TEXTBOOK SCIENCE MATHAYOM. ISBN First Published Pelangi Publishing (Thailand) Co., Ltd. 2017

Transcription

1

2

3 TEXTBOOK SCIENCE MATHAYOM 2 Pelangi Publishing (Thailand) Co., Ltd All rights reserved. No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means without permission of Pelangi Publishing (Thailand) Co., Ltd ISBN First Published 2560

4 Contents Food and Addictive Substances Classes of Food Importance of a Balanced Diet Drugs Alcoholic Drinks Smoking 19 STEM Activity: Happy meal 23 Mastery Practice 25 Systems in Humans and Animals Digestive System in Humans Digestive Systems in Animals Circulatory System in Humans Circulatory Systems in Animals Respiratory System in Humans Respiratory Systems in Animals Excretory System in Humans Excretory Systems in Animals 51 STEM Activity: Artificial lungs 55 Mastery Practice 57 Reproduction Sexual and Asexual Reproduction Male Reproductive System Female Reproductive System Menstrual Cycle Fertilization and Pregnancy Importance of Pre-Natal Care Importance of Research in Human Reproduction Biotechnology in Animal Reproduction 81 Mastery Practice 85 Coordination and Responses Stimuli and Responses in Humans and Animals Human Nervous System 92 Mastery Practice 105 Elements, Compounds and Mixtures Elements Compounds Mixtures Separation Techniques Radioactive Elements 119

5 STEM Activity: A clean-up water project 122 Mastery Practice Energy and Chemical Changes Physical and Chemical Changes Chemical Equations Energy and Chemical Reactions Factors Affecting the Rate of a Reaction Chemical Reactions and Chemical Substances in Everyday Life 140 STEM Activity: New recipe of play dough 146 Mastery Practice 148 Forces and Motion Understanding Force Resultant Forces on a Same Plane (Net Force) Resultant Forces on Static Objects and Moving Objects with Constant Velocity 155 STEM Activity: Moving a structure without breaking it 160 Mastery Practice 162 Light Properties of Light Reflection of Light Refraction of Light Light and Colors Uses of Light 174 STEM Activity: New model! 178 Mastery Practice 180 Soil Soil Soil Formation Soil Uses and Soil Improvement 188 STEM Activity: Solving soil erosion problem 194 Mastery Practice 196 The Earth Layers of the Earth Rocks Minerals Fossil Fuels Natural Water 209 STEM Activity: Earth model 213 Mastery Practice 215

6 Special Features Amazing Facts Learning Outcomes Science at Work in This Book States the learning objectives of each chapter. Hot Tips Provides extra information and/or statistical information that are relevant to the concepts learned. Explains how scientific concepts are applied in our daily life. Experiment Common Mistakes & The Truth Points out the common mistakes that students make and the correct ways of answering questions. Basic Recall Helps students to recall the concepts & definitions learned in the chapter. Conceptual Map Points out the important tips for students to take note. Guides students to test a hypothesis in order to make a discovery. Test Yourself Into the Future Provides information on the potential developments of science and technology. Includes the latest development and / or extra information on science and technology. ICT Corner Mastery Practice Career Guide STEM Activity Activity QR Quiz Evaluates the understanding of the students for every subtopic. Provides direct access to useful websites by scanning the QR codes given. Provides an activity that engages in the application of knowledge of scientists, mathematicians and engineers. Provides subjective questions covering the entire learning outcomes of each chapter. Guides students to find an answer through observation using scientific methods. Assists students in reviewing the entire chapter. Science, Technology & Society Explains the scope of career which requires the relevant knowledge of scientific concepts. Provides direct access to the interactive exercises by scanning the QR codes given.

7 1 Food and Addictive Substances By the end of this chapter, you should be able to experiment, analyze and explain nutrients in food with energy quantities and proportions suitable to gender and age. discuss the effects of addictive substances on various systems of the body and guidelines for self-protection from addictive substances. Why do we need food?

