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Physical SciencesChemistry Grade 12

Textbook and Workbook

Santie du Plessis • Carlien FanoyAnnalize Ferreira • Lettie Fischer

Patricia Lees-Rolfe • Judy McDougallJanetta Nel • Karen Reyneke

Pieter van der MerweSample

Doc ScientiaPosbus 7011

Ansfrere 1711

www.docscientia.co.za

For any queries and feedback: [email protected]

Jacques Fanoy or Stephan FanoyOffice: 011 472 8728

Fax: 086 546 1423

ISBN: 978-1-920537-21-0

First edition December 2009Second edition December 2010

Revised edition December 2011; 2012Third edition December 2013

Revised edition December 2014; 2015; 2016

Graphic design: Helene Jonck

All rights reserved. No part of this publication may be reproduced in any form or by any means –

mechanical or electronic, including recordings or tape recordings and photocopying – without the prior permission of the publisher.

Sample

Dear Grade 12 learner

To study Physical Sciences is challenging and hard work. The rewards are excitement, new discoveries and creative thoughts.

The knowledge you have gained each year has been building blocks in a greater picture. If there are any blocks missing, the picture does not make sense. Therefore, we must be aware of the fact that all the blocks have to be taken with us from one year to the following. It is a good idea to always have your Grade 10 and 11 Workbooks close by for reference.

You need the following skills:• Common sense There is a lot of logic in science, because it deals with everyday happenings, like cars that crash, rugby balls being kicked and so much more.• Calculator skills Be sure you know how to use your calculator.• Know your formula page. Know what each symbol stands for and in which unit each amount is measured.• Reading skills A lot of information will come to you in the form of words. Learn to read with insight and use a highlighter to emphasize the facts you will need, or draw circles around it. • Draw pictures. There is nothing that helps you think as logically as pictures.• Practise, practise, practise. It still is the best method of learning something. It means that you always have to do your own homework. Work through old exam papers and our Exercise book; it provides valuable experience.

The short explanations, examples, summaries, mind maps and exercises will help you gain the necessary knowledge to master Physical Sciences.

Use the QR codes to understand some of the terms better.

We trust it will be a successful year filled with excitement and achievements.

