《基础化学》英文教学课件：chapter_5

1、Chapter 5. Colloids, 5-1. colloids 5-2. Sol 5-3. Macromolecular solution 5-4. Surfactants and associated colloids,1 胶体分散系 明确分散系；分散相；分散介质；均相体系；非均相体系；相的概念； 明确比表面；表面能的概念； 明确 分散相的分类方法； 2 溶胶 明确 溶胶；电泳；电渗；临界聚沉浓度的概念； 理解溶胶的性质：光学性质；动力学性质；电学性质 明确溶胶的结构：胶核；胶粒；吸附层；扩散层；双电层概念 理解胶粒的电属性； 理解溶胶的稳定性及聚沉；,Learning Objecti

2、ves,3 高分子溶液 明确 高分子溶液；等电点的概念； 理解 高分子溶液的属性； 理解 盐析，电泳分离和纯化蛋白的机制； 4 表面活性剂和缔合胶体 明确 表面能；表面张力；增溶的概念； 明确 胶束；临界胶束浓度；缔合胶体的概念； 理解 表面活性剂的分类；,1. Colloids,A solution is a homogeneous (均相的) mixture of two or more substances, consisting of ions or molecules.,A colloid (胶体) is a dispersion of particles (1 100 nm) of

3、 one substance throughout another substance or solution.,Concept introduction:,NaCl aqueous solution: Na+, Cl-, H2O,Fog is an example of a colloid: it consists of very small water droplets in air.,Proteins, nucleic acids, blood, body fluid, cell.,T.Thomas Graham (18051869),Peter P. von Weymarn (1879

4、 1935),扩散速度小，不能透过半透膜，溶剂蒸发后不结晶，而是形成无定形胶状物的物质。,T.Thomas Graham (18051869),任何能结晶的物质在一定介质中用适当的方法都能成为胶体,胶体是物质的一种分散状态的概念,1. Colloids,1. Colloids,I. Dispersed system,Dispersed phase (分散相): to be dispersed, discontinuous,Dispersed medium (分散介质): to disperse, continuous,A dispersed system (分散系) is formed by

5、dispersing one or more substances throughout another substance.,1. Colloids,Classification of dispersed systems: A,A heterogeneous system (非均相体系) is a mixture that consists of physically distinct parts, each with different properties.,A homogeneous system (均相体系, also known as a solution) is a mixtur

6、e that is uniform in its properties throughout given samples.,K2CrO4 + Fe fillings,1. Colloids,A phase (相) is one of several different homogeneous materials present in the portion of matter under study.,These heterogeneous systems all consist of two different phases.,K2CrO4 + Fe fillings,1. Colloids

7、,Classification of dispersed systems: B,Classification according to the size of dispersed phase.,Sol 固-液,Sol 液-气,Sol 固-气,乳状液,Milky Way,?,凝胶,The Milky Way is the galaxy that contains our Solar System.,An image of the Milky Ways Galactic Center in the night sky above Paranal Observatory,The Milky Way

8、is the galaxy that contains our Solar System.,鲁迅 (1881年9月25日-1936年10月20日） 呐喊狂人日记阿Q正传,1. Colloids,II. Colloid dispersed system,A colloid is a dispersion of particles (1 100 nm) of one substance (the dispersed phase) throughout another substance or solution (the dispersed medium or the continuous phas

9、e (连续相).,Sol (溶胶),Macromolecular solution (高分子溶液),Associated colloid (缔合胶体),1. Colloids,1. Sol,A sol (溶胶) is a colloid consisting of solid particles (collection of atoms, molecules, or ions) dispersed in a liquid.,heterogeneous and unstable,1. Colloids,Degree of dispersion (分散度):,A cube with a size

10、of 1 cm:,Specific surface area (比表面, S0): surface area occupied by the substance of a unit volume.,1. Colloids,Disperse the cube to cubes with a size of 1 m, the number of smaller cubes is:,Then,Disperse the cube to cubes with a size of 1 nm, the number of smaller cubes is:,Then,1. Colloids,A molecu

