation-process.jpeg on 8/11/11.

Distillation• Process by which a

mixture of liquids or a liquid and a solid can be separated by different boiling points.

Fractional Distillation of Petroleum

Distillation of Saltwater

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Image taken from http://www.tutorvista.com/content/chemistry/chemistry-iii/organic-compounds/distillation.php on 8/11/11.

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Three Ways Compounds Differ from Mixtures

1. Compounds are chemically combined elements. Mixtures are physically combined substances.

2. Compounds are formed from a definite proportion. Mixtures can have varying proportions. (Compounds have a definite formula or “recipe”.

3. Compounds have different properties than ingredients. Mixtures retain the same properties of the ingredients.

Image taken from http://www.personal.kent.edu/~cearley/ChemWrld/Reaction/H2_O2.gif on 8/11/11.

NaCl (s)

NaCl (aq)

Molecular Models of Matter

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•Can you identify the following pics as …

•element, compound or mixture ???

•solid, liquid or gas???

More visualsOnline practice

Properties of Gases• Fluids

• Low Density

• Highly Compressible

• Completely Fill a ContainerPropane gas can be compressed in tanks for home heating and gas barbeques. It can be so highly compressed it becomes a liquid.

Pressure of Gases• Pressure

• Amount of force exerted per unit area of surface.

• Measured with barometer or manometer.• ex: atmospheric pressure• Units of pressure

– Atmospheres– Pascals– mm of Hg– Torr

Images taken from http://ths.talawanda.net/~BrambleN/classroom/Chemistry/Notes/Section%204A/PressureandTemperature.htm on 8/11/11.

Evangelista Torricelli1606-1647

How a barometer worksHow a manometer works

How Std. Atm. pressure is determined

Demo: pressure breaking stick Demo: Can Crush

STP• Use Reference Table A

• For Gases,• 273K = 0oC• 1atm = 29.92 inHg =

760mmHg = 760 torr = 101.3kPa

• For liquids and solids,• 25oC = ?K• Same pressure

Standard Temperature and Pressure

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Graham’s Law of Effusion (Diffusion)• Diffusion- spreading out from area of high to low

density.• Effusion-movement of gas through a small

opening into an evacuated chamber.• The rate of diffusion of a gas is inversely

proportional to the square root of the gas’s density.

Image taken from http://images.tutorvista.com/content/matter-states/diffusion-effusion-process.gif on 8/11/11.

Video

Kinetic Theory of Gasesor

Kinetic Molecular Theory (KMT)1. Gas-composed of individual particles which are

in continuous, random straight line motion2. Not all particles have same KE, avg KE of

particles=temp of gas3. Elastic collisions between particlestransfer of

energy w/ no loss(Total energy stays the same.)4. Volume of gas particles ignored compared to

volume of space in which they contain.5. Gas particlesno attraction to each other

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Ideal Gases• Gases that follow the 5

points of KMT.• Best examples are gases

with small molecular masses like H2 and He.

• Low pressure and high temperature conditions are the best for ideal gases.

Image taken from www.wix.com on 8/11/11.

Real Gases deviate from KMT.• Especially under High pressure and Low

temperatures.

• Can you think of ways gases would deviate (not follow) from KMT?

KMT

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Gas Laws• Boyle’s

• Charles’

• Gay-Lussac

• Combined

• Ideal

Boyles’ Law• At constant temp., volume of a

given mass of gas varies inversely with pressure

• PV=K or V1/V2 = P2/P1

• Example: Robert Boyle (1627-91)

Image taken from http://en.wikipedia.org/wiki/Robert_Boyle on 8/11/11.

Animation

Animation 2 w/ graphing

Charles’ Law• At constant pressure, the volume

of a given mass of gas varies directly with Kelvin temperature.

• V1/V2=T1/T2 or V/T=k

• Example:

Animation

Balloon Demo

Jacques Charles (1746-1823)

Image taken from http://www.scientificamerican.com/article.cfm?id=what-is-charles-lawon 8/11/11.

V

Gay-Lussac• At constant volume, the Kelvin

temperature of a gas is directly related to the pressure.

• P1/T1 = P2/T2

• Example:

Joseph Gay-Lussac (1778-1850)

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Animation

Pressure Cooker

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Combined Gas Law• Changes in volume, pressure and

temperature of a gas often occur simultaneously.

• Combine Boyle’s, Charles’ & Gay-Lussac’s.• Formula on Ref Table T, remember K temp.• Example:

Narrated Animation of all Gas Laws

Examplesa) A sample of 150.0 mL of oxygen gas is under

760.0 mmHg of pressure. What will be the new volume of O2(g) if the pressure is reduced to 750.0 mmHg?

b) A 250.0 mL Helium balloon is at a temperature of -23.0oC. What is the size of the balloon going to be if the system is warmed to 7.00oC?

c) A 175mL sample of gas is at 20.0oC and 1.00 atm. What will the new volume be if the temperature is lowered to 10.0oC and the pressure is raised to 1.50 atm?

Partial Pressures• Pressure exerted by each of the

gases in a gas mixture.• Total P = sum of partial pressures

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solve?solve?

John Dalton (1766-1844)

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Avogadro’s Hypothesis• Equal volumes of gases under the

same conditions of temp. & pressure contain equal numbers of particles.

• Avogadro’s #=1 mole=6.02 X1023

Amedeo Avogadro (1776-1856)

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Image taken from http://library.thinkquest.org/12596/bonus_avogadro.gif on 8/11/11.

Ideal Gas Law• Includes the number of moles of gas

related to P (atm. or kPa), T (K) &V (L).

• Derived from KMT.

• PV=nRT• Which variables are directly related? Inversely related?

• Example:

n= number of moles of gas

R is the gas constant

R=0.0821 L.atm/mol.K

a) At 5.00 atmospheres pressure and 70.0oC, how many moles are present in 1.50 liters of O2 gas?

R=8.314 L.kPa/mol.K

b) How many moles of gas are contained in 22.41 liters at 101.325 kPa and 0.00oC?