🔙 Quay lại trang tải sách pdf ebook Tiếng Anh Chuyên Ngành Hoá Học Ebooks Nhóm Zalo CHAU VAN TRUNG jsjjii urn] umiii iiciiiiu HO A HOC NHA XUAT BAN GIAO THONG V A N TAI T I E N G A P i H C f f l J Y E N N G A N H KS. CHAU VA N TRUNG CHUYEN NGANH & (Basic English for Chemistry) N H A X U A T B A N G IA O T H O N G V A N T A I LUYEN KY NANG DOC HIEU & DICH THUAT TIENG ANH CHUYEN NGANH ■ ■ HOA HOC Chau Van Trung Chiu track nhiem xuat ban TS N G U Y EN XU AN TH U Y Bien tap NGO THAN H LOAN Sita ban in THANH LOAN Bia LAM VU NHA XUAT RAlfGIAO THONG VAN TAI In 700 cuon, kho 16 x 24cm tai Nha in Thanh Nien, 62 Tran Huy Lieu - Q.PN-TP. HCM - DT : 8440038 - 8445308. Giay phep xuit ban so 230/XB-QLXB do Cue Xuat ban cap ngay 3/03/2005. Giay trich ngang so 70/XB ngay 05/9/2005. In xong v& nop luu chieu qui IV n&m 2005. LCJl n o i d a u TrUdc nhufng p h it trien khoa hpc d iin ra hing ng^y vdi mpt toe dp chdng m3t tren the gidi, nhu cau nim b it, tim hieu tiep can nhufng thcinh ti/u n iy la nhu cau cap thiet nhat. Tuy nhien gidi sinh vien hoc sinh cung nhu nhQng ngifdi lim cong tic khoa hpc doi luc v ln con bj rao c in ngon ngO che chin nhat l i Tieng Anh khoa hpc. De d ip ufng nhu cau dpc hieu tieng anh khoa hoc cd b in , chung toi bien soan quyen "Tieng Anh chuyen nganh Hoa hpc" n^y. Sich gom 20 chu diem trinh bay nhOng k h ii nipm, dinh nghTa djnh luat c3n b in ve Hoa hoc. Md dau mdi chu diem co phan gidi thipu muc dfch yeu ciu, phan bo cuc bing tieng Anh va hudng d in doc hieu blng tieng Vipt, ke tiep la c ic noi dung c3n b in co chufa trong chu diem. De ren ky nSng doc hieu tieng Anh Hoa hpc, sau m6i npi dung trong diem chung toi co phan chu g iii tC/ vi/ng va bai dich m lu - cuoi chu diem la phan bai tap thi/c hanh. Cuoi sich cd phan phu luc danh muc tCf vi/ng tieng Anh Hoa hoc nhim giup ban dpc hp thong hoa cac thuat ngO chuyen nganh can thiet. Bi/dc dau, du het sufc cd ging nhi/ng sich khong kh6i trin h dupe nhufng sai sdt ngoai y muon; rat mong nhan di/pc nhufng gop y chan tinh cua ban doc. T a c g ia . v a n h o m C Q n g ta c BA5IC CONCEPTS cAc khAi miCm c o bAm Mgc BICH y £u c A u - O bjectives 1.1 To classify m atter into types to make the weath of information about m atter manageable 1.2 To use properties to help identify substances 1.3 To distingguish between matter and energy, as w ell as among m atter, mass, and w eight 1.4 To w rite symbols for the im por tant elem ents and names of these elem ents from the symbols 1.5 To begin to classify the elements in a systematic manner. To identifu periods, groups, and sections of the periodic table by names ans number 1.6 To d is tin g g u is h am o n g law s, hypothess, and thearies b6 CUC - L a y o u t 1.1 Classification of Matter 1.2 Properties 1.3 Matter and Energy 1.4 Chemicall Symbols 1.5 The Periodic table 1.6 Laws. Hypotheses, and Theories Jiudng ddn doc hieu muc dich yeu cau vd bo cuc 1.1 Phdn loqi vat chat thanh tiCng loqi de tqo ra thong tin vat lieu phong phu, 1.2 Dung tinh chat de giup xdc dinh vdt chdt, 1.3 Phdn biet giUa vdt chdt vd ndng luqng cung nhu vat chdt, khdi luqng vd trong luqng, 1.4 Viet ky hieu cho nguyen to quan trong vd ten cua nhitng nguyen to tit cdc ky hieu, 1.5 Loqi cdc nguyen to trong m6t he thong phdn loqi de xdc dinh chu ky, phdn nhom vd chia nho bang phdn loqi bai ten vd so, 1.6 Phdn biet giQa cdc quy ludt, gid thuyet vd ly thuyet. 1.1 Phdn loqi vdt lieu, 1.2 Tinh chat, 1.3 Vat chat vd ndng luqng, 1.4 Ky hieu hoa hoc, 1.5 Bang he thong tudn hoan cdc nguyen to, 1.6 Cdc quy ludt, gid thuyet vd cdc ly thuyet. 7 Topic I: /insic concepts Introduction to chemistry Chemistry is the study of matter and energy Matter includes all the m aterial things in the universe In Section 1 1 . you will learn to classify matter into various types— elements compounds, and mixtures based on composition Properties-the characteris tics by which samples of matter may be identified are discussed in Section 1 2 Energy may be defined as the ability to do work. We often carry out chem ical reactions for the sole purpose of changing energy from one form to another for ex ample, we pay large sums of money for fuels to burn in our homes or cars The rela tionship between energy and matter, an important one for chem ists, is explored in S ec tion 1 3 Sym bols introduced in Section 1.4, are used to represent the elem ents The periodic table, introduced in Section 1 5, groups elem ents with sim ilar proper ties Chem ical sym bols and the periodic table are both designed to decrease the effort required to learn a great deal of chem istry Section 1 6 presents scientific laws hy potheses. and theories that generalize and explain natural phenom ena For convenience, chem istry is often divided into the following five sub-disciplines organic chem istry, inorganic chem istry, analytical chemistry, physi-cal chem istry and biochem istry Organic chemistry deals with most compounds of carbon These com ­ pounds are introduced system atically in Chapter 19. Inorganic chem istry deals with all the elements and with compounds that are not defined as organic Analytical chem ­ istry involves finding which elements or compounds are present in a sample or how much of each is present Physical chemistry deals with the properties especially quan titative (measurable) properties of substances Biochemistry deals with the chem istry of living things These subdivisions of chem istry are somewhat arbitrary A chem ist specializing in any one of the first four subdivisions uses all of the first four and often biochem istry as well A biochem ist uses all five specializations For exam-ple, the modern organic chem ­ ist often uses inorganic compounds to convert starting m aterials to desired products and then analyzes the products and mea-sures their properties In addition many or ganic chemists now are investigating compounds of biological interest The importance of science in general and of chem istry in