11、le at the surface experiences a net force toward the interior of the liquid, whereas a molecule in the interior experiences no net force.,There is a tendency for the surface area of a liquid to be reduced as much as possible. This explains why falling raindrops are nearly spherical (the sphere has t

12、he smallest surface area for a given volume of any geometrical shape).,1. Colloids,Surface energy (表面能): The energy required to increase the surface area by a unit amount. (Jm-2). OR. The molecules at the surface have higher energy than those in the interior.,Sol is highly dispersed and has a higher

13、 surface energy. It has a tendency to aggregate to decrease the surface energy. Therefore, sol is an unstable system.,energy,1. Colloids,The dispersed phase is single (large) molecules, macromolecular solutions are stable systems.,2. Macromolecular solution (高分子溶液),1. Colloids,The dispersed phase is

14、 molecular cluster. Associated colloids are stable systems.,3. Associated colloid (缔合胶体),Sodium stearate (硬脂酸钠),2. Sol,Multi-phase;,Highly-dispersed;,Unstable.,2. Sol,I. Properties of sol,1. Optical properties (光学性质) : Tyndall effect,The scattering (散射) of light by colloidal-size particles is known

15、as the Tyndall effect.,A light beam is visible perpendicular to its path only if light is scattered toward the viewer.,2. Sol,Scattering of (strong) laser beams by air molecules,2. Sol,2. Sol,Rayleigh formula:,I0: Incident light intensity : Incident light wavelength V: particle volume c: concentrati

16、on of particles n: refractive index (折光指数),2. Sol,Although all gases and liquids scatter light, the scattering from a pure substance or true solution is quite small and usually not detectable. However, because of the considerable depth of the atmosphere, the scattering of light by air molecules can

17、be seen. The blue color of the sky is due to the fact that blue light is scattered more easily than red light.,Rayleigh formula:,I0: Incident light intensity : Incident light wavelength V: particle volume c: concentration of particles n: refractive index,两眼一眨不眨 勇敢的盯着太阳 直到太阳和我都变瞎 天黑了地黑了太阳也黑了 好久好久才醒过来

18、 感觉到天地由黑转白 黎明从我这里向四面八方展开,Rayleigh scattering is more evident after sunset. This picture was taken about one hour after sunset at 500m altitude, looking at the horizon where the sun had set.,早霞不出门，晚霞行千里,2. Sol,2. Dynamic properties (动力学性质), Brownian movement (布朗运动): The phenomenon that colloidal part

19、icles move irregularly and continuously in the medium.,2. Sol,It is resulted from the unbalanced collision from medium molecules. Decreasing sol particle size and viscosity (粘度) of medium, or increasing the temperature, favors Brownian movement.,Sol: dynamically stable system.,2. Sol, Diffusion and

20、sedimentation equilibrium:,Diffusion (扩散): The phenomenon that colloidal particles shift from a region with higher concentration to that with lower concentration. Reason: Brownian movement; Driving forces: concentration difference.,2. Sol,Sedimentation (沉降): The phenomenon that colloidal particles t

21、end to sink due to gravitation.,Sedimentation equilibrium: when diffusion and sedimentation are at equilibrium, a concentration gradient (梯度) occurs.,It takes a very long time to reach this equilibrium, to accelerate this process ,Ultracentrifugation (超速离心法),2. Sol,在密度均一的介质中由低速到高速逐级离心，用于分离不同大小的细胞和细胞

22、。,differentialcentrifugation 差速离心,densitygradientcentrifugation 密度梯度离心 用一定的介质在离心管内形成一连续或不连续的密度梯度，将细胞混悬液或匀浆置于介质的顶部，通过重力或离心力场的作用使细胞分层、分离。,A等速度沉降，分离密度相近而大小不等的细胞或细胞器。 B等密度沉降 , 适用于分离密度不等的颗粒。,2. Sol,3. Electric properties, Electrophoresis:,2. Sol,Electrophoresis (电泳): directional movement of charged collo

23、idal particles in an electric field.,Positively-charged Fe(OH)3 colloidal particles,Applications: separation and identification of amino acids, polypeptides, proteins, and nucleic acids.,2. Sol,Instrument for electrophoresis.,Separation and identification proteins by electrophoresis.,2. Sol,2. Sol,E

