Constructing Ideas in Physical Science

Constructing Ideas in Physical Science

Joan Abdallah , AAASDarcy Hampton, DCPS

Davina Pruitt-Mentle, University of Maryland

CIPS Institute for Middle School CIPS Institute for Middle School Science TeachersScience Teachers

AAAS/DCPS CIPS Workshop 8/2-8/13 2

Session 8 DebriefingSession 8 Debriefing

• What do you remember from yesterday’s session (no peeking at text or notes)

• What were the “essential questions” being asked/explored

• What conclusions did “we” decide


Deeper QuestionsDeeper Questions

• What deeper questions could you envision students asking?

• What misconceptions or misinterpretations can you foresee?

• How or what would you say?


Deeper Questions or Possible Deeper Questions or Possible MisinterpretationsMisinterpretations

“What makes light”?“What makes energy”?“What makes different

colors”?

What would you say?


Electromagnetic SpectrumElectromagnetic Spectrum

How Roy G. BV Lost a VowelThis was originally "ROY G. BIV", because it used to be common to call the region between blue and violet "indigo". In modern usage, indigo is not usually distinguished as a separate color in the visible spectrum; thus Roy no longer has any vowels in his last name.


Radiant EnergyRadiant Energy

See Handout: Continuous and Line Spectra

Read Aloud


So….So…. Things are made up of atoms Atoms

Protons Electrons

Electrons do a lot of spinning and hopping around (that’s what causes things to have certain shapes and textures)

When electrons get excited, they jump from lower ground state to excited state and then back to rest again

This jumping back and forth = radiant energy


How Do you Measure Radiant Energy?How Do you Measure Radiant Energy?

• In order to understand behavior of e-, you need to know their:– Velocity– Location

• Werner Heisenberg (highs-en-berg), German, showed that it is impossible to know both the exact position and the exact momentum of an object (e-) at the same time (Heisenberg’s Uncertainity Principle)– Can not measure where the e- is since the “nature” of measuring is

to “move” something– To know location you would have to “measure” it –but when you

measure it would effect (change) the velocity– Smaller something is the more uncertain the position will be after

measuring it– (Δx) (Δmv) h/4

• (Δx) = change in position• (Δmv) = momentum = mass x velocity (related to KE)

– h/4 = some constant (Planck’s constant/4)

Need more coffee?


The de Broglie HypothesisThe de Broglie Hypothesis

• 1923, de Broglie (French)

• Used Planck’s/(and Einstein) idea…that radiation is made up of packets of energy (this gave waves properties of particles)

• He wanted to prove that particles could have properties like waves

• This enabled de Broglie to predict the wavelength of a particle when given mass (m) and velocity.

• General Trend – as mass (e-)

increases, decreases– e- mass ↑ ↓


The de Broglie Hypothesis cont.The de Broglie Hypothesis cont.

• Using E = mc2 (Einstein) and E = h (Planck)• Derived: mc2 = h • Substituted v (general velocity) for c• Substituted v/ for , because the frequency of a

wave is equal to its velocity/by its wavelength• mv2 = h/ • or = h /mv2 = h/mv

See: http://cougar.slvhs.slv.k12.ca.us/~pboomer/chemtextbook/cch9.html


The de Broglie Hypothesis cont.The de Broglie Hypothesis cont.

• From this, shown that e- stream acts in the same way as a ray of light

• Given credit for indicating how to predict the wavelength of particular electrons

• Also showed that e- have properties of both waves and particles = wave-particle duality of nature

• This is why you can not measure the velocity & location of e- at the same time


Two FormulasTwo Formulas (m) X (s-1) = c (where c =speed of light or 3.00 x 108 m/s)

• Louis de Broglie suggested that the e- in its circular path about the nucleus has associated with it particular wavelengths, and also that the wavelength of the e- depends on its mass and velocity

• He called this matter waves, and used it to describe the wave characteristics of material particles

= h/mv – mv also called momentum – h= Planck’s constant 6.63 x 10-34 J.s (1 J = 1 kg m2/s2)

Show Subscripts and Symbols See handout (5.2)


Making the ConnectionMaking the Connection

• De Broglie = e- act as waves (properties of and )

• Schrodinger = e- act as particles -- different (energy property) & (mass)

• The link between these two concepts = h = Planck’s constant

• Wave-particle duality of nature


Wave-particle Duality of NatureWave-particle Duality of Nature

• Shows or proves that a beam of e- will produce a diffraction pattern like light patterns

