EXERCISE / LATIHAN

HYDROCARBON / HIDROKARBON

1 The table below shows the formulae of three organic compounds.

Jadual berikut menunjukkan formula bagi tiga sebatian organik.

Organic compound / Sebatian organik P ^Q ^R

Formula / Formula C₄H₈ C₄H₉OH CH₃COOH

a. i. What is meant by unsaturated hydrocarbon? / Apakah yang dimaksudkan dengan hidrokarbon tak tepu?

Compounds that contain element carbon and hydrogen only with at least one double covalent bond between ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

carbon atoms

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

ii. Which of the organic compound in the table above is unsaturated hydrocarbon?

Antara sebatian organik dalam jadual di atas, yang manakah merupakan hidrokarbon tak tepu?

P // C4H8

b. i. State the homologous series for compounds P and Q. / Nyatakan siri homolog bagi sebatian P dan Q.

Compound P / Sebatian P: –––––––––––––––––––– Alkene Compound Q / Sebatian Q: –––––––––––––––––––– Alcohol c. Compound P can be produced from compound Q through a chemical reaction.

Sebatian P boleh dihasilkan daripada sebatian Q melalui suatu tindak balas kimia.

i. What is the name of the reaction? / Apakah nama bagi tindak balas tersebut?

Dehydration

ii. Write the chemical equation for the reaction. / Tuliskan persamaan kimia bagi tindak balas tersebut.

C₄H₉OH Porcelain chips

C₄H₈ + H₂O

iii. Draw the set-up of apparatus for the reaction in (c)(ii). / Lukiskan susunan alat radas bagi tindak balas di (c)(ii).

Glass wool soaked with ethanol

Porcelain chips

Heat

Gas

Water

d. Draw the structural formula for compound R, circle the functional group.

Lukiskan formula struktur bagi sebatian R, bulatkan kumpulan berfungsi.

H O

H C C OH

i. State the general formula for compound R. / Tuliskan formula am bagi sebatian R.

C_nH_{2n + 1} COOH

ii. Another compound, S, is in the same homologous series as R. S has five carbon atoms. Write the molecular formula for S. / Sebatian lain, S adalah dalam siri homolog yang sama dengan R. S mempunyai lima atom karbon.

Tuliskan formula molekul bagi S.

C₄H₉ COOH

e. i. What is meant by isomerism? / Apakah yang dimaksudkan dengan keisomeran?

Isomerism is the phenomenon where a compound has the same molecular formula but different structural ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

formulae.

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ii. Draw the structural formula for compound P. Name all the isomers using IUPAC nomenclature.

Lukiskan formula struktur bagi sebatian P. Namakan semua isomer menggunakan sistem penamaan IUPAC.

H H H H H H H H H

H C C C C H H C C C C H H C H

H H

H H H H

H C C C

H H

n-but-1-ene n-but-2-ene 2-metylprop-1-ene

f. When compound Q is added into a test tube containing acidified potassium dichromate(VI) solution and heated for a few minutes, a chemical reaction occurs. / Apabila sebatian Q ditambah ke dalam tabung uji yang mengandungi larutan kalium dikromat(VI) berasid dan dipanaskan untuk beberapa minit, tindak balas kimia berlaku.

i. Name the type of reaction that occurs. / Namakan jenis tindak balas yang berlaku.

Oxidation

ii. State one observation for this experiment. / Nyatakan satu pemerhatian dalam eksperimen ini.

The orange colour of acidified potassium dichromate(VI) solution turns green.

iii. Write a chemical equation for the reaction. / Tuliskan persamaan kimia bagi tindak balas ini.

C₄H₉OH + 2[O] C₃ H₇ COOH + H₂O

g. Compound Q undergoes complete combustion in excess oxygen. / Sebatian Q terbakar dengan lengkap dalam oksigen berlebihan.

i. Write chemical equation for the complete combustion of Q. / Tuliskan persamaan kimia bagi pembakaran lengkap Q.

