Perfect Guide. Lower Secondary SCIENCE. Notes. Book B. Christopher N. Prescott

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1 Perfect Guide Lower Secondary SCIENCE Notes Book B Christopher N. Prescott

2 CHEMISTRY Preface PERFECT GUIDE TO LOWER SECONDARY SCIENCE NOTES is a study aid for school examinations. With comprehensive notes, this study guide promises to build knowledge and facilitate understanding for effective learning. These books can be used in conjunction with the Lower Secondary Science Matters (2nd Edition) textbooks. Textbook links are provided for convenient referencing and further reading. Features in these books IMPORTANT TERMS AND POINTS are highlighted in bold. These terms are also found in the Glossary. Concise STUDY NOTES with ample illustrations and photographs. Each LEARNING OUTCOME is followed by study notes. 2 SEPARATION TEchNIquES TOPIC 2.1 STUDY NOTES LEARNING OuTcOME (a) Recognise that many useful substances are found as mixtures which have to be separated to obtain the pure substance. Many useful substances are found as mixtures. For example air, seawater and crude oil are mixtures. These contain some very important and useful substances which need to be separated, like oxygen from the air or pure water or sodium chloride (common salt) from seawater. Scientists use different methods to separate mixtures depending on the physical properties of the constituents of the mixture. Separation Methods Magnetic Filtration Evaporation Distillation Paper Reverse attraction chromatography osmosis These separation methods are physical methods as they do not involve any chemical change. No new substance is formed. Link Lower Secondary Science Matters Volume A (2nd Edition) Section 4.1 LEARNING OuTcOME (b) Show an awareness of the basic principles of the physical separation technique of magnetic separation and state some examples of the applications of magnetic separation. Magnetic attraction can be used to separate magnetic material from that which is not affected by a magnetic force. Magnetic material usually contains metals like iron or cobalt or nickel, or their alloys like steel. Electromagnets can be used to pull magnetic metals and their alloys from non-magnetic material. This type of separation is common in scrap metal yards to separate iron and steel objects for recycling. out by evaporation from the leaves 2013 Marshall Cavendish International (Singapore) Private Limited Topic 2 Separation Techniques 17 TEXTBOOK LINK For further reading in by up through the xylem tubes BIOLOGY osmosis through the roots Link Movement of water through a plant Lower Secondary Science Matters Volume B (2nd Edition) Section 10.4 COMMON ERROR Refutes common misconceptions. Mineral salts diffuse into the root hairs in plants. Common Error As the concentration of mineral salts inside the root hair is higher than outside, diffusion would send the salts out of the plant. Therefore plants have to use energy and pump the minerals in by active transport. Diffusion facilitates the movement of gases (oxygen and carbon dioxide) and mineral salts in and out of plants. Osmosis facilitates the absorption of water by the roots. (d) Identify the parts of the human circulatory system including heart, blood vessels and blood. The human transport system is called the circulatory system. It is made up of the heart, blood vessels and blood. The heart is a muscular organ that pumps blood around the body. The pumping action is as follows: When the heart muscles contract (systole phase), blood is forced out. When the heart muscles relax (diastole phase), blood is pulled in Marshall Cavendish International (Singapore) Private Limited Topic 8 Transport System In Living Things 73 Just like a computer system that has various components each with a specific function, so does a system in a living organism. For example, the heart and blood vessels are organs that make up the circulatory system which pumps blood around the body. The heart has muscle tissue to pump the blood around. The blood itself has different cells each with a special job to do. Red cells carry oxygen gas in the blood whereas the white blood cells are important in defence against disease. Muscle cell Muscle tissue Heart Circulatory system This division of labour between cells, tissues, organs and systems ensures that the multicellular organism functions smoothly and efficiently. Cells become specialised in carrying out certain tasks, for example nerve cell, muscle cell etc. This division of labour on a cellular level increases efficiency as it breaks down the workload into smaller and more specific tasks. 7.2 GLOSSARY OF TERMS Cell The tiny basic unit of living material. All living organisms are made up of one or more cells. Cell membrane A thin partially-permeable outer skin around the cell which allows substances to diffuse through. Cell sap Liquid found in the vacuole of a plant cell. It contains mainly water and dissolved sugars and minerals. Cell wall A thick, rigid outermost layer of a plant cell. Cellulose The substance found in the cell wall of plants which makes the cell wall rigid. Chlorophyll A pigment found in plants which absorbs light energy from the sun to start the photosynthesis process. Chloroplast The structure (organelle) in the cytoplasm of the plant cell which contains chlorophyll Marshall Cavendish International (Singapore) Private Limited Topic 7 Cell: The Basic Unit Of Life BIOLOGY 67 EXAM TIP Useful hints for exams. GLOSSARY OF TERMS at the end of every chapter provides explanations to various scientific terms. iii

3 Contents CHEMISTRY Topic 1 : Chemical Composition of Matter 1 Topic 2 : Separation Techniques 22 Topic 3 : The Particulate Nature of Matter 34 Topic 4 : Atoms and Molecules 45 Topic 5 : Chemical Changes 54 BIOLOGY Topic 6 : Diversity of Living Things 76 Topic 7 : Cell: The Basic Unit of Life 90 Topic 8 : Transport System in Living Things 100 Topic 9 : Digestion in Human Beings 115 Topic 10 : Human Sexual Reproduction System 127 Topic 11 : Ecosystems 148 iv