Doc Scientia

Sample

INDEXUnit Page

KNOWLEDGE AREA MATTER AND MATERIALS 15

Unit 1 ORGANIC MOLECULES 15

1.1 Organic compounds 16

1.2 Structure of organic molecules 17

Experiment 1 23

Experiment 2 25

1.3 Isomers 29

Exercise 1 30

1.4 Naming organic structures 35

1.4.1 Alkanes 37

1.4.2 Cycloalkanes 38

Exercise 2 39

1.4.3 Alkenes 44

1.4.4 Cycloalkenes 44

1.4.5 Dienes 45

Exercise 3 46

1.4.6 Alkynes 50

1.4.7 Alkyl halides (haloalkanes) 50

Exercise 4 52

1.4.8 Alcohols 55

1.4.9 Aldehydes 57

1.4.10 Ketones 58

Exercise 5 59

1.4.11 Carboxylic acids 62

1.4.12 Esters 63

Activity 1 64

Exercise 6 64

1.5 Structural relationships and physical properties 66

1.5.1 Boiling points 69

1.5.2 Melting points 73

1.5.3 Vapour pressure 76

1.5.4 Physical state (gases (g), liquids (ℓ) and solids (s)) 79

1.5.5 Density 82

1.5.6 Flammability 85

1.5.7 Odour 85

1.5.8 Molecular shape 86

Exercise 7 88

1.6 Application of organic chemistry 97

1.6.1 Combustion 97

1.6.2 Preparation of esters 98

Experiment 3 99

Exercise 8 102

1.7 Reactions 107

1.7.1 Substitution reactions 107

1.7.1.1 Substitution in alkanes 107

1.7.1.2 Substitution in alcohols 108

1.7.1.3 Substitution in haloalkanes (alkyl halides) 109

Sample

1.7.2 Addition reactions 110

1.7.2.1 Hydrohalogenation 111

1.7.2.2 Halogenation 112

1.7.2.3 Hydration 112

1.7.2.4 Hydrogenation 113

Experiment 4 (demonstration) 114

1.7.3 Applications of addition reactions 117

1.7.4 Elimination 118

1.7.4.1 Dehydrohalogenation 118

1.7.4.2 Dehydration 120

1.7.4.3 Cracking 121

Exercise 9 122

Summary of Unit 1 133

Mind maps of Unit 1 142

Unit 2 PLASTICS AND FIBRES 149

2.1 What is a polymer? 150

2.2 Plastics 151

2.2.1 Addition reactions 151

Experiment 5 152

2.2.2 Properties and uses 155

Activity 2 157

Activity 3 158

2.3 Fibres 159

2.3.1 Condensation polymerisation 159

2.3.1.1 Nylon 159

2.3.1.2 Polyesters 160

2.3.1.3 Polylactic acid (PLA) 161

Experiment 6 163

Experiment 7 164

Experiment 8 165

Experiment 9 167

2.4 Identify 169

2.4.1 Monomer 169

2.4.2 Reaction 170

2.5 Recycling 172

Activity 4 173

Exercise 10 173



Question paper 185

KNOWLEDGE AREA CHEMICAL CHANGE 201

Unit 1 RATE OF REACTIONS 201

1.1 What is reaction rate? 202

1.2 What is required for reactions to occur? 203

1.3 Factors that influence reaction rate 204

1.3.1 Nature of reactants 205

1.3.2 Concentration 205

Experiment 10 206

1.3.3 State of division (reaction surface) 209

Experiment 11 209

Sample

1.3.4 Temperature 211

Experiment 12 212

1.3.5 Catalyst 214

Experiment 13 215

Exercise 11 217

1.4 Graphic presentation 222

1.5 Experimental determination 224

1.5.1 Colour change 224

1.5.2 Volume and mass changes 224

1.5.3 Temperature change 225

1.5.4 Change in pH 225

1.5.5 Turbidity 225

Experiment 14 225

Experiment 15 230

Experiment 16 232

Experiment 17 235

Exercise 12 237

1.6 Reaction mechanisms 242

1.6.1 Activation energy 242

1.6.2 Activated complex 243

1.6.3 Energy changes during chemical reactions 243

Exercise 13 245

1.7 Maxwell-Boltzmann distribution 247

1.7.1 Effect of temperature change 248

1.7.2 Effect of concentration 248

1.7.3 Effect of a catalyst 249

Exercise 14 251



Unit 2 EQUILIBRIUM AND CHEMICAL REACTIONS 259

2.1 Open, closed and isolated systems 260

2.2 Reversible changes 261

2.2.1 Physical changes 261

2.2.2 Chemical reactions 262

2.3 Conditions of equilibrium 265

2.4 Catalyst 265

2.5 The equilibrium constant 266

Exercise 15 268

2.6 Irreversible chemical reactions 272

2.7 Calculation of equilibrium concentrations 273

Exercise 16 276

2.8 Dynamic chemical equilibrium system 286

2.8.1 Le Chatelier’s principle 286

2.8.2 Dynamic chemical equilibrium in solutions 290

Experiment 18 292

Experiment 19 292

Exercise 17 298

2.9 Equilibrium and reaction rate graphs 305

2.9.1 Equilibrium in an isolated system 305

2.9.2 Reactants change 305

Sample

2.9.3 Products change 306

2.9.4 Temperature change 307

2.9.5 Pressure change 308

2.9.6 Catalyst 310

Exercise 18 311

2.10 Equilibrium in industrial chemical processes 319

2.10.1 Haber process 319

2.10.2 Contact process 320

Exercise 19 321



Unit 3 ACIDS AND BASES 329

3.1 Properties 330

3.1.1 Acids 330

3.1.2 Bases 331

Activity 5 332

3.2 Acid-base theory 332

3.2.1 Arrhenius 332

3.2.2 Brønsted-Lowry 333

3.3 Monoprotic and polyprotic acids 334

Experiment 20 335

3.4 Acid-base reactions 337

3.4.1 Conjugate bases 337

