What is Ceramic? Ceramic consists of non-metal substance that is formed from heat reaction at a very high temperature. Ceramic is made from clay. The main component in clay is aluminium silicate. Ceramic can withstand high temperature and high pressure. Ceramic is also very hard, brittle, chemically inert and does not rust. In addition, ceramic is also a good insulator of heat and electricity. Photograph 9.9 Aluminium silicate Photograph 9.10 Ceramic dishes Aim: To provide reviews from a sharing session about a visit to glass and ceramic factory, or through watching a video. Instructions: 1. Participate in a sharing session or watch a video on the manufacture of glass and ceramic. 2. Gather information on the manufacture of glass and ceramic and record the information obtained in your notebook. 3. Based on the information obtained, write a review on the manufacture of glass and ceramic. Activity 9.2 ... ... Think-Pair-Share 21st Century Skills 9.2.2 9.2.3 The Use of Glass and Ceramic in Daily Life Based on the properties of glass and ceramic that we have learned, we know that glass and ceramic are used to produce many things in our daily life. Hence, this develops the glass and ceramic industry in our country. 190
Tableware is made of ceramic because of its resistance to heat and corrosion. Ceramic flower pots are hard and strong. Ceramic tiles used for flooring have sparkling property that make the floor look clean and nice. Ceramic is used to make dentures because of its hardness and inert to chemicals. Photograph 9.11 Applications of glass Photograph 9.12 Applications of ceramic 9.2.2 The glass prism made of lead crystal glass is used to study the dispersion of light because it has high refractive index. The bulb is usually made of soda-lime glass because of its resistance to heat and it is easily shaped. Laboratory apparatus such as beaker and conical flask are made of borosilicate glass because of its high resistance to heat and chemicals. Transparent glass window allows light to enter the house. Ceramic is used in the manufacture of various goods. The following shows some examples of applications of ceramic. Applications of Glass and Ceramic Glass has unique properties that make it suitable for the manufacture of various goods. The following are some examples of applications of glass. Chemicals in Industry 191 Chapter 9
9.3.1 Formative Practice Formative Practice 9.2 1. What is the main component in glass and ceramic? 2. State three applications of glass and ceramic. 9.3 Polymer What is a Polymer? A polymer is a large molecule formed by chains of smaller molecular units. The smaller molecular unit that makes up this polymer is known as a monomer. Polymers can be classified into natural polymers and synthetic polymers. Did you know that all of the items shown in Photograph 9.13 are made of polymers? Photograph 9.13 Products from polymer 192
Polymerisation and Depolymerisation Polymers are produced through the process of polymerisation. Polymerisation is the process of joining the monomers through the formation of chemical bonds to produce a long-chain polymer. Depolymerisation refers to the process of splitting a long-chain polymer into its monomers through chemical reactions. Polymerisation Monomer Depolymerisation Polymer Figure 9.5 Polymerisation and depolymerisation Polymerisation that involves a monomer of the same type by breaking a double bond into a single bond is known as addition polymerisation. Polythene is one of the example of polymers produced through the addition polymerisation from its monomer, ethene (Figure 9.6). H H | | C C | | H H n n H H | | C — C | | H H Ethene Polythene Figure 9.6 Addition polymerisation 9.3.1 9.3.2 Natural polymers are polymers that exist naturally. Synthetic polymers are man-made polymers using chemical substances. Natural polymer Monomer Use Starch Glucose Produces energy Protein Amino acid Builds cells and body tissues Natural rubber Isoprene To make rubber-based products Synthetic polymer Monomer Use Polythene Ethene To make plastic bottles, plastic bags and pails Polystyrene Styrene To make packing container for electrical equipment Perspex Methyl methacrylate To make aeroplane mirrors, windows for vehicles Synthetic rubber Neoprene To make gloves, tyres and shoe soles Table 9.3 Natural polymers Table 9.4 Synthetic polymers Chemicals in Industry 193 Chapter 9
9.3.3 Natural Rubber The milky fluid obtained from tapped rubber trees is called latex. Latex is then processed into natural rubber. These natural polymers contribute greatly to the economic growth of our country. Natural rubber is elastic, soft, cannot withstand heat, a good electrical insulator and is not permeable to air. The Action of Acid and Alkali on Latex In latex, rubber molecules in the form of chains are covered with a layer of protein membrane. Negative charges surround the outer surface of the membrane. This causes the rubber molecules to repel each other. Thus, latex remains in liquid form. How can latex be converted into solid form? When an acid is added to the latex, positively-charged hydrogen ions from the acid will neutralise the negative charges on the surface of the protein membrane. Without these negative charges, the rubber molecules will collide with one another. This will break the protein membrane and the chain of the rubber polymer is now free to coagulate to form solid lumps. Addition of acid – – – – – – – – – – – – – – – – – – – – – – – Protein membrane Negative charge Chain of rubber polymer – – – – – – – – – – – + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – – Neutralised rubber particle Positive charge from acid Chain of rubber polymer coagulates Broken membrane Figure 9.7 Coagulation of latex by acid Latex left without the addition of acid will, over time, form solid lumps due to the action of bacteria that produces acid which neutralises the protein membranes of rubber molecules. So, how can latex be preserved in liquid form? When an alkali is added to the latex, the hydroxide ions from the alkali will neutralise the hydrogen ions from the acid. Without the acid, negative charges remain on the protein membrane and the rubber molecules repel one another, and do not collide. Thus, the rubber molecules will remain in liquid form. – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – + + + + + + + + + + + + + + + + + + + + + + + – – – – – – – – – – – – Addition of alkali Negative charge from alkali Chain of rubber polymer Neutralised rubber particle Positive charge from acid (due to the actions of bacteria) Protein membrane Figure 9.8 Alkali reaction on latex 194
9.3.3 9.3 9.4 Activity Activity Inquiry Inquiry Aim: To study the properties of natural rubber. Materials: Rubber sheet, water Apparatus: Boiling tube, retort stand and clamps, Bunsen burner A The elasticity of natural rubber Procedure: 1. Test the elasticity of natural rubber by stretching and twisting the rubber sheet. 2. Observe and record your observations. Question: Is the rubber sheet able to return to its original shape? B The effect of heat on natural rubber Procedure: 1. Cut a piece of natural rubber from Activity A and put it into a boiling tube containing water. 2. Heat it slowly with a Bunsen burner (Figure 9.9). 3. Test the elasticity of the rubber piece after it has cooled. Question: What happens to the rubber piece after heating? Bunsen burner Rubber piece Boiling tube Figure 9.9 Setup of apparatus Aim: To study the action of acid and alkali on latex. Materials: Latex, ethanoic acid, ammonia solution Apparatus: Beakers, droppers, glass rods Procedure: 1. Label three beakers as P, Q and R. Then, add 20 ml of latex into each beaker. P Latex Dropper Ethanoic acid Glass rod Q Latex Ammonia solution R Figure 9.10 Setup of apparatus 2. Add 10 drops of ethanoic acid into beaker P and stir. 3. Add 10 drops of ammonia solution into beaker Q and stir. 4. Leave beaker R without adding acid or alkali. 5. Observe the changes occurring in all three beakers and record your observations in the table on page 196. 21st Century Skills 21st Century Skills Photograph 9.14 Stretching Photograph 9.15 Twisting Safety precautiom precaution Wear gloves when handling ethanoic acid and ammonia solution. Let us carry out Activity 9.3 and Activity 9.4 to study the properties of natural rubber. Chemicals in Industry 195 Chapter 9
