Scheme of work Combined Science: Trilogy - Foundation Chemistry – Bonding, structure and the properties of matter This resource provides guidance for teaching the Bonding, structure, and the properties of matter topic from our new GCSE Combined Science: Trilogy specification (8464). It has been updated from the draft version to reflect the changes made in the accredited specification. These changes are also reflected in the learning outcomes with some additions to the resources. The scheme of work is designed to be a flexible medium term plan for teaching content and development of the skills that will be assessed. It is provided in Word format to help you create your own teaching plan – you can edit and customise it according to your needs. This scheme of work is not exhaustive; it only suggests activities and resources you could find useful in your teaching. 5.2 Bonding, structure and the properties of matter 5.2.1 Chemical bonds, ionic, covalent and metallic Spec ref. Summary of the specification content Learning outcomes What most students should be able to do Suggested timing (hours) Opportunities to develop Scientific Communication skills Opportunities to develop and apply practical and enquiry skills Self/peer assessment Opportunities and resources Reference to past questions that indicate success 5.2.1.1 There are three types of strong chemical bonds: ionic, covalent and metallic. For ionic bonding the particles Be able to explain chemical bonding in terms of electrostatic forces and the transfer or sharing of electrons. 1 Recall the structure of an atom. Define an ion and valence electrons. Use large cardboard circle templates for atoms, with an inner circle for a nucleus, and at least 3 energy levels.
are oppositely charged ions. For covalent bonding the particles are atoms which share pairs of electrons. For metallic bonding the particles are atoms which share delocalised electrons. Ionic bonding occurs in compounds formed from metals combined with non-metals. Covalent bonding occurs in non-metallic elements and in compounds of Metallic bonding occurs in metallic elements and alloys. Define ‘electrostatic forces’ of attraction. Describe the ions formed by metals and non-metals. Pupils cut out a nucleus, and add the symbol and proton number. Add electrons using split pins onto the correct energy level. Draw an electron dot diagram of the atom. Remove the valence electrons (or add more) to get to the nearest full energy level. Draw an electron dot diagram of the ion. Indicate whether the ion is positive or negative. 5.2.1.2 When a metal atom reacts with a non-metal atom, electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged Draw dot and diagrams for ionic compounds formed by metals in Groups 1 and 2 with non-metals in Groups 6 and 7. Work out the charge on the