3.4.2 Conjugate acids 337

3.4.3 Conjugate acid-base pairs 337

Exercise 20 340

3.4.4 Ampholytes 342

3.5 Strong and weak acids and bases 343

3.5.1 Acids 343

3.5.2 Bases 344

3.6 Hydrolysis 345

Exercise 21 348

3.7 Reactions of acids 350

3.7.1 Acid-metal reactions 350

3.7.2 Acid-metal oxide reactions 350

3.7.3 Acid-metal hydroxide reactions 350

3.7.4 Acid-metal carbonate reactions 350

3.8 Neutralisation reaction between acids and bases 351

Experiment 21 352

Experiment 22 354

Experiment 23 356

Experiment 24 358

3.9 Indicators 361

Exercise 22 362

3.10 Solutions 365

3.10.1 Calculations 365

3.10.2 Preparation of a standard solution 368

Experiment 25 368

3.10.3 Dilution 371

Exercise 23 373

Sample

KNOWLEDGE AREA:MATTER AND MATERIALS

Doc Scientia CHEMISTRY textbook and workbook - Grade 12 149

UNIT 2 PLASTICS AND FIBRES

Nylon

Polyesters

Polylactic acid (PLA)

We are surrounded by polymers. There are natural polymers like wood, wool, cellulose, starch, sugars, proteins, DNA and RNA, to name a few.Synthetic polymers are divided into plastics and fibres, depending on the process used. Plastics are flexible and can be shaped. Fibres are long thin strings from which textiles for clothes, curtains and upholstery are made.

Synthetic polymers have so many uses and applications that we cannot live without it anymore.

Examples of the uses of synthetic polymers:Agriculture: FertiliserMedicine: Various biomaterials are used for, amongst others, synthetic heart valves.Consumer science: Plastic containers, bags, packaging material, floor coverings, textiles and clothesIndustries: Car parts, windshields, pipes, insulation material, packaging, containersSport: Equipment, various balls, synthetic tracks, swimming pools, head gear

Plastics and fibres

What is a polymer?

Plastics

Fibres

Identify

Recycling

Addition polymerisation

Uses

Condensation polymerisation

Monomer

Reaction

Synthetic

Polymers

Natural

Examples: wool, wood, starch, proteins

Plastics FibresSample

matter and materials

150 Doc Scientia CHEMISTRY textbook and workbook - Grade 12

2.1 What is a polymer?

Polymers are large molecules (macromolecules) that consist of many small molecules which repeat to form a long chain.These small molecules are called monomers and usually have double bonds. Alkenes are therefore often used as monomers. Various ethene molecules are attached to each other to form a chain. The length of this chain varies, depending on the number of molecules being joined.

Polymers are macromolecules with large molecular masses.It can consist of tens or hundreds or even more monomers (simple building block of molecules) which are connected to each other.

Different products are formed, depending on:• the monomers used,• the functional groups it contains,• the way it is connected to each other.

This way, chloroethene as a monomer will form the product PVC.

There are two types of synthetic polymers.

Interesting factsOnly carbon atoms have the ability to form long chains. Therefore, macromolecules are organic compounds (carbon compounds).

With the study and investigation of addition polymers, the focus will be on polythene only. Polythene is also known as polyethylene.

C CC C CC CC C C

H HH H HH HH H H

R

H HH H HH HH H H

R

C C C CC C C C

H H H HH H H H

Cℓ Cℓ Cℓ CℓH H H H

vinyl monomer

Plastics Fibre

Synthetic polymers

Addition CondensationSample



2.2 Plastics

Alkenes are usually used for the addition polymerisation. Addition means that double bonds break and molecules are added together.

The alkenes come from the cracking of long chain hydrocarbons of crude oil which is a limited, non-renewable resource.When crude oil is divided by fractional distillation, some of the substances, e.g. ethene, can be used as monomers.

2.2.1 Addition reactions

The same type of monomer is repeated.

n(CH2=CH2) → (–CH2–CH2–)n

Reaction conditions: High pressure Fairly high temperatureInitiator: Small quantity of organic peroxide, e.g. benzoyl peroxide

To explain the reaction:To start the reaction, there must be a substance that causes polymerisation to start. It is called the initiator. It is a very reactive substance with a free radical.

Quick factsPolyethene is called polythene or polyethylene.

Quick factsA free radical is an atom, molecule or ion that has unpaired valence electrons or an open electron shell. It can be seen as a “hanging” or incomplete covalent bond.