9.3.3 Vulcanisation of Rubber The properties of natural rubber which is soft and not resistant to heat makes it an unsuitable material for tyres of vehicles. Due to Malaysian hot weather, tyres made of natural rubber will become soft and melt when exposed to hot road surfaces. So, how can the properties of natural rubber be improved to make it a suitable material for making various things? Observation: Beaker Observation P Q R Questions: 1. What happens when ethanoic acid is added to latex? 2. What happens when ammonia is added to latex? 3. How can coagulation of latex be prevented? 4. Why do latex coagulate when exposed to air? Vulcanisation can improve the properties of rubber and make it stronger. Vulcanisation is a process of heating rubber with sulphur. During vulcanisation, sulphur atoms are added to the chain of natural rubber polymer molecules. The rubber obtained through this process is called vulcanised rubber. + Sulphur S Sulphur cross-links Chain of natural Vulcanised rubber rubber polymer S S S S S S S S S Figure 9.11 Vulcanisation of rubber The molecular structure of vulcanised rubber has a bond between each chain of rubber polymer. This however, cannot be seen in natural rubber. This is due to the added sulphur atoms that produces cross-links between the rubber polymer chains. Therefore, when a force is applied, it is difficult for the chain of vulcanised rubber polymer to slide over each other. When heat is applied, the structure of vulcanised rubber molecules is difficult to break. Thus, the vulcanised rubber is harder and has high resistance to heat. Charles Goodyear (1800 – 1860) He founded the vulcanisation process in 1839. He heated a mixture of natural rubber with 1% – 3% of sulphur according to its mass. Renowned Scientist 196
Photograph 9.16 Items made of vulcanised rubber Aim: To sketch the molecular structure and describe the properties of vulcanised rubber. Instructions: 1. Carry out this activity in groups. 2. Sketch the molecular structure of natural rubber and vulcanised rubber on a piece of flip chart paper. 3. Present your sketch to your friends in the class and describe the suitability of the properties of vulcanised rubber in producing various items. ... ... Activity 9.5 Result Showcase 9.3.3 Figure 9.12 shows the properties of vulcanised rubber. Properties of vulcanised rubber Resistant to heat Good electrical insulator Not permeable to liquid and air Difficult to be oxidised in air Does not react with acid and alkali Hard and more elastic Figure 9.12 Properties of vulcanised rubber Vulcanised rubber is suitable to make tyres for vehicles, rubber gloves and shoe soles. 21st Century Skills Chemicals in Industry 197 Chapter 9
The Latest Rubber-based Technology Rubber is one of the major commodities of Malaysia. The rubber industry has improved the economy of the country. Research and development on rubber that is carried out by the Malaysian Rubber Board needs to be continued for the rubber industry to grow in our country. Some discoveries have been made using the special properties of rubber in the manufacturing and construction field. What are these technologies? Cuplump Modified Asphalt (CMA) acts as the concrete asphalt for the pavement to last longer, resist heat, reduce noise and road cracks. Getah Colour is a paint produced from latex to be used for visual arts. The rail pad made of rubber is placed between the railway and the train’s engine to reduce vibration and sound. Photograph 9.17 Some of the latest rubber-based technology What about other potential uses of rubber in the future? Can you think of any potential future use of rubber? Aim: To gather information and present the latest rubber-based technology. Instructions: 1. Carry out this activity in groups. 2. Using the Internet and other media, gather information about the latest rubber-based technology other than those specified in the textbook. 3. Based on the information obtained, discuss in groups on products that can be manufactured using rubber. 4. Present your ideas to the class. Your presentations must include: • sketches of the product • the manufacturing purpose • the special properties of the rubber in the product Activity 9.6 Formative Practice Formative Practice 9.3 1. Name two natural polymers and synthetic polymers and their monomers. 2. Compare the properties of natural rubber and vulcanised rubber. 3. Describe how vulcanised rubber is produced from natural rubber. ... ... Result Showcase 9.3.4 21st Century Skills 198
Alloy Composition Properties Uses CHEMICALS IN INDUSTRY Glass and Ceramic Component ApplicationNatural rubber Natural Vulcanised rubber The latest rubber-based technology Synthetic Vulcanisation Polymer Definition of monomer, polymer Polymerisation process Addition polymerisation Depolymerisation process Chemicals in Industry 199 Chapter 9
9 1. Photograph 1 shows two objects. Object P Object Q Photograph 1 (a) What is the type of alloy used to manufacture P and Q? (b) Give two other uses of the alloy used to manufacture P and Q. (c) Why is a bronze block stronger than a copper block? (d) In your opinion, can the alloy which is used to make object P be used to build a ship? Explain your answer. After studying this chapter, you are able to: 9.1 Alloy Define and give examples of alloys based on their composition of elements. Carry out an experiment to compare the properties of alloys with their pure metals. Justify the use of alloys in daily life. 9.2 Glass and Ceramic Describe the components of glass and ceramic. Explain the applications of glass and ceramic with examples. Justify the suitability of using glass and ceramic in daily life. 9.3 Polymer Explain natural polymers and synthetic polymers. Explain the process of addition polymerisation. Communicate the characteristics and process of vulcanisation of rubber. Generating ideas on the latest rubber-based technology. Self-reflection Self-reflection Summative Practice Summative Practice 9 Objective Questions http://bukutekskssm. QUIZ my/Science/F4/Q9 200
2. Photograph 2 shows the laboratory apparatus made of glass. Photograph 2 (a) What type of glass is used to make the products above? (b) How is the type of glass you stated in question 2(a) selected in the manufacture of the above products? (c) Give examples of another type of glass that may be suitable in producing the above product. Explain your answer. (d) Is the glass used to make the product above suitable to make drinking water containers to be used in restaurants? Justify your answer. 3. Superconductor alloys have many uses now and in the future. Photograph 3 shows one of the uses of superconductor alloy in Maglev trains. Photograph 3 (a) How is a superconductor alloy used in the construction of the Maglev train? (b) Give two other uses of superconductor alloys in daily life. (c) In your opinion, can the superconductor alloy be used in the antigravity car manufacturing? Describe the process. Mind Challenge Challenge 4. A Form 4 student found his bicycle tyre punctured on his way home from school. Then, he went to the workshop to repair his tyres. When the mechanic was repairing the tyre, the student discovered that the rubber tube of the tyre he was holding has different elasticity compared to the coagulated latex in his school laboratory. Referring to the above statement, plan an experiment in the laboratory to study the elasticity of the two types of rubber. Your plan should include the following: (a) aim (e) procedure (b) hypothesis (f) setup of apparatus (c) variables (g) tabulation of data (d) materials and apparatus Chemicals in Industry 201 Chapter 9