4 TOPIC 1 CHEMICAL COMPOSITION OF MATTER CHEMISTRY 1.1 STUDY NOTES (a) State that elements are the building blocks of living and non-living matter and recognise if a substance is an element. All living and non-living matter matter consist of basic units called elements. Scientists have discovered about 116 elements of which 92 occur naturally on Earth. An element is a substance which cannot be broken down into two or more simpler substances by chemical means. Some elements occur uncombined on Earth. Examples of these elements are gold and silver in the ground or nitrogen and oxygen in the air. Most elements occur combined with other elements. For example, the element hydrogen mainly occurs combined with the element oxygen in the form of water. Most metallic elements combine with oxygen or sulphur to form ores or minerals. Galena, which is a lead ore, contains lead chemically combined with sulphur Experiment Is water an element? oxygen gas hydrogen gas carbon electrode water acidified with dilute sulphuric acid 6V battery Electrolysis of water: Water Oxygen + Hydrogen 2013 Marshall Cavendish International (Singapore) Private Limited Topic 1 Chemical Composition of Matter 1

5 How can you tell if water is an element? Remember that by definition, an element cannot be broken down into two or more simpler substances. However, if we pass electricity through water, it is broken down into its constituent elements hydrogen and oxygen. The water has to be acidified with a little acid since pure water is a poor conductor of electricity. This decomposition of a substance by passage of electricity is called electrolysis. The most abundant element in the air is nitrogen, which makes up 78% of air. This is followed by oxygen which makes up 21% of air. In the Earth s crust, the two most abundant elements are oxygen (about 47%) and silicon (about 28%). Link Lower Secondary Science Matters Volume A (2nd Edition) Section 3.1 Elements contain only one type of atom whereas compounds and mixtures always contain more than one type of atom. (b) Recognise that the Periodic Table is an organised chart of all the elements. All known elements are arranged in a chart called the Periodic Table. A group is a vertical column of elements. H non-metals He Li Na K Be Mg Ca Sc Ti V Cr metals Mn Fe Co Ni Cu Zn B Al Ga C Si Ge N O F P S Cl As Se Br Ne Ar Kr A period is a horizontal row of elements. Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hi Ta W Re Os Ir Pt Au Hg TI Pd Bi Po At Rn Fr Ra Ac + more than 30 other elements The Periodic Table Every element is represented by a chemical symbol. For example, oxygen is represented by O and hydrogen by H. Each vertical column in the Periodic Table is called a group. Elements within a group have similar chemical properties. Each horizontal row in the Periodic Table is called a period. The elements, as we go from left to right across the period, change from solid metals to liquid or gaseous non-metals. 2 Topic 1 Chemical Composition of Matter 2013 Marshall Cavendish International (Singapore) Private Limited

6 The zigzag staircase line going across the Periodic Table separates metals and non-metals. Below the staircase line on the left hand side are the metals. Above the staircase line on the right hand side are the non-metals. The elements near the zigzag line are called metalloids. These elements have the properties of both metals and non-metals. CHEMISTRY Aluminium foil Silicon ingots Argon gas The Periodic Table is a list of elements in order of increasing atomic size. Vertical columns are called groups and elements within a group have similar chemical properties. Horizontal rows are called periods and across a period from left to right the elements change from metal to non-metal. (c) Recognise that elements are classified into metals and non-metals according to their properties. Elements in the Periodic Table can be classified into metals and non-metals according to their different physical properties. Metals Non-metals Good conductor of heat Good electrical conductors Can be pulled into wires (ductile) Can be beaten into shape (malleable) Give a ringing sound (sonorous) Shiny to look at (lustrous) High densities Poor conductor of heat Poor electrical conductors Non-ductile Brittle and snap easily Not sonorous Dull appearance Low densities 2013 Marshall Cavendish International (Singapore) Private Limited Topic 1 Chemical Composition of Matter 3

7 The most common metals in the Earth s crust are aluminium and iron. The most abundant non-metals in the Earth s crust are oxygen and carbon. Name Chemical Symbol Appearance Metals Aluminium Al Silvery solid Copper Cu Reddish-brown solid Iron Fe Grey solid Magnesium Mg Silvery solid Mercury Hg Silvery liquid Zinc Zn Greyish solid Non-Metals Carbon C Black solid Hydrogen H Colourless gas Iodine I Black solid Nitrogen N Colourless gas Oxygen O Colourless gas Sulphur S Yellow solid Some uses of common metals and non-metals are shown in the following tables. Metal Uses Aluminium Copper Iron Magnesium Mercury Zinc Kitchen foil, aircraft construction, drink cans, window frames Water pipes, electrical wires, brass and bronze alloys Construction work, engine blocks, gates, steel alloys Fireworks, medicines (Epsom salts) Fluorescent lamps, thermometers, dental fillings Galvanised roofs, casing of dry cells, brass pins of plugs 4 Topic 1 Chemical Composition of Matter 2013 Marshall Cavendish International (Singapore) Private Limited