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Module 5　A Lesson in a Lab 實驗是進(jìn)行科學(xué)研究最重要的環(huán)節(jié)，做實驗時，我們一定要遵守實驗室的規(guī)章制度，要注意安全，要熟悉每種儀器的用途和使用方法。做實驗固然十分好玩，但是千萬不能不注意安全哦！ Laboratory safety rules Science is a handson laboratory class.You will be doing many lab activities which may need the use of chemicals or equipment.To make sure of a safe science classroom，we provide you with a list of rules.These rules must be followed at all times. GENERAL GUIDELINES 1．Never work alone.No student may work in the lab without a teacher present. 2．When first entering a lab，do not touch any equipment，chemicals，or other materials in the lab until you are asked to do so. 3．Do not eat，drink，or chew gum in the lab.Do not use lab glassware as containers for food or drink. 4．Know the positions and operating procedures of all safety equipment，including the firstaid kit and the fire extinguisher.Know where the fire alarms and the exits are. 5．Check the labels on chemical bottles twice before removing any of the chemicals.Take only as many chemicals as you need. 6．Most chemicals in the lab are considered to be dangerous.Do not touch，taste，or smell any chemicals unless specifically asked to do so. 7．At the end of your experiment，clean everything carefully and return your equipment to where you got it.Wash your hands with soap and water after performing all experiments. WHAT TO WEAR 1．Dress properly during a lab activity.Long hair must be tied back and shoes must completely cover the feet. 2．Contact lenses should not be worn in the lab unless you are allowed by your teacher. 3．Any time chemicals，heat，or glassware is used，students will wear lab goggles.Nobody should break this rule! ACCIDENTS AND INJURIES 1．Report any accident or injury to the teacher immediately. 2．If a chemical should get into your eye(s)or onto your skin，go to see a school nurse immediately. 1．handson adj.　　　　 實際操作的 2．guideline n. 準(zhǔn)則 3．procedure n. 程序 4．firstaid kit 急救包 5．fire extinguisher 滅火器 6．label n. 標(biāo)簽 7．goggles n. 護目鏡 1．What should you do at the end of an experiment in the laboratory? ________________________________________________________________ 【答案】　Clean everything carefully and return the equipment to where it was.Wash hands with soap and water. 2．If a chemical should get into your eye(s)，what would you do? ________________________________________________________________ 【答案】　Report it to the teacher and go to see a school nurse immediately. Section Ⅰ　Introduction & Vocabulary and Speaking—Preparing 根據(jù)提示寫出下列單詞 1．expand vi.　　　　　 膨脹 2．contract vi. 收縮 3．substance n. 物質(zhì) 4．mixture n. 混合物 5．electricity n. 電 6．stage n. 階段；時期 7．conclusion n. 結(jié)論 8．a(chǎn)im n. 目標(biāo)；目的 9．reaction n. 反應(yīng) 10．electrical adj. 與電有關(guān)的；用電的 11．equipment n. 設(shè)備；裝備 12．react vi. (化學(xué))反應(yīng) 13．partial adj. 部分的；局部的 14．boil vt. 煮；煮沸 15．ordinary adj. 普通的；平常的 看單詞　學(xué)構(gòu)詞 動詞＋ment→名詞，ment表示“行為，狀態(tài)，過程，手段及其結(jié)果”。常見的有：achieve＋ment→achievement n.功績；成就；announce＋ment →announcement n.通知；通告；punish＋ment→punishment n.懲罰；state＋ment→statement n.陳述；聲明；treat＋ment →treatment n.對待；治療等。 根據(jù)提示補全下列短語 1．a(chǎn)dd...to... 往……加入…… 2．react with 與……起(化學(xué))反應(yīng) 3．in_conclusion 最后；總之 4．put...in order 把……按順序排列 5．keep...out of 把……關(guān)在外面 6．think of 想；考慮 7．find out 弄清楚；查明 根據(jù)提示補全下列教材原句 1．Twothirds_of the earths surface is water. 