To stop the reaction, a terminator (inhibitor), which is an inactive radical, is connected to the end of the chain.

}

small quantity acid

C C C C C C+ + + +C C

HH H H H H H

H H H H H H

H

HH

C C CC C

H H

HH

C C

H H H H H

H H H HH

Double bonds break and form free radicals.

Polymer forms.Sa

mple



Experiment 5 Date:Aim: To prepare a polymer from an addition reaction.

Investigative question:

_________________________________________________________________________________

Hypothesis:

_________________________________________________________________________________

_________________________________________________________________________________

Variables:

Independent variable(Which is changed.)

Dependent variable(Which is measured.)

Controlled variable(s)(Which remain(s) the same.)

Apparatus: • Gloves and safety goggles • Glass tube pushed into a rubber stopper with one hole – 20 cm in length.• Test tube – 15 cm long and 2,5 cm in diameter• 250 cm3 glass beaker• 100 cm3 glass beaker• Retort stand with a clamp• Glass rod to stir.• Filter paper• Electric plate – if a bunsen burner is used, the chemicals must be kept far away from the flame.

Chemicals:• Phenylethene or styrene • Di(dodecanyol) peroxide (lauroyl peroxide)• Ethanol• Propanone for washing.• NaOH – 1 M solution• Anhydrous Na2SO4

C

C

C

C

H C

C

C

C

C

C

C

C C

C

C

C

C

C

C

C

C

C

H

H

H

H

H

H

H

H

H

H

H

H H

H

H

H

H

H

H

H

H

O O C

O

H

H

H

H

H

H

H

H

OH

H

H

H

H

H

H

H

H

H

H

H H

HSample



Safety measures:• Phenylethene is harmful, flammable and can cause deafness. Ventilate the room!• The peroxide is irritating and oxidising.• Ethanol is highly flammable.• This experiment must be done in a well-ventilated room.• Wear safety goggles.• If a bunsen burner is used, the other chemicals must be kept far away from the

flame.Note:It could be necessary to treat the phenylethene beforehand. For this, chemical-resistant gloves should be worn.Most phenylethene samples contain an inhibitor, which must be removed before the experiment can be conducted.Use a separating funnel for the following:Wash (mix and shake) the phenylethene with 1 M sodium hydroxide solution, NaOH (aq), in a separating funnel. Separate the mixture.Wash (mix and shake) it thereafter with water. Separate the mixture.Dry the phenylethene over anhydrous Na2SO4(s) for 10 minutes.All apparatus used must be rinsed with propanone as soon as possible.

Method:1. Pour boiling water into a 250 cm3 glass beaker, which must serve as the water bath.2. Place it on an electric plate so the water keeps boiling.3. Add 0,1 g didodecanyol peroxide to 5 cm3 phenylethene in a test tube.4. Place the rubber stopper with the glass tube in it onto the test tube. It serves as a reflux tube and allows the fumes to condensate in it, and flow back into the test tube.5. Set up the apparatus as shown in the sketch.6. Heat for approximately 30 minutes until the liquid becomes jelly-like. Switch the plate off or extinguish the flame and remove the test tube from the water bath.7. Allow the contents of the test tube to cool down.8. Add the contents of the test tube to 50 cm3 of ethanol, which is in a glass beaker. Remember the ethanol is highly flammable.9. Use a glass rod to press the polyphenylethene together, which is starting to set, and stir until a ball forms. Pour out the ethanol.10. Dry the polymer, which is now a solid, on filter paper.

Observations:

_________________________________________________________________________________

_________________________________________________________________________________

Quick factsRemember NaOH is corossive.

clamp

boiling tube

water bath

didodecanol peroxide and phenyletheneSa

mple



Quick factsWith addition polymerisation, no molecules are separated from the original molecule.

Results:Answer the following questions:1. Why are safety measures necessary?

