海洋浩瀚的溶液

1、Unit 3 The ocean (P.37)第3節 海洋3.1 Sea water: a vast solution (P.37)3.1 海洋：浩瀚的溶液Sea water covers over 70% of the surface area of the Earth. Sea water is a vast water solution containing 3.5% by mass of dissolved solids. The dissolved solids are different salts. The main one is common salt sodium chlor

2、ide.海洋覆蓋超過70%地球的表面面積。海水是一個浩瀚的溶液， 其中已溶解的固體的質量百分比為3.5%。這些已溶解的固體是各種不同的鹽，主要的是食鹽氯化鈉。Solute and solvent溶質和溶劑A solution forms when one substance dissolves in another. The substance that dissolves is called the solute. The substance that does the dissolving is called the solvent.Substances that dissolve in

3、a solvent are said to be soluble in that solvent. Substances that do not dissolve in a solvent are insoluble in that solvent.A dilute solution contains a small amount of solute in a given volume of solution. A concentrated solution contains a large amount of solute in a given volume of solution. The

4、 concentration of a solution is the mass of a solute dissolved in a certain volume of the solution. A saturated solution is a solution that has dissolved the most solute it can, at a given temperature.一種物質溶解在另一種物質裏，便形成溶液。溶解的物質稱為溶質，溶解其他物質的是溶劑。物質能在某種溶劑裏溶解，即是可溶於該溶劑。物質不能在某種溶劑裏溶解，即是不可溶於該溶劑。在定量的溶液只含少量的溶質的

5、稱為稀溶液。在定量的溶液含大量的溶質的稱為濃溶液。某一體積的溶液含有的溶質的質量，稱為該溶液的濃度。在一定温度下，已溶解所有它能溶解的溶質的溶液稱為飽和溶液。3.2Obtaining common salt from sea water (P.39)3.2 從海水獲取食鹽Decantation傾析Decantation is a quick method for separating a much denser solid from a liquid. For example, we can separate coarse sand from sea water by decantation.

6、傾析是把較重的固體和液體分離的快捷方法，例如我們可以用傾析的方法把粗沙和海水分離。Filtration過濾Filtration is another common method for separating an insoluble solid from a liquid. For example, we can separate mud from sea water by filtration.To separate mud from sea water, pour the mixture into the funnel fitted with a piece of filter paper

7、. There are millions of tiny holes on the filter paper. The water particles and those of the dissolved salts can pass through these holes but the mud particles are too large to do so. The mud that remains on the filter paper is called the residue. The sea water that passes through the filter paper i

8、s called the filtrate.過濾是把不能溶解的固體和液體分離的另一種方法，例如我們可以用過濾的方法把泥和海水分離。要把泥和海水分離，先把混合物傾入已鋪上濾紙的漏斗中。濾紙上有百萬個微細的小孔，水粒子和溶於海水中的鹽的粒子都可通過小孔流出，但泥土粒子太大，不能通過小孔。留在濾紙上的泥稱為殘餘物。通過濾紙的海水稱為濾液。Evaporation蒸發The change of a liquid to a vapour which occurs at a temperature below the boiling point is called evaporation.液體在沸點以下的温

9、度轉變成蒸氣的過程稱為蒸發。Evaporating off the liquid is effective if we want to obtain the solid (as in obtaining common salt from sea water).如果我們想從混合物獲取固體，可以把液體蒸發掉（例如從海水獲取食鹽）。Crystallization結晶Many solids exist as crystals. All crystals have regular shapes.Crystallization is the process of forming crystals. It

10、is another method for separating a solute from a solution.許多固體以晶體的形態存在，所有晶體都有固定的形狀。結晶是形成晶體的過程，是另一個把溶液中的溶質分離出來的方法。By cooling a hot concentrated solution冷卻高濃度的熱溶液To obtain crystals from an unsaturated solution, heat the solution to remove some of the solvent. The solution becomes more concentrated. Wh