地球表面的三分之二是水。 2．It_is_hard_to_think_of a world without metals. 很難想象一個沒有金屬的世界。 　閱讀P44－45教材課文，選擇最佳答案 Passage A 1．The first sentence “It is hard to think of a world without metals.” will make us think ________. A．metals make up the world B．metals play a greatly important role in the world C．there would be no world if there were no metals D．it is difficult for us to live in the world of metals 2．The table in the passage is arranged in order of ________. A．metal kinds B．reaction activities C．values of metal D．the first letters of the words 3．According to the table，which metal is most suitable to make our daily kitchenware(廚房)? A．Zinc.　　　　　　 B．Iron. C．Copper. D．Magnesium. Passage B 4．Which is NOT the apparatus that is required in the experiment of “Iron in dry air”？ A．Cotton wool. B．Oil. C．Iron nails. D．Test tube holder. 5．Which is required as one of the apparatus in the experiment of “Iron in ordinary water”？ A．Oil. B．Cotton. C．Bunsen burner. D．Test tube holder. 6．The purpose of these two experiments is________. A．to find out how iron reacts with water and air B．to find out how important iron is C．to find out how to do the experiment of irons reaction with water and air D．to find out how to keep iron rustless 【答案】　1－6　BBCBDD 　閱讀P44－45課文，在空白處填入適當(dāng)?shù)膬?nèi)容(1個單詞)或括號內(nèi)單詞的正確形式 Metals are very important in 1.the world.Different metals have different 2.uses(use)．For example，steel 3.is_used(use)in cars，and iron in 4.electrical(electricity)equipment.When we use metals，it is important 5.to_know(know)they react 6.with different substances，for example，water and oxygen.The 7.reaction(react)of metals with these substances can 8.be_put(put)in order.Potassium，sodium，calcium，magnesium，aluminium and zinc react most，9.and iron and copper react 10.least(little)． Section Ⅱ　Introduction & Vocabulary and Speaking—Language Points conclusion n．結(jié)論；結(jié)束 (1)draw/come to/arrive at/reach a conclusion 　　　　　　　　　　 得出結(jié)論 jump to a conclusion 匆忙下結(jié)論 in conclusion 最后，作為結(jié)論地；總之 (2)conclude v. 得出結(jié)論；結(jié)束 ①They drew different conclusions from these facts. 他們從這些事實中得出了不同的結(jié)論。 ②I soon arrived_at/came_to/reached the conclusion that shed been lying. 我不久就得出結(jié)論，她在撒謊。 【導(dǎo)學(xué)號：67550053】 ③In conclusion，Id like to say that you are the kindest person that I have met. 最后，我想說你是我遇到的最善良的人。 ④When the group discussion is nearing its end，be sure to_conclude(conclusion)it with important points. 當(dāng)小組討論接近尾聲的時候，一定要歸納出重點來結(jié)束。 aim n．目標(biāo)，目的；瞄準(zhǔn)v. 瞄準(zhǔn)，對準(zhǔn)；旨在；目的是 (1)aim...at...　　　 用……瞄準(zhǔn)/對準(zhǔn)…… aim to do sth.＝ aim at doing sth. 旨在做某事，打算做某事 (2)with the aim of... 為了…… without aim 無目的地 achieve ones aim 達(dá)到目的；實現(xiàn)目標(biāo) take aim at 瞄準(zhǔn) ①(2014 浙江高考單項填空)The aim of education is to teach young people to think for themselves and not follow others blindly. 教育的目的是教會年輕人自己思考，而不是盲目地仿效別人。 ②The hunter took aim at the lion and fired. 獵人瞄準(zhǔn)獅子并開了槍。 ③His brother studies hard，aiming to_pass(pass)the 2017 College Entrance Exam. 為了通過2017年高考，他哥哥努力學(xué)習(xí)。 ④Aiming(aim)at a more comfortable life，the couple worked hard and took on more parttime jobs. 為了過上更舒適的生活，這一對夫婦努力工作，并且承擔(dān)了更多的兼職工作。 ⑤He didnt answer，with his gun aiming(aim)at David. 他沒有回答，把槍瞄準(zhǔn)了戴維。 think of 想象；考慮；想起；認(rèn)為 (教材P44)It is hard to think of a world without metals.很難想象一個沒有金屬的世界。 　