particular in our e very day lives can hardly be overstated For example, color television, com puters and the modern copy machines all stem from chemical advances of the past few decades (Color TV requires com pounds that glow intensely in red blue or green when bom barded with electron beams The modern computer works with chips made from specially treated metalloids. Copy machines require materials that "re m e m b er’ how much light has fallen on them.) However, today s and tomorrow s chemists are still faced with m onu mental tasks cleaning up the environm ent and providing sufficient food for an ever growing world population to mention just two. Table 1.1 Classification of M atter Pure substances Kloments Compounds Mixtures Heterogeneous mixtures Homogeneous mixtures 'solutions) 8 Topic 1: Basic concepts Chu thich tCf - cum t£f va huong dan dpc hieu - Organic chem istry: hda In7a co - Physical chem istry: hda ly - Inorganic chem istry: hda vd co - Biochemistry: hda sinlt - A nalytical chem istry: hoa phan licit Nhap mon hoa hoc Hoa hoc la stf nghien ctfu ve vat chat va ndng htqng. Vat chat bao gom tat cd cdc vat lieu trong vu tru. Trong muc 1.1 ban se hoc cach phdn loqi vat chat thanh cac dang khac nhau nhu nguyen to, hap chat, lion hap dtfa tren cdc thanh phan. Tinh chat, dac tinh cua vat chat co the dtfqc xdc dinh vd lliao luan trong muc 1.2. Ndng luqng cd the ditqc xdc dinh bdi It lid ndng thtfc luen cong. Chung ta thildng thtfc hieu phdn ling hoa hoc dp (hay doi ndng htqng lit dang nay sang dang khac, vi du. chung ta trd mot so lien Ian mua nltien lieu de dot trong sinh lioqt gia dinh vd trong xe hoi. Mdi quan lie giita ndng htqng vd vat chat rat quan trong trong lioa hoc ditqc gidi thich trong muc 1.3. Cdc ky hieu ditqc gidi thieu trong muc 1.4 ditqc stf dung de mo ta cdc nguyen to hoa hoc. Bang phdn loqi ditqc gidi thieu trong muc 1.5. nhom nguyen to vdl cdc tinh chat titang ling. Cd hat ky liieu lioa hoc vd bang phdn loai ditqc thiet lap de gidm no hie dtfqc yen can de nghien ciiu mot so htqng Ion hoa chat. Muc 1.6 gidi thieu cdc quy ludt, gid thiet, ly thuyet khoa hoc de long qudt lioa rd giai tliicli hien htqng til nhien. De cho tliiidn hen. hoa hoc ditqc cltia thanh ndm nhom: hoa ln?u co. lioa cd ca, lioa phdn licit, hoa ly i d hoa sinh. Iloa hitu co lien quan den hdu hel cdc hop chat cua car bon. nhilng hop chat nay se ditqc gidi thieu trong chitong 19. Hoa vd, co hen quan den phdn Ion cdc nguyen to id cdc hop chat in a Ithong phai Id chat hitu co. Hoa phdn tich Id tiin cdc nguyen to hay cdc hop chat cd trong mau hoac dinh litqng chung. Hoa ly lien quan den so tinh chat (do litdng) tinh chat cua cdc chat. Hoa sinh lien quan den hoa hoc cua sinh vat. Stf phdn cltia mon hoc nay cd sit ngau nhien. Mot chuyen gia hoa hoc chuyen ve mot trong bon nganh dau tien cd the dp dung ditqc bon nganh dau tien va cd nganh hoa sinh. Mot chuyen gia hoa sinh sii dung ndm nganh hoa tren. Vi du, mot nha hoa hu'u co luen dqi tlutong sit dung cdc hop chat co ca de chuyen hoa cat chat thanh san pham niong muon vd sau do phdn tich san pham va xdc dinh tinh chat cua chung. Trong sit cdng them do, bay gio nhieu nha lioa lit?u co lai nghien ciiu cdc hop clidt cua cdc sinh cat ditqc quan tdm. Sit quan trong cua khoa hoc noi chung cd ciia hoa hoc noi neng trong cuoc song hang ngay kho cd the noi het ditqc. Vi du, ti vi mau. May vi tinh vd may sao cliep luen dqi, tat cd deu xuat phdt tit stf phat tnen cua hoa hoc trong vai thap ky qua. (Ti vi mdu doi lioi hop chat cd ctfdng do mdu do, xanlt Id hay mdu xanh da trdi khi bdn phd chum tut electron. May tinh luen dqi lain dec edi "chip" ditqc lam lit cdc cat hen dqc biet 1a a kim. May sao chep. dot hoi cat lieu cd the "nha” ditqc bao nhieu anh sang rcri tren chung. Tuy nhien. cdc nha hoa hoc horn nay vd titang lai can dang dot mat edi nluem vu Ian do Id lam sach moi trtfdng cd cung cap du tlutc pham cho sit gia tang dan so the gidi ' a Topic 1: Basic concepts Chu diem 1.1: Classification of Matter________________________________ Matter is defined as anything that has mass and occupies space All the mate rials in the world are composed of a few more than a hundred elements. Elements are the sim plest form of m atter and cannot be broken down chem ically into sim pler stable substances. They can be thought of as building blocks for everything in the universe The same elem ents that make up the Earth also make up the Moon, as shown by actual analysis of Moon samples. Moreover, indirect evidence obtained from analysis of light from stars shows that the rest of the universe is composed of the same ele ments. Clearly the num ber of different combinations of elements must be huge to get all the varieties of matter in the universe. But elements can combine in only two funda mentally different ways: by physical changes to form mixtures or by chem ical changes to produce compounds. Chemical changes, also called chemical reactions, change the composition (or structure) of a substance. Physical changes do not alter the com ­ position. The breaking of glass into small pieces is an example of a physical change. The glass still has the same composition and the same p’roperties as before, but its external form is changed. The burn-ing of charcoal (mostly carbon) in air (or in pure oxygen) to get carbon dioxide, a colorless gas, is an example of a chem ical reaction. Not only the form of the material but also its composition has changed. The gas has both carbon and oxygen in it, but the charcoal had no oxygen. If a sample of matter cannot be broken down into sim pler substances by ordinary chem ical means, the sample is an element. [Ordinary chem ical means includes any methods except nuclear reactions (Chapter 20).] An element has a definite set of prop erties. A compound is a chem ical com bination of elem ents that has its own set of properties and a definite com position. For example, pure water obtained from any