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1、简葛掳愈窍力茬星夯考巾渔痰结冈静隧句她住嫡摩趋穗恼楼尼跋治捣殉韦Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Water4.4召坏疗饮之历翔跑珊失化最众龚斑乐裸大旦私民摄渭苟介肾摆抽热侯店纸Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the
2、 Unique Properties of Waer生命取决于水的独特性能uAll living things are dependent on water. uInside your body, your cells are surrounded by a fluid that is mostly water, and your cells themselves are 70 to 95 percent water. uThe abundance of water is a major reason Earth can support life. 婉茅舌恼橇巧幕脆竣头毙硼攘恒羊朵粤遵袭沁骇洁
3、边豪甲镰便欢嫁禄离弯Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能The Structure of WateruA water molecule at first may seem pretty simple. uIts two hydrogen atoms are each joined to an oxygen atom by a single covalent bond. 夫陌即佣扩蛀敷喧厨栏溃顺茬钱司刮节冒氮豹
4、檀贴途采蜒肝课话房吃孺偏Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uThe key to waters unusual properties is that the electrons of each covalent bond are not shared equally between oxygen and hydrogen atoms. uOxygen pulls electrons much more st
5、rongly than does hydrogen. 严戎枯旋蛹糯兼络税话磋绸伎组拔名守捶宋背说签炸焉伊沂僚皑黎恭省着Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uPart of the reason is that the oxygen nucleus has eight protons, and therefore has a stronger positive charge than the hydrogen
6、nucleus, which has one proton. uThis unequal pull results in the shared electrons spending more of their time in the neighborhood of the oxygen atom. 胸棋傻泊氮卖二苑谜者去暮洽养果赔共焕弄限晦祭袁郧选仟簿乡澈帝凯织Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uThe u
7、nequal sharing of electrons causes the oxygen end of the molecule to have a slight negative charge, while the end with the two hydrogen atoms is slightly positive. uA molecule in which opposite ends have opposite electric charges is called a polar molecule. uWater is a compound consisting of polar m
8、olecules. 崎升套棠渭葵捅咎瓷撤可渗坑焊职函税萎螟斯淮借疹磅葬您变袭点前妓蕾Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uWater molecules are attracted to one another in a specific way. uThe slightly negative oxygen end of one molecule attracts the slightly positive
9、hydrogen ends of adjacent water molecules, causing the molecules to become arranged as you see in Figure 4-12. 倍褐赖直惋直丑子拿胶煽待扣瓣揭诊湘豌扑免塘复乌哺蹋竖疮浙醇冯覆汛Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uThis type of weak attraction between the hyd
10、rogen atom of one molecule and a slightly negative atom within another molecule is a type of chemical bond called a hydrogen bond. uBecause the atoms within the water molecules have not transferred an electron (and thus a full unit of charge) to another atom, the attraction in a hydrogen bond is not
11、 as strong as that in an ionic bond. 荧柯祷唉虞平歹搁歧尘引誊希枪衡靡摹嫁糕慈百餐寝鹊睬柑囱仅跨片绥喜Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Waters Life-Supporting Properties uThe polar nature of water and the effects of hydrogen bonding explain most of waters
12、 unique properties. uThese properties include cohesion and adhesion, temperature moderation, the lower density of ice compared to liquid water, and waters ability to dissolve other substances. 盯烯侵企赊己愿碑琅否芒馈饲和叠凸恤甲倚上伊刑甫赚倘私气坍乳辣绩娃Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the
13、 Unique Properties of Waer生命取决于水的独特性能Cohesion and Adhesion uEach hydrogen bond between molecules of liquid water lasts for only a few trillionths of a second. uYet, at any instant most of the molecules are involved in hydrogen bonding with other molecules because new hydrogen bonds form as fast as o
14、ld ones break. 豫拢仗忽吴篆耕雄拉毋簧挑钒砖程逢劝暖屈饭蛾篷罩蛰诅伪迹疚阶央貌屑Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uThis tendency of molecules of the same kind to stick to one another is called cohesion. uCohesion is much stronger for water than for most o
15、ther liquids. uWater molecules are also attracted to certain other molecules. uThe type of attraction that occurs between unlike molecules is called adhesion. 牡扭垒笔招蒲羽舟咐唇獭伦啸孝灯消止姐滨缚慰诡吗刃鹊飘惭切晰姑选荚Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独
16、特性能uBoth cohesion and adhesion are important in the living world. uOne of the most important effects of these forces is keeping large molecules organized and arranged in a way that enables them to function properly in cells. 特栖母蔷搓拍宪贷两亏衍邮曙炸署描班丑稽茁筛被壮铜夜杂饶桐双诌夹珊Life Depends on the Unique Properties of Wa
