SUBJECT: PHYSICAL SCIENCE GRADE: 10 CHAPTER / MODULE 4: MATTER AND MATERIALS UNIT / LESSON TOPIC: MATERIALS A MACROSCOPIC VIEW

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1 SUBJECT: PHYSICAL SCIENCE GRADE: 10 CHAPTER / MODULE 4: MATTER AND MATERIALS UNIT / LESSON TOPIC: MATERIALS A MACROSCOPIC VIEW LESSON: 1. INTRODUCTION It is very important to us to know more about the types of material (matter) that we use in everyday life and the reason why we use it. Houses are build with specific types of material: Bricks, stones, polystyrene, zink. Each one of these materials has advantages and disadvantages. Bricks are quite expensive but are an excellent insulator. Stones are difficult to get because is must be a specific shape, but is also an excellent insulator. Polystyrene is a new method for building houses and are not readily available, it is also very expensive, but it is the best insulator. Corrugated zinc is the cheapest material, easily available but it is a very poor insulator and one has to use lots of innovative ways to insulate it to make living in it comfortable. Clothes are made of specific materials for specific purposes. The clothes of a biker are made to protect the person while clothes that we wear in summer are made to keep us cool. Hats that we wear are also made for different purposes. A helmet and a sun hat are made from different types of material because it is used for different purposes.

2 2. CLASSIFYING OF MATTER Matter Pure substance Mixtures Heterogeneous mixtures Homogeneous mixtures Elements Compounds Metals Semi - metals Non - metals Organic Inorganic A mixture is when two or more substances are mixed. The ratios in which the substances are mixed are irrelevant. There are no chemical bond between the substances and it can be separated with physical methods like sifting, filtering a magnet etc. A homogeneous mixture is when the substances are in the same phase. A heterogeneous mixture is when the substances in the mixture are in different phases. A pure substance is a single substance; it can be a single element or a single compound. An element is the simplest type of pure substance. It can not be broken down in smaller of simpler types or substances. A compound is a pure substance that consists of two or more elements that are chemically bonded. 3. THE PERIODIC TABLE OF ELEMENTS. The periodic law states that if elements are arranged according to its atomic number show periodic change in its properties. The modern periodic table is organised in rows (periods) and columns (groups). There are 7 periods. There are 8 main groups; the elements are arranged to have similar chemical and physical properties in the same group. 2

3 3 THE PERIODIC TABLE OF ELEMENTS 1 (I) 2 (II) (III) 14 (IV) 15 (V) 16 (VI) 17 (VII) 18 (VIII) 2,1 1 H 1 2 He 4 1,0 3 Li 7 1,5 4 Be 9 2,0 5 B 11 2,5 6 C 12 3,0 7 N 14 3,5 8 O 16 4,0 9 F Ne 20 0,9 11 Na 23 1,2 12 Mg 24 1,5 13 Al Si 28 2,1 15 P 31 2,5 16 S 32 3,0 17 Cl 35,5 18 Ar 40 0,8 19 K 39 1,0 20 Ca 40 1,3 21 Sc 45 1,5 22 Ti V Cr 52 1,5 25 Mn Fe Co Ni Cu 63,5 30 Zn Ga Ge 73 2,0 33 As 75 2,4 34 Se 79 2,8 35 Br Kr 84 0,8 37 Rb 86 1,0 38 Sr 88 1,2 39 Y 89 1,4 40 Zr Nb Mo Tc 2,2 44 Ru 101 2,2 45 Rh 103 2,2 46 Pd Ag 108 1,7 48 Cd 112 1,7 49 In Sn Sb 122 2,1 52 Te 128 2,5 53 I Xe 131 0,7 55 Cs 133 0,9 56 Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi 209 2,0 84 Po 2,5 85 At 86 Rn 0,7 87 Fr 0,9 88 Ra Ac 58 Ce Pr Nd Pm 62 Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa 92 U Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf 99 Es 100 Fm 101 Md 102 No 103 Lr 29 Cu 63,5 Symbol Electronegativity Approximate relative atomic mass Atomic number KEY

4 Chemical symbols are used to represent elements. The first letter of the symbol is always a capital letter and the second letter (if any) will be a small letter. Two capital letters next to one another indicates a compound where two elements are chemically bonded. 4. METALS, SEMI-METALS AND NON-METALS Meals are good conductors of heat and electric current. Metals are usually shiny Metals are malleable (can be pounded into shape). Metals are ductile (can be drawn into long threads). Metals are solids at room temperature. Mercury is the only exception. Metals have high melting and boiling points. Non-metals are dull. Non-metals are good insulators. Non-metals do not conduct electricity or heat. Many non-metals are gasses at room temperature. Non-metals have low melting and boiling points. Semi-metals have metal and non-metal properties. Semi-metals are solids at room temperature. Semi-metals are not malleable or ductile. Semi-metals give greater resistance than metals to conduct electricity and heat at room temperature. If semi-metals react with metals it acts as non-metals. If semi-metals react with non-metals it acts as metals. Metals are found on the left hand side of the Periodic Table. Non metals are found on the right side of the Periodic Table. The semi-metals are found between the metals and the non-metals. 5. CHEMICAL FORMULAE When compounds form there is specific ways in which this compounds is named. It is important to be able to classify the elements in the compound as metals and non-metals so that the rules can be applied. When a metal bond to a non-metal: 4