8 1.1 Classes of Food Food is a collection of chemicals taken into an organism for the following purposes: (a) It provides energy for cellular activities. (b) It provides raw materials for growth and repair of worn-out tissues. (c) It keeps the organism healthy. The process of making or obtaining food is called nutrition. There are seven classes of food: (a) Carbohydrates (e) Minerals (b) Proteins (f ) Fibre (c) Fats (g) Water (d) Vitamins Food is not only tasty but also useful. Carbohydrates Carbohydrates are food substances consisting of carbon, hydrogen and oxygen in their molecules. The H:O ratio in carbohydrate molecules is 2:1. Carbohydrates include sugars, starch, glycogen and cellulose. Sugars are crystalline compounds that taste sweet and are water-soluble. Examples of sugars are glucose (grape sugar), sucrose (cane sugar), lactose (milk sugar) and maltose (malt sugar). Starch is stored in plant cells. Rice, potatoes and tapioca contain plenty of starch. Glycogen is also known as animal starch because it is stored in animal cells. Glycogen is stored mainly in the liver and muscles. 2 Science Focus Smart + MATHAYOM 2

9 Cellulose forms the greater part of the cell walls of plants. Starch, glycogen and cellulose are all made up of glucose molecules. Starch and glycogen can be readily converted to glucose when needed. Importance of carbohydrates: (a) Main source of energy for cell activities. (b) Forms supporting structures, such as cell walls in plants. (c) Can be converted to proteins and fats. Proteins Proteins are food substances that contain carbon, hydrogen, oxygen and nitrogen. Sulfur and phosphorus are present too. Every protein molecule is made up of basic units called amino acids. Meat, fish and eggs contain animal proteins while beans, nuts and seeds contain plant proteins. Importance of proteins: (a) Needed for growth and repair of worn-out or damaged cells. (b) Used for the synthesis of enzymes and some hormones. (c) Important components of antibodies which help the body to fight diseases. (d) A source of energy. Insufficient protein in a child s diet may lead to a disease called kwashiorkor. Fats Fats consist of carbon, hydrogen and oxygen. Unlike carbohydrates, however, fats contain less oxygen in proportion to hydrogen. Fats which are liquid at room temperature are called oils. Examples are palm oil and coconut oil. Each fat molecule consists of a glycerol molecule and three fatty acid molecules. 1 3

10 Food rich in fats includes butter, margarine, cooking oil and fatty meats. Importance of fats: (a) An efficient source and storage of energy. Each gram of fat provides about twice the amount of energy supplied by carbohydrates or proteins. Excess fats are stored as fatty tissue under the skin and around internal organs such as kidneys and heart to protect the organs from physical injury. (b) Acts as solvent for fat-soluble vitamin A, D, E and K. (c) An important component of cell membrane. (d) Fats under the skin also act as an insulator to reduce heat loss from the body. A diet rich in fats, however, increases the risk of heart diseases. Vitamins Vitamins are organic compounds that are required in very small amounts for maintaining good health. Vitamins are not energy providing foods. Vitamins are divided into water-soluble vitamins and fat-soluble vitamins. The water-soluble vitamins are vitamin B and C. The fat-soluble vitamins include vitamin A, D, E and K. Diseases caused by a lack of vitamins in our body are called vitamin deficiency diseases. We should eat a varied diet to obtain all the different types of vitamins that our body needs. 4 Science Focus Smart + MATHAYOM 2

11 Vitamin Source Function Deficiency disease A Tomatoes, carrots, fish liver oil, green vegetables, egg yolk, liver For night vision or vision in dim light Healthy skin Night blindness Skin infections B Whole grain bread, cereals, eggs, milk, green vegetables Healthy skin Healthy nervous system Development of red blood cells Release of energy from carbohydrates Beri-beri (paralysis) Dermatitis (skin disorder) Pellagra (mental disorder and skin disease) Anemia (deficiency in red blood cells) C Fresh fruits, green vegetables Healthy tissues Healing of wounds Resistance to diseases Scurvy (bleeding gums, internal bleeding in muscles and skin) D Liver, fish liver oil, egg yolk, formed in skin by sunlight Promotes absorption of calcium and phosphorus Formation of healthy teeth and bones Rickets (bowed legs and knock knees) Osteomalacia (softening of bones) E Whole grain, wheat germ, vegetable oil May be needed for reproduction Sterility (failure to reproduce) K Green vegetables, tomatoes, egg yolk, made by bacteria in the large intestine Essential for blood clotting Prolonged bleeding Sources, functions and deficiency diseases of vitamins Minerals Minerals are inorganic chemical elements that are needed in small amounts. Minerals are required to regulate body processes. A lack of minerals can cause deficiency diseases. Iron is required for the formation of strong teeth and bones. Calcium, phosphorus and vitamin D are needed for the formation and maintenance of bones. 1 5

