WELCOME TO CHEM 110 CHEMICAL PRINCIPLES PROF:

Transcription

1 WELCOME TO CHEM 110 CHEMICAL PRINCIPLES PROF: John Asbury SECTIONS: LECTURES: MWF 9:05

2 Forum Dr. Asbury Office Hours 3 5 pm, Wed. and Thurs. Room 112 Chem. Building Chemistry building Whitmore

3 HOW CHEM 110 RUNS Lectures: Mon & Fri Lecture notes available on web in advance (they are not complete) Recitation on Wed or Thurs run by teaching assistant (TA) TA office hours all day every day in 211 Whitmore Free tutoring in evenings in 211 Whitmore

4 REQUIRED TEXTBOOK AND MATERIALS Textbook Chemistry, The Central Science, 11 th Ed. Brown, LeMay, Bursten, and Murphy Chem 110 Course packet Syllabus on Chem 110 web site course information syllabus supplementary problems old exams Calculator

5 RESOURCE ROOM 211 Whitmore Chem 110 TA Office Hours Mon through Fri 9:05 to 4:25 Free Tutoring Free Tutoring Evenings Sun through Thurs 6:30 to 10:30

6 GRADING OF CHEM 110 Three midterm exams (34 points each) 102 Final exam 58 Quizzes (14 quizzes in recitation) 15 Homework (14 collections in recitation) 15 Basic Skills Tests (8 tests by Apr. 23) points total Grade distribution given in syllabus curve: no adjustments: perhaps competition: no Grade Percent Points A, A B+, B, B C+, C D F

7 COURSE EXPECTATIONS Plan to spend many hours per week outside of class on Chem 110 Read the assigned text material before class Attend all lectures Do all the homework & supplementary problems and then some work alone or in groups Form a study group Seek help if you need it, don t wait

8 Class Rules We re In This Together

9 Chemistry: The Central Science Chemistry = the study of matter and its transformations Materials Environment Chemistry Life Sciences Engineering Agriculture

10 Life Sciences drugs, proteins, DNA are organic molecules cells are reactions vials Engineering energy materials properties Materials organic, inorganic, polymers separations: purifying materials requires knowledge of chem & phys props Environmental global warming ozone depletion resource management Agriculture fertilizers using ag bioproducts for fuels: ethanol pesticides, herbicides are org compounds

11 SOME QUESTIONS ABOUT EVERYDAY OBSERVATIONS Why does rain fall as drops instead of cubes or cylinders? Why can some animals walk on ceilings? Why does salt help to clear snow from roads? Why is the sky blue? Why can some insects walk on water? Why is ozone depletion bad? I thought too much ozone was bad for your lungs. How are plastics made, and why are there so many different kinds?

12 Methods of Science You all know that table salt contains Na + and Cl - ions the earth s atmosphere is 20% O 2 DNA is a double helix But How do you know these facts? EXPERIMENTAL EVIDENCE INDIRECT EVIDENCE, LOGIC

13 CHEMISTRY A basic science Key feature: exptal observations Deals with matter and its changes structure properties transformations Chemistry s unique perspective: MOLECULES macroscale what we can observe nanoscale what is happening on the molecular level macroscale and nanoscale are connected

14 Connecting macroscale nanoscale Properties of what is around us determined by molecules

15 Connecting macroscale nanoscale MATTER (stuff) HETEROGENEOUS MATTER HOMOGENEOUS MATTER SOLUTIONS (salt water) PURE SUBSTANCES COMPOUNDS ELEMENTS Chemical combinations of elements

16 CHEMICAL AND PHYSICAL CHANGES CHEMICAL 2 H 2 +O 2 2 H 2 O firewood burns metals corrode cement sets eggs fry PHYSICAL evaporation H 2 O steam freezing dry ice CO 2 gas [reactions]

17 UNCERTAINTIES Precision: agreement Accuracy: correctness SIGNIFICANT FIGURES Determine number of sig figs rules in text How to carry uncertainty through calculations

18 Important Number The Mole Dozen = 12 = 1.2*10 1 Mole = 6.022* Dozen Eggs = 12 Eggs 1 Dozen Atoms = 12 Atoms 1 Mole Eggs = 6.02*10 23 Eggs 1 Mole Atoms = 6.02*10 23 Atoms Mass of 1 Mole H 2 = Mass of 1 Mole H 2 O = 2 g 18 g

19 COMPONENTS OF ATOMS mass charge (a.m.u.) (a.u.) proton p 1 +1 electron e 0 1 neutron n 1 0 N solar system atom model electron cloud atom model

20 Almost all of an atom is empty space Atomic diameter = 0.10 to 0.50 nm Nuclear diameter = 10-5 nm 10-5 = nm = 10-9 m Ratio of nucleus size to atomic size is 10-4 Carbon atom diameter = nm

21 Example of Relative Size of Nucleus and Atom Nucleus: pencil eraser d = 1/8 Atom: 1/8 x 10,000 = in/ft = 100 ft a nucleus the size of a pencil eraser is at the center of an atom the size of 108 Forum

22 NEUTRAL ATOM 19 9 F 9 protons 10 neutrons 9 electrons ION Na + 11 protons 12 neutrons 10 electrons The number of protons defines atomic number and the identity of the element