natural source contains 88.8% oxygen and 11.2% hydrogen by mass Com pounds can be separated into their constituent elements only by chem ical reaction Snapshot Review - On tap nhanh *- We classify matter so that we can learn the general properties of each type to enable us to answer specific questions about individual samples *■ All substances have definite compositions. A. Does the compound hydrogen peroxide have a definite com position7 • Chung ta phdn loqi vat chat de cd the nghien ciiu cac tinh chat chung cua tung loqi nham cung cap cho chung ta cau tra lai nhUng cau lioi ve cdc mau rieng biet • Tat cd cdc chat cd thanh phdn xac dinh A. Cd phdi liqp chat hydrogen peroxide cd mot thanh phan xdc dinh khong f Chu thich tQ - cum to va hifdng dan dpc hieu - chemical changes: cdc thay doi hda hoc - chemical reactions: cdc phan ting hoa hoc - physical changes: cdc thay doi vat ly - compound: hap chat - definite composition: cac thanh phdn, cdc hon hap xdc dinh 10 Topic 1: Basic concepts Phan loai vat chat Vat chat la tat cd cdc vat cd khoi luqng chiem cho trong khdng gian. Tat cd cdc vdt lieu tren the gidi duac tqo ra ti/ it ham 100 nguyen to. Cdc nguyen to dan gian nhat cua vdt chat thi khdng the phdn chia thanh cdc nguyen to dan gian lion, chat on dinh. Chung cd the duac nghi la cdc thanh phdn ca ban tqo nen moi thit trong vu tru. Cdc nguyen to cung loqi tqo nen trai dal cung tqo nen mat trang, duac cluing minh bai phdn tich thtfc te cua mau vdt lieu tren mat trang. Ilan the ni2a, bang cluing gian tiep dat duac tit stf phdn tich anh sang cua cdc ngoi sao cluing minh rang phan con lai cua vu tru dtfqc tqo ra cung tit cdc nguyen to gidng nhtf d tren. Ro rang so Itfong cua stf kit hap khac nhau cua cdc nguyen to la rat Idn de tqo nen stf khac nhau cua vat chat trong vu tru. Nhtfng cdc nguyen to cd the ket hap tlieo hai cach ca ban sau: bang cdch thay doi vat ly de tqo thanh hon hap hodc thay dot hda hoc de tqo thdnli hap chat. Stf thay doi hoa hoc dtfqc goi la phdn ting hda hoc, lam thay doi thanh phdn cau true cua vat chat. Stf thay doi vat ly khdng lam thay doi thanh phdn hda hoc. Stf va gitang tqo thanh nhtfng mieng nho la mot vl du cua stf thay doi vat ly. Guang (kinh) van cd tlianh phdn vd tinh chat nhtf tritdc do nhUng hinh dang ben ngoai bi thay doi. Sit dot chdy than (lidu het la carbon) trong khdng khi (hoac trong oxy tinh khiet) de tqo nen cacbon dioxit, mot khi khong mdu 1a mot vi du cua mot phdn tfng hda hoc. No khdng chi lam thay doi vdt chat md con lam thay doi cd thanh phdn. Khi sinh ra cd cd carbon vd oxy. con than tlii khdng cd oxy. Neu mot mdu vat chat khdng the vd ra tlianh cdc chat dan gian hon bai cdc phtfang phdp hda hoc thong thtfdng, mdu la mot nguyen to [phtfang phdp hda hoc thong thtfdng gom bat ctf phtfang phdp nao ngoqi trit phdn tfng hat nhan (chi/cfng 20)/ Mot nguyen to cd mot so tinh chat xdc dinh. Mot hop chat la mot stf kit hap hda hoc cua cdc nguyen to cd cdc tinh chat vd thanh phan xdc dinli. Vi du, ntfdc tinh khiet trong thiin nhien chtfa 88,8% oxy va 11,2Vc ve khdi luqng. Hap chat cd the ditqc tach ra thanh cdc nguyen to chi bdng phtfang phdp hda hoc. Chu diem 1.2: Properties Every substance has a definite set of properties. Properties are the characteris-tics by which we can identify something. For example, we know that pure water is a color less, odorless, tasteless substance that is a liquid under the conditions usually found in an ordinary room W ater puts out fires, and it dissolves sugar and salt. Liquid water can be changed into a gas (called water vapor or steam) by heating it, or into a solid (ice) by cooling it. Salt has a different set of properties than water does; sugar has yet another set Chem ical properties are the characteristic ways a substance can react to pro duce other substances Physical properties are the ways a substance can be identi fied without changing its characteristic composition. For example, water can react with very active m etals to produce hydrogen and another compound. That reactivity is a chem ical property of water. W ater can also freeze to ice at 0°C (equal to 32°F) or it can evaporate to water vapor, neither of which changes it from H20. These are physi cal properties of water. Some properties of a sample of a substance depend on the quantity of the sample These properties are called extensive properties. For example, the weight of a solid sample depends on how much of the substance is present. Other properties, such as I I Topic 1: Basic concepts color and taste, do not depend on how much is present These properties are known as intensive properties. Intensive properties are much more useful for identifying sub stances Some of the most important intensive properties that chem ists use to identify sub stances are ones that they measure: they are called quantitative properties Two such properties are the freezing point and the normal boiling point of a substance which are the tem peratures at which a liquid freezes to form a solid and boils to form a gas under normal atm ospheric conditions, respectively. We will discuss quantitative proper ties in more detail in Chapter 2. We can distinguish com pounds from mixtures because of com pounds's character istic properties. M ixtures have properties like those of their constituents The more of a given com ponent present in a mixture, the more the m ixture's properties will resemble those of that com ponent. For example, the more sugar we put into a glass of water, the sweeter is the solution that is produced An experim ent will illustrate how properties are used to distinguish between a com ­ pound and a mixture. We place small samples of iron filings and powdered sulfur on separate watch glasses to investigate their properties. We note that both are solids We place the sam ples in separate test tubes and then hold a m agnet beside the first tube. We find that the iron is attracted to the magnet. When we hold