Chemicals in Medicine and Health Traditional medicine Modern medicine Complementary medicine Misuse of medicine Free radical Oxidation of food Active ingredient Keywords 10 Chapter 202
Kitab Tib Kitab Tib is an ancient Malay handwritten traditional medical manuscript. This book is a reference for the Malay society in ancient times to cure various diseases. This book contains methods to treat diseases such as stomach aches, cough and eye sore using natural substances from trees and plants mixed with herbs. Kitab Tib medical manuscript, is named after the Arabic language Al-Qanun Fi Al-Tibb by Ibnu Sina. Source: www.pnm.gov.my/manuskrip/ melayu/03koleksi/306_perubatan.htm (Access on 19 August 2019) Anda akan belajar tentang: traditional medicine, modern medicine and complementary medicine free radicals antioxidant substances health products Digest Science What are the common medical treatments in Malaysia? What type of medicine is generally given to treat patients? Do you know what free radicals mean? What is the effect of antioxidant substance on free radicals? What does active ingredient in health products refer to? You will learn about: Chemicals in Medicine and Health 203 Chapter 10
Traditional Medicine, Modern Medicine and Complementary Medicine 10.1 When we are sick, we need to get medical attention and take medication to heal ourselves. What are the medical options available to us? Criteria of Traditional, Modern and Complementary Medicine There are three medical options you need to know, namely traditional medicine, modern medicine and complementary medicine. Can you distinguish these three types of medicine? Traditional medicine is a medical treatment that uses plants, animals and natural substances that are specifically applied or combined for diagnosis and treatment of diseases. Each race in Malaysia practises their own traditional medicine. Figure 10.1 shows the criteria of traditional medicine. 10.1.1 Figure 10.1 Criteria of traditional medicine Treatment using natural substances from plants and animals Inherited and practised from generation to generation Activity 10.1 Aim: To gather information on traditional medicine practise among the people of Malaysia. Instructions: 1. Carry out this activity in groups. 2. Gather information from various sources about traditional medicine practised among the people of Malaysia. 3. Present the information in the form of multimedia presentation. Result Showcase ... ... Effectiveness proven with experience Low treatment cost 21st Century Skills Effectiveness of the treatment is slow and takes time Criteria of traditional medicine 204
10.1.1 Modern medicine refers to the combination of the art of medicine in various fields of sciences that relate to health science and biomedical such as clinical medicine, medical research and surgery in the treatment of ailments. Figure 10.2 shows the criteria of modern medicine. Criteria of modern medicine Treatment uses synthetic medicine Clinically tested High treatment cost Using modern methods such as surgery, laser treatment and radiotherapy Treatment is effective and fast Figure 10.2 Criteria of modern medicine Complementary medicine refers to various methods of health care that originates from many cultural backgrounds. This method covers two main parts; natural product, and mind and body practices. This method is sometimes used with the modern treatments to treat diseases such as cancer. Figure 10.3 shows the criteria of complementary medicine. Criteria of complementary medicine Does not involve surgery and stitches on body Does not use medicine, drug and synthetic chemical substances Considers the views of modern and traditional medical practitioners Figure 10.3 Criteria of complementary medicine Chemicals in Medicine and Health 205 Chapter 10
10.1.2 Medicines used in Traditional, Modern and Complementary Medicine Now that you have read about the three medical approaches to treatment, let us find out more about the medicine used in traditional, modern and complementary medicine. Medicines are drugs or substances taken to control health, treat or prevent diseases. These drugs and treatments need to be obtained from accredited bodies. Traditional medicine is medicine derived from natural sources such as plants and animals without being processed chemically. This medicine has been used since ancient times. How is a plant or animal used to treat diseases? Name some examples of traditional medicine you know. The gel from the leaves can be applied on the skin to reduce pain due to sunburn or exposure to hot objects. A popular herb used in Chinese traditional medicine to maintain good health. Relieves swelling, bodily pain and bloatedness. The leaves relieve headache and prevent hair loss. The bark of Cinchona sp. is used to make medicine for malaria. Hibiscus plant Quinine Aloe vera Ginseng Ginger Science Career Pharmacist A person who is trained in the field of pharmacology and is qualified to prepare and dispense medicinal drugs. Medicinal Plants http:// bukutekskssm.my/ Science/F4/Pg206_2 Photograph 10.1 Traditional medicines INFORMATION Medicines http:// bukutekskssm.my/ Science/F4/Pg206_1 INFORMATION 206
10.1.2 Modern medicine is a drug manufactured in the laboratory for consumers and is widely marketed. Modern medicine is available in many forms such as pills, capsules, paste, suspension and solution. Modern medicine is classified into three types, which are analgesics, antibiotics and psychotherapeutic. • This medicine relieves pain. • Examples of analgesics are aspirin, paracetamol and codeine. Antibiotics • This medicine kills or inhibits the growth of infectious bacteria. • This medicine is produced from microorganisms such as fungi or bacteria that can fight the bacteria that cause diseases. • This medicine can be produced by synthesis of chemical substances. • This medicine should be taken according to prescription to ensure that the bacteria are destroyed. • Examples of antibiotics are penicillin and streptomycin. • This medicine is used to treat psychiatric patients. • This medicine should not be taken arbitrarily and need to follow the dosage prescribed by the doctor because it can cause mood swings, thought disorder and changes in a person’s behaviour. • These medicines can be classified into three types: stimulants − these medicines stimulate and activate the brain activity, body and feelings of the patient; example, amphetamine antidepressants − these medicines treat depression; examples, imipramine and amitriptyline antipsychotics − these medicines have sedative effects; examples, tranquiliser, barbiturates, doxepin and haloperidol Analgesics Psychotherapeutic Paracetamol http://bukutekskssm. my/Science/F4/Pg207 Photograph 10.2 Types of modern medicines INFORMATION Chemicals in Medicine and Health 207 Chapter 10