• Bohr and Schodinger called this : wave or quantum mechanics

• i.e., where are we more likely to “find” e- at a given moment in time

1s _2s_

2p _ _ _ • 1 & 2 = shells• S,p,d,f = subshells• _ = orbitals• Distance between the rings =

“nodes”, places where you will not find e-


SummarySummary• Planck’s hypothesis stated that energy

is given off on quanta (photon) continuously

• Bohr showed that absorption of light at set correspond to definite changes in energy of the e-

• Reasoned that orbits (rings) around nucleus must have a definite diameter and that e- could occupy only certain orbits


Summary cont.Summary cont.

• The energy absorbed when the atom was excited = the energy difference between orbits

• Because these orbits represent definite energy levels, a definite amount of energy is radiated

• The size of the smallest orbit an e- can occupy (one closest to nucleus), the ground state, can be calculated

• Energy is determined by the movement of e- between energy levels that are specific for each element

• The same set of energy levels will always produce the same spectrum


To Learn MoreTo Learn More

• CEA Light Tour [Local]

From: http://cse.ssl.berkeley.edu/light/light_tour.html

See Handout

http://cse.ssl.berkeley.edu/light/light_tour.html


Other ResourcesOther Resources

• Waves –Virtual Lab [Local]

• Exploring Earth [Local] Observe the change in a star's spectrum as its motion changes

• Electromagnetic spectrum - Wikipedia

• Discovery-The Color Spectrum How does it work? [Local]

http://www.hazelwood.k12.mo.us/~grichert/sciweb/waves.htm


But I can not see e-, so how do we know?


States of MatterStates of Matter

• Matter- has mass, occupies space• Physical states of matter

– Solid– Liquid– Gas– Plasma

One of the four states of matter. (The other three are solid, liquid and gas.) Consists of a gas of positively charged and negatively charged particles with approximately equal concentrations of both so that the total gas is approximately charge neutral. A plasma can be produced from a gas if enough energy is added to cause the electrically neutral atoms of the gas to split into positively and negatively charged atoms and electrons. See also: The Plasma State of Matter. www.spacescience.org/ExploringSpace/Glossary/1.html


Kinetic Molecular Theory of MatterKinetic Molecular Theory of Matter

• States:– All matter is in constant

motion– An increase in

temperature increases motion and decreases attraction forces holding the matter together

– S L G P

Solid Liquid Gas

Own definite shape

Indefinite shape

Indefinite shape

Own definite volume

Definite volume

Indefinite volume

Independent of container shape

Takes shape of container (until it fills it)

Takes shapes of container and fills it


Physical vs. Chemical PropertiesPhysical vs. Chemical Properties

Physical Properties• Can be observed without

changing form– Color– Odor– Taste– Size– BPo

– MPo

– Density– Specific heat (Cp)– Hardness– Solubility– Mass– Temperature– Heat capacity

Chemical Properties• Undergoes changes in

chemical composition– Flammability or not

flammable– Reacts/failure to react

with another – Decomposes– Rusting– Combustion


Properties can also be classified as:Properties can also be classified as:

Intensive• Values do not

depend on size of portion – Temperature– MPo

– BPo

– FPo

Extensive• Depend on sample

size– Mass– Volume– Length


PropertiesProperties• Molecules vibrate faster when they are

stirred-therefore, this helps them dissolve faster

• When heated dissolves faster• At certain temperature (w/ a solid) when heat

added, the heat breaks the bonds. Solid matter changes to liquid (Melting Point MPo)

• With a solid when freezes, attractive forces cause molecules to lock together into solid state (Freezing Point FPo)


Liquid ChangesLiquid Changes

• Change of liquid into vapor evaporation• Change of vapor into a liquid condensation• Opposite of condensation evaporation• Opposite of evaporation condensation


Changes cont.Changes cont.• As temperature falls, and the gaseous molecules slow down,

their weak attractive forces get an opportunity to bind the molecules together and change the gas (vapor) into a liquid. When water vapor touches cool dust particles in the air, condensation takes place. The droplets of water, suspended in the air, form clouds and rain– Gas Condensation Liquid

• The changing of a solid into a gas without becoming liquid sublimation. A lot of heat is added to the solid. This added heat causes the molecular vibrations to become so violent that the molecules of the solid completely break away from each other and enter into a gaseous state– Solid Sublimation Gas

• Ex. Mothballs, vaporization (nuclear fallout)


Changes cont. Changes cont. • We know that water vapor will condense on a cool

speck of dust. If the water vapor touches a very cold speck of dust in the air, the gaseous water may crystallize without condensing first. The ice crystals, suspended in the air, form clouds. If conditions are right, these crystals may fall to the ground as snow.– The changing of a gas into a solid = sublimation

• By definition, sublimation can indicate going from gas to solid or from solid to gas…although in “chemistry” usually implies going from the solid state to a gas state.