寫出下列句子think of的含義 ①The picture made me think of my past.想起 ②He is thinking of changing his job.考慮 ③What do you think of your English teacher？認(rèn)為 ④You can think of what the city will be in twenty years.想象 (1)think highly/well/much of　　 對……評價很高 think little/poorly of 對……評價不高 think of...as... 把……看作…… (2)What do you think of...? 你認(rèn)為……怎么樣？ (3)think about 考慮 think over 仔細(xì)考慮 ⑤We all think of her as a responsible teacher. 我們都認(rèn)為她是一位負(fù)責(zé)的老師。 ⑥May I think about it for a moment? 我可以考慮一下嗎？ react v．反應(yīng)，起作用 (教材P44)When we use metals，it is important to know how they react with different substances，for example，water and oxygen. 使用金屬時，要了解金屬和不同的物質(zhì)如何發(fā)生反應(yīng)，這一點很重要，比如，水和氧。 (1)react to　　 對……作出反應(yīng)；起反應(yīng) react with 與……產(chǎn)生反應(yīng) (2)reaction n. 反應(yīng)；起作用(常與介詞to連用) ①(牛津詞典)Iron reacts with water and air to produce rust. 鐵與水和空氣起化學(xué)反應(yīng)而生銹。 ②(朗文辭典)How did Wilson react to your idea? 威爾遜對你的想法有什么反應(yīng)？ ③—Whats the managers reaction(react)to your suggestion? 經(jīng)理對你的建議反應(yīng)如何？ —I dont know.He remains silent. 我不知道。他保持沉默。 [語境助記]　We all wanted to see her reaction to this matter，but she didnt react at all. 我們想看看她對此事的反應(yīng)，但她對此毫無反應(yīng)。 put...in order把……按順序排好 (教材P44)The reaction of metals with these substances can be put in order. (不同的)金屬與這些物質(zhì)的反應(yīng)程度可以按順序排列起來。 (1)in order of　　　　　 按……順序 (2)in order 有序(地)；整齊 out of order 無序(地)；發(fā)生故障 (3)in good/bad order 井然有序/亂七八糟 ①Put everything in the room in order before you leave the room. 離開房間前把房間里的所有東西整理好。 ②Everything in the room is in_good_order today. 今天房間里的一切都井然有序。 【導(dǎo)學(xué)號：67550054】 ③My clock is out_of_order and it waked me up at 3 this morning. 我的鬧鐘發(fā)生故障了，今天早晨3點就把我叫醒了。 [語境助記]　All the things in the room were out of order，but she soon put them in order. 房間里的東西擺放得亂七八糟的，但是她很快就把它們收拾整齊了。 form vt.& vi.形式；養(yǎng)成n.形狀；表格；形式 (教材P44)Burns to form an oxide燃燒形成氧化物 (1)in the form of　　　　 以……形式 take the form of 采取……形式 fill in/out a form 填表格 (2)form the habit of 養(yǎng)成……的習(xí)慣 ①As they chatted，the idea of spending holiday together gradually formed. 他們聊天時，一起度假的想法慢慢形成了。 ②I_have_formed(form)the habit of getting up early since I became a senior high school student. 自從我成了高中生我就養(yǎng)成了早起的習(xí)慣。 ③Water exists below zero in_the form of solid. 水在零度以下以固體的形式存在。 ④Please fill in/out the form before going into the hall. 進(jìn)入大廳前需填表。 ordinary adj.普通的；平常的 (教材P45)Iron rusts in ordinary water.鐵在普通水中會生銹。 ①The novel describes the way of life of the ordinary people there. 這部小說描寫的是那里的普通人的生活方式。 ②We were dressed up for the party but she was still in her ordinary clothes. 我們都為聚會盛裝打扮，但她仍然穿著平常的衣服。 [明辨異同]　common/ordinary/usual/normal ordinary “普通的；平常的”，指沒有什么特別的地方。 common “常見的；共同的”，指許多人或事物所共同具備因而常見，強調(diào)事物的共同性。常見短語：common sense “常識”；have...in common “與……相同”。 usual “通常的；慣常的”，指經(jīng)常出現(xiàn)而不變。常見短語：as usual“像往常一樣”。 normal “正常的；常態(tài)的；合乎標(biāo)準(zhǔn)的”。常見短語：return to normal“恢復(fù)正?！?。 　common/ordinary/usual/normal Here is a story about an ③ordinary girl named Mary，which is a ④common name.She went to school as ⑤usual.On the way，she sent an injured old man to hospital.She didnt go home until the old man returned to ⑥normal. add...to...把……添加到…… (教材P45)Add some oil to the water.在水中加些油。 (1)add to　　　　　 增加；增添 add up 加起來 add up to 加起來達(dá)到 (2)add that... 補充說…… ①Would you like to add more sugar to your coffee? 你想要在咖啡里再加些糖嗎？ ②Every failure one meets with adds_to ones experience. [諺語]吃一塹，長一智。 ③Add_up_all the figures and find out what they add_up_to. 把這些數(shù)字加起來，弄清楚總計是多少。 [圖形助記]　 keep...out of...使……不進(jìn)入……；使……置身于……之外 (教材P45)This will keep air out of the water. 這樣做可防止空氣進(jìn)入水中。 keep sth.out(of sth.)　 使不進(jìn)入；把……關(guān)在外面 keep off 避開；使……不接近 keep away(from) 遠(yuǎn)離；不接近 keep up with 跟上；不落后；趕上 ①I told my kid to keep out of trouble while I was away. 我告訴孩子在我外出時不要惹麻煩。 ②The plastic house will keep the cold air out to protect the vegetables. 塑料大棚會把寒氣擋在外面以此保護蔬菜。 ③Please keep_off the grass. 請勿踐踏草坪。 ④As long as you can keep_away_from_them，youll be safe. 只要遠(yuǎn)離他們，你就會安全。 ⑤He is studying hard to keep_up_with his classmates. 他正努力學(xué)習(xí)以趕上他的同學(xué)。 【導(dǎo)學(xué)號：67550055】 Ⅰ.語境填詞 用所給單詞的正確形式填空 1．Every classroom in our school is equipped with modern equipment.(equip) 2．In my opinion，each of us should have an aim of our own.But some of us lead an aimless life every day.(aim) 3．Jack said he could conclude from Janes expression that Jane had stolen his money.But everyone knew Jack always jumped to conclusion without any evidence to support his conclusion.In conclusion，nobody was likely to believe Jane was a thief.(conclude) 4．The reaction showed us how the company reacted to the need of the customer.(react) 5．The chemistry teacher let each student put a finger into the mixture that he had mixed and tasted it.(mix) Ⅱ.選詞填空 1．Close the door and keep the cold air out_of the room. 2．I will think_of my childhood every time I see the picture. 3．Look! Tony，your books are everywhere.Please put_them in_order. 4．Please add_some milk to_my coffee. 5．He decided to find_out who had taken his computer. (教材P41)Twothirds_of the earths surface is water. 地球表面三分之二是水。 【要點提煉】　“分?jǐn)?shù)(百分?jǐn)?shù))＋of＋名詞(代詞)”作主語時，謂語動詞的單復(fù)數(shù)形式取決于of后的名詞或代詞的單復(fù)數(shù)形式。 ①Over fourfifths of the students in our school are from the countryside. 我們學(xué)校五分之四以上的學(xué)生來自農(nóng)村。 ②Only onethird of the work has_been_done(do)by now. 到現(xiàn)在為止僅完成了三分之一的工作。 ③Twofifths of the country is_covered(cover)with water. 這個國家的五分之二被水覆蓋。 [名師點津]　在英語中，表示分?jǐn)?shù)時，分子用基數(shù)詞，分母用序數(shù)詞；分子大于1時，表示分母的序數(shù)詞要用復(fù)數(shù)，并且可在分子和分母之間加上連字符“”。例如，1/3 onethird；4/5 fourfifths；3/7 threesevenths。 (教材P44)It_is_hard_to_think of a world without metals.很難想象一個沒有金屬的世界。 【要點提煉】　本句為“It is＋形容詞＋to do”句型，其中it為形式主語，不定式短語是真正的主語。 it作形式主語的常見句型： (1)It is＋adj.＋(for/of sb.)to do sth. (2)It is＋adj./n.＋that 從句 (3)It is no good/no use/useless doing sth.做某事是沒有好處/用的 ①It is very important to learn a foreign language. 學(xué)一門外語非常重要。 ②Its a pity that George cant make it to the party. 真遺憾，喬治不能來參加這次聚會了。 ③Its no use arguing(argue)with her—she wont listen. 跟她爭論沒有用——她不會聽的。 ④Its careless of you to make so many mistakes in this exam. 在這次考試中你出了這么多錯真是太粗心了。 ⑤It is difficult for us to finish the task in such a short time. 在這么短的時間內(nèi)讓我們完成這項任務(wù)很困難。 [名師點津]　在“It is/was＋adj.(for/of sb.)＋to do sth.”結(jié)構(gòu)中，for前面的形容詞通常是difficult，necessary，important，quick，easy等，這些形容詞多與事物的特征有關(guān)。而of前面的形容詞常常是wise，kind，stupid，silly，bright，nice，good等，這些形容詞常常與人的性格特點有關(guān)。 完成句子 1．我三分之一的業(yè)余時間都用來讀書。 Onethird of my spare time is_spent(in)reading books. 2．三分之一的學(xué)生不知道這個問題的答案。 Onethird of the students dont_know_the_answer_to_the_question. 3．你不敲門就走進(jìn)別人的房間是不禮貌的。 It_is_not_polite_of_you_to_enter others room without knocking at the door. 4．有時候，孩子們自己做出選擇是必要的。 