10.1.2 Complementary medicine does not focus solely on the treatment of diseases but also ensures that the patient is holistically, physically, mentally and emotionally healthy. Complementary medicine is an additional treatment performed with modern medicine to treat diseases. What are some of the common complementary medical practices used in Malaysia? Chiropractic does not use medicine. Instead a chiropractor uses his hands to make adjustments to the bone position. Chiropractic is effective for back and neck pain, joint pain, headaches and sports injuries. Massage is a method of manipulating soft tissues in the body using the hands, fingers and the fist. Massage soothes anxiety, pain, fatigue, muscle tension and nerve problems. Sterile needles are inserted into specific points on the skin, called acupuncture points. They are inserted slowly and gently to stimulate the nervous system to relieve pain. Chiropractic Traditional massage Acupuncture 208
The Use of Traditional Medicine, Modern Medicine and Complementary Medicine Traditional medicine, modern medicine and complementary medicine complement one another. Each method has its own strengths and weaknesses. As a student, can you explain the strengths and weaknesses of the three methods? Carry out Activity 10.2 with your friends. Activity 10.2 Aim: To discuss the effectiveness of traditional, modern and complementary medicine. Instructions: 1. Carry out this activity in groups. 2. Choose one medical method, whether traditional medicine, modern medicine or complementary medicine. 3. Gather information from various sources on the effectiveness of the selected medical method and discuss the information obtained. 4. Present the information obtained in the form of multimedia presentation. 10.1.2 10.1.3 ... ... Result Showcase Photograph 10.3 Types of complementary medicines Proper medication is given to patients based on the symptoms shown or complaints by patients such as fever, pain or cough. The medicine given strengthens the body’s immunity against infectious disease, rather than killing the germs that cause the disease. Herbal therapy uses plants or parts of the plants that cure diseases. Consumers have the confidence in using these herbs because they do not have any side effects and do not contain drugs which are harmful to health. Homeopathy Herbal therapy 21st Century Skills Chemicals in Medicine and Health 209 Chapter 10
Aim: To study man-made medicines and medicines from natural resources. Instructions: 1. Carry out this activity in groups. 2. Gather information from the Internet, reference books, magazines and articles related to: • advantages and disadvantages of vitamin C from natural and man-made resources • side effects of natural and man-made medicines 3. Present your findings by conducting a Gallery Walk. ... ... Activity 10.3 10.1.4 The Use of Man-made Medicines and Medicines from Natural Resources Medicines are from two sources, either man-made (synthetic) or from natural resources. Traditional medicines are usually derived from natural resources, while most modern medicines are produced by preparing the chemical compounds that have the same molecular structure or similar molecular structure to the active ingredient in a traditional medicine. Table 10.1 shows the comparison of properties between the medicines. Table 10.1 Comparison of properties between man-made medicines and medicines from natural resources Man-made medicines Medicines from natural resources Made in the lab and commercialised for the use of consumers (Example: Vitamin C sold as pills in pharmacies) Derived from plants and animals (Example: Vitamin C from fruits) Must be taken regularly (usually for chronic diseases) or stopped when the sickness has healed Must be taken or used continuously for a long time to be effective Evidence of healing is based on clinical tests Evidence of healing is by trust and past experiences There is a risk of side effects if: • used without the advice of a doctor • the patient does not follow the correct dosage There is a risk of side effects if: • used without the advice of a doctor • the patient does not follow the correct dosage Gallery Walk 21st Century Skills 210
Formative Practice Formative Practice 10.1 1. State three methods of medicine currently in practice. 2. Name three types of modern medicine and give examples. 3. Lai Yee and her family went for a vacation at Pulau Perhentian. After returning from the vacation, her skin was red and painful. Which traditional medicine is able to relieve her condition? Explain your answer. 4. Give two examples of complementary medicine and two reasons why some patients choose complementary medicine. 10.1.5 The Effects of Misuse of Medicine Medicines must be used for the right purpose, which is to cure diseases. Misuse of medicine occurs when a person does not use medicine for its intended purpose or does not follow the doctor’s prescription. This creates a risk of side effects. Side effects are undesirable effects of drug use. Aim: To discuss the effects of misuse of medicine. Instructions: 1. Carry out this activity in groups. 2. Gather information from the Internet, reference books, magazines and articles on the effects of the misuse of medicine due to: • drug abuse • dependence on medicines • consumption of medicines not according to the age specified • consumption of medicines not according to the dosage prescribed such as antibiotics, cough syrup and paracetamol 3. Create a mind map to show the cause and effect of the misuse of medicine. 4. Paste your group work on the notice board of your class. ... ... Activity 10.4 Causes death Causes severe side effects such as allergies, vomiting, headache, fever and dizziness Causes addiction if the medicine is taken excessively such as cough syrup Causes the medication to be less effective. Hence, the disease is not cured The effects of misuse of medicine Figure 10.4 The effects of misuse of medicine Gallery Walk INFORMATION Misuse of Medicine http:// bukutekskssm.my/ Science/F4/Pg211 21st Century Skills Chemicals in Medicine and Health 211 Chapter 10
10.2.1 10.2.2 10.2 Free Radicals Definition of Free Radicals The term ‘free radicals’ often appear in newspapers, magazines, television advertisements and is debated in health talks. Do you know what free radicals are? What are the effects of free radicals on human health? Free radicals are atoms or molecules that lack one electron which makes the atoms or molecules unstable, reactive and tend to attack other atoms or molecules. The Effects of Free Radicals on Human Health Oxidation is a chemical reaction that occurs when a substance loses electrons in its reaction. The oxidation process occurs naturally inside a body to produce free radicals. This situation triggers a chain reaction to produce more free radicals. Metabolism and inflammation are two internal factors that produce free radicals in the body (Figure 10.5). There are also external factors which affect the amount of free radicals in the body such as cigarette smoke, exposure to radiation, sunlight and air pollution (Figure 10.6). Too many free radicals in the body will affect human health. Free radicals damage our DNA structure by removing electrons from molecules that build DNA. Then, it forms carcinogenic substances that may cause mutations and cancer. Free radicals also: • cause diseases such as cardiovascular disease and infertility • damage the kidneys, liver and lungs • cause premature aging conditions such as wrinkles and grey hair Figure 10.5 Internal factors that produce free radicals in the human body Internal factors Causes DNA damage Mitochondria White blood cell Free radicals Key: Metabolism Inflammation 212