____________________________________________________________________________

2. What process took place when the phenylethene and the peroxide were heated?

____________________________________________________________________________

3. Give the chemical equation for the reaction that takes place.

4. What is the common name of the product that formed?

____________________________________________________________________________

5. Name five items that can be manufactured using the product.

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

Conclusions:

_________________________________________________________________________________

_________________________________________________________________________________Sample



2.2.2 Properties and uses

Polythene has various properties that make it useful:• It is strong and light.• Durable• It can be manufactured in any colour.• Easily shaped.• Hardness and flexibility can be manipulated by adding different elements during the manufacturing process.• It is an electric insulator.• It is not affected by weather and does not rust.• Versatile• Hygienic and therefore safe to use as food packaging.

Depending on the pressure and temperature that are used, different types of plastic are produced from polythene. If the length of the carbon chain changes, the strength of the plastic will also change.Different plastics are used for the production of a wide variety of products.

Polythene will form the following polymers at different temperatures and pressures if ethene molecules bond during an addition chain reaction.

Temperatures and pressure

Hard or soft plastic Uses

200°C and 1 200 atmosphere

Soft plasticLDPE (low density polyethene)

Freezing bags; squeeze bottles for syrup, tomato sauce, etc., flexible lids for containers; cables

50°C and 1 – 25 atmosphere and a catalyst

Hard and more dense plasticHDPE (high density polyethene)

Plastic bottles, e.g. shampoo, plastic pipes, crates, shopping bags and toysSample



Quick factsThe type of monomers also determine the different types of plastic that can be produced. Other chemicals that are added, determine the hardness, elasticity, etc.

Two other types of polymers which form in exactly the same way are polypropylene and PVC.

Manufacturing of polypropylene or polypropene:During a polymerisation reaction, polypropylene can be manufactured. Propene is used during this addition reaction.Polypropylene is a very hard type of plastic and has various uses, like the manufacturing of synthetic grass for hockey fields, mud guards for cars, synthetic carpets, material for clothes and tents, rope for mountain climbers, etc.Monomer:

Polymer:

Manufacturing of PVC:The IUPAC name of PVC is polychloroethene, but is commonly known as polyvinyl chloride. It forms when chloroethene joins into long chains. It is a versatile plastic that is used for the manufacturing of, for example, hose pipes, gutters, paint and plastic containers.Monomer:

Polymer:

C CC CC CC CC CC CC CC C

H HH HH HH HH HH HH HH H

H HH HH HH HCH3CH3CH3

CH3CH3CH3CH3

CH3

C CCC CC

Cℓ

H

Cℓ

H

Cℓ

H

H HH

H HH

C C

H

CH

H

HH

H

C C

Cℓ H

HHSample



Interesting factsExamples:n(propene) polypropylene Uses: manufacturing of car parts, ropes and carpets

n(chloroethene) PVC Uses: manufacturing of rulers, table cloths, floor tiles, etc.

n(tetrafluoroethene) Teflon Uses: manufacturing of non-stick surfaces in pots and pans

n(C12H8NC(H)=CH2) polystyreneUses: manufacturing of insulation material, egg boxes, margarine containers

Activity 2 Date:Search for information on or read articles about:• the discovery of polythene and • the development of addition polymers.

The following websites can be visited:http://www.eng.buffalo.edu/Courses/ce435/Polyethylene/ce435_intro.htmlhttp://www.bookrags.com/research/polyethylene-woc/http://www.personal.rdg.ac.uk/~spsolley/pe.htmlhttp://www.wisegeek.com/what-is-polyethylene-plastic.htm#slideshowhttp://www.wisegeek.com/what-is-polyethylene-plastic.htm#slideshowhttp://matse1.matse.illinois.edu/polymers/time.html

Answer the following questions:1. Who, in 1907, made the first recorded plastic as an electrical insulator?

__________________________________________________________________

2. Who published “Polymerisation” in 1920?

__________________________________________________________________

3. In which year was polystyrene developed?

__________________________________________________________________

4. What great discovery was made in 1941 in connection with polymers?

__________________________________________________________________

C C

F

F F

F

tetrafluoroethene

Sample



5. In what year and by whom was nylon developed?

____________________________________________________________________________

6. What great breakthrough did Dr Karl Ziegler make in 1953 in Germany?

____________________________________________________________________________

Activity 3 Date:Aim: To build polymers with Jelly Tots and Jelly Babies to understand the concept better.