C₄H₉OH + 6O₂ 4CO₂ + 5H₂O

ii. 7.4 g of compound undergoes complete combustion at room conditions. Calculate the volume of carbon dioxide gas released. [1 mol of gas occupies 24 dm³ at room conditions, Relative atomic mass: H, 1; C, 12]

7.4 g sebatian Q terbakar dengan lengkap pada suhu bilik. Hitung isi padu gas karbon dioksida yang terbebas. [1 mol gas memenuhi 24 dm³ pada suhu bilik, Jisim atom relatif: H, 1; C, 12]

Number of mol of C₄H₉OH = 7.4

74 = 0.1 mol

From the equation, 1 mol of C₄H₉OH : 4 mol of CO₂ 0.1 mol of C₄H₉OH : 0.4 mol of CO₂ Volume of CO₂ = 0.4 × 24 dm³ = 9.6 dm³

2 The diagram below shows series of reaction involving organic compound.

Rajah di bawah menunjukkan siri tindak balas yang melibatkan sebatian organik.

Heat gently with ethanoic acid and concentrated sulphuric acid Panaskan perlahan-lahan dengan asid ettanoik dan asid sulfurik pekat

Acidified potassium manganate(VII) solution Larutan kalium manganat(VII)

berasid

Y Propane

Propana I Propene

Propena II Propanol

Propanol III X

a. i. Name the reaction I. / Namakan tindak balas I.

Hydrogenation.

ii. State the conditions for the reaction I. / Nyatakan keadaan bagi tindak balas I.

Temperature 180°C in the presence of nickel/platinum as a catalyst.

b. i. Write the molecular formula for propane and propene. / Tuliskan formula molekul bagi propana dan propena.

Propane / Propana: ––––––––––––––––––––––––––C3H8 Propene / Propena: ––––––––––––––––––––––––––C3H6

ii. Combustion of propene produces more soot than propane. Explain why. [Given relative atomic mass: H; 1, C;

12]. Pembakaran propena menghasilkan lebih banyak jelaga berbanding propana. Terangkan mengapa. [Diberi jisim atom relatif: H; 1, C; 12]

Percentage of carbon by mass in propane = 12 × 3

12 × 3 + 8 × 1 × 100%

= 81.8 % Percentage of carbon by mass in propene = 12 × 3

12 × 3 + 6 × 1 × 100%

= 85.7 %

Percentage of carbon by mass in propene is higher than propane.

c. The table below shows the results of a test to differentiate between propane and propene.

Jadual di bawah menunjukkan keputusan suatu ujian untuk membezakan antara propana dengan propena.

Procedure / Kaedah Observation / Pemerhatian

Bromine water is added to propene.

Air bromin ditambah kepada propena. Brown colour is decolourised.

Warna perang luntur.

Bromine water is added to propane.

Air bromin ditambah kepada propana. Brown colour remains.

Warna perang tidak berubah.

Based on the table above, explain why there is a difference in these observations.

Berdasarkan jadual, terangkan mengapa terdapat perbezaan dalam pemerhatian.

Propene is an unsaturated hydrocarbon/has double bond between carbon atoms.

––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––

Addition reaction occurs.

C₃H₆ + Br₂ → C₃H₆ Br₂

Propane is a saturated hydrocarbon/has single bond between carbon atoms.

Addition reaction does not occur.

d. Compound X is produced when propanol heated gently in the reaction III. / Sebatian X terhasil apabila propanol dipanaskan dengan perlahan-lahan dalam tindak balas III.

i. What is the observation in process III? / Apakah pemerhatian dalam proses III?

The purple colour of acidified potassium manganate(VII) solution turns colourless.

ii. Name and write the chemical formula for compound X. / Namakan dan tuliskan formula kimia bagi sebatian X.

Name / Nama: –––––––––––––––––Propanoic acid Chemical formula / Formula kimia: –––––––––––––––––C2H₅COOH iii. Compound X can react with magnesium. Write the chemical equation for the reaction. / Sebatian X boleh bertindak

balas dengan magnesium. Tuliskan persamaan kimia bagi tindak balas tersebut.

2C₂H₅COOH + Mg → (C₂H₅COO)₂Mg + H₂

e. Propanol reacts with ethanoic acid through reaction IV to form compound Y.