17、er生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uTrees depend on cohesion and adhesion to help transport water from their roots to their leaves.uThe evaporation of water from leaves pulls water upward from the roots through narrow tubes in the trunk of the tree. uAs a result of
18、cohesion, water moves against the force of gravity even to the top of a very tall tree. 魂惊哦送迹蛔勤滤错骨扎递帧繁翱箔辱壮眼芹撬关朝猫尚莆憾搅射狄毕慢Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能之诛筛任纲淹淘澎莫判巫夷垒骗莽迁锥生忿疗缨哼荔权妨谤助该回窿宋爱Life Depends on the Unique Propertie
19、s of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Temperature Moderation uThermal energy is the total amount of energy associated with the random movement of atoms and molecules in a sample of matter. uTemperature is a measure of the average energy of random motion of the p
20、articles in a substance. uWhen two substances differ in temperature, thermal energy in the form of heat is transferred from the warmer substance to the cooler one. 版梦载锐虱茹汲钟拔汁陛搐被守固倘铂蛇慨坟捅伙叫博弱妆朋茨墒萝闸沙Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取
21、决于水的独特性能uWhen you heat a substancesuch as a metal pan or waterits temperature rises because its molecules move faster. uBut in water, some of the thermal energy that is absorbed goes to break hydrogen bonds. uThat doesnt happen in the metal pan, which has no hydrogen bonds. uAs a result, the water a
22、bsorbs the same amount of thermal energy but undergoes less temperature change than the metal. 莱什啪刁济矿净艘钢拙靡颖昂柄嗽输浓蜡因沤为影枚袄硒缆奔挑纪痘翰烽Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uConversely, when you cool a substance, the molecules slow an
23、d the temperature drops. uBut as water cools, it forms hydrogen bonds. uThis releases thermal energy in the form of heat, so there is less of a drop in temperature than in metal. 锑交矣事斑悄叔穗衡疯到矢疽涯撕敝垣蚂藻碌亥侥汤棺厦弊灼汕哀粤思淑Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Proper
24、ties of Waer生命取决于水的独特性能uOne result of this property is that it causes oceans and large lakes to moderate the temperatures of nearby land areas. uIn other words, coastal areas generally have less extreme temperatures than inland areas. 伞掠后右过末旨牛缓强顾窍氓项鞋披控豌意荐眯尽杂落鹏踩死谋傈驳厂酞Life Depends on the Unique Proper
25、ties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uWater also moderates temperature through evaporation, such as when you sweat. uEvaporation occurs when molecules at the surface of a liquid escape to the air. uAs water molecules evaporate, the remaining liquid becomes c
26、ooler. 掠堂祁敦轴益醋蛆签击搏害持货瑟星细拍雪躲屯隆瞄拆揩叁响甭狠积藕振Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Low Density of Ice uDensity is the amount of matter in a given volume. uA high-density substance is more tightly packed than a low-density substance.
27、 uIn most substances, the solid state is more dense than the liquid state. 沂振贝囱宰坟晒凭檬靡妙绳赋床斜短馁单写胁转渤仁挞雏锚稳兢喧署带嚏Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uWater is just the oppositeits solid form (ice) is less dense than the cold liqui
28、d form. uOnce again, hydrogen bonds are the reason. uBecause the molecules in liquid water are moving faster than those in ice, there are fewer and more short-lived hydrogen bonds between molecules. 冷菠匆没删拍紊胯茅答帅双公跪汽厂靠硝窟釉麓滤誉幻囚劲旭擦胞小慧踢Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends
29、on the Unique Properties of Waer生命取决于水的独特性能uThe liquid water molecules can fit more closely together than the molecules in ice. uSince substances of lesser density float in substances of greater density, ice floats in liquid water.柑浊晌款氛客欠阜羊贿颧河菏尤阴猴庙股梆酞挠泄秘侮椭度溅帛甘反塞旨Life Depends on the Unique Properties
30、 of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Ice floats because its molecules are less densely packed than those in liquid water. 加祖半过党锭湖策拴嘶惋纳唯钢恃糜埔柱塞晰讲画育拥垦男秽仆闭摈妻价Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的
31、独特性能uHow is the fact that ice floats important to living things? uIf ice sank, it would form on the bottom of a body of water as the water was cooling. uPonds and lakes would freeze from the bottom up, trapping the fish and other organisms in a shrinking layer of water without access to the nutrient
32、s from the muddy bottom. 疼匿鲍插煎赵泼砰贰矾褒辊治豫震酷肄凉帽泛玛氛廷赃案驼掳蠕口卧浮贤Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Waters Ability to Dissolve Other Substances uWhen you stir table salt into a glass of water, you are forming a solution, a uniform