12 Mineral Source Function Deficiency disease Calcium Milk, cheese, eggs, anchovies, yogurt, green vegetables Building healthy bones and teeth Clotting of blood Normal functioning of muscles and nerves Rickets Delayed clotting Muscular cramps Sodium Table salt, salty fish, salty eggs, cheese Normal functioning of nerves Maintenance of tissue fluids Muscular cramps Iron Liver, kidneys, eggs, green vegetables Needed for the formation of red blood cells Activates certain enzymes Anemia Iodine Iodised salt, sea fish, shellfish Needed to make hormone of the thyroid gland Control body growth Goiter (swelling of the thyroid gland in the neck) Phosphorus Milk, whole grain bread, cereals, meat Formation of healthy bones and teeth Proper functioning of muscles Formation of chemical substances that store energy Rickets Weakness Potassium Meat, milk, fish, mushrooms, bananas Normal functioning of nerves Maintenance of tissue fluids Regulation of heartbeat Weak muscles Paralysis Sources, functions and deficiency diseases of minerals Dietary fiber (roughage) Dietary fiber consists mainly of cellulose that is indigestible because we do not have enzymes to digest it. Fruits and vegetables are rich in dietary fiber. Importance of dietary fiber: (a) Provides bulk to the intestinal contents. (b) Stimulates peristalsis (rhythmic muscular contractions passing along the digestive tract). Lack of dietary fiber in the diet leads to constipation (failure to pass motions). 6 Science Focus Smart + MATHAYOM 2

13 Water Water is very essential for life because 60% to 70% of our body weight is water. We can survive for several weeks without food but would die in a few days without water. Importance of water: (a) Acts as a solvent in which chemicals dissolve. (b) Acts as a transporting agent for digested food, excretory products, hormones and antibodies. (c) Takes part in biochemical reactions (for example: digestion). (d) A major component of blood, body fluids, digestive juices and urine. (e) Regulates body temperature by evaporation of sweat from the skin. We require at least 1.5 litres of water daily to replace water lost in sweat, urine, faeces and exhaled air. Food tests We can carry out tests to find out substances contained in food. We use different tests to test for different food substances. Testing for glucose, starch, protein and fats Materials/Apparatus: 10% glucose solution, 1% starch solution, 1% albumen solution, cooking oil, Benedict s solution, iodine solution, Millon s reagent, ethanol, distilled water, dropper, test tubes, beaker, water bath, tripod stand, wire gauze and Bunsen burner Procedure and result: Procedure 1. Benedict s test for glucose 2 cm 3 of glucose solution is mixed with 2 cm 3 of Benedict s solution in a test tube. The mixture is heated in a hot water bath for 5 minutes. Result A brick-red precipitate is produced. 1 7

14 Procedure 2. Iodine test for starch 2 cm 3 of starch solution is put into a test tube. A few drops of iodine solution are added to the starch solution. 3. Millon s test for proteins 2 cm 3 of albumen solution is placed into a test tube and 2 drops of Millon s reagent are added. The mixture is heated in a hot water bath for 5 minutes. 4. Emulsion test for fats 5 drops of ethanol and 2 drops of cooking oil are put into a test tube. The mixture is shaken. Then, 3 cm 3 of distilled water is added to the mixture and shaken thoroughly. The contents in the test tube are left to stand for 2 minutes. Result A blue-black color is formed. A red coagulation is produced. A milky solution is formed. Conclusion: 1. Benedict s test: A brick-red precipitate indicates the presence of glucose. 2. Iodine test: A blue-black color indicates the presence of starch. 3. Millon s test: A red coagulation indicates the presence of protein. Water Wire gauze Bunsen burner xxxxxxxxx xxxxxx Mixture Tripod stand 4. Emulsion test: A milky solution indicates the presence of fat. A water bath TEST Yourself 1.1 Q1. (a) What is dietary fiber? (b) Why is dietary fiber important in our diet? Q2. (a) Why does our body need vitamin C? (b) What would happen if there is a lack of vitamin C in our diet? (c) State one major source of vitamin C. Q3. How would you test a solution for the presence of: (a) starch (b) glucose 8 Science Focus Smart + MATHAYOM 2