Requirements:• Pink and green Jelly Tots – any two colours will work.• Jelly Babies• Thirty half toothpicks

Method: 1. The green Jelly Tots represent the initiators and the pink Jelly Tots represent the inhibitors. The other Jelly Babies are the monomers. Put different quantities in different containers as indicated in the table.

ContainerInitiators

(green Jelly Tots)Inhibitor

(pink Jelly Tots)Monomers

(Jelly Babies)

1 1 1 8

2 1 1 12

3 1 1 16

2. With the contents of each container, build a polymer in the following way:3. Take out an initiator (green Jelly Tot) and attach it to a monomer (Jelly Baby) with half of a toothpick. Repeat the process (see sketch) until all monomers are used.

Interesting factsIn Greek poly means many and meros means particles. Therefore, polymers means many particles. Polymers can occur naturally or be produced synthetically.

Polymers (plastics) are macromolecules and consist of repeating units called monomers.

Sample



4. Place an inhibitor (pink Jelly Tot) on the end to stop the reaction.5. Attach the polymer of container 1 to the polymer of container 2.

Questions:1. Are all the monomers of containers 1 – 3 equally long?

____________________________________________________________________________

____________________________________________________________________________

2. Is there a limit on how long the polymers can be?

____________________________________________________________________________

3. How long is the polymer that was built out of containers 1 and 2?

____________________________________________________________________________

4. How is the reaction stopped?

____________________________________________________________________________

2.3 Fibres

Polymers can also be formed through an elimination process.

2.3.1 Condensation polymerisation

It is the reaction in which two molecules with different functional groups react with each other, and a small molecule is eliminated (removed). These small molecules are usually water.

2.3.1.1 NylonNylon was the first fibre to be produced. It is a polyamide.The polymer consists of two different types of monomers. During the condensation polymerisation reaction, water is eliminated (removed).A simple presentation of the process is:

–A–B–A–B–A–B–A–B–… + H2OTwo types of monomers, viz. A and B.

1,6-diamine-hexane Hexanedioic acid Polyethylene (nylon-6,6)+200 – 300°C

+ H2O

}Sample



ExamplesOne of the polyesters is terylene (1,2-ethandiol and benzene-1,4-dicarboxylic acid)

Polyhydrous alcohols Polybasic acids Polyester

Benzene Polybasic acids Polyester

+ H2O

+ H2O

+

+

dacron

repeating unit

HO2C HO2CCO2H + HO OH OHheat

-H2O

O

O

repeat

O

OO

O O

O

O

O

n

Nylon is a solid. The solid is pushed through thin holes. The strings that come out are cooled down to set. The molecular chains in the string get intertwined (tangled) with each other and are then stretched out to form thin strings.The strings are used to weave textiles.There are various kinds of nylon. The name comes from the number of carbon atoms that are found in the two different monomers.

2.3.1.2 Polyesters

The condensation reaction during which polyesters are formed is esterification.During the process water is eliminated (removed).The link group of polyesters is the functional group of esters, viz.

Polyesters (terylene) are not as strong as nylon.

Quick factsThe number of C atoms of the amine is written first and the number of C atoms of the acid is written last.

Quick factsThe most common form is nylon-6,6. Another form of nylon is nylon-6,10.

C

O

O

Esterification (a condensation reaction) to produce a polyester.

Sample



Examples of specific polyesters are:• Kevlar:

The aliphatic hydrocarbon chain of nylon is replaced with benzene rings. Kevlar is a lot stronger and less flexible than nylon.Kevlar is five times stronger than steel if it is compared according to weight. It is also fireproof.It is used in the aeroplane manufacturing industry, for the manufacturing of cables, ropes and protective clothing.

• Mylar: It is a special type of stretched-out polyester film.

It has the following properties:• Electric insulator• Transparent• High tensile strength• Chemically stableMylar is used for making shiny helium-filled balloons, sun filters, space blankets, protective plastic layers or insulators.

2.3.1.3 Polylactic acid (PLA)

The monomers of synthetic polymers come from petroleum.With research, a new polyester polymer, viz. polylactic acid (PLA), was developed. The monomers used for PLA, come from the biological fermentation of plant material. This plant material can be tapioca roots, potatoes, sugar cane or another starch.The reaction for the formation of the polymer PLA is as follows:

The polymer is biodegradable. It can be manufactured to be broken down fast or be preserved for years.During the breakdown process, PLA is converted to lactic acid again, which can then be used in the manufacturing process of PLA.