10.2.2 Aim: To gather information on free radicals. Instructions: 1. Carry out this activity in groups. 2. Gather information from the Internet, reference books, magazines and articles on: • the formation of free radicals • how free radicals can be found in the body • how free radicals act on body cells • the importance of free radicals in the human body 3. Write a report based on your findings. ... ... Activity 10.5 Formative Practice Formative Practice 10.2 1. What are free radicals? 2. Explain how free radicals are formed. 3. Give two reasons why there are free radicals in the body. Writing Report Figure 10.6 External factors that produce free radicals and attack the cells of the human body 21st Century Skills External factors Toxic waste Ionising radiation Ultraviolet rays Cigarette smoke Air pollution Causes DNA damage Free radicals Key: Chemicals in Medicine and Health 213 Chapter 10
10.3.1 10.3 Antioxidant Substances Definition of Antioxidant Substances Antioxidants are chemical substances that are needed by our body to slow down or to stop the oxidation process. This substance protects body cells from damage by free radicals and is considered as a defensive line against diseases. Our bodies are capable of producing antioxidant substances, but as we grow old, this ability decreases. Therefore, we need to get antioxidants from food. What are the examples of antioxidants found in foods? Beta carotene is commonly found in most red, yellow or orange coloured food such as carrots, mangoes and sweet potatoes. Lutein is often associated with healthy eyes. These antioxidants are found in high quantities in green leafy vegetables such as spinach, cabbage and broccoli. Lycopene is an antioxidant substance found in fruits such as papaya, guava, watermelon, tomato, apricots, grapefruit and oranges. Vitamin C is a water-soluble vitamin which is also known as ascorbic acid. This antioxidant is found in citrus fruits, spinach, broccoli, kiwi fruit, strawberries, cranberry, cabbage, green pepper and cereals. Vitamin E which is also known as alpha-tocopherol is an antioxidant found in many types of oil including palm oil, wheat germ oil, corn oil and soybean oil. It is also found in apricots, broccoli, legumes and mangoes. Photograph 10.4 Antioxidant substances in food 214
10.3.2 The Action of Antioxidants on Free Radicals Antioxidants are chemical compounds that can be obtained from chemical synthesis or natural plants. When antioxidants react with free radicals, more stable compounds will be produced and this stops the oxidation process. Factors Affecting Food Oxidation Oxidation can be seen when foods are exposed to the air. This process causes fruits such as apples and bananas to become brown when left exposed to the air. Freshly cut apple Apple which is left exposed to the air Photograph 10.5 Oxidation on apple Based on your knowledge of antioxidants, how can the oxidation process be slowed down? Let us carry out Experiment 10.1. Aim: To watch a video on the action of antioxidants against free radicals. Instructions: 1. Watch a video presentation about the action of antioxidants against free radicals. 2. Discuss the action of the antioxidant seen in the video in pairs. ... ... Activity 10.6 Think-Pair-Share 21st Century Skills Chemicals in Medicine and Health 215 Chapter 10
10.3.3 Aim: To study the effects of different types of solution on the oxidation of apples. Problem statement: What can slow down the oxidation process on apples? Hypothesis: Solutions containing antioxidant can slow down the oxidation process on apples. Variables: (a) manipulated: The type of solution (b) responding: Colour changes on apple slices (c) constant: Surrounding temperature, size of apple slice Materials: Apple, sugar solution, lime juice, sodium bicarbonate solution, common salt solution Apparatus: Petri dishes, beakers, forceps Procedure: Apple Petri dish Sugar solution Lime juice Sodium bicarbonate solution Common salt solution Figure 10.7 Setup of apparatus 1. Prepare four types of solutions as shown in Figure 10.7. 2. Cut an apple into five equal slices. Put one of the apple slices in a Petri dish as a control. 3. Use a forceps to soak each apple slice into sugar solution, lime juice, sodium bicarbonate solution and common salt solution as shown in Figure 10.7. 4. After 1 minute, place the apple slices from the four solutions into a Petri dish and leave them to be exposed to air for 15 minutes. 5. After 15 minutes, observe the changes to the apple slices in the four types of solution with the apple not soaked in any solution. Result: Type of solution Colour changes on apple slices Sugar solution Lime juice Sodium bicarbonate solution Common salt solution Conclusion: Is the hypothesis of this experiment accepted? What is the conclusion of this experiment? Questions: 1. Which apple slice did not turn brown? 2. Why did the apple slices become brown? 3. Which substances can slow down the oxidation process? Experiment 10.1 Formative Practice Formative Practice 10.3 1. What is meant by antioxidant substances? 2. Give three examples of antioxidant substances found in food. 216
10.4.1 10.4 Health Products Active Ingredients in Health Products All health products, whether in the form of pills, powders or lotions contain active ingredients that play a role in improving health. What is the meaning of active ingredients? Active ingredients are specific components of a product that have effects on the cure or prevention of disease. Ingredient Active Ingredient Purpose Vitamin C .................................. Antioxidant Figure 10.8 Example of a health product labelled with active ingredient The active ingredient will have the same effect or purpose even when used in products of different brands. Sometimes, two or more active ingredients cannot be used together because they can react and cause harm to health. There is an increase in the number of health products manufactured and sold in the market nowadays. However, are all of these products good for health and help in curing sickness? What is the content in the products? How do we know the effectiveness of the products to our health? Chemicals in Medicine and Health 217 Chapter 10
10.4.2 The Use of Health Products Available in the Market Currently, the demand for health products is increasing. Why is this happening? However, people need to be more careful in choosing the right health products. Therefore, we need to seek medical advice and always check the label first before buying or using any health product to avoid unwanted effects. Formative Practice Formative Practice 10.4 1. What is meant by active ingredients in health products? 2. Give two reasons for the use of health products in Malaysia. Activity 10.7 Aim: To gather information on health products available in the market. Instructions: 1. Carry out this activity in groups. There is an abundance of health products in local market nowadays. Students are encouraged to gather information of these health products. By referring to the official website of the Ministry of Health Malaysia, identify the active ingredients found in the products and their effects on health. 2. Find different products with different active ingredients. 3. Present the findings of the project as posters or brochures to be pasted on the notice board around the school and in the classroom. Sometimes, health products such as supplements are taken to treat diseases and to maintain our health. Good health products can guarantee normal growth and prevent diseases. For example, multivitamins promote growth among children. More people are relying on health products for better health due to their busy lifestyle and unbalanced diet. Research-based Learning 21st Century Skills 218