Propanol bertindak balas dengan asid etanoik dalam tindak balas IV untuk membentuk sebatian Y.

i. Name compound Y. / Namakan sebatian Y.

Propil ethanoate.

ii. Draw the structural formula for Y. / Lukiskan formula struktur bagi Y.

H O H H H

H C C O C C C H

H H H H

iii. State one special characteristic of compound Y. / Nyatakan satu sifat istimewa sebatian Y.

Sweet smell

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3 The information below is regarding substance X. / Maklumat di bawah adalah mengenai bahan X.

Carbon /

• Karbon 85.70%

Hydrogen /

• Hidrogen 14.3%

Relative molecular mass /

• Jisim molekul relatif = 56

Determine the empirical formula and molecular formula of substance X. [Given that the relative atomic mass of C = 12 , H = 1] / Tentukan formula empirik dan formula molekul bagi bahan X. [Diberi jisim atom relatif bagi C = 12 , H = 1]

Element C H

Mass/g 85.70/12 14.30/1

Mol atom 7.14 14.3

Simplest Ratio 1 2

The empirical formula CH₂. (CH₂)n = 56

[12 + 2(1)]n = 56 n = 56/14 = 4 The molecular formula C₄H₈.

Fats / Lemak

1 Fats and oils are esters. / Lemak dan minyak adalah ester.

a. Fat is a natural ester found in animal and human tissue (solid at room temperature). / Lemak ialah ester semula jadi yang dijumpai dalam haiwan dan tisu manusia (pepejal pada suhu bilik).

b. Oil is a natural ester found in fish tissue and plants (liquid at room temperature). / Minyak ialah ester semula jadi yang dijumpai dalam tisu ikan dan tumbuh-tumbuhan (cecair pada suhu bilik).

c. Formed by esterification of alcohol glycerol (alcohol with 3–OH) with fatty acid. (organic acid with long carbon chain, C_nH_2n+1COOH, n is about 10 to 20). / Terbentuk melalui pengesteran alkohol gliserol (alkohol dengan 3–OH) dengan asid lemak (asid organik dengan rantai karbon yang panjang, C_nH_{2n + 1}COOH, n adalah di antara 10 hingga 20).

d. Esterification reaction between glycerol and fatty acid: / Tindak balas pengesteran antara gliserol dengan asid lemak:

⇒ Glycerol / ^Gliserol + Fatty acid / Asid lemak Oil or fat / Minyak atau lemak + Water / Air

H O H H

H C O H + H O C R H C O C R

O O + 3 H – O – H

H C O H + H O C R' H C O C R'

O O

H C O H + H O C R'' H C O C R''

H H

1 mol of glycerol 1 mol gliserol

3 mol of fatty acid 3 mol asid lemak

1 mol of fat/oil 1 mol lemak/minyak

3 mol of water 3 mol air

e. Fats are triesters (triglyceride). Lemak ialah triester (trigliserida).

2 The importance of oils and fats: / Kepentingan minyak dan lemak:

a. Fats and oils provide energy for our bodies. / Lemak dan minyak membekalkan tenaga untuk badan kita.

b. Build membrane cell and certain hormones. / Membina sel membran dan hormon-hormon tertentu.

c. Dissolve certain vitamins for absorption. / Melarutkan vitamin-vitamin tertentu untuk penyerapan.

3 Source of fats and oils: / Sumber lemak dan minyak:

a. Fats found in animals like cows and goats, are –––––––––– at room temperature. The example of animal fats are solid butter, cheese and etc. / Lemak dijumpai dalam haiwan seperti lembu dan kambing, adalah –––––––––pepejal pada suhu bilik.

Contoh lemak haiwan ialah mentega, keju dan lain-lain.

b. Fats from plants are –––––––––– at room temperature. They are called liquid ––––––––––. The example of oils are oils peanut oil, soybean oil and corn oil. / Lemak daripada tumbuh-tumbuhan adalah –––––––––cecair pada suhu bilik. Ia dipanggil

minyak

–––––––––. Contoh minyak ialah minyak kacang, minyak kacang soya dan minyak jagung.