the m agnet next to the tube with the sulfur, nothing happens; the sulfur is not attracted by the magnet When we pour carbon disulfide, a colorless, flammable liquid, on the sul fur sample the solid sulfur disappears, and the liquid turns yellow. The sulfur has dissolved, forming a solution with the carbon disulfide When we pour carbon disulfide on the iron noth ing happens; the iron stays solid, and the liquid stays colorless If we had large pieces of each element, we could pound them with a hammer and find that the sulfur is brittle and easily powdered but that the iron does not easily break into small pieces Iron is malleable that is, it can be pounded into various shapes. Table 1.2 lists the properties discussed so far of the two elements. Next we pour some iron filings and some powdered sulfur into a large test tube and stir them together. The sample appears to be a dirty yellow, but if we look closely, we can see yellow specks and black specks. If we hold a m agnet next to the test tube, the black particles (with some yellow par-ticles clinging to them) are attracted by the magnet When we pour some carbon disulfide on the sample, the liquid turns yellow We pour off that liq uid and pour on more carbon disulfide until no yellow solid re mains in the sample When we evaporate the carbon disulfide in a fume hood we get a yellow solid again If we place a magnet next to the black material left in the large test tube, we find that it is attracted to the magnet It seems that m ixing the two sam ples Table 1.2 Some Properties of Iron, Sulfur, and an Iron-Sulfur Compound Iron Sulfur Iron-Sulfur Compound Solid Solid Solid Shiny Dull Dull M agnetic N ot m agnetic Yellow Black N ot magnetic Black M alleable B rittle B rittle Insoluble in carbon Soluble in carbon Insoluble in carbon disulfide disulfide disulfide 12 Topic 1: Basic concepts of elements has not changed their properties. The sulfur is still yellow and still soluble in carbon disulfide; the iron is still black and still m agnetic. The two elem ents have retained their properties and their identities; they are still elements. This combination of the two is a m ixture. A mixture does not have a definite com position, and it has properties related to the properties of its components. Now we place two new, carefully measured samples of iron filings and powdered sulfur in another large test tube and heat the mixture strongly with a Bunsen burner. After a time, a red glow appears in the bottom of the tube and gradually spreads through out the sample. This is evidence of a chemical reaction. Some sulfur escapes into the gas phase because of the heat and then deposits on the test tube wall. A black solid results from the chemical reac tion. When we remove the solid from the test tube (we may have to break the tube to get it out), we can pulverize the solid with a hammer that is. it is brittle. If we try to dissolve the material in carbon disulfide, it does not dissolve. If we bring the magnet close to it, it is not attracted. This material has its own set of prop erties: a dull black color, brittleness, insolubility in carbon disulfide, lack of attraction to a magnet. It is a compound a chemical combination of iron and sulfur. Snapshot Review - On tap nhanh *- Extensive properties depend on how much sample is present; intensive prop erties do not Intensive properties are useful for identifying substances. Each substance has its own characteristic set of properties. A Consider the statement: “There is 1 liter (L) of colorless soda in the can." Which of the two properties is intensive and which is extensive? B. A certain fam iliar substance freezes at 0°C. Does this property help identify the substance? • ('dc tinh chat bao quat phu thudc vdo so Itfong mdu (long cd; con cac tinh chat tang ctfdng thi khong. • Cac tinh chat tang ctfdng hi'tu dung trong viec nhdn biet cdc clidt. • Moi chat cd tap hop cdc dqc tinh cua rieng no. A. Khdo sat rnenh de "Co 1 lit (I) soda khdng mdu trong thung chtfa". Tinh chat nao trong hai tinh chat Id tinh chat tang ctfdng vd tinh chat nao la tinh chat bao quat? B. Mot chat quen thuoc dong dqc tai 0°C. Tinh chat nay cd giup nhdn biet chat do hay khdng? Chu thich to - cum to va hUdng dan dpc hieu heterogeneous m ixtures: hon hop di the homogeneous mixtures: lion hop dong the - physical properties: cac tinh chcit vdt ly - chemical properties: cdc tinh chat lioa hoc - extensive properties: cdc tinh chat long quat - intensive properties: cdc tinh chat tang ctfdng - q u a ntita tive properties: cdc tinh chat ve dinh luqng 13 - substances: cdc chat - solutions: cdc dung dich - m ixtures: cdc hon hop - malleable: cd the uon cong - properties: cdc tinh chat - dissolved: hda tan. phdn gidi Topic !: Basic concepts Tinh chat Moi chat cd moi so tinh chat xdc dinh. Tinh chat la cac dqc tinh ma chung ta cd the nhdn ra dtfqc. Vi du, chung ta biet ntfdc tinh khiet khdng co mdu, khdng rnui, khdng vi va d dang long trong dieu kien thtfdng (phdng). Ntfdc dap tdt Ida, no hda tan dtfdng va muoi. Ntfdc cd the chuyen doi thanh hoi (dtfqc goi la hoi ntfdc) khi cung cap nhiet, hay d dang rdn (da) khi lam lanh. Muoi cd tinh chat khac ntfdc, dtfdng cung cd tinh chat neng. Tinh chat hda hoc Id dac tinh ma mot chat cd the phdn ilng de tqo thanh san pham la mot chat khac. Tinh chat vat ly la cach ma mot chat cd the dtfqc nhdn ra ma khdng lam thay doi thanh phan dac trtfng cua no. Vi du, ntfdc cd the phan tfng vdi rat nhieu kim. loai hoqt dong de tqo thanh hydro vd hqp chat khac. Hoat tinh do la mot tinh chat lioa hoc cua ntfdc. Ntfdc cd the llidrih dd d 0"C (bang 32"F) hay no cd the bay hot thanh hoi ntfdc ma khdng lam thay doi thanh phan ntfdc. Day Id tinh chat vdt ly cua ntfdc. Mot so tinh chat cua mot mau cua mot chat phu thuoc vdo so Itfqrig mdu. Tinh chat nay dtfqc goi la tinh chat tong quat (chung). Vi du, trong Itfong cua mot mdu chat rdn phu thuoc vdo so Itfong chat hien