Health Products CHEMICALS IN MEDICINE AND HEALTH Active ingredients Antioxidant Substances Free Radicals Methods of Medicine Modern Types of medicines Effects of misuse of medicines Traditional Complementary Action against free radicals Impact on human health Chemicals in Medicine and Health 219 Chapter 10
Summative Practice Summative Practice 10 1. Photograph 1 shows two types of medical methods. Photograph 1 After studying this chapter, you are able to: 10.1 Traditional Medicine, Modern Medicine and Complementary Medicine Explain the criteria of traditional medicine, modern medicine and complementary medicine. Explain the medicines used in traditional, modern and complementary medicine. Justify the use of traditional, modern and complementary medicine. Justify the use of man-made medicine and medicine from natural resources in treatments and healthcare. Conclude the effects of misuse of medicine. 10.2 Free Radicals Define free radicals. Discuss the impact of free radicals on human health. 10.3 Antioxidant Substances Describe antioxidants. Explain the action of antioxidants on free radicals. Carry out an experiment to investigate the factors that affect the oxidation of food. 10.4 Health Products Explain the meaning of active ingredients in health products. Justify the use of health products available in the market. Self-reflection Self-reflection Method M Method N Objective Questions http://bukutekskssm. my/Science/F4/Q10 QUIZ 220
(a) What are the types of medical approaches of M and N? (b) Give one health problem which can be treated using method M. (c) Give three types of medicines used in method N and their respective uses. (d) Method M is said to be used together with the method N under certain conditions. Justify the use of method M together with method N and give one appropriate example. 2. Free radicals cause health problems among individuals. (a) Describe how free radicals are formed. (b) State two factors of free radical formation. (c) Explain why free radicals are not a problem for some individuals but can cause health problems for others. 3. Photograph 2 shows fruits that are rich in antioxidants. Photograph 2 (a) What is meant by antioxidants? (b) Explain the role of antioxidants in the human body. (c) Give three types of antioxidants and their natural resources. Chemicals in Medicine and Health 221 Chapter 10
Mind Challenge Challenge 5. A Form 4 student has dry and dull skin. This is because of several factors related to poor dietary intake of antioxidants. Describe how this problem can be avoided. Your description should contain: (a) statement of the problem (b) the cause of the problem (c) three solutions 6. Currently, there are many health products in the market. Explain the justification for an individual to consume the health products. 7. Hasnah is a factory worker who works 12 hours a day. In your opinion, what are the health problems she may experience and how does she overcome them without changing her job? Your description should contain: • possible health problems • solutions for every health problem stated above 4. Figure 1 shows one of the complementary medical treatment methods. Figure 1 Describe the massage method used in this medical method. 222
Energy and THEME Sustainability of Life Energy and Sustainability of Life • What is the velocity of a racing car? • Have you heard of the term inertia? • What is your opinion on the use of nuclear energy to generate electricity in Malaysia? 223 4
11 Keywords Distance Displacement Speed Velocity Acceleration Displacement-time graph Velocity-time graph Value of gravitational acceleration Free fall Inertia Force and Motion 224 Chapter
Electric Trains in Malaysia The electric train service (ETS) in Malaysia which is operated by Keretapi Tanah Melayu Berhad (KTMB) has revived public interest to again use trains as a means of transport to their respective destinations. The electric train from Kuala Lumpur arrives at Padang Besar, Perlis in 4 hours 15 minutes compared to 12 hours by diesel train. It can reach a speed of about 160 km h–1. Based on the information from the KTMB website, the ETS has also begun its operation connecting Padang Besar to Gemas. Digest Science Anda akan belajar tentang: linear motion linear motion graphs gravitational acceleration and free fall mass and inertia What is the difference between distance and displacement? How do we determine the speed of an object? What will happen to a parachutist if the gravity of Earth suddenly disappears? Why are we hurled forward when the vehicle we are travelling in suddenly stops? You will learn about: 225 Force and Motion Chapter 11
NAGESH 11.1 Linear Motion Linear motion is the motion of an object in a straight path. Figure 11.1 Examples of linear motion of objects Figure 11.2 Distance and displacement What is the S.I. unit for distance and displacement? The S.I. unit for distance and displacement is metre (m). HAIKAL Distance and Displacement 11.1.1 End Start 80 m 113.14 m 80 m GROCERY STORE N Distance is the total path length travelled by an object. Distance = 80 m + 80 m = 160 m Displacement is the distance of the shortest path that connects two locations in a specified direction. Displacement = 113.14 m in the northwest direction 226
Distance and displacement are quantities that can be measured. What is the method to measure distance and displacement on a map? Let us carry out Activity 11.1. Aim: To measure the distance and displacement between two locations. Materials: Ruler, sketch map Instructions: 1. Carry out this activity in pairs. 2. Look at the sketch map given below. Kg. Paya Pasir Kg. Chenor Contour River Jungle Sandy beach Grass Swamp Paddy Oil palm Coconut tree Road Bridge Drainage Groyne Mosque Scale 20 40 80 60 100 120 140 Sek. Sek. T.A. Kg. Jengka Pekan Juaseh Sungai Jengka Kg. Nerek Kg. Awah T.A. Key N School 0 1 2 3 km Figure 11.3 Sketch map 3. Measure the distance and displacement between the following locations using a ruler: (a) Kampung Nerek to Kampung Chenor (b) Kampung Awah to the mosque (c) Kampung Awah to Kampung Nerek (d) Kampung Jengka to Kampung Nerek 4. The distance between two locations on the map can be calculated based on the scale given. Scale is the ratio of distance on the map to actual distance on the surface of Earth. Look at the scale on the map. Use the scale to convert the distance of location on the map to the actual distance. 5. Discuss the difference between the distance and displacement of two locations that you have obtained. Activity 11.1 11.1.1 Think-Pair-Share Device for Measuring Distances http://bukutekskssm. my/Science/F4/Pg227_1 Distance Measuring Wheels http://bukutekskssm. my/Science/F4/Pg227_2 INFORMATION INFORMATION 21st Century Skills 227 Force and Motion Chapter 11
Speed Speed is defined as the rate of change of distance. Average speed is the rate of change of total distance travelled. Speed = Distance Time Average speed = Total distance Total time The S.I. unit for both speed and average speed are metre per second (m s–1). • A 100 m runner will experience change in distance the moment he starts running from the starting line. • The change in distance increases as the runner becomes increasingly further away from the starting line. • The speed of the runner can be determined by the distance and time taken. • The following are examples of calculations for the speed of the runner: 11.1.2 Figure 11.4 Positions of a runner (a) Speed of the runner at position A Speed = Distance Time = 10 m 2 s = 5 m s–1 (b) Speed of the runner at position B Speed = Distance Time = 50 m 6 s = 8.33 m s–1 10 seconds 6 seconds 2 seconds 0 m 10 m A 50 m B 100 m C • The following is an example of calculation for the average speed of the runner: Average speed = Total distance Total time = 100 m 10 s = 10 m s–1 228