11、en the hot and concentrated solution cools, the solvent cannot hold all the solutes. The extra solutes then separate out as crystals.要從未飽和的溶液中獲取晶體，首先要把溶液加熱，讓部分溶劑逸走，溶液會變得較濃。高濃度的熱溶液冷卻後，溶劑便不能容納所有的溶質，多餘的溶質會分離出來，結成晶體。Slow evaporation of a solution at room temperature讓溶液在室温下慢慢蒸發We can also obtain crystals

12、 by evaporating a solution at room temperature. As the solvent evaporates, the remaining solution becomes more and more concentrated. It finally becomes saturated. Further evaporation makes the extra solutes separate out as crystals. Finally, we can separate the crystals from the solution by filtrat

13、ion.我們也可以讓溶液在室温下慢慢蒸發，獲取晶體。隨着溶劑蒸發逸走，餘下的溶液會變得愈來愈濃，最後變成飽和溶液。進一步的蒸發令多餘的溶質分離出來，結成晶體。最後可用過濾法把晶體和溶液分離。Both evaporation and crystallization can be used to obtain common salt from sea water. The common salt obtained by evaporation is impure, while the common salt obtained by crystallization is purer.利用蒸發和結晶的

14、方法，都可以從海水獲取食鹽。用蒸發的方法獲取的食鹽含有較多雜質，用結晶的方法獲取的食鹽則較為純淨。3.3 Obtaining pure water from sea water (P.42)3.3 從海水獲取純水Distillation蒸餾The change of a vapour to a liquid is called condensation. The process of evaporating a liquid and subsequently condensing the vapour is called distillation.In an experimental set-

15、up for distillation, the apparatus which cools the vapour into a liquid is called a condenser. The condenser consists of two tubes one inside the other.When the sea water is heated, the water vapour escapes and passes through the inner tube of the condenser. The vapour is cooled by the cold water fl

16、owing around it. The water vapour condenses to form liquid water. The pure water collected in the conical flask is called the distillate.蒸氣轉變成液體的過程稱為凝結。讓液體蒸發，再把蒸氣凝結成液體的過程稱為蒸餾。在蒸餾的實驗裝置中，把蒸氣冷卻成為液體的儀器稱為冷凝器。冷凝器有內外二管。海水受熱時，海水中的水會變成蒸氣進入冷凝器的內管。在外管流動的冷水會把蒸氣冷卻成為水。錐形瓶收集到的純水稱為餾液。Notice that a few anti-bumping

17、granules are added into the sea water before heating. This is to ensure even boiling.留意在加熱前把數顆防漰沸小粒放在海水中，以確保海水沸騰時保持均勻穩定。STSE ConnectionsFresh water from sea water從海水獲取食水The following table shows the different categories of water on Earth.下表列舉地球上不同類別的水。Table 3.1 Different categories of water on Earth

18、地球上不同類別的水Category of waterPercentage水的類別百分比Sea97.4%海水Ice-caps, glaciers and groundwater (fresh water)2.59%冰帽、冰川和地下水（淡水）Lakes, rivers, atmosphere and soil moisture (fresh water)0.01%湖泊、河流、大氣和土壤水分（淡水）People living in developed countries have access to high quality drinking water. However, more than a

19、billion people on Earth (one in six) lack access to drinking water. In the Middle East, fresh water is scarce whilst sea water is readily available in many areas. However, sea water is not suitable for human consumption.生活在已發展國家的人民都能享用高質量的食水， 但全球超過十億人（即每6人中有1人）缺乏食水供應。在中東地區，十分容易可以獲得海水，但食水卻極之匱乏。然而，海水並

20、不適宜飲用。Obtaining fresh water from sea water從海水獲取食水One possible method of converting sea water into fresh water is by removing the dissolved salts. The process is called desalination.Two methods of desalination are thermal distillation and reverse osmosis.Osmosis is the natural tendency for a solvent