dien. Tinh chat khac nhtf mdu, vi khdng phu thuoc vdo so Itfong chat hien dien. Nhilng tinh chat nay dtfqc xem nhtf 1a tinh clidt rieng Tinh chat rieng nay thi hQu ich cho viec nhan dang cdc chat. Mot so tinh chat tang ctfdng quan trong nhat md nhilng nha hda hoc stf dung de nhan biet cdc chat dd Id dac diem md ho do dtfqc; nhilng dqc diem nay dtfqc goi la cdc tinh chat dinh Itfong. Hai tinh chat nhtf the la diem dong dqc vd diem soi chuan cua mot chat, tile la nliiet do tai dd chat long dong dac de tqo thqnh mot chat rdn vd hda hoi de tqo nen mot chat khi trong cdc dieu kien dp suat binh thtfdng ttfong ling. Chung ta se thdo luan cdc tinh chat dinh Itfong chi tiet hon trong chtfong 2. Cd the phdn biet cdc hop chat vdi cac hon hqp do bdi cdc tinh chat dac trtfng cua hqp chat. Cdc hon hqp thi cd cdc tinh chat y het nhtf cdc tinh chat cua thtfc the tao nen chung. Thanh phdn dd dtfqc cho hien dien trong mot hon liqp cang nhieu thi tinh chat cua hon hqp dong nhat vdi thanh phdn dd cang nhieu. Vi du, cang cd nhieu dtfang trong mot ly ntfdc thi do ngot dtfqc tqo ra trong dung dich cang Idn. Mot thi nghiem minh hoa cdch md cdc tinh chat dtfqc dung de phdn biet giUa hop dial vd lion hop. Chung la dat cdc mdu bot sal nho vd sulfur bot Iren hai ly tdch roi nhau de ddnh gia dac tinh cua chung. Ltfu y rang cd liai deu d trang that rdn. Dat cdc mau trong cdc dug nghiem neng biet vd giU mot nam chain ben cqnh ong nghiem ihtf nliat Ta thay rang sal bi hut ve phia nam chain. Luc giQ nam chain cqnh ong nghiem cd clitfa sulfur thi khong cd dieu gi xay ra; nhtf vay sulfur khdng bi nam chain hut. Luc dd disulfide carbon, mot chat long de bat hia vd khong cd mau, vao mot mau sulfur thi sulfur dqc bien mat, vd chat long chuyen sang mdu vdng. Sulfur dd bi hoa tan tqo nen mot dung dich vdi disulfide carbon. Luc chung ta do disulfide carbon vao trong sal thi khdng cd dieu gi xay ra; sat van gal trang thai rdn vd chat long van giii trang thai khdng mdu. Neu ta cd cdc mieng Idn cua moi nguyen to thi ta cd the gia chung vdi mot biia ren vd thay rang sulfur cd tinh don vd de bieii thanh bot nhtfng sal thi khdng de dang bi ngdl thanh nhilng mieng nho. Sat cd tinh deo - cd nghia rang no cd the dtfqc gia de chuyen thanh cdc hinh dang khac nhau Hang 1.2 het ke cac dac tinh dtfqc de cap chuyen sdu hon ddnh cho hai nguyen to nay. Ke tiep chung ta do moi it bot sat vd mot it bot sulfur vdo mot ong nghiem Ion hon vd khudy deu cluing. Mdu xuat luen cd mdu vdng nhat, nhtfng neu quan sal k\ ta tha\ rang cd cdc quang vdng vd quang den. Neu giu mot nam chain ke ben mot ong nghiem. thi cdc hat den Ivoi moi so hat cang .rung quanh chung bi hut bdi nam chdm. Luc ta do 14 Topic 1: Basic coticepls disulfide carbon tren mau thi chat long chuyen sang mau vdng. Ia do ra ngoai chat long do va dtfa vao them disulfide carbon cho den khi khdng con chat ran mau vang nao gid lai trong mdu nda. Luc lam hda hai disulfide carbon trong mot ong nung, ta lai nhan duoc mot chat ran mau vdng. Neu dat mot nam chain ke ben vat lieu mdu den d ong nghiem Idn hon, ta thay rang no bi hut ve phia nam chain. Dieu do cd nghla rang hon hqp cua hai man nguyen to khong thay doi tinh chat. Sulfur van gilt mau vdng ra vat co the duac hda tan trong disulfide carbon; sat van gida mdu den va van mang tit tinh. Ilai nguyen to nay van gid dac tinh va nhdng dac trUng chuyen biet cua chung; chung van Id cdc nguyen to. To hop cua liai nguyen to nay la mot hon hop. Mot hon hop thi khdng cd mot hqp chat xdc dinh, no cd cdc dac tinh co lien quan den cdc dac tinh cua moi mot thanh phan. Bay gid chung ta dat hai mdu mdi duac do can than bot sat vd bot sulfur vdo mot ong nghiem Idn hon, nung ndng hon hqp vdi mot den Bunsen. Sau mot khoang thai gian, cd mot chat quang dd xuat hien d day cua ong nghiem vd dan dan Ian rong khap mdu. Day la chdng cd cua phdn ling hoa hoc. Mot so sulfur dd chuyen sang trang thai khi do bdi sdc ndng roi long dong tren tlianh cua ong nghiem Chat rdn mdu den hinh tlianh tit ket qua cua phan ling hda hoc. Luc chung ta loai bo chat rdn klioi ong nghiem (chung la pluii lain be ong nghiem de do no ra ngoai). Ta cd the go chat rdn ra bang cdch dung moi cai bua cd nglila rang tqo do gtdn cho no. Neu chung ta thd phdn gidi vdt chat trong moi disulfide carbon, thi no khong phdn giai duqc. Neu chung ta dua mot nam chain den, no van khdng bi hut. Vat lieu nay cd mot tap hqp cdc dac trUng chuyen biet cua no, mdu den dam, gion, khdng the hda tan trong disulfide carbon, khdng bi hut bdi moi nam chdm. Day la mot hon hqp - tdc la mot to' hqp hda hoc cua sat vd sulfua. Chu diem 1.3: Matter and Energy Matter is anything that has mass and occupies space All the material things in the universe are composed of matter, including anything you can touch as well as the planets in the solar system and all the stars in the sky. The mass of an object measures how much matter is in the object. Mass is directly proportional to weight at any given place in the universe. If you leave the surface of the Earth, your mass remains the same, but your weight changes An astronaut positioned between two celestial bodies such that their gravitational attractions pull equally in op posite directions is weightless, but the astronaut's mass remains the same as it was on Earth Because chem ists ordinarily do their work on the Earth s surface and because mass and weight are directly proportional here, many chemists use the terms mass and weight interchangeably, but you should remember that they differ. Energy is the capacity to do work. You cannot hold a sound or a beam of light in your hand; they are not forms of matter but forms of energy. The many forms of en ergy are outlined Energy cannot be created or destroyed, but it can be converted from one form to another This statement is known as the law of conservation of energy. Snapshot Review Matter has mass and occupies space. *- Mass is a measure of the quantity of matter in a sample (but energy also has a mass equivalent). A W hich has a greater mass a large wooden desk or a sewing needle? 