24、lectroosmosis (电渗): directional movement of dispersed medium in an electric field. Reason: charging state of colloidal particles and medium.,2. Sol,II. Structure of sol,AgNO3 + KI AgI + KNO3 KI in excess;,1. Structure of sol,2. Sol,2. Sol,Adsorption layer (吸附层): the thin layer composed of adsorbed i

25、ons on the colloidal nucleus surface and part of the confined counterions (反离子). Diffusion layer (扩散层): the layer composed of the rest of counterions diffusing around the adsorption layer. Electric double layer (双电层): the two-layer structure of oppositely-charged adsorption layer and diffusion layer

26、.,Absorption (吸收),2. Sol,AgNO3 + KI AgI + KNO3 AgNO3 in excess;,2. Sol,FeCl3 + 3H2O Fe(OH)3 + 3HCl Fe(OH)3 + HCl FeOCl + 2H2O FeOCl FeO+ + Cl-,2. Sol,2. Electrically-charged colloidal particles,1). Selective adsorption to the colloidal nucleus surface:,Fe(OH)3 colloidal particles appear to be positi

27、vely-charged due to selective adsorption of FeO+.,2. Sol,AgNO3 + KI AgI + KNO3,AgNO3 in excess,KI in excess,2. Sol,Silica sol colloidal particles appear to be negatively-charged.,2). Dissociation of surface molecules around colloidal nucleus:,Silica sol:,Nucleus: xSiO2yH2O Surface: H2SiO3,2. Sol,3).

28、 Effect of electrolyte,2. Sol,III. Stability of sol,Electrically-charged colloidal particles: Electrostatic repulsion among colloidal particles. Protection of hydrated membrane (水合膜) around colloidal particle: Elastic membrane. Brownian movement.,A colloid of gold particles (negatively-charged) in w

29、ater prepared by Michael Faraday in 1857 is still preserved in the British Museum in London.,Solutions of gold nanoparticles of various sizes. The size difference causes the difference in colors.,2. Sol,免疫金标记技术(Immunogold labelling techique) 在金标蛋白结合处，在显微镜下可见黑褐色颗粒，当这些标记物在相应的配体处大量聚集时，肉眼可见红色或粉红色斑点，因而用于

30、定性或半定量的快速免疫检测方法中，这一反应也可以通过银颗粒的沉积被放大，称之为免疫金银染色。,纳米金即指金的微小颗粒，其直径在1100nm，具有高电子密度、介电特性和催化作用，能与多种生物大分子结合，且不影响其生物活性。,2. Sol,accumulations of gold particles over the neural granules,2. Sol,2. Sol,IV. Coagulation of sol,Coagulation (聚沉) is the process by which the dispersed phase (colloidal particles of sol

31、) is made to aggregate and thereby separate from the dispersed medium (continuous phase).,An example is the coagulation of a colloidal suspension of soil in river water when the water meets the concentrated ionic solution of an ocean. The river delta (三角洲) was formed in this way.,Nile River delta, a

32、s seen from Earth orbit. The Nile is an example of a wave-dominated delta that has the classic Greek delta (,) shape after which river deltas were named.,2. Sol,Deltas on Mars Finding deltas is a major sign that Mars once had a lot of water.,2. Sol,2. Sol,Electrolyte can push counterions to the adso

33、rption layer and neutralize (中和) the charging state of colloidal particles. Two colloidal particles can approach close enough to aggregate.,Critical coagulation concentration (CCC, 临界聚沉浓度): the minimum concentration of electrolyte needed to coagulate a certain amount of sol within a specified time.,

34、1. Effect of electrolyte,2. Sol,Critical coagulation concentration (mmolL-1),2. Sol,A. The greater the magnitude of the charge of the counterion, the lower the CCC is.,Shulze-Hardy rule:,B. Same magnitude of the charge of the counterion , coagulation capacity: For negatively-charged sol: H+ Cs+ Rb+