C C

O O

O H H OH

R + n(HOCH2CH2OH)nn

C COCH2CH2OR

O O

+ 2H2OSample



Uses: It is mostly used for packaging material, like that of take-away meals. Other uses are the manufacture of coffee mugs, items used in the construction and the car industries, medical implants such as screws and pins, compost bags, disposable tableware. In the form of fibres and non-weaved textiles, PLA also has many potential uses, like furniture, disposable clothing, sunscreens, female hygiene products and nappies.

Interesting factsMedical implants, such as screws and pins, can take between 6 months to two years to dissolve in the body.

C C

H

H

H C O

H

H

O

H OH2O

C C CC C C C

C CC

H

H H H

H

H O O O

H H

C

H O HH

H H

O O O

OH H

HO C

C

C

C

OC

CH

H

H

H

H

H

H

H

O

O

Voor- en nadele van PLA:

Advantages Disadvantages

Versatility; can be used for various products.

The replacement of other plastics and polyesters (from petroleum), leads to a saving of fossil fuels.

BiodegradableBreakdown will take three months under controlled conditions at certain temperatures and with certain bacteria.

Is very slow to break down without special conditions.Analysts predict that a PLA bottle in a compost heap can take between 100 and 1 000 years

Helps to reduce the release of greenhouse gases.

Does not give off toxic gases when it is burned.

Can possibly relieve the problem of overloaded dumping sites.

PLA cannot be mixed with other plastics when recycled.

No significant loss in quality versus the other synthetic polymers.

Sample



Experiment 6 Date:Aim: To prepare a rubber ball from sodium silicate and ethanol.


_________________________________________________________________________________

Apparatus:• 50 mℓ glass beaker• 150 mℓ glass beaker• Stirring rod• Gloves Chemicals:• Ethanol or phenolphthalein• Sodium silicate

Safety measures:

• Wear gloves, because the sodium silicate can sometimes irritate the skin.

Method: 1. Measure 20 mℓ sodium silicate and pour into the 150 mℓ beaker.2. Measure 5 mℓ ethyl ethanol/phenolphthalein.3. Add to sodium silicate and stir immediately.4. As soon as the mixture is a solid, press it into a ball.5. Let the ball drop from the table and observe what happens.

Answer the following questions:1. What type of compound is formed during the experiment?

____________________________________________________________________________

2. What happens when the ball falls from the table?

____________________________________________________________________________

3. Explain the observation in Question 2.

____________________________________________________________________________

4. What will the difference in the product be if ethyl alcohol is replaced with phenolphthalein?

____________________________________________________________________________

Sample



Experiment 7 Date:Aim: To prepare plastic sulfur.


_________________________________________________________________________________

Apparatus:• Test tube• Glass beaker• Spoon• Test tube pliers/clothes peg• Paper towel

Chemicals:• Water• Sulfur powder

Safety measures:• Sulfur has a boiling point of 444ºC.• The test tube must be moved around in the flame so it does not overheat locally

and then burst.

Method: 1. Pour approximately 150 mℓ water in the glass beaker.2. Scoop sulfur powder into the test tube so approximately one third of the test tube is filled.3. Pinch the test tube with the test tube pliers/washing peg and heat carefully over the flame.4. Heat the sulfur until it all discolours and is a liquid.5. Quickly pour the molten sulfur into the cold water.6. When the sulfur is cooled down in the water, take it out and let it dry on a paper towel.

bservations:

Descriptions Colour of sulfur

Before it is heated.

While it is heated and melted.

After it is cooled down in the water.

Answer the following questions:1. What happens while the sulfur is heated?

____________________________________________________________________________

Sample



2. What does the sulfur look like after it is poured into the water?

____________________________________________________________________________

____________________________________________________________________________

3. What do you observe if the cooled sulfur is pulled apart slowly?

____________________________________________________________________________

4. Explain your observation in Question 3.

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Experiment 8 Date:Aim: To prepare slime from white wood glue and borax.