Sometimes，its_necessary_for_children_to_make their own choices. 5．玩網(wǎng)絡(luò)游戲是沒有好處的。 It_is_no_good_playing computer games. 【導(dǎo)學(xué)號：67550056】 Here is a table with the metals that react most at the top，and the metals that react least at the bottom. 【分析】　句子的主干：Here is a table。with the metals為with短語作定語，修飾table；that react most at the top和that react least at the bottom都是that引導(dǎo)的定語從句，修飾metals。 【翻譯】　表中金屬反應(yīng)最強的排在上面，反應(yīng)最弱的排在下面。 學(xué)業(yè)分層測評(十三) Ⅰ.單句語法填空 1．—Mum，the soup is a little salty. —Try adding(add)some water to it. 2．Its wise of you to_think(think)twice before you make the final decision. 3．—Have you got in touch with Tom? —Oh，sorry.I couldnt think of his phone number at the moment. 4．It was difficult to guess what his reaction(react)to the news would be. 5．We have been working on it for several hours but we havent reached any conclusion(conclude)that was practical. 【導(dǎo)學(xué)號：67550085】 6．They will start their project aiming(aim)at helping the poor children to be educated in Chinas west. 7．Please observe the mixture(mix)and write down what you will have seen. 8．After the experiment，everything is put in order in the cupboard. 9．Threefifths of the students in our class are(be)girls. 10．China Daily has nine websites in three languages and three mobile platforms，forming(form)Asias biggest network of Englishlanguage news and information. Ⅱ.單句改錯 1．Please close the windows to keep flies out the room. ________________________________________________________________ 【答案】　out后加of 2．These newlybuilt gardens added up to the beauty of the city. ________________________________________________________________ 【答案】　去掉up 3．It is impossible of him to sleep on such a small bed. ________________________________________________________________ 【答案】　of→for 4．Im not sure how she will react on the decision. ________________________________________________________________ 【答案】　on→to 5．About a quarter of the wall are painted blue. ________________________________________________________________ 【答案】　are→is Ⅲ.完形填空 It was the first morning of the New Year and the weather was very cold.I have always been an early bird and my morning walks have been the __1__ for the last 7 years，so I put on my shoes to __2__ for my first walk of the New Year. There was complete __3__ outside.Litter could be seen everywhere.It seemed that everyone had an allnight __4__.It was too cold to __5__ anyone to be awake to clear all the walkways at 5 in the morning.I was __6__ to walk on the dirty walkways and decided to go back home. I was about to leave __7__ I saw Sam cleaning the garden.He is an employee of our society association and is __8__ to take care of the walkways and the garden.I walked up to Sam as it was a(n)__9__ to see him there cleaning at that time.He saw me and politely __10__ me，“Happy New Year！” “How come you are here and doing all this on the very first day of a New Year？” I asked.Sam answered __11__，“It is the first day of the year.I do not want people to walk on __12__ walkways.It is the first day of the year so they should feel good and special.For me，today is like any other day and my job starts with the __13__.” It was good to see someone so __14__ at heart.Like other staff members，Sam could have taken a day __15__，but he woke up early and came for all of us.I suddenly realized life does not __16__ when the clock strikes twelve at midnight and a New Year begins.We __17__ all night，drinking and feeding ourselves.Then we leave the place in high spirits，leaving the surroundings dirty.Life goes on and others need to __18__ up early and clear the garbage. Isnt the very next morning a new day of a New Year for all those who clear our garbage？