21、(water in this case) to move through a membrane from a region of higher solvent concentration to a region of lower solvent concentration. However, osmosis can be reversed. If sufficient pressure is applied to the sea water side, sea water can be forced through a series of membranes. These membranes

22、contain tiny pores that allow the smaller water molecules to pass but prevent larger particles of contaminants (Fig. 3.8). This is the basic principle of desalination by reverse osmosis.把海水變成食水的一個方法，是去除海水中的鹽，這個過程稱為海水淡化（或脫鹽）。海水淡化的兩個主要方法分別是熱蒸餾法和逆滲透法。滲透是溶劑（在這情況是水）從高溶劑濃度區域穿越薄膜向低溶劑濃度區域移動的自然傾向。在特定條件下，滲透的方

23、向可以逆轉。參照圖3.8，在海水那一方施加足夠的壓力，海水便會被迫通過一系列的薄膜，這些薄膜上有很多微細的小孔，細小的水粒子可以通過小孔，但其他雜質的粒子較大，不能通過。這就是利用逆滲透法把海水淡化的基本原理。Reverse osmosis currently represents around 60% of the global desalination market. It is predicted that this will increase to 65% by 2015.逆滲透法現時約佔全球海水淡化市場的60%。至2015年，這數字預計將增加至65%。The worlds large

24、st producer of desalinatedwater Saudi Arabia全球最大規模地進行海水淡化的國家 沙地阿拉伯Desalination meets 70% of the drinking water requirements in Saudi Arabia. Several new desalination plants are under construction. Once completed, the countrys network of desalination plants will have a capacity of 800 million gallons

25、 a day.在沙地阿拉伯，海水淡化能滿足當地70% 的食水需求。數個新的海水淡化廠正在興建中，一旦開始運作，整個海水淡化廠網絡的產量將達到每日8 億加侖。Questions問題1Instead of importing water from Guangdong province, desalination is an alternative means of providing fresh water to Hong Kong people. Discuss the pros and cons of using this alternative.1除了從廣東省輸入食水外，海水淡化可以為香港市

26、民提供食水。討論採用這個方法的利弊。2Fresh water is a precious resource. Suggest how you can help save it.2淡水是珍貴的資源，建議一些節約用水的方法。Problem SolvingConsider the bottle of chemical waste collected in a laboratory shown on the right. Suggest how you could remove the oil and the common salt from the chemical waste.右方展示的是在實驗室

27、收集得的一瓶化學廢料。試建議如何把油和鹽從該化學廢料中去除。3.4 Showing what species common salt contains(P.46)3.4 顯示食鹽含有甚麼物種Flame test焰色試驗When compounds of some metals are burnt in a Bunsen flame, different brightly coloured flames will result. We can identify the metallic element in a compound by the flame colour produced. The

28、 procedure is known as a flame test.把某些金屬的化合物在本生焰中加熱，會令火焰呈現不同的光亮顏色。我們可以憑着火焰的顏色，鑑定化合物所含的金屬元素，這步驟稱為焰色試驗。Table 3.2 Flame colours of some metal compounds一些金屬化合物的火焰顏色Compound of化合物所含的金屬Flame colour火焰顏色Potassium鉀lilac淡紫Sodium鈉golden yellow金黃Calcium鈣brick-red磚紅Copper銅bluish green藍綠Test for chlorides silver

29、 nitrate test氯化物的試驗 硝酸銀試驗Compounds made up of chlorine are called chlorides. To test whether a sample is a chloride, first dissolve the sample in water, then add excess dilute nitric acid, followed by silver nitrate solution. Appearance of a white precipitate suggests that the sample is a chloride.含