Putting It All TogetherPutting It All Together

GAS

SOLID LIQUIDMelts

Freezes

Sublim

ation

Depos

ition

EvaporationCondensation


Property ChangesProperty Changes

Physical Change• No new substance is

ever formed– Tearing paper– Sulfur & iron– Sharpening– Bite– Chew– Breaking glass

Chemical Change• Involves a change in

basic nature (chemical composition)

• Change in at least one new substance– Sulfur & iron heated– Burning paper– Digesting– Sour milk– Detonation


QuizQuiz• Rust• Melts• Sharpening• Digesting• Biting• Burning• Slicing• Detonation• Souring• Breaking

• C• P• P• C• P• C• P• C• C• P


Break?Break?


CIPSCIPS

• Unit 4– Cycle 1– Activity 1,2 & 3


Energy & HeatEnergy & Heat

• Physical and chemical changes are always accomplished by energy transfer

• The most common form of energy transform or change is heat– Heat is a form of energy that

flows between a system and its surroundings

– Heat flows from a warmer object to a cooler one

Ex. Object A = 25°CObject B = 20°C

What happens when they are mixed?

Energy will continue to transfer until the temperature of the objects are equal.

The energy transfer as a result of a temperature difference is called heat and is represented by the letter (q).


Energy (continued)Energy (continued)• If energy is absorbed = endothermic reaction• If energy is given off = exothermic reaction

– Match = exothermic– Cold pack = endothermic

• Both forms require a certain amount of energy to get started – activation energy

• Quantitative measurements of energy changes are expressed in joules (J). This is a derived SI unit– Older unit = calorie– One calorie (c) = 4.184 J– (C) dietary unit calorie (c)– The heat needed to raise 1 g of a substance by 1°C is called specific heat (Cp)

of the substanceExamples: Sand and water – different Cp values

Which gets hotter at the beach?

Which cools down faster?


Dietary CaloriesDietary Calories

• The heat required to increase the temperature of 1g of water 1°C = 4.184J

• Dietary Calories (C) are 1000 times as large as a calorie (c)• Caloric values are the amount of energy the human body can obtain

by chemically breaking down food• The Law of Conservation of Energy shows that in an insulated

system, any heat loss by 1 quantity of matter must be gained by another. The transfer of energy takes place between 2 quantities of matter that are at different temperatures until they both reach an equal temperature

Example: An average size backed potato (200g) has an energy value of 686,000 J. How many calories is this?

4.184J = 1 c, 1000 c = 1 C

686000J/4.184 J = 164,000 c

164,000 c/ 1000 C=164C


Energy TransferEnergy Transfer

• The amount of heat energy transferred can be calculated by:– (heat gained) = (mass in grams)(change in T)(specific heat)– q = (m)(T)(Cp) T = Tf - Ti

Example: How much heat is lost when a solid aluminum block with a mass of 4100g cools from 660.0°C to 25°C? (Cp = 0.902 J/g°C)

q = (m)(T)(Cp)

T = 660.0°C - 25°C = 635°C

therefore: q = (4110g)(635°C)(0.902 J/g. °C) = 2,350,000 J


MatterMatter

Mixture• Most Natural Samples• Physical combination of

2 or more substances• Variable composition • Properties vary as

composition varies• Can separate by

physical means

Pure Substance• Few naturally pure gold

& diamond• Only 1 substance• Definite and constant

composition• Properties under a

given set of conditions


MixtureMixture

Heterogeneous• Visible difference in

parts and phases– Oil and vinegar– Cookie– Pizza– Dirt– Marble– Raw Milk

Homogeneous• Only 1 visible phase

– Homogenized milk– Air (pure)– Metal Alloy (14K

gold)– Sugar and Water– Gasoline


Pure SubstancePure SubstanceCompound

aspirin, H2O, CO2

• Can be broken down into 2 or more simpler substances by chemical means

• Over six million known chemical combinations of 2 or more elements

• 7000 more discovered per week with chemical abstracts service

• Definite-constant element composition

ElementAu, Ag, Cu, H+

• Pure and cannot be divided into simpler substances by physical or chemical means