15 Sources Food tests Energy value Balanced diet Classes of food Age Body size Factors affecting the amount of energy / food needed Sex Occupation Food Climate Addictive substances State of health Drugs Cigarette smoke Types Damages caused Ways to avoid Content Damages caused Ways to avoid Alcoholic drinks Damages caused Ways to avoid 1 21

16 Fill in the blanks with the given words. addiction food water drugs calorific value climate ethanol fat vitamins damage drug abuse fibre minerals protein slow down iodine solution carbohydrates Millon s reagent cigarette smoke balanced diet alcoholic drinks Benedict s solution 1. is important because: it provides us energy. it supplies us raw materials to build new cells and to repair damaged cells. it keeps us healthy. 2. There are seven classes of food: (a) (rice, potatoes, wheat) to supply energy (b) (meat, fish, eggs) for growth and repair of tissues (c) (butter, cooking oil, fatty meat) to help absorption of vitamins and to supply energy (d) (fruits, vegetables, milk) for health and growth (e) (nuts, vegetables, milk) for health and growth (f) (fruits, vegetables) to stimulate peristalsis (g) (drinks, fruits, vegetables) as a medium for bodily chemical reactions and for transporting digested food. 3. Some important food tests: (a) Glucose produces a brick-red precipitate with. (b) Starch turns blue-black with. (d) Fat produces a milky solution when shaken with. 4. A contains all the seven classes of food in the right proportion. 5. The amount of food or energy required by a person depends the age, gender, body size,, occupation, state of health. 6. indicates the energy content of food. It is measured in calories (cal) or joules (J) using a calorimeter. 7. are substances that affect the way our nervous system works. 8. is taking drugs without a doctor's advice, causing harm to the body. 9. Drug abuse our mental and physical health, causes addiction and social problems. 10. contain ethanol, a type of alcohol. 11. Alcoholic drinks our brain functions and damages our brain, liver and stomach. 12. contains tar, carbon monoxide, nicotine, irritants and carcinogens that are harmful. 13. Cigarette smoke causes, lung cancer, heart attack, bronchitis and emphysema. (c) Protein produces a red coagulation with. 22 Science Focus Smart + MATHAYOM 2

17 Happy meal Obesity is getting prevalent among our school-going kids. Many younger Thais are rejecting certain aspects of our traditional lifestyle as they label them as un-cool and old-fashioned. In fact, they eagerly embrace certain aspects of the western culture or lifestyle including diet and exercise. Most of them prefer fast food and soda which contribute greatly to obesity. You and your team are nutritionists who advise people on matters of food and nutrition impacts on health. You are required to create a happy meal for kids ranging from 7 to 9 years old. Guidelines: 1. How does fast food contribute to obesity among kids? 2. What are the basic healthy eating guidelines recommended by our government? 3. How will you incorporate fruits, vegetables and meat into your meal? 4. Does your meal require a fork, a knife or a spoon? 5. Will you include any healthy drinks? What is your need? Define or describe the problem and set your goal. What do you have to know? Carry out a research and cite the sources that your group used. What are your possible solutions? Brainstorm various solutions and choose the best one. 1 23

18 What is your plan? Draw a prototype in great detail and list the materials needed. Build your prototype. Follow your plan and build a prototype to make your ideas real! Does it work? Record your observations and / or measurements. Do not forget to take pictures for your presentation. Prepare your presentation. Reflect on your solution design. 24 Science Focus Smart + MATHAYOM 2

19 Subjective Questions 1. An analysis of the contents of a packet of instant noodles is shown in Table 1. Class of food Percentage Proteins 14 Fats 20 Carbohydrates 57 Table 1 (a) Which of the contents (i) includes sugars and starch? (ii) is essential for growth and repair of body tissues? (b) What percentage of the contents is not included in Table 1? (c) A packet of instant noodles weighs 80 g. The energy value of proteins is 18 kj g 1. Calculate the amount of energy from proteins in a packet of noodles. (d) State two other classes of food not shown in Table 1. (e) Name the enzyme that digests fats in our body. 2. (a) Name the type of alcohol found in wine. (b) What type of drug is it? (c) State four effects of consuming excessive amounts of alcohol. (d) What is the effect of excessive alcohol on the (i) brain, (ii) liver, (iii) stomach. 1 25

20