4 Saturated and unsaturated fat / Lemak tepu dan lemak tak tepu

a. Fat and oil molecules are made up of two parts i.e derived from –––––––––– and glycerol ––––––––––. / fatty acid Molekul lemak dan minyak terdiri daripada dua bahagian iaitu diperoleh daripada –––––––––gliserol dan diperoleh daripada –––––––––asid lemak ^.

b. Saturated fats molecules are esters of saturated fatty acids. Saturated fatty acids contain –––––––––– carbon- single carbon (– C – C –) covalent bonds. / Molekul lemak tepu adalah ester bagi asid lemak tepu. Asid lemak tepu mengandungi ikatan kovalen karbon-karbon (–C–C–) –––––––––tunggal ^.

Example: / Contoh: Glyceryl tristearate / Gliseril tristearat

H O

H C O C (CH₂)₁₆ — CH₃ O

H C O C (CH₂)₁₆ — CH₃

H C O C (CH₂)₁₆ — CH₃ H

Derived from glycerol

Diperoleh daripada gliserol Derived from fatty acid (hydrogen chains contain single covalent bonds between carbon atoms)

Diperoleh daripada asid lemak (rantai karbon mengandungi ikatan kovalen tunggal antara atom karbon)

c. Unsaturated fat molecules are esters of unsaturated fatty acids that contain –––––––––– and single –––––––––– covalent double bonds between carbon atoms in their hydrocarbon chain. / Molekul lemak tak tepu ialah ester bagi asid lemak tak tepu yang mengandungi ikatan kovalen –––––––––tunggal ^atau–––––––––^{ganda dua} di antara atom-atom karbon dalam rantai hidrokarbonnya.

Example: / Contoh: Glycerol trilinolate / Gliseril trilinolat

H O

H C O C (CH₂)₇ — (CH₂)₇CH = CHCH₂CH = CH(CH₂)₄CH₃ O

H C O C (CH₂)₁₆ — (CH₂)₇CH = CHCH₂CH = CH(CH₂)₄CH₃

H Hydrocarbon chains contain double covalent bonds between carbon atoms Rantai hidrokarbon mengandungi ikatan kovalen ganda dua antara atom-atom karbon

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d. The fats and oils are mixture of saturated and unsaturated fats molecules:

Lemak dan minyak ialah campuran molekul lemak tepu dan tak tepu:

i. An oil or fat is classified as ––––––––––––––––– if it has more saturated –––––––––– fat molecules compared to saturated unsaturated

––––––––––––––––– fat molecules, for example animal fats. / Suatu minyak atau lemak dikelaskan sebagai –––––––tepu jika ia mengandungi lebih banyak molekul lemak –––––––––tepu berbanding molekul lemak –––––––––tak tepu , contohnya lemak haiwan.

ii. An oil or fat is classified as ––––––––––––––––– if it has more unsaturated ––––––––––––––––– fat molecules compared unsaturated to saturated fat molecules, for example vegetable oils except coconut oil.

Suatu minyak atau lemak dikelaskan sebagai –––––––––tak tepu jika ia mengandungi lebih banyak molekul lemak –––––––––tak tepu berbanding molekul lemak tepu, contohnya minyak sayuran kecuali minyak kelapa.

5 Converting unsaturated fats to saturated fats / Menukar lemak tak tepu kepada lemak tepu

a. The double covalent bonds between carbon atoms in ––––––––––––––––– fats are easily oxidised. When this unsaturated happens, the fat turns rancid. / Ikatan kovalen ganda dua di antara atom-atom karbon dalam lemak –––––––––tak tepu ^boleh teroksida dengan mudah. Apabila ini terjadi, lemak menjadi tengik.

b. Unsaturated fats can be converted to saturated fats through ––––––––––––––––– process such as in the manufacture hydrogenation of margarine. Catalyst used is nickel at 180ºC: / Lemak tak tepu boleh ditukarkan kepada lemak tepu melalui proses

penghidrogenan

–––––––––––––––––, contohnya dalam pembuatan marjerin. Mangkin yang digunakan ialah nikel pada 180°C:

H H

~ C C ~ + H₂ ^{Nickel /}_180ºC^nikel

H H

~ C C ~

H H

Unsaturated fat (liquid)

Lemak tak tepu (cecair) Saturated fat (solid)

Lemak tepu (pepejal)

c. Sources of unsaturated fats are palm oil, soybean oil and corn oil. / Sumber bagi lemak tak tepu ialah minyak sawit, minyak kacang soya dan minyak jagung.