• 90 naturally occurring• 22 synthetic

CompoundElement

Simpler Compound

Element

Element

Matter

Heterogeneous materials Homogeneous materials

Solutions Pure substances

Mixtures Compounds Elements


CIPSCIPS

Unit 5


Subatomic ParticlesSubatomic ParticlesBuilding Blocks of AtomsBuilding Blocks of Atoms

• Proton: (+)– 1.673 x 10-28 g– Discovered by Goldstein

(1886) – Inside the nucleus

(credit given to Rutherford – beam of alpha particles on thin metal foil experiment. Explained nucleus in core, made up of neutrons and protons)

• Neutron: (no charge)– 1.675 x 10-24 g– Discovered by James

Chadwick (1932)– Inside nucleus

• Electron: (-)– Outside ‘e’ cloud– 9.109 x 10-28 g (1/1839 of a

proton)– Discovered by Joseph John

Thomson (1897)• It’s charge to mass ration

(e/m) = 1.758819 x 108 c/g– c = charge of electron in

Coulombs– Millikan determined mass

itself


AtomsAtoms

• Atom – smallest particle of an element that can exist and still hold properties• “Atomos” – Greek – uncut/indivisible. Democritus proposed that elements are

composed of tiny particles• John Dalton (1808) published The Atomic Theory of Matter

1. All matter is made of atoms2. All atoms of a given type are similar to one another and different from all other types3. The relative number and arrangement of different types of atoms contained in a pure

substance determines its identity (Law of Multiple Proportions)4. Chemical change = a union, separation , or rearrangement of atoms to give a new

substance5. Only whole atoms can participate in or result from any chemical change, since atoms are

considered indestructible during such changes (Law of Conservation of Mass)• Antonine Lavoier demonstrated via careful measurements that when combustion

is carried out in a closed container – the mass of the products = the mass of the reactants


Formula MassFormula Mass

H = 1O = 16H2O

2 x 1 = 21 x 16 = 16

Total = 18

Billy = 150Susie = 100Billy4Susie = 800

H2SO4

H = 2x1 = 2S = 1 x 32 = 32O = 4 x 16 = 64

Total 98

2CaCl2

Ca = 2x40 = 80S = 4 x 36 = 144

Total 224


Abundance of Elements in Abundance of Elements in MatterMatter

Universe• H 75-91%• He 9%

Earth• O2 49.3%• Fe 16.5%• Si 14.5%• Mg 14.2%

Atmosphere• N2 78.3%

• O2 21%

Human Body• H2 63%

• O2 25.5%• C 9.5%• N2 1.4%

Earth’s Crust• O2 60%• Si 20%• Al 6%• H2 3%• Ca 2.5%• Mg 2.4%• Fe 2.2%• Na 2.1%


Element Names – based onElement Names – based on

• Geographical Names– Germanium

(German)– Francium (France)– Polonium (Poland)

• Planets– Mercury– Uranium– Neptunium– Plutonium

• Gods– He (helios – sun’s

corona)• Properties (color)

– Chlorine - chloros – greenish/yellow

– Iridium –iris – various colors


Chemical SymbolsChemical Symbols

• 1814 – Swedish – Jons Jakob Berzelius– Symbols = shorthand for name

• N = nitrogen• Ca = Calcium

– Latin or other name– Latin

Iron Fe FerrumGold Au AurumAntimony Sb StibiumCopper Cu CuprumLead Pb PlumbrumMercury Hg HydrargyrumPotassium KKaliumSilver Ag ArgentumSodium Na NatriumTin Sn Stannum

– German Tungsten W Wolfram


Generic Nomenclature: Generic Nomenclature: Provisional NamesProvisional Names

• International Union of Pure and Applied Chemistry (IUPAC)

• Latin – Greek Names– 0 =nil, 1=un, 2=bi, 3=tri, 4=quad, 5=pent, 6=hex, 7=sept,

8=oct, 9=enn– + ium– i.e.

• 104 un nil quad ium Unq• 105 un nil pentium Unp• 106 un nil hex ium Unh• 110 un un nil ium Uun

– Most nave been given names anyway

Constructing Ideas in Physical Science

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