15 Topic /; Ha sic concepts • Vat chat co khoi Itfong va chiem gn7 khoang trong trong khong gian • Khoi Itfong La mot so do ve dqi Itfong vat chat trong mot mdu Inhtfng nang Itfong cung co mot stf Itfong dtfong vdi khoi Itfong). A. Phdn nao co khoi Itfong Idn hon mot bdri go Idn hay mot cay kim may! Table 1.3 Forms of Energy Ile a l Chcm ical Nuclear Mechanical K inetic (energy of motion) Potential (energy o f position) K lectrical Sound Klectrom agnetic (lig h t) V isible lig h t U ltra v io le t X -rays Gamma rays Infrared Radio waves M icrowaves S olar” ‘ Solar energy is a combination of several form s of light Chu thich tQ - cum tCf va hUcrng dan dpc hieu m atter: vdt chat - energy: ndng Itfong mass: khoi luong - weight: trong Itfong - law o f conservation: dinh ludt bdo toan Vat chat va nang luong Vat chat la bat cd thd gi co khoi Itfong vd cliiem clw trong khdng gian Trong tat ca moi vdt trong vu tru la thanh phdn cua vdt chat, ke cd bat cd dieu gi ma ban cd the so md cling nhtf cdc hdnh tinh trong thai dtfong lie vd tat cd ngoi sao tren bdu trdi. Khoi Itfong cua mot vat do do Idn cua vdt chat. Khoi Itfong ty le thudn cat trong ItfOng o' tai bat cd noi nao trong vu tru. Neu ban dl chuyen be mat cun trdi dot. thi klioi Itfong cua no rdn gi/T khong doi. nhtfng trong htqng cua no thay doi Mot nha du lianli vu tru dung glda hai thien the sao cho sdc hut trong trtfong cua chung bang nhau to theo chieu doi ngliich tin ngtfdi nay a trang thai khong trong Itfong. tu\ nhien khoi hionii ciiu nha du hanh vu tru do rdn gu7 khong dol y het nhtf tren mat dot Hoi t i cac nha hoa hoc thtfc hien cdng viec cua lio mot cdcli binh thtfdng tren be mat trdi dat ca b j| 25 hour 7 dollars 1 hour= 175 d ollars Snapshot Review - On tap nhanh *- In the factor label method, units may be canceled like variables (.v, y) in alge bra. Placement of the units so that they cancel to give the desired units is the essence of the method. *■ Some factors are constant, such as the number of cents in a dollar; others are variable, such as the number of miles traveled by a car per hour, and these must be given in the statement of a problem. A. (a) Calculate the number of quarters in $15.50. (b) Calculate the value in dol lars of 217 quarters. • Trong phuang phdp he so ghi nhdn, cdc dan vi cd the duac khii vai nhau giong nhu cdc bien so (x,y) trong dai so. Viec sdp xep cdc dan vi sao cho khii duac vdi nhau de co duac cdc dan vi mong muon Id mot chinh yeu trong phuang phdp nay. • Mot so he so la hang so, vi du nhu so cent trong mot do la, mot so khdc la cd the thay doi, vi du nhu so d$m mot xe hai di duac tren gia va he so nhu vdy phdi duac cho trong phdn ddu de cua bdi todn. A. (a) Tinh so phdn tu do la trong 15,50 do la. (b) Tinh gid tri bdng do la cua 217 phdn tu do la. 37 topic 2: Measurement Chu thich ttf - cum ttf va hiicmg dan dpc hieu - inches: inch - feet: feet - hours: gtf), thai gian hour: gid - dollars: do la - factor label method: plii/ang phdp ghi chu thita so - conversion factor: thi/a so hien doi PhUdng phap he so ghi nhan Moi phep do deu cho ket qua la mot con so vd mot dan vi. Viec ghi dan vi cung quail trong nhu viec ghi con so. Vi du, se hodn todn khdc nhau khi noi rang rang con veil nuoi ciia ban cao 4 inche hay cao 4 feet.' Dan vi Id mot phdn nguyen cua bat ctf so do ndo, tit ban ddu, bail phdi lam quen vdi viec chi ro dan vi cho nidi dqi litang da ditqc vd cho moi dqi luqng tinli todn duqc tit cdc so lieu dd do. Luon ludn sit dung each ghi day du hoac nhilng chit viet tat tieu cliuan cho tat cd cdc dan vi. Trong rat nhieu trUdng hqp, ban co the sit dung cdc dan vi nliU mot ddu mdc de tlitfc luen phep tinh pliep nhdn hay phep chia trong nhilng tinh todn vdi cdc dqi Itfqng dd dtfqc do. Cdc dan vi ditqc do cd the dtfqc xem nhtf dqi Itfqng dqi so trong phep tinh toan Vi du. ban cd the tinh tong tien cong cua mot sinli vien tra giang kiem duac 7 do la tren gid sau 25 gid lam viec nhtf sau: Tong tien cong = (gid lam viecXdinh mite tien cong gid) 25 iioTfrs7 dollars 1 fMJifr 175 dollars Dan vi gid (h) trong tlidi gian khtf vdi dan vi gid trong dinh mite tien cong. de con Iqi dan vi do la trong Idi giai. Moi dan vi dtfqc xem xet nhu moi long the, khong ke dan vi dd bao gom bao nhieu cliil edi. Han nila, doi vdi cdc dan vi dtfqc kliit di, vi dan i i la so it hay so nhieu ciing khdng anh htfdng gi. Neu ta kliong biet chitang trinh de tinh tong tien cong, ta cd the ghi tlidi gian vdi dan vi gid vd nhdn vdi dinh mite tien cong, dinh mtfc ndy ciing co dan vi gid d moi so. Cdc dan vi cho ta biet rang chung ta phdi nhdn! Phep tinh vita rdi Id mot vi du cua viec sii’ dung phu'ting ph ap he so gh i nhdn trong do mot dqi Itfong dtfqc nhdn vdi mot he so bang vdi 1 Cdc dan vi co hen quan trong lie so Id nhilng nhdn . Trong vi du vita rdi. 7 dd ta titang ditang vdi mot gio 'Ay ra linli todn lam thay dot so gid dd him viec thanh so do la titang ditang !)■'’ sit dung phuang phap he so ghi nhdn. tritdc het ban phai ghi dai litang dd cho rdi nhdn i ai mot he so chuyen doi (mot dmh sudt liay mot ty sol phep nhdn nay se lam thus doi cac dan vi dd cho tlidnli rdi dan vi mong muon trong Idi gidi. lie si) cd the Id mot hd'ig so md ban dd biet hay mot gid tri dtfac cho trong bai todn cua ban De tom htqc cdc bitdc trong phtfang phdp he so ghi nhdn: 1. Ghi ra dqi litang dd cho (hay, doi khi khi la mot ty so can dtfac chuyen dot' 2. Nhdn dqi litang ndy vdi mot hay nlueu lie so • cdc dinh mtfc liay cdc ty so phep nhdn nay se thay doi cdc dan vi dd cho thanh cdc dan vi dd mong muon 38 Topic 2: Measurement trong Idi gidi. Cdc hi so chuyen doi co the duac cho trong cdc bdi todn, hay chung co th i la nhilng h&ng so gid tri dd biet. D i sic dung phuang phdp he so ghi nhdn mot cdch hieu qua, ban phdi biet cdc dan vi cua tdt cd cdc dqi luang liin quan. Nhilng sa do nhd cho