Why cant we also keep our __19__ clean so that everyone can have a New Year the very next day？It is true that small things can make a big __20__ in our lives. 1．A.manner　　　　　 B．a(chǎn)pproach C．routine D．a(chǎn)ccess 2．A.look B．head C．long D．send 3．A.waste B．freedom C．silence D．a(chǎn)bsence 4．A.conclusion B．tradition C．celebration D．pollution 5．A.order B．expect C．trust D．catch 6．A.tired B．scared C．puzzled D．bothered 7．A.because B．though C．unless D．when 8．A.advised B．designed C．supposed D．determined 9．A.pleasure B．success C．surprise D．honour 10．A.advised B．wished C．a(chǎn)sked D．congratulated 11．A.coldly B．hopefully C．partially D．quietly 12．A.dirty B．narrow C．busy D．cold 13．A.beginning B．same C．special D．new 14．A.devoted B．curious C．honest D．polite 15．A.over B．out C．up D．off 16．A.change B．improve C．return D．happen 17．A.sleep B．party C．work D．clean 18．A.put B．stay C．wake D．pick 19．A.surroundings B．conditions C．backgrounds D．locations 20．A.decision B．difference C．promise D．suggestion 【語篇解讀】　作者在新年第一天晨練，走在臟亂的街道上，作者很心煩，沒想到遇見了清潔工薩姆。為了給大家營造干凈的環(huán)境薩姆不能休息。作者意識到一個小的舉動就能有大的不同。 1．C　“我”一直是個早起的人，晨練是“我”過去七年里的慣例。manner方式；approach方式，接近；routine慣例；access通道，機會。 2．B　新年的第一天也不例外，“我”穿上鞋子前往自己新年的第一次散步中。head for前往。 3．C　后文交代了作者是早晨五點鐘去晨練的，因此當(dāng)時外面是很安靜的。waste浪費；freedom自由；silence安靜；absence缺席。 4．C　看起來大家都經(jīng)過了整夜的慶?？駳g。conclusion結(jié)論；tradition傳統(tǒng)；celebration慶祝；pollution污染。 5．B　外面如此冷以至于不會期望能見到有人在五點醒來清理街道。expect期望，期待。 6．D　“我”走在臟亂的街道上，心里感到很不舒服，決定要回家。tired厭倦的；scared害怕的；puzzled困惑的；bothered惱火的。 7．D　“我”正打算離開，這時看到薩姆在打掃花園。be about to do sth...when...正要做某事，這時……。 8．C　他是社區(qū)里的雇員，打掃街道和花園是他的分內(nèi)之事。be supposed to do sth.應(yīng)該做某事。 9．C　因為這么早就看到他在那里打掃衛(wèi)生，“我”感到很驚訝，于是“我”走向薩姆。surprise驚訝。 10．B　由“...‘Happy New Year！’”可知是薩姆看到“我”后有禮貌地祝福“我”新年快樂。 11．D　面對“我”的問題，薩姆平靜地回答。quietly平靜地。 12．A　薩姆說他不想讓人們在新年的第一天走在臟兮兮的街道上。 13．B　薩姆說在新年的第一天人們應(yīng)該有個好心情，對于他來說，打掃只不過是在做與平時相同的工作。 14．A　devoted獻(xiàn)身的?？吹剿麑ぷ魅绱双I(xiàn)身， “我”感到很好。 15．D　take a day off 休一天假。薩姆本能像其他員工一樣休一天假的。 16．A　“我”突然意識到人生不是時鐘夜里敲響12點的時候改變的。 17．B　“我們”整夜狂歡聚會，喝酒，享用美食。 18．C　“我們”留下一片狼藉高興地離開，而其他人卻要早起去清理垃圾。 19．A　“我們”為什么不能保持周圍的環(huán)境衛(wèi)生，讓每個人在第二天都能過上新年？ 20．B　make a difference有影響。小小的舉動卻有很大的影響。 Ⅳ.閱讀理解 Were surrounded by chemistry in everyday life.Sometimes it is easy to see，like when your science teacher does a big experiment in class.At other times，it can be pretty hard to see everyday chemistry at work，but nearly everything you touch or use has some element of chemistry in it. Something as simple as toothpaste contains at least three chemicals，if not more.It is the mixture of them and its chemical reaction that keeps your teeth clean.Other things you use every day are created by chemistry，such as hair products，shampoo and soap.Adding detergent(洗滌劑)to water involves chemistry.Without chemistry，we would never have known that we need soap to get the oil out of clothes or skin. Chemistry not only helps us make products for use，but also helps us understand the world around us.Chemistry helps us understand what the ozone layer(臭氧層)is and ho