6 The effect of fats on health / Kesan lemak ke atas kesihatan

a. There are two types of cholesterol, LDL cholesterol and HDL cholesterol: / Terdapat dua jenis kolestrol, kolestrol LDL dan kolestrol HDL:

i. LDL cholesterol causes –––––––––– deposits on the walls of veins or arteries which will lead to heart attack plaque and stroke. / Kolestrol LDL menyebabkan pengenapan –––––––––plak pada dinding salur darah vena atau arteri yang boleh menyebabkan sakit jantung dan angin ahmar.

ii. HDL cholesterol –––––––––– deposits on the artery walls. / reduces Kolestrol HDL –––––––––––––––––mengurangkan pengenapan pada dinding arteri.

b. –––––––– fats (saturated fats) contain higher LDL cholesterol whereas Animal –––––––––– oils (unsaturated fats) contain vegetable higher HDL cholesterol. / Lemak –––––––––haiwan (lemak tepu) mengandungi kolestrol LDL yang lebih banyak manakala minyak –––––––––sayuran (lemak tak tepu) mengandungi lebih banyak kolestrol HDL.

c. Eating food high in animal fats increases the level of ––––––– in blood.LDL

Memakan makanan yang tinggi dengan lemak haiwan akan meningkatkan kandungan –––––––LDL dalam darah.

7 Palm oil / Minyak sawit

a. Palm oil is extracted from fresh oil palm fruits. / Minyak sawit diekstrak daripada buah sawit yang segar.

b Palm oil contains 49% of saturated fats and 51% of unsaturated fats. It is classified as –––––––––––– fat. / unsaturated ^Minyak sawit mengandungi 49% lemak tepu dan 51% lemak tak tepu. Ia dikelaskan sebagai lemak –––––––––tak tepu ^.

c. Palm oil is used in cooking and manufacture margarine and shortening, chocolate, cakes, ice creams and noodles.

Minyak sawit digunakan untuk memasak dan membuat marjerin dan coklat, kek, aiskrim dan mee.

d. The advantages of palm oil compared to other oil are: / Kelebihan minyak sawit berbanding minyak lain adalah:

i. rich in vitamin E which is a powerful antioxidant. / kaya dengan vitamin E yang merupakan antioksidan yang kuat.

ii. rich in beta-carotene which contains vitamin A. Vitamin A helps to strengthen the immune system.

kaya dengan beta-carotene yang mengandungi vitamin A. Vitamin A membantu menguatkan sistem imuniti.

iii. it is cholesterol free. / tiada kolestrol.

Natural Rubber /Getah Asli

1 Natural polymers are polymers that exist in nature and are not man-made.

Polimer semula jadi ialah polimer yang wujud secara semula jadi dan bukannya buatan manusia.

Example: / Contoh:

Natural polymer / Polimer semula jadi Monomer / Monomer Protein / Protein Amino acid / Asid amino Cabohydrate / Karbohidrat Glucose / Glukosa Natural rubber / Getah semula jadi Isoprene / Isoprena 2 The structure of rubber / Struktur getah

a. Rubber is a natural polymer. It is formed from the monomer ––––––––––. Molecular formula of isoprene –––––––––– is isoprene C₅H₈. / Getah ialah polimer asli. Ia terbentuk daripada monomer –––––––––isoprena . Formula molekul –––––––––isoprena ^{ialah C}⁵^H⁸^. b. Isoprene molecules are joined together by addition ––––––––––––––––– process to form the polymer of natural polymerisation

rubber, polyisoprene: / Molekul isoprena terikat bersama oleh proses –––––––––––––––––pempolimeran penambahan untuk membentuk polimer getah semula jadi, poliisoprena:

H H CH₃ H

n ( C C C C )

H H

H H CH₃ H

( C C C C )

H H

n n is large numbers n ialah nombor yang besar

Isoprene (2-methylbut-1, 3-diene)

Isoprena (2-metilbut-1, 3-diena) Polyisoprene Polimer getah 3 Coagulation of latex / Penggumpalan lateks

a. Latex is milk like liquid obtained from tapped rubber tree. Latex is a –––––––––– which contains suspension of colloid rubber particles in water. / Lateks ialah cecair seperti susu yang diperoleh daripada pokok getah yang ditoreh. Lateks ialah

koloid

––––––––– yang mengandungi zarah-zarah getah yang tersebar dalam air.

b. The rubber particles are made up of long chain rubber polymers [(C₅H₈)_n] surrounded by a protein membrane

––––––––––––––––– . The ––––––––––––––––– is protein membrane –––––––––– charged. The forces of repulsion between negatively negatively charged particles prevent them from combining or coagulating. / Zarah-zarah getah terdiri daripada polimer getah berantai panjang [(C₅H₈)_n] yang dikelilingi –––––––––––––––––membran protein ^.–––––––––––––––––Membran protein adalah bercas –––––––––negatif ^. Daya tolakan di antara zarah-zarah bercas negatif menghalang zarah-zarah tersebut daripada bergabung atau bergumpal.

Negative charge Rubber polymer

Water Bercas negatif Polimer getah

Air Repulsion

Tolakan

c. Latex coagulates when: / Lateks tergumpal apabila:

i. acid is added to it such as methanoic acid (formic acid), ethanoic acid (acetic acid) or any other weak acids.

asid seperti asid metanoik (asid formik), asid etanoik (asid asetik) atau asid lemah lain ditambah ke dalamnya.

ii. Left aside for 1 – 2 days due to bacterial action on latex. Bacteria from the air enter latex. Activity of bacteria in the latex produce ––––––––––––––––– that contains lactic acid ––––––––––––––––– which causes coagulation of latex. hydrogen ions (H⁺) Coagulate latex is semi solid. / Dibiarkan selama 1 – 2 hari untuk tindakan bakteria ke atas lateks. Bakteria dari udara masuk ke dalam lateks. Aktiviti bakteria di dalam lateks menghasilkan –––––––acid yang mengandungi –––––––––––––––––ion hidrogen (H⁺) yang menyebabkan penggumpalan lateks. Menggumpal lateks adalah separa pepejal.

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d. When acid is added to latex, coagulation of latex occurs:

Apabila asid ditambah kepada lateks, penggumpalan lateks berlaku:

i. Positively charged hydrogen ions from the acid –––––––––– the negative charges on the surface of the protein neutralises membrane. A neutral rubber –––––––––– is formed. / particle Ion hidrogen bercas positif daripada asid –––––––––––––meneutralkan cas-cas negatif pada permukaan membran protein. –––––––––Zarah getah yang neutral terbentuk.

Collide Perlanggaran

Breaking of protein membrane Neutralised rubber particle

Membran protein pecah Zarah getah yang neutral

H⁺H⁺ H⁺H⁺ H⁺

H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺

H⁺ H⁺H⁺ H⁺H⁺

H⁺ H⁺

H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺ H⁺

Repulsion Tolakan

ii. The –––––––––– particles no longer neutral –––––––––– each other. These repel –––––––––– particles neutral –––––––––– with collide each other, causing the membrane to ––––––––––. The rubber polymers are freed and they break –––––––––– by coagulate combining together to form large lump of rubber polymer. The latex has coagulated.

Zarah-zarah –––––––––neutral tidak lagi –––––––––menolak di antara satu sama lain. Zarah-zarah –––––––––neutral ⁱⁿⁱ–––––––––^berlanggar ^di antara satu sama lain, menyebabkan membran –––––––––pecah . Polimer getah terbebas dan –––––––––bergumpal dengan bergabung untuk membentuk gumpalan getah yang besar. Lateks telah tergumpal.