30、氯的化合物稱為氯化物。要測試一個樣本是否氯化物，可先把樣本溶於水，然後加入過量的稀硝酸，跟着加入硝酸銀溶液。如果有白色沉澱物出現，即表示樣本是氯化物。Table 3.3 Test for a chloride氯化物的試驗Procedure步驟Result結果1add excess dilute nitric acid加入過量的稀硝酸2add silver nitrate solution加入硝酸銀溶液a white precipitate appears有白色沉澱物生成3.5 Test for the presence of water in a sample (P.48)3.5 顯示樣本含水

31、的試驗Water turns blue cobalt(II) chloride paper pink. We can use it to test for the presence of water in a sample.水會把藍色氯化鈷(II)試紙變成粉紅色。我們可利用這種試紙檢測一個樣本是否含水。Checkpoint1The set-up shown below is used to study the effect of heating copper(II) sulphate crystals在某實驗裏，以右圖展示的裝置來把硫酸銅(II)晶體加熱。a)Suggest the colou

32、r of the copper(II) sulphate crystals before and after heating.指出硫酸銅(II)晶體受熱前後的顏色變化。b)Suggest how you can show that the crystals contain water指出你會如何顯示晶體含有水。c)Explain why the boiling tube is held in a downward slanting position as shown.解釋為甚麼要把大試管保持向下傾斜，如右圖所示。2A and B are two unlabelled bottles. One

33、of them contains potassium chloride solid while the other contains sodium chloride solid. Suggest how you can distinguish between them.A和B是兩個沒有標籤的試劑瓶，其中一個盛載固體氯化鉀，另一個則盛載固體氯化鈉。建議一個辨別它們的方法。3.6 Electrolysis of sea water (P.49)3.6 電解海水We can use chemical methods to break down a compound into simpler subs

34、tances. For example, passing electricity through water can break it down into hydrogen and oxygen. The process is called electrolysis.There are four major elements in sea water: sodium, chlorine, hydrogen and oxygen.Passing electricity through sea water can rearrange the constituent elements to make

35、 other useful substances.我們可以用化學方法把化合物分解成較簡單的物質，例如可以把電流通入水，把它分解成氫和氧，過程稱為電解。海水含有四種主要元素：鈉、氯、氫和氧。把電流通入海水能把四種組成元素再排列，從而獲取有用的物質。The electrode connected to the positive terminal of the d.c. supply is the positive electrode. The electrode connected to the negative terminal of the d.c. supply is the negativ

36、e electrode.When we pass electricity through sea water, chlorine gas is formed at the positive electrode. Hydrogen gas is formed at the negative electrode. Eventually, the solution in the setup becomes sodium hydroxide solution.連接直流電源正端鈕的電極是正電極；連接直流電源負端鈕的電極是負電極。我們把電流通入海水時，氯氣會在正電極生成，氫氣在負電極生成。最後，裝置內的溶

37、液會變成氫氧化鈉溶液。3.7Use of the products obtained by the electrolysis of sea water (P.50)3.7從電解海水獲取的物質的用途3.8 The particle theory of matter (P.51)3.8 物質的粒子理論Matter is made up of particles.The particle theory of matter states that all matter is made up of very small particles.物質由粒子組成。物質的粒子理論指出，所有物質都是由十分細小的粒子

38、組成的。Table 3.4 Two experiments demonstrating the particle theory of matter兩個說明物質的粒子理論的實驗Placing a piece of potassium permanganate crystal in a beaker of water把高錳酸鉀晶體置於水中potassium permanganate particles leave the crystal and mix with the water particles高錳酸鉀粒子離開晶體，混入水粒子中Placing a jar of air upside down

39、 on top of another jar containing bromine vapour把一盛載空氣的集氣瓶倒置在一盛載棕色溴蒸氣的集氣瓶上bromine particles mix with the air particles溴粒子混入空氣粒子中3.9 Physical and chemical changes (P.52)3.9 物理變化和化學變化Matter can undergo two types of change, physical and chemical.物質經歷的變化可分為兩類：物理變化和化學變化。During a physical change, no new s