thdy cdc dan vi ban ddu vd cdc dan vi sau cung duqc noi vai nhau bdng hi so chuyen doi duqc sit dung trong sdch ndy d i cho thdy cdch de bien doi mot dqi luqng til mdt dan vi ndy sang mot dan vi khdc. Vi du, de tinh tong tien cong cua sinh viin trq gidng, chung ta svC dung sa do sau day: 25 hour 7 dollars 1 hour= 175 dollars Nhitng sa do nhu vay se di kem vdi cdc Idi gidi trong cdc vi du trong bdi. Khi ban gidi cdc bdi tap thuc hdnh vd cdc bdi tdp a cuoi chuang, ban co ve rieng nhilng sa do cua minh. Chu diem 2.2: The Metric System The metric system and its more modern counterpart SI (for Systeme International d'Unites) are systems of units designed to make calculations as easy as possible. It was designed to make every word mean one and only one thing. Its subdivisions and multiples of units are powers of 10 times a primary unit. Each of its prefixes means the same thing, no matter what unit it is attached to. The abbreviations for the quanti ties and prefixes are easy to remember. All these features have been built into the metric system to make it easy. Learning the following six words is essential to understanding the metric system: 1. meter 4. centi 2. gram 5. milli 3. liter 6. kilo- (A few more words will be added as we progress.) Meter, gram, and liter are the units of length, mass, and volume, respectively, in the metric system. Just as the En glish system has subdivisions of its primary units (12 inches (in.) in a foot, for example), so does the metric system. But the metric system uses prefixes that mean the same thing no matter what primary unit they are used with. Centi-, milli-, and kilo- are pre fixes that indicate certain multiples or divisions of any primary unit. Other less impor tant prefixes are given along with these in Table 2.1. The m eter is the primary unit of length in the metric system. Its abbreviation is m. The meter is defined in such a way that it can be duplicated precisely in any well equipped laboratory in the world. It has been denned as the distance between two marks on a metal bar kept at the Bureau of Weights and Measures in Paris. (It now has an even more precise definition.) A meter is 39.37 in. Long 3.37 in. longer than a yard to give you an idea of its length. 39 Topic 2: Measurement Table 2.1 Metric Prefixes Prefix Abbreviation Meaning Giga- G One billion l ,000.000.000 Mega- M One m illion 1,000.000 Kilo- k One thousand 1000 Deci- d One-tenth 0.1 C enti- c One-hundredth 0.01 M ill i- m One-thousandth 0.001 Micro- V O ne-m illionth 0.000001 Nano- n O ne-billionth 0.000000001 Pico- P O ne-trillionth 0.000000000001 T he most im portant prefixes are given in boldfacc type. Table 2.2 Primary Metric Units U n it Symbol E q u iv a le n c ie s Distance M eter m Mass Gram g Volume L ite r L Volume Cubic meter m J 1000 L = 1 m Volume Cubic centim eter cm ' 1000 cm-' = 1 L Table 2.3 English-M etric Conversions L e n g th M ass V o lu m e 1 m = 39 37 in 1 kg = 2.2045 lb 1 L= 1.059 ()t 2.540 cm = t in 153.6 g = 1 lb (avoirdupois) 29 57 m l. = 1 fl oz 1.609 i 1 m ile 28.35 g = 1 oz (avoirdupois) 3.777 L = 1 US gal 31.103g = 1 oz(troy)* 0.472 L = 1 US pt 1 m etric ton = 2204.5 lb ght is generally used for gold and silver 40 Topic 2: Measurement A standard is an agreed upon quantity with which like quantities can be compared. For example, the meter is the agreed standard of length, to which other lengths can be compared. In the measurement of most quantities, the primary unit is also the standard. With mass, however, the standard is different from the unit. The gram is the primary unit of mass in the metric system. The gram, abbreviated g, is such a small mass that the kilogram has been chosen as the legal standard of mass in the United States and as the worldwide standard in SI. Mass is measured by comparison with standard masses. The kilogram (kg) is a mass equivalent to about 2.2 pounds (lb). The cubic m eter (m3) is the primary unit of volume in SI. A smaller unit, the li ter, is the primary unit of volume in the metric system. The abbreviation for liter is L. You need to know both the cubic meter and the liter. Table 2.2 summarizes the pri mary metric units of distance, mass, and volume. The prefix centi- means one-hundredth of any primary unit. For example, a centi meter (cm) is 0.01 m, and a centigram (eg) is 0.01 g. The prefix milli- means onethousandth. No matter which primary unit it is used with, it always means 0.001 times that unit. A millimeter (mm) is 0.001 m, a milliliter (mL) is 0.001 L, and so on. The prefix kilo- means 1000 times the primary unit, no matter which primary unit it is used with. For example, a kilogram (kg) is 1000 g, and a kilometer (km) is 1000 m. To convert a value expressed in a primary metric unit to its equivalent in a subunit, or vice versa, use a conversion factor with a 1 in front of the subunit and the equivalent value in front of the main unit. Note that you will have either the prefix abbreviation or its equivalent in front of the symbol for the primary unit: Prefix Equivalent value Kilo 1000 Centi 0.01 Milli 0.001 For example, either of the following conversion factors is correct: 1 centimeter) 0.01 meter J Thus, to convert 239 cm to meters: 239 cm ^ O .O lm ^ lc m To convert 4.91 m to centimeters: 0.01 meter 1 centimeter = 2.39 m ^ lcm ^ 4.91 m0.01 m= 491 cm Some conversions between English and metric system units are presented in Table 2.3. Engineers must know how to do such conversions because they still use some English system units. However, scientists rarely use English system units, and there fore, these conversions are less important for them. (The use of a metric unit that is becoming familiar to the general public is shown. Note that 80 km/h is about 50 mph.) 41 Topic 2: Measurement W hen we add or subtract m easured quantities, we treat the units just as we treat variables (such as x. y. and z) in algebraic m anipulations (see A ppendix 1) The