Velocity Velocity is defined as the rate of change of displacement. Velocity = Displacement Time The S.I. unit for velocity is the same as speed, which is metre per second (m s–1). 11.1.2 Figure 11.5 Position of a car O 0 m 2 seconds 4 m 2 seconds 8 m 2 seconds 12 m A B C N • The car above starts to move from initial point O to final point C which has a displacement of 12 m to the east. The car experiences a change in displacement. • The velocity of the car can be determined by the displacement and time taken by the car to reach point C. • The following is an example of the calculation for velocity of the car: (c) Velocity of the car from point O to C Velocity = Displacement Time = 12 m 6 s = 2 m s–1 to the east (b) Velocity of the car from point A to B Velocity = Displacement Time = (8 m − 4 m) 2 s = 4 m 2 s = 2 m s–1 to the east (a) Velocity of the car from point O to A Velocity = Displacement Time = 4 m 2 s = 2 m s–1 to the east • The positive and negative signs in the value for velocity show the direction of motion of the car. • Referring to Figure 11.5, when the car travels to the east, its velocity is written with a positive sign. The velocity of the car in the opposite direction would be written with a negative sign. 229 Force and Motion Chapter 11
A body or object which experiences a change in velocity is said to have acceleration. Acceleration is defined as the rate of change of velocity. Acceleration, a = Change of velocity Time taken = Final velocity (v) – Initial velocity (u) Time taken (t) The S.I. unit for acceleration is metre per second per second (m s–2). 11.1.2 Acceleration Acceleration, a = Change of velocity Time taken = Final velocity (v) – Initial velocity (u) Time taken (t) = 4 m s–1 − 0 m s–1 5 s = 0.8 m s–2 • The bicycle in the figure above which is stationary starts to move with the velocity as stated above. The bicycle is pedalled with increasing velocity. • This situation shows that the bicycle is experiencing acceleration. • The following is an example of calculation for acceleration of the bicycle: Velocity = 0 m s-1 Velocity = 2 m s-1 Velocity = 4 m s-1 5 seconds • If the brakes are applied, the bicycle will slow down and the velocity of the bicycle will decrease. This situation shows that the bicycle experiences deceleration. Figure 11.6 Velocity of a bicycle 230
Solving Problems involving Speed, Average Speed, Velocity and Acceleration in Daily Life The change in speed, velocity and acceleration of an object can be shown more clearly using formulae. Problems involving linear motion often occur in our daily life. Average speed = Total distance Total time = 100 m 12.58 s = 7.95 m s–1 a = v – u t a = 10.44 m s–1– 0 m s–1 9.58 s a = 1.09 m s–2 (a) Car speed = Distance Time = 800 m 65 s =12.31 m s–1 (b) Displacement = 800 m – 350 m = 450 m (c) Velocity = Displacement Time = 450 m 95 s = 4.74 m s–1 (a) Distance = 100 m + 150 m + 100 m = 350 m (b) Average speed = Total distance Total time = 350 m 60 s = 5.83 m s–1 (c) Displacement = 150 m to the east (d) Velocity = Displacement Time = 150 m 60 s = 2.5 m s–1 to the east Example 3 What is the acceleration of Usain Bolt if he starts from rest and attains a velocity of 10.44 m s–1 at the 100 m finish line in 9.58 seconds? Example 1 A student participates in a 100 m race. He recorded 12.58 seconds in the event. What is his average speed? Example 4 S R U T 100 m 100 m 150 m N Figure 11.8 Syafiq runs from point R to S which is 100 m to the north of R. He then runs to T, 150 m to the east of S. He continues running to U, 100 m to the south of T. The total time taken is 60 seconds. Calculate the: (a) distance (c) displacement (b) average speed (d) velocity A car travels 800 m from point A to point B in 65 seconds. Then, the car turns back 350 m from point B to point C in 30 seconds. (a) What is the speed of the car at point B? (b) Determine the total displacement of the car. (c) What is the velocity of the car? A C B Figure 11.7 Example 2 11.1.3 231 Force and Motion Chapter 11
How can we take measurements on the ticker tape to determine the velocity, displacement and acceleration of an object in motion? Let us carry out Activity 11.2. Aim: To determine the velocity and acceleration of an object using a ticker timer. Material: Ticker tape Apparatus: Ticker timer, runway, wooden block, trolley, metre rule, A.C. power supply 12 V Procedure: A.C. power supply Runway Ticker tape Wooden block Trolley Ticker timer Figure 11.10 Setup of apparatus 1. Arrange the apparatus as shown in Figure 11.10. 2. Switch on the ticker timer and let the trolley move down the runway. 3. Collect the ticker tape obtained. Activity 11.2 Inquiry The velocity and acceleration of an object in motion can be determined through activities carried out in the laboratory using a ticker timer. The ticker timer vibrates at 50 vibrations per second (50 Hz). One tick is the time interval between two adjacent dots on the ticker tape (Figure 11.9). Therefore, one tick represents 1 50 seconds or 0.02 seconds. 1 tick Figure 11.9 Ticker tape The velocity of the ticker tape which has 5 ticks can be calculated using the following formula: 10 cm Direction of motion Photogate is a timing device used to measure very fast motion or short time intervals accurately. Photogate is suitable for determining acceleration due to free fall, period of oscillation of pendulum or speed of trolley moving down a track. Science Science Gallery Displacement = length of ticker tape = 10 cm Time taken = 5 ticks × 0.02 s = 0.1 s Velocity = Displacement Time taken = 10 cm 0.1 s = 100 cm s–1 Example 1 tick 10 ticks Direction of motion Figure 11.11 Ticker tape 11.1.3 21st Century Skills 232
11.1.3 4. Cut the ticker tape into 5 strips of 10 ticks each. Paste them side by side to form the chart as shown in Figure 11.12. 5. Record the length of each strip of ticker tape. 6. Calculate the velocity of each strip using the following formula: Velocity = Displacement Time = Length of ticker tape with 10 ticks Time to make 10 ticks * Time for 1 tick = 0.02 seconds 7. Based on the tape chart in Figure 11.12, calculate the acceleration using the following formula: Acceleration, a = v – u t Initial velocity, u = Velocity of ticker tape 1 Final velocity, v = Velocity of ticker tape 5 Time interval, t from ticker tape 1 to ticker tape 5 = (5 – 1) × 0.2 s * *Time for 10 ticks on one strip = 10 ticks × 0.02 s = 0.2 s 8. Record the results in the table. Observation: Velocity Ticker tape Time to make 10 ticks (s) Length of 10 ticks (cm) Velocity (cm s–1) 1 0.2 2 0.2 3 0.2 4 0.2 5 0.2 Acceleration Ticker tape 1 5 Velocity (cm s-1) Time interval (s) Acceleration (cm s-2) Questions: 1. What can be observed from the ticker tape? 2. Is the length of each 10-tick strip the same? What inference can be made based on your observation? Length of ticker tape (cm) Ticker tape 0 1 2 3 4 5 2 4 6 8 10 1 3 5 7 9 Figure 11.12 Ticker tape chart 233 Force and Motion Chapter 11