40、ubstance is formed.在物理變化過程中，沒有新的物質生成。In a chemical change, one or more new substance(s) is / are formed.在化學變化過程中，會有一種或以上新的物質生成。Changing the state of water a physicalchange改變水的狀態 物理變化Water can be a solid (ice), a liquid (water) and a gas (water vapour or steam). We can change its state by heating or

41、cooling. No new substance is formed. Therefore the process is a physical change.Water is made up of very small particles. Differences between the three states of water are due to differences between the arrangements of particles.水可以是固體（冰）、液體（水）和氣體（水蒸汽）。把水加熱或冷凍可以改變它的狀態，過程中沒有新的物質生成，因此過程是物理變化。水是由十分細小的粒

42、子組成的。水的三種狀態之間的差別是因為粒子的排佈的不同。Table 3.5 Arrangements of particles of water at different states在不同狀態下水的粒子的排佈State狀態Diagram of particles粒子圖Arrangement of particles粒子的排佈Particles in a solid are packed tightly in a fixed pattern. There are stronger forces holding them together. They can only vibrate about

43、 fixed positions.粒子緊密地排列在一起，粒子之間的引力較強，它們只能在固定的位置振動。Particles in a liquid can move about and slide past each other. They are still close together. The forces that hold them together are weaker than those in a solid.粒子仍然緊密地在一起，但它們可以互相滑過，粒子之間的引力比在固態時弱。Particles in a gas are far apart. They move about v

44、ery quickly. There are almost no forces holding them together.粒子彼此相距很遠，移動的速度很快，粒子之間幾乎沒有引力。Sublimation a physical change昇華 物理變化A few substances, when heated, change straight from the solid state to the vapour state without passing through the liquid state. This change is called sublimation. Cooling c

45、auses the vapour of these substances to change directly back to a solid. Carbon dioxide and iodine both sublime.一些物質受熱時，會由固態直接變成氣態，無須經過液態的階段，這種變化稱為昇華。這些物質的蒸氣受冷時會直接變回固體。二氧化碳和碘都會昇華。Key Terms溶解d _ _ _ _ _ _ _ 溶液s _ _ _ _ _ _ _溶質s _ _ _ _ _溶劑s _ _ _ _ _ _可溶s _ _ _ _ _ _不可溶i _ _ _ _ _ _ _ _稀溶液d _ _ _ _ _

46、 s _ _ _ _ _ _ _濃溶液c _ _ _ _ _ _ _ _ _ _ _ s _ _ _ _ _ _ _濃度c _ _ _ _ _ _ _ _ _ _ _ _飽和溶液s _ _ _ _ _ _ _ _ s _ _ _ _ _ _ _傾析d _ _ _ _ _ _ _ _ _ _過濾f _ _ _ _ _ _ _ _ _殘餘物r _ _ _ _ _ _濾液f _ _ _ _ _ _ _蒸發e _ _ _ _ _ _ _ _ _ _晶體c _ _ _ _ _ _結晶c _ _ _ _ _ _ _ _ _ _ _ _ _ _蒸餾d _ _ _ _ _ _ _ _ _ _ _凝結c _ _

47、 _ _ _ _ _ _ _ _ _冷凝器c _ _ _ _ _ _ _ _餾液d _ _ _ _ _ _ _ _ _焰色試驗f _ _ _ _ t _ _ _氯化物c _ _ _ _ _ _ _沉澱物p _ _ _ _ _ _ _ _ _ _電解e _ _ _ _ _ _ _ _ _ _ _正電極p _ _ _ _ _ _ _ e _ _ _ _ _ _ _ _負電極n _ _ _ _ _ _ _ e _ _ _ _ _ _ _ _物質的粒子理論p _ _ _ _ _ _ _ t _ _ _ _ _ of m _ _ _ _ _昇華s _ _ _ _ _ _ _ _ _ _碘i _ _ _ _ _Revision1Sea water contains _ by mass of dissolved salts, the main one is common salt _ .2A _ forms when one substance dissolves in another. The substan