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Apparatus:• Two polystyrene cups• Plastic spoon to stir.• Spoon for measuring.

Chemicals:• White wood glue (polyvinyl alcohol)• Borax• Water

Method: 1. Pour 125 mℓ water (½ cup) and

½ teaspoon (2,5 mℓ) borax powder into one of the polystyrene cups.

2. Pour approximately 2,5 cm3 glue into the other polystyrene cup.

3. Add 20 mℓ water to the glue and stir.

borax solution

spatula

polystyrenecup

polyvinylalcoholsolution

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4. Add some of the borax solution to the glue.5. Stir.6. Let the mixture stand for 30 seconds. The slime is now ready.

Answer the following questions:1 Test the following properties of the slime:1.1 Pull it apart slowly. What happens?

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1.2 Try to quickly pull the slime into a string. What happens? Give an explanation for this.

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1.3 Roll the slime into a ball and drop it. What happens?

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1.4 Pour the slime out on a smooth surface. Press on it with your palm. What happens?

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2. What is unique about a polymer like slime? Explain your answer.

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3. What role does the borax play in the product?

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4. How will the amount of borax used influence the final product?

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5 The polymer of the slime contains the following cross-bonds: Give the structural formula of:

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5.1 polymer of PVA glue

5.2 borax.

6. Why does a polymer like slime have the property to “flow”?

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C

C

C

C

C

C

C

C

H

H

H

H

HH

C

C

O

H

O

H

O

O

B

O

O

O

H

H

O

H

O

H

O

H

H

H

H

HHH

H

H

H

H

H

Experiment 9 Date:Aim: To prepare “silly putty” with polymers of different ratios and compare the physical properties thereof.


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Variables:

Independent variable(Which is changed.)

Dependent variable(Which is measured.)

Controlled variable(s)(Which remain(s) the same.)

Sample



Apparatus:• Two empty 500 mℓ yoghurt containers• 250 mℓ yoghurt container for measuring.• Plastic spoon to stir.• Four Zip-lock bags• Marking pen• Measuring spoon (5 mℓ) for measuring.

Chemicals:• White wood glue• Borax• Water

Method: 1. Mark the Zip-lock bags from 1 – 4 with the marking pen.2. Make a solution of glue by adding together 125 mℓ (½ cup) glue and 125 mℓ (½ cup) water in the yoghurt container. Stir well. Mark the container as glue.3 Make a borax solution by doing the following:3.1 Pour one cup (250 mℓ) warm water into the other yoghurt container.3.2 Add one measuring spoon (5 mℓ) borax powder to the water.3.3 Stir well.3.4 Mark the container as 4% borax solution. 4. The different ratios for each Zip-lock bag are indicated in the table. First pour the glue solution into each bag. Thereafter add the different amounts of borax solution.5. Seal the bag and knead the mixture in the bag with your fingers.6. Roll balls and let them fall from the same height.7. Note your observations.

Observations:

Zip-lock bag Glue solution Borax solution Observation

1 10 mℓ 30 mℓ

2 20 mℓ 20 mℓ

3 30 mℓ 10 mℓ

4 50 mℓ 10 mℓ

Answer the following questions:1. Why are the balls that were formed dropped?

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2. What is the property called that is demonstrated by the bouncing?

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3. Which ball bounces highest?

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4. Explain the property of “silly putty” that was tested in Question 1.

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5. How will the quantity of borax solution used influence the final product?

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6. Name factors that could influence this property.

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7. Why can toys not be made of this?

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Conclusions:

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2.4 Identify2.4.1 Monomer

By looking at the structural formula of a polymer, it can be determined from which monomers it is composed.Remember that for addition polymerisation the monomer is an alkene that undergoes addition. Therefore, look for the recurring component(s) in the polymer and deduce which alkene/alkenes was/were used to make the polymer.For condensation polymerisation, there are sometimes two different molecules: a carboxylic acid and an alcohol. For polylactic acid it is carboxylic acid 2-hydroxypropanoic acid.

Sample

Polymers

Plastics Fibres

Addition reaction

ExamplesExample

Uses Uses

Condensation reaction

SYNTHETIC POLYMERS

Simple presentationSimple presentation

Sample

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