Aim: To carry out an activity to study the type of motion and to determine the velocity and acceleration of a motion using a ticker timer. Material: Flip chart paper Instructions: 1. Carry out this activity in groups. 2. Observe the figures below which show three strips of ticker tape for three different motions of an object. Direction of motion 10 cm Direction of motion 0.4 cm 1.6 cm Direction of motion 4 cm 6 cm 10 cm A B C D E 8 cm (a) (b) (c) 3. Discuss the type of motion, velocity and acceleration of each ticker tape above. 4. Present the results of your group’s work to the class. Activity 11.3 ... ... Formative Practice Formative Practice 11.1 1. State the meaning of the following terms: (a) Distance (b) Displacement (c) Velocity (d) Acceleration 2. The figure shows a strip of ticker tape that was pulled through a ticker timer vibrating at 50 ticks per second. What is the displacement and velocity shown by the strip of ticker tape? 11.1.4 10 cm Direction of motion Types of Linear Motion The type of linear motion can be determined from the distance between dots on the ticker tape. Ticker tape Distance between dots Type of motion Distance between dots is constant Uniform velocity Distance between 2 consecutive dots increases uniformly Velocity increases uniformly (Uniform acceleration) Distance between 2 consecutive dots decreases uniformly Velocity decreases uniformly (Uniform deceleration) Distance between 2 consecutive dots is not constant Non-uniform velocity Direction of motion Direction of motion Direction of motion Direction of motion Table 11.1 Round Table 21st Century Skills 234
11.2 Linear Motion Graphs 11.2.1 Sometimes, it is difficult for us to explain motion in words. Therefore, we can use graphs to explain the motion of an object in detail. Linear motion graphs are used to present information and data regarding a motion. There are two types of linear motion graphs that you have to learn, which are the displacement-time graph and the velocity-time graph. Displacement-time graph The displacement against time graph is used to show the displacement of an object changing with time. Figure 11.13 shows a displacement against time graph for the motion of a boy. Can you describe the motion of the boy? Displacement (m) O 50 100 Time (s) 2 A B C D 8 12 16 Gradient of displacement-time graph = velocity Figure 11.13 Displacement-time graph OA: The gradient of OA is positive and uniform. • Its velocity is uniform. (The boy moves 50 m from the starting point with uniform speed.) AB: The gradient of AB is zero. • Its velocity is zero. (The boy is at rest from the 2nd to the 8th second.) BC: The gradient of BC is positive and uniform. • Its velocity is uniform. (The boy moves 50 m with uniform speed.) CD: The gradient of CD is negative and uniform. • Its velocity is negative and uniform, that is moving in the opposite direction. (The boy turns back 100 m to the starting point with uniform speed.) 235 Force and Motion Chapter 11
Velocity-time graph The velocity against time graph allows the displacement, velocity and acceleration of an object in motion to be determined. The velocity against time graph below shows the motion of a motorcycle which starts to move from point O. Explain the motion of the motorcycle. Velocity (m s–1) O 8 Time (s) 5 A B C D 10 15 20 Area under velocity-time graph = displacement Gradient of velocity-time graph = acceleration Figure 11.14 Velocity-time graph OA: The gradient of OA is positive and uniform. • The velocity of the motorcycle increases uniformly. • Acceleration of the motorcycle is uniform. AB: The gradient of AB is zero. • The velocity of the motorcycle is constant. • The acceleration of the motorcycle is zero. BC: The gradient of BC is negative and uniform. • The velocity of the motorcycle decreases uniformly. • The motorcycle is moving with negative acceleration or uniform deceleration. CD: The gradient of CD is zero. • The velocity of the motorcycle is zero (motorcycle is stationary). • The acceleration of the motorcycle is zero. Aim: To draw and interpret the linear motion graphs for: (a) displacement-time (b) velocity-time Materials: Pencil and paper Instructions: 1. Carry out this activity in groups. 2. Choose envelops of different colour provided by your teacher. 3. Discuss and draw a graph based on the situation described in the envelop chosen by your group. 4. Present the results of your work to the class. Activity 11.4 11.2.1 Result Showcase ... ... 21st Century Skills 236
Solving Numerical Problems involving Linear Motion Graphs 1 The graph below shows the linear motion of a remote control toy car. Displacement (m) 0 Time (s) 1 2 3 4 5 6 2 4 6 8 (a) What is the displacement of the toy car after the first 4 seconds? (b) What is the velocity of the toy car from the 3rd to the 5th second? Solution (a) Displacement = 6 m (b) Velocity = gradient of displacement-time graph Velocity of the toy car = (8 – 4) m (5 – 3) s = 4 m 2 s = 2 m s–1 Displacement (m) 0 Time (s) 1 2 3 4 5 6 2 4 6 8 2 The graph below shows the motion of a motorcycle along a straight track. Displacement (m) 0 Time (s) 2 4 6 8 10 12 5 10 15 20 (a) What is the displacement of the motorcycle after 4 seconds? (b) What is the velocity of the motorcycle from the 6th to the 12th second? Solution (a) Displacement = 15 m (b) Velocity = gradient of displacement-time graph Velocity of the motorcycle = (0 – 15) m (12 – 6) s = –2.5 m s–1 Displacement-time graph Figure 11.15 Figure 11.16 11.2.1 237 Force and Motion Chapter 11
(b) Displacement = area under the velocity-time graph = area of triangle + area of rectangle = [ 1 2 × (6 s)(15 m s–1)] + [(10 s − 6 s)(15 m s–1)] = 105 m Velocity-time graph 11.2.1 1 The motion of a ball can be represented by the graph below. (a) What is the displacement of the ball in the first 4 seconds? (b) Determine the acceleration of the ball from the 8th to the 12th second. Solution (a) Displacement = Area under the (b) Acceleration = gradient of velocity-time graph Acceleration of ball = (0 – 3) m s–1 (12 – 8) s = –0.75 m s–2 velocity-time graph = 4 s × 1 m s–1 = 4 m 2 The velocity-time graph below shows the motion of a motorcycle. (a) Determine the velocity when (i) time = 4 seconds (ii) time = 8 seconds (b) Find the displacement in the time interval between 0 and 10 seconds. Solution (a) (i) Velocity at = 10 m s–1 4 seconds (ii) Velocity at = 15 m s–1 8 seconds Figure 11.17 Velocity (m s–1) 0 Time (s) 2 4 6 8 10 12 1 2 3 4 Figure 11.18 Velocity (m s–1) 0 Time (s) 2 4 6 8 10 12 5 10 15 20 238
Formative Practice Formative Practice 11.2 1. What is represented by the gradient of the graph in the displacement-time graph? 2. What is represented by the area under the graph in the velocity-time graph? 3. A toy car moves down a smooth runway and then moves over a rough flat surface until it stops. Sketch the velocity-time graph which describes the motion of the toy car. 4. Interpret the motion of the object based on the graph shown below. 11.3 Gravitational Acceleration and Free Fall 11.3.1 Toy car Smooth runway Rough flat surface Displacement (m) 0 Time (s) You have been introduced to the term gravitational force in Form 2. All objects around us are pulled towards the centre of Earth by Earth’s gravitational force. Gravitational force causes an object to always fall downwards. An object such as the apple that falls due to Earth’s gravitational force will experience gravitational acceleration. The symbol used to represent gravitational acceleration is g. What is the value of g? How can we determine the value of g in the laboratory? Let us carry out Experiment 11.1. Brain Teaser Tease What will happen if there is no gravitational force on Earth? He starts to think about the force that causes the apple to fall, then he realises that ... The apple falls due to gravitational force! Gravitational Acceleration Isaac Newton is sitting under an apple tree when an apple falls from the tree. 239 Force and Motion Chapter 11