Broken protein membrane Rubber polymers coagulate Membran protein pecah Polimer getah menggumpal

4 Coagulation of latex can be prevented by adding ––––––––––––––––– to it. The ammonia solution ammonia (alkali) (containing OH^– ions) will neutralise any acids that may be produced by the bacteria. / Penggumpalan lateks boleh dihalang dengan menambah –––––––––––––––––ammonia (alkali) kepadanya. Larutan ammonia (mengandungi ion OH^–) akan meneutralkan sebarang asid yang dihasilkan oleh bakteria.

5 Describe how the presence of an alkali can prevent the coagulation process of latex: / Huraikan bagaimana alkali boleh menghalang proses penggumpalan lateks:

a. Hydroxide ions, OH^– from alkali –––––––––– hydrogen ions, Hneutralise ⁺ produced by –––––––––– as a result of bacterial acid attack on protein. / Ion hidroksida, OH^– daripada alkali –––––––––––––meneutralkan ion hidrogen, H⁺ yang dihasilkan oleh –––––––acid disebabkan serangan bakteria ke atas protein.

b. The protein membrane remains –––––––––– charge because there is no hydrogen ions. / negatively Membran protein kekal bercas –––––––negatif kerana tiada ion-ion hidrogen.

c. The rubber particles –––––––––– each other. / repel Zarah-zarah getah –––––––menolak di antara satu sama lain.

d. The rubber polymers cannot combine and –––––––––––––––– . / coagulate Polimer-polimer getah tidak boleh bergabung dan menggumpal

––––––––––––––^.

6 Properties and uses of natural rubber / Sifat-sifat dan kegunaan getah asli a. Properties of natural rubber / Sifat-sifat getah asli

Property

Sifat Description / Penerangan Uses / Kegunaan

Elastic Kekenyalan

When it is ––––––––––, it straighten out. It stretched –––––––––– back to returns its original shape once the –––––––––– force is released. / stretching ^Apabila diregangkan

–––––––––, ia menjadi lurus. Ia –––––––––kembali kepada bentuk asal apabila daya –––––––––regangan dilepaskan.

Rubber tube, gloves, rubber bands and shoe soles. / Tiub getah, sarung tangan, getah pengikat dan tapak kasut.

The natural rubber polymers are easily –––––––––– due to the oxidised presence of double bonds. / Polimer getah asli –––––––––teroksida ^dengan mudah kerana kehadiran ikatan ganda dua.

These properties make the usage of natural rubber limited. / Sifat-sifat ini menjadikan kegunaan getah asli terhad.

Effect of heat Kesan haba

When it is heated, it is –––––––––– and become soften ––––––––––.sticky Apabila dipanaskan, getah menjadi –––––––lembut dan menjadi –––––––––melekit ^. When it is cooled, it becomes –––––––––– and hard ––––––––––. brittle Apabila disejukkan, ia menjadi –––––––––keras ^dan–––––––––^rapuh ^. Effect of

solvent Kesan pelarut

Natural rubber is –––––––––– in organic, alkaline and acidic soluble solution.

Getah asli –––––––––larut dalam larutan organik, beralkali dan berasid.

b. The properties of natural rubber can be improved through the vulcanisation process. / Sifat-sifat getah asli boleh diperbaiki melalui proses pemvulkanan.

7 Vulcanisation of rubber: / Pemvulkanan getah:

a. Natural rubber is elastic (it will return to its original shape after stretching force is released). / Getah asli adalah kenyal (ia akan kembali kepada bentuk asal apabila daya regangan dilepaskan).

b. When the rubber is over stretched, the rubber molecules do not return to their original positions. The rubber has lost its elasticity. / Apabila getah diregang secara berlebihan, molekul getah tidak kembali kepada kedudukan asal. Getah telah hilang sifat kekenyalannya.

c. Natural rubber becomes stronger and more elastic after vulcanisation:

Getah asli menjadi lebih kuat dan kenyal selepas pemvulkanan:

In document 4_Chemistry FORM 5 (Page 85-95)