chapter 5 energy 화학반응에서 에너지의 역할. energy energy is the capacity of do work...
TRANSCRIPT
Chapter 5
Energy
화학반응에서 에너지의 역할
Energy
• Energy is the capacity of do work– work is a measure of energy
• 에너지는 생성 / 소멸되지 않는다– 열역학 제 일 법칙– 에너지 보존의 법칙
Work and Force• May the force be with you!
Energy for Gravity• Gravity
– force of attraction between bodies
– imparts energy to bodies
• Potential Energy (P.E. ; V)– position dependent; stored energy
• Kinetic Energy (K.E. ; T)– energy of movement
Energy for chemical system
• Potential Chemical Energy– electron moves away from nucleus– electron moves toward each other
• Kinetic Chemical Energy– electrons are in constant motion– atoms, molecules, solids are also in motion
Energy
• Chemical Reaction– require a change in energy to occur– reactions absorb or release energy
• Forms of Energy– Heat – Light (electromagnetic wave, EMW)– Motion
Heat
• Heat – motion of atoms and molecules– 일종의 운동 에너지– K.E. = (3/2)RT
• Temperature– measure of the average kinetic energy
• Celsius(oC) and Kelvin(K)– scales for the measurement of temperature
섭씨 , 절대온도 , 화씨
Light• Light
– visible form of electromagnetic wave (EMW) or radiation
• Electron absorb light to move from lower energy levels to higher energy levels
• Light can cause reactions
• Other form of electromagnetic radiation– microwaves– UV(ultra violet) radiation
Light
• Speed of light = 3.0 X 108 m/s
• wavelength – 400 - 750 nm
• frequency– 1015 Hz = 1000 THz
• frequency = speed of light/wavelength
Energy Transfer• Energy Content
– H = enthalpy at constant pressure H = enthalpy change
= H(final) - H(initial)
• Energy released– exothermic ( -H )
• Energy absorbed– endothermic ( +H )
Energy Unit
• Energy Unit = Joule (J)– 1 cal = 4.184J– 1 kcal = 1000 cal = 4184 J– 1 Cal = 1000 cal
• cal > J
• Calorimeter
Bond Energies• Reaction break and form bonds
– Table 5.2 “mean” bond energy
• Electrons and atoms are reorganized– change in energy is required
• Reaction = bond reorganization– Bond breaking - endothermic– Bond making - exothermic
Energy of Reaction
Fuel Research
– -98kJ/mol exothermic reaction– reaction product = gas
– www.abc.net.au/science/news/stories/s63460.htm
Why Do Reaction Happen?
• Matter has a tendency to disperse energy
• Entropy - – measure of disorder– disorder in matter & energy
• Tendency for Entropy constantly increases– 열역학 제 이 법칙– 계와 환경 전체의 엔트로피 고려
Spontaneous Reaction• Spontaneity -
– ability of a reaction to disperse matter and energy
• Spontaneous Reaction– reactant go to products without input of energy
• Non-spontaneous Reaction– reactants need constant energy to become
products
Entropy
2 H2O 2 H2 + O2 H = +286kJ/mol
• Entropy?– Matter dispersion ; Liquid gas + gas – Energy concentration ;
• Spontaneous?– NO but needs something else (battery)
Chemical Kinetics• 화학 반응 속도론• Activation Energy (Ea, 활성화 에너지 )
• Energy from Collisions– atoms, molecules, ions– kinetic energy
Chemical Kinetics• Chemical Kinetics
– study of the rates of reactions– macroscopic rate
• Factors that affect Rates– temperature = kinetic energy
• 10 도 상승에 속도 2 배 상승
– concentration (mol/L)• 요오드 시계 반응
Catalyst
• 촉매– 반응에 관여하여 반응속도를 증가시키나– 변하지 않고 회수되는 물질– 적은 양으로 충분
• 촉매의 원리– 활성화 에너지를 낮춘다– 반응 경로의 변화– 반응속도 10 억 배 이상 증가
Catalytic Converter• 12 장 참조
Pd & Ptcatalyst
Enzyme - bio catalyst
• 아미노산 사슬= 단백질 분자
• 기질 (substrate) 선택성• blocking the enzyme
Homework
• 교과서 190 쪽 5 장 연습문제– 2, 4, 5, 11 번– 마감 1/7 일 시험시작전
• 1/7 ( 월 ) 9 시 15 분부터 중간시험– 범위 서문부터 6 장 탄소에 의한 창조 까지– 계산기 준비
• 중간시험 후 수업 합니다 .
References• http://www.hhmi.org/news/burley.html
– Blocking the enzyme, aminoglycoside 3-N-acetyltransferase (right), could prevent bacteria from inactivating antibiotics, says HHMI investigator Stephen K. Burley.
• http://www.abc.net.au/science/news/print/print_63460.htm– H2O2 : rocket fuel for the 21C