35、NH4+ K+ Na+ Li+ For positively-charged sol: F- Cl- Br- I- CNS-,2. Sol,2. Coagulation of mixed sols with opposite electric charges,+,3. Macromolecular Solution,Macromolecule (polymer): a chemical species of very high molecular weight (10,000) made up from many units of low molecular weight linked tog

36、ether.,Macromolecular solution is a kind of molecular solution. It is a homogeneous and stable system. However, the size of macromolecules falls into the range of colloidal dispersed system.,Polymers are natural or synthetic (next slide).,I. Macromolecules,3. Macromolecular Solution,Flexible-chain:,

37、good solvent,3. Macromolecular Solution,3. Macromolecular Solution,A polymer(聚合物) is a chemical species of very high molecular mass made up from many structural unit or monomer of low molecular mass covalently linked together. A compound used to make a polymer (and from which the polymers unit arise

38、s) is called a monomer(单体).,3. Macromolecular Solution,“团结就是力量”,3. Macromolecular Solution,“锁链化学”,Celluloid, discovered around 1868, was the first commercial plastic. Initially it was used as a cheap substitute for ivory in making billiard balls. Cellulose (纤维),Cellulose nitrate (guncotton) is made

39、by soaking a cellulose material such as cotton in a mixture of nitric and sulfuric acids. it catches fire and burns explosively.,Table tennis balls,celluloid film,3. Macromolecular Solution,Bakelite, a hard plastic produced from formaldehyde, HCHO, and phenol, C6H5OH.,Leo Baekeland 利奥 贝克兰 (1863 1944

40、),Bakelite buttons,Bakelite 酚醛树脂(1907),3. Macromolecular Solution,Natural rubber is a homopolymer(同聚物), a polymer whose monomer units are all alike.,A copolymer(共聚物) is a polymer consisting of two or more different monomer units. Styrenebutadiene rubber (SBR) is an important synthetic rubber;,3. Mac

41、romolecular Solution,Polyesters (聚酯) A substance with two alcohol groups reacts with a substance with two carboxylic acid groups to form a polyester, a polymer whose repeating units are joined by ester groups.,Dacron(涤纶),The product, although interesting, tended to decompose in hot water and had a l

42、ow melting point, so as a fabric it would hardly withstand washing or ironing.,3. Macromolecular Solution,Polyamides (聚酰胺) When a compound containing two amine groups reacts with a compound containing two carboxylic acid groups, a condensation polymer called a polyamide is formed.,Nylon-6,6 (尼龙，1935

43、),A condensation polymer(缩合聚合物) is a polymer formed by linking together many molecules by condensation reactions. A condensation reaction is one in which two molecules are joined by the elimination of a small molecule such as water.,3. Macromolecular Solution,Wallace Carothers 华莱士卡罗瑟斯 (1896年1937年),3

44、. Macromolecular Solution,Plexiglass (acrylic) 有机玻璃 (丙烯酸树脂),Teflon 特氟龙 (聚四氟乙烯),3. Macromolecular Solution,“不粘锅”涂层,3. Macromolecular Solution,PETE Polyethylene terephthalate 聚对苯二甲酸乙二醇酯,PP Polypropylene 聚丙烯,3. Macromolecular Solution,3. Macromolecular Solution,PS Polystyrene 聚苯乙烯,PVC Polyvinyl chlorid

45、e 聚氯乙烯,3. Macromolecular Solution,PC Polycarbonates 聚碳酸酯,Bisphenol A 双酚,3. Macromolecular Solution,3. Macromolecular Solution,II. Protein solution,1. Protein,Protein (蛋白质) are biological polymers of amino acids linked by peptide bonds.,Amino acid (氨基酸),R:,3. Macromolecular Solution,2. Isoelectric po

46、int,Lower pH,Higher pH,Side chains become protonated and carry positive charges.,Side chains become deprotonated and carry negative charges.,Protonation (质子化) means the gain of a proton; Deprotonation (去质子化) means the loss of a proton.,3. Macromolecular Solution,The pH at which a protein carries no