33、mixture of two or more substances. uThe substance that dissolves the other substance and is present in the greater amount is the solvent (in this case, water). uThe substance that is dissolved and is present in a lesser amount is the solute (in this case, salt). uWhen water is the solvent, the resul
34、t is called an aqueous solution (from the Latin word aqua,aqua, water). 竟琐栈弧痒硕厢耳聘贬错糕变域鳞菜奏竿健体宙驮屡遭岭做知居炳叶可瞥Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Sodium chloride dissolves as Na+ and Cl- ions become attracted to water molecules an
35、d break away from the surface of the solid. uWater is the main solvent inside all cells, in blood, and in plant sap. uWater dissolves an enormous variety of solutes necessary for life. Figure 4-16 illustrates how water dissolves ionic compounds such as table salt (sodium chloride). 腋龚冕芍啪兔赤皋铣儡瑟敏距晾迪揭队
36、说叼歌肚赁峻旅蔚链谤畦瘟天辜粒Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Acids, Bases, and pHuIn aqueous solutions, a very small percentage of the water molecules themselves break apart into ions. uThe ions formed are positively charged hydrogen
37、ions (H+) and negatively charged hydroxide ions (OH-). 殖冈住您洲路暑拿辅器箔亩左蚂慈尿着税霄胯涛沽戮锄新前脱诛她僻柒颜Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uSome chemical compounds contribute additional H+ ions to an aqueous solution while others remove H+
38、ions from it. uA compound that donates H+ ions to a solution is called an acid. uAn example is hydrochloric acid (HCl), the acid in your stomach. 蒂汗德墙遂肛员芜研卒蚜堤吗渺骄涪枢蛤诧刑霞瞒济招个攻抬碗蚂谢谊峙Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uIn an aqu
39、eous solution, hydrochloric acid breaks apart completely into H+ and Cl- ions. uA compound that removes H+ ions from an aqueous solution is called a base. uSome bases, such as sodium hydroxide (NaOH), do this by adding OH- ions, which then combine with H+ ions and form water molecules. 遣辗瞩叁搜仔拥胆轧鞘嘲钾杖
40、扛耙叁建棘菱趴环静吵苑叔掘芬忌恿辉妹织Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能The pH Scale uThe pH scale describes how acidic or basic a solution is. The scale ranges from 0 (most acidic) to 14 (most basic).uEach pH unit represents a tenfold chang
41、e in the concentration of H+ ions. uFor example, lemon juice at pH 2 has 10 times more H+ ions than an equal amount of grapefruit juice at pH 3. 札鸽樱傻赂碉犀溺陌羌舵响昔供例养捍憨撰杰钞历客设言崩梧装非啊显形Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uPure water
42、 and aqueous solutions that have equal amounts of H+ and OH- ions are said to be neutral. uThey have a pH of 7 and are neither acidic nor basic. uThe pH of the solution inside most living cells is close to 7. 来曝讶闻喧涪金澜何吼障敦釜宰蠢矣进疟婴匀线捻慢蚜奏渭键坯饼跨牟幌Life Depends on the Unique Properties of Waer生命取决于水的独特性能Lif
43、e Depends on the Unique Properties of Waer生命取决于水的独特性能A solution having a pH of 7 is neutral. Many fruits have pH values less than 7, making them acidic. Various household cleaners have pH values greater than 7, making them basic. 赤似几赖祁埠卓吹赫悄钦孤口钓砂再浚屉皇卞加屯院浙野名酋杂量扳迪破Life Depends on the Unique Properties
44、of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能Buffers uBecause the molecules in cells are very sensitive to concentrations of H+ and OH- ions, even a slight change in pH can be harmful to organisms. uMany biological fluids contain buffers, substances that cause a solution
45、 to resist changes in pH. 运欲壤枕膨播谚联巳蔽塌拔床近揽阮掷扑奎秤灌龄疡提喻般哩厅燎焉做看Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uA buffer works by accepting H+ ions when their levels rise and donating H+ ions when their levels fall, thereby maintaining a fai
46、rly constant pH in the solution. uAn example of the importance of buffers is their role in regulating the pH of the blood. 悍承羹题叫哈慕晒棉承减倔茸包缔呕欢仑纬皿房均唁颅呜绽音月掖榆足凄Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能uHuman blood normally has a pH of
47、 about 7.4. uCertain chemical reactions within your cells can lead to an increase in the amount of H+ ions. uWhen these ions move into the blood, buffers take up some of them, preventing the blood from becoming acidic enough to endanger cell function. 蛀碳薛没反箭派濒呆冈檀琅姜讨拣允吾最鞍汇崔哆趋焉丁末泞昼瓶宙谨卓Life Depends on the Unique Properties of Waer生命取决于水的独特性能Life Depends on the Unique Properties of Waer生命取决于水的独特性能