23 For a given element, the number of protons is fixed. BUT. the number of neutrons can vary ISOTOPES Cl Cl 17p 18n 17p 20n

24 35 17 Cl ISOTOPES amu (75.78%) Cl amu (24.22%) Atomic weight of Cl = amu

25 ENERGY KINETIC ENERGY mechanical (moving mass ½ mv 2 ) [ joule = kg m 2 /s 2 ] electrical (moving charge) light (photons) POTENTIAL ENERGY mechanical (mass in a place where force can act) chemical (bonds) nuclear (binding energy) sound (molecules moving uniformly) heat (molecules moving randomly)

26 ENERGY orders of magnitude energy of a photon λ= 500 nm (color?) A) E = 4*10 19 J B) E = 4*10 5 J C) E = 4*10 5 J D) E = 4*10 10 J energy of a lightning bolt energy of a 2200 lb car moving at 65 mph A) E = 4*10 19 J B) E = 4*10 5 J C) E = 4*10 5 J D) E = 4*10 10 J A) E = 4*10 19 J B) E = 4*10 5 J C) E = 4*10 5 J D) E = 4*10 10 J

27 ENERGY CONVERSION Energy can be converted from one form to another When it is converted, the total energy remains constant Law of Conservation of Energy First Law of Thermodynamics All energy lost by a system under observation is gained by the surroundings During energy conversion, some heat is always produced

28 First Law of Thermodynamics Conservation of Energy The energy of the universe is constant. ΔE universe = ΔE system + ΔE surroundings = 0 Energy is neither created nor destroyed, only converted from one form to another. ΔE system = q + w q is heat gained or lost by the system w is work done by or on the system

29 ENERGY CHANGES ΔE = E final E initial ΔE is a state function State function: a function whose value does not depend on pathway used to get to present state. System energy Surroundings ΔE is Surroundings energy System ΔE is + ΔE = q + w work (work done to system +) heat (heat added to system +)

30 ELECTRONIC STRUCTURE OF ATOMS Electromagnetic energy its nature and properties Then into quantum theory Then into atomic orbitals Electron configurations Periodic trends

31 Light, and other electromagnetic radiation, behaves as a wave waves are in motion A amplitude intensity A 2 wavelength λ frequency (ν) = no. of wavelengths per unit time λν= c c = speed of light = 3.00 x 10 8 m/s 1 Hz = 1 cycle/s Light behaving as a wave is observable Examples: diffraction patterns

32 DIFFRACTION OF LIGHT its wave-nature Diffraction 1 st 0 th 1 st λ Laser beam E-field λ length

33 However, the wave theory can not account for some observations Interaction of light and matter A new theory was developed QUANTUM THEORY atoms emit or absorb energy in quanta energy of light is quantized as photons Energy = h ν photon energy frequency Planck s constant x J s

34 The electromagnetic spectrum Wavelength region Potentially harmful? X ray Ultra-violet Visible Infrared Microwave Radio Yes Yes Yes Yes Yes Yes No No No No No No

35 Photon Energy Example 1 What is the energy of one photon of red light of λ = 650 nm? ν = c λ = E = hν = E = extremely small amount of energy in 1 photon

36 Photon Energy Example 2 What is the longest wavelength of light that can break a C O bond if it takes 1072 kj/mol to break the bond? BE..( J ) = E E BE.. = = N C O A = hν E ν = = h c λ = = ν Is this visible to your eye?

37 DUAL NATURE OF LIGHT Wave properties λν = c Particle properties E = hν One example supporting the particle theory of light photoelectric effect Another example line spectra

38 PHOTOELECTRIC EFFECT Direct observation of quantum effects (Einstein Nobel Prize 1921) for explanation Electrons are emitted by metal only if light has freq greater than certain min. value, no matter how intense the light When electrons are emitted, the number emitted is proportional to light intensity E k = hν E b KE of emitted photoelectron photon energy binding energy

39 PHOTO-ELECTRIC EFFECT E k = hν E b KE of emitted photoelectron photon energy binding energy

40 LINE SPECTRA Light emitted by excited atoms Atoms emit light of only certain frequencies and energies E = hν Therefore, only certain energy changes are possible for electrons in atoms Thereform, electrons in atoms can only have certain specific energies E 3 E 2 excited states E 1 ground state

41 Two postulates: BOHR MODEL 1913 (1) Energy level an electron can only have specific energy levels in an atom E = hcr H n = 1, 2,... n 2 R H Rydberg constant hcr H = x J n principal quantum no. (2) Transitions an electron in an atom can change energy only by going from one specific energy level to another Energy of photon = E i E f = h ν = ΔE

42 QUANTITATIVE TREATMENT OF TRANSITIONS ΔE = E f E i hcr H hcr H 1 1 Δ E = = hcr 2 2 H 2 2 n f n i nf n i but ΔE = hν so 1 1 Δ E = hν = hcrh n n 2 2 f i If n f > n i then ΔE is + absorb photon If n f < n i then ΔE is emit photon

43 QUANTITATIVE TREATMENT OF TRANSITIONS (Example) Calculate wavelength of light emitted By a transition from n=4 n=2 in the Hydrogen atom