units m ust be the sam e for the addition or subtraction of num bers that rep resent m easurem ents A sum or difference will have the same units as the quantities being added or subtracted Mass As stated earlier, the prim ary unit of mass in the metric system is the gram Be cause the gram is so small, however, the standard mass in SI and the legal standard in the United States is the kilogram. Volume Volum e can be measured in two ways (1) using the capacity of a certain con tainer, and (2) using the space defined by a cube of length/on each side The second method uses the cube of a length (and thus one possible unit for volum e is the cube of a length unit). The volume of a rectangular solid is given by Volum e = length x width x height V = I x w x h A cube is a special case for which I = w = h. so the volum e of a cube is V = P The metric system unit of volume is the liter (L), originally denned as the volume occupied by a cube exactly 10 cm on each side. In SI, the cubic m eter is the stan dard. Because the cubic m eter is a rather large volume (about half the capacity of a small cem ent truck), the liter is favored by chem ists 1.00 L = (10 cm )3 = 1000 cm 3 = 1000 mL Thus, 1,00cm 3 = I.OOmL Snapshot Review - On tap nhanh *- The metric system is easy because all the conversions are powers of 10 all the prefixes mean the same thing no matter what unit they are attached to. and all the sym bols are meaningful *■ English-m etric conversions are most often presented, if at all to give you an idea of the size of the metric unit They are not used intensively in this course *- Volume can be presented in liters (or its subdivisions) or in the cube of a unit of length (such as m ' or cm 3). The centi- in cm 3 does not m ean one-hundredth of 1 m3 because the 0 01 must be cubed A. Com plete each of the following parts by inserting the correct m etric unit (a) Volume of a can of soda 0.366 (b) Height of a professional basketball player 1 8 (c) Volume of water in a backyard swim m ing pool 2 (d) Mass of a U S quarter (25) 5.7 B, Calculate the num ber of (a) meters in 2217 mm (b) liters in 2217 mL and (c) grams in 221 7 mg C Calculate the num ber of (a) liters in 0 350 m3 and (b) liters in 275 cm 5 42 Topic 2: Measurement • H i met la d i sit dung vi tdt ca nhitng phep chuyin doi deu la luy thiCa cua 10, tdt cd cdc tiep ddu ngit co y nghla giong nhau khong ke la chung duac gdn vdo dan vi nao, vd tdt cd cdc ky hieu deu co y nghla. • Nhilng phep chuyin doi hi Anh - hi met thitong it duoc gidi thiiu, neu co thi cung chi de cho ban co mot y niem ve kich thuoc cua dan vi he met. Nhilng hiin tuong ndy khong duac sit dung nhieu trong giao trinh ndy. • The tich co the duoc biiu dien bdng lit (hay cdc don vi nho hon) hodc lap phuong cua mot don vi chieu dai (nhu m3 hay cm3). Chit centi- trong cm3 khong co nghla Id mot phdn trim cua mot met khoi, vi 0.01 phdi duoc lap phuong lin. A. Hodn chinh nhitng phdn sau day bdng cdch viit theo don vi met dung: (a) T h i tich cua mot Ion soda 0.366_______ (b) Chieu cao cua mot van dong viin bong ro chuyin nghiep 1 .8_______ (c) The tich nUdc trong ho bcri d sau nhd 2 _______ (d) Khdi luang cua mdt phdn tu do la (25c) 5.7_______ B. Hay tinh so (a) met trong 217 mm, (b) lit trong 2217 mL vd (c) gam trong 2117 mg. C. Hay tinh so (a) lit trong 0.350 m3 vd (b) lit trong 275 cm3. Chu thich tCf - cgm tCf va hiiamg dan dpc hieu - quantity: dai luang - given: duac cho - required: theo yeu cau - metric system: he met - SI: he SI - meter: met - standard: tieu chudn H$ met - meter: met - primary unit: don vi so cap - gram: gam - cubic meter: met khdi - liter: lit - centi: centi - milli: mili i/p m et vd phdn bo sung cua no mdi hon la he SI (viit tdt cho Systeme Interna tional d’Unites) la nhitng he don vi duac thiit k i d i lam cho viec tinh todn trd nin de ddng nhdt. No duac thiet ke sao cho mdi tic duac dung d i chi cho mot vd chi mot sit vat. Udc so vd boi so cua cdc don vi trong he ndy la 10 Idn hon hay nho hon dan vi so cap. Moi tiep ddu ngit cua he deu co ciing y nghla, khong k i la tiep ddu ngit duac gdn vdo vdo. Nhitng chit viet tdt cho dai luong vd cho tiep ddu ngit de nhd. Tdt cd nhitng ddc diem tren dd duac xdy dung trong he met de cho ngudi dung ngay nay duac de ddng. Viec hoc thuoc sau tit sau day la dieu thiet yeu d i hiiu duac he met: 1. met 4. centi 2. gram 5. milli 3. lit 6. kilo- (Mot so it tit khdc nda se duoc bo sung them trong qua trinh hoc.) Met, gram vd lit la nhitng don vj tuong itng cua chieu dai, khdi luong va th i tich trong he met. Cung giong nhu trong he Anh co cdc Udc so cua cdc don vi set cap vi du 12 inch (in) trong mot foot), he met cung cd nhitng udc so nhu vdy. Nhung he met sit dung cdc tiep ddu ngd de chi cung mot y nghla khong k i Id tiep ddu ngit ndy duac sit dung vdi don vi so cap nao. 43 Topic 2: Measurement centi-, milli- ua kilo- la nhilng tiep ddu ngU chi ra rang mot dan vi sa cap bat k\ ditac nlian len hay chia di bao nhieu lan. Nhilng hep dau ngU khac it quan trong hon ditac lie! ke vai nhilng tiep dau ngil nay trong bang 2. 1. M et Id dan vi cliieu dai sa cap trong lie met. No ditac viet tdt Id >n M et duac dinli nghla theo mot phitang thilc sao cho no cd the ditac sao chep Iqi mot cdch chinli xdc trong bat cur phong thi nglnein nao duac trang bi tdt tren the gnu Met duac dmh nghla nhd khodng cdch giila hai vach tren mot thanh kun loai duac gii7 a ran phong trong luang vd do litang d Paris. INgay nay met dd cd mot dmh nghla chinh xdc hail). De cho ban cd mot y niem ve dd dai ciia met. thi mdt met Id .'19.37 in. ddi hon mdt yard 3.37 in. Mot tieu cliudin Id mot quy Udc duac thou thudn ve mdt dai lining ma cac dai luang litang IU cd the ditqc so sanh vdi no. Vi du, met Id lieu chuan quy Udc cua chieu dai. cac dd dai khdc co the dilqc so sdnh vdi met. Trong viec do litang, phdn Ian cac dqi luang. dan vi sa cap cung Id lieu chuan. Tuy nhien, vdi khoi luqng, lieu chudin khdc i