5 Write the metal (which is more to the left o the periodic table) first followed by te non-metal. Write the name of the metal, then the name of the non-metal followed by the suffix -ide. NaCl: sodium chloride. MgO: magnesium oxide When a transition metal bond to a non-metal: Write the name of the transition-metal (which is more to the left) first, then the charge of the transition metal (in roman numerals) and lastly the name of the non-metal with the prefix ide. FeCl 3 : Iron (III) chloride CuO: copper (II) oxide When two non-metals bond to one another: Write the name of the non-metal that is more to the left on te Periodic Table first, then the number of atoms for the second non-metal, the name of the second non-metal and the prefix ide. CO 2 : Carbon di oxide NO 3 : Nitrogen trioxide. When elements combine, it always happen in fixed ratios. To know which ratio to use we have to look at the valence electrons and the valency of each element. The valence electrons are the number of electrons in the outer energy level of an atom. The number of valence electrons are equal to the group number of the element. For a metal the valency is equal to the group number. For a non-metal the valency is equal to 8 the group number. When two elements combine we use the valencies to determine the ratio in which the elements will combine. The number ot atoms of an element that is needed for the bond is indicated with a small number after the symbol of the element. 5

6 When potassium (K) bonds to oxygen (O) the following ratio occur: Potassium (K) has a valency of 1, oxygen has a valency of 2. The valencies will now cross to indicate the ratio: K + O K 2 O 1 2 When a group of non-metals bond together and a group form an ion it is called s radical or a poly-atomic ion. Name of the radical Symbol Valency Ammonium + NH 4 1 Hydroxide OH - 1 Nitrate - NO 3 1 Bicarbonate - HCO 3 1 Sulphate 2- SO 4 2 Carbonate 2- CO 3 2 Phosphate 3- PO MACRO AND MICROSCOPIC PROPERTIES When we refer say that salt is a solid and water at liquid at room temperature, we refer to the macroscopic properties of salt and water. Macroscopic properties are properties such as temperature, pressure and volume. If you want to explain these properties we have to talk about the particles and the forces between them. This is the microscopic forces. Particles in a liquid move faster at a higher temperature, which is why a warmer liquid will evaporate faster than a cooler liquid. When the particles move faster, it is possible for them to have enough speed to escape from the attraction forces exerted on them by the surrounding particles. 6

7 The shape of a solid can not be changed because the particles have fixed positions. Because the particles vibrate in its fixed position, the temperature of a solid can change. The solid will be become warmer when the particles vibrate faster in its fixed position. If the particles gain enough speed it will break loose and the solid will melt into a liquid. Gasses will spread faster when it is warmer because the particles will move faster at a higher temperature. We can thus conclude that for all phases of matter (solid, liquid and gas), a higher temperature means that the particles move faster. The kinetic theory of matter states that the matter is made up of tiny particles that move all the time. All matter is made up of tiny, invisible, moving particles. The particles can be atoms, molecules or ions. Whether matter is a solid, liquid or gas, the particles move all the time. The higher the temperature, the faster the particles will move. Gas phase: The average distance between the particles is much greater than the distance in liquids or solids. Because of the big distances the force of attraction between the particles are very small. The molecules move all the time. Because they collide and change direction all the time we find a random motion. A gas will fill the whole container it is kept in. The average kinetic energy is directly proportional to the temperature of the gas. Liquid phase The particles are quite close together, but the force of attraction is smaller than in a solid, but greater than in a gas. The particles have more freedom of movement than in a solid but less than in a gas. Liquids can flow past each other. The average kinetic energy is directly proportional to the temperature of the liquid. Solid phase: The particles attract each other strongly with intermolecular forces. The particles are arranged in a fixed way. Particles can vibrate. The particles are arranged in a regular way and form beautiful crystals. The average kinetic energy is directly proportional to the temperature of the solid. 7

8 The density of a substance is the mass of 1cm 3 of the substance. The density depends on the mass of the particles and how close the particles are packed. ACTIVITIES: Activity 1: Name the following compounds: Na 2 S; HCl Activity 2: Give the formulae for the following compounds. Magnesium chloride; Phosphorous tri fluoride. Activity 3: Explain the difference in the movement of the three phases of matter PORTFOLIO EXERCISE: 1. Classify everything that you can get in the class as metals, non-metals, mixtures and pure substances. REVIEW QUESTIONS 1. Name the following compounds: MgO NaF ZnBr 2 CO Al 2 O 3 H 2 SO 4 2. Write the formula for the following compounds. Hydrogen fluoride 8

9 Calcium sulpide Iron (III) sulphate Ammonium oxide Calcium iodide 3. Classify the following as mixtures or pure substances. Pure orange juice; dairy milk chocolate, copper sulphate; honey 4. Classify the following elements as metals and non-metals. Iron, oxygen, sulphur, cobalt, phosphorus, lithium. 9

Atoms and the Periodic Table

Atoms and the Periodic Table Parts of the Atom Proton Found in the nucleus Number of protons defines the element Charge +1, mass 1 Parts of the Atom Neutron Found in the nucleus Stabilizes the nucleus