47、net charge (same amount of negative charges and positive charges) is called the isoelectric point (等电点, pI) of this protein.,pH pI :negatively-charged.,The isoelectric point of bovine serum albumin (牛血清白蛋白, BSA) is 4.6.,Isoelectric point and electrophoresis, solubility.,More specifically, the pI of

48、any amino acid is the average of the two acid-dissociation constants that involve the neutral zwitterion. For the 13 amino acids with a neutral side chain, pI is the average of pKa1 and pKa2 . For the four amino acids with either a strongly or weakly acidic side chain, pI is the average of the two l

49、owest pKa values. For the three amino acids with a basic side chain, pI is the average of the two highest pKa values.,3. Macromolecular Solution,3. Macromolecular Solution,3. Salting out,The primary structure (一级结构) of a protein refers to the sequence of the amino-acid units in the protein. The seco

50、ndary structure (二级结构) refers to the relatively simple coiled or parallel arrangement of a protein molecule. The tertiary structure (三级结构) refers to the structure associated with the way the protein coil is folded.,Three-dimensional structure of myoglobin (肌球素),3. Macromolecular Solution,Due to the

51、ion-dipole forces (离子-偶极作用力), the charges (ions) along protein molecules attract water molecules and are thus hydrated. Hydration (水合作用) of ions favors the dissolving of protein molecules in water.,Hydration of ions. Note that a cation (a) is surrounded by water molecules with the O atoms closer to

52、the ion, whereas an anion (b) has water molecules attached through their hydrogen atoms.,3. Macromolecular Solution,When inorganic salt (for example, (NH4)2SO4) are added into protein solution, the hydration of protein molecules is highly weakened due to the strong hydration of inorganic ions. The s

53、olubility of protein is lowered and protein molecules precipitate out of the solution. This process is referred to as salting out (盐析).,The structure of protein molecules remains when salted out. Salting out is a routine procedure to separate and purify proteins.,Organic experiments last term ? glob

54、in (球蛋白) and albumin (清蛋白),4. Surfactants and Associated colloid,I. surface tension,Surface energy (表面能): The energy required to increase the surface area by a unit amount. (Jm-2).,Surface tension (表面张力, ): The force exerted on a unit length of the surface to contract the surface area.,Surface energ

55、y and surface tension have the same value.,4. Surfactants and Associated colloid,The surface tension of liquid water is 73 mN m-1. Organic solvents have much lower surface tensions.,4. Surfactants and Associated colloid,II. Surfactant (表面活性剂) (Surface-active-agent),A: Inorganic additives such as NaC

56、l, KNO3. B: Organic additives such as alcohol(醇), aldehyde(醛), carboxylic acid(羧酸), and ester(酯). C: Surfactants such as soaps and detergents.,The surface tension of a liquid can be affected by dissolved substances.,4. Surfactants and Associated colloid,1. Structure of surfactant molecules,Amphiphil

57、e (两亲分子),Hydrophilic (亲水的),Hydrophobic (疏水的) or lipophilic (亲油的),head,tail,4. Surfactants and Associated colloid,sodium dodecyl sulfate (十二烷基硫酸钠),2. Classification of surfactants,Anionic: (阴离子表面活性剂),Cationic: (阳离子表面活性剂),Zwitterionic: (两性离子 表面活性剂),Nonionic: (非离子表面活性剂),4. Surfactants and Associated co

58、lloid,4. Surfactants and Associated colloid,4. Surfactants and Associated colloid,(surfactant),Organic substances have much lower surface tension than water, the surface tension of the solution is greatly reduced.,III. Associated colloid,A micelle (胶束) is a colloidal-sized particle formed in water b

59、y the association of surfactant molecules.,The minimum concentration of surfactants at which the micelle starts to form is referred as critical micelle concentration (CMC, 临界胶束浓度).,4. Surfactants and Associated colloid,The hydrophobic ends point inward one another, and the hydrophilic ends are on the outside of the micelle facing the water.,4. Surfactants and Associated colloid,A colloid in which the dispersed phase consists of micelles is called an associated colloid (缔合胶体).,The micelles could be spherical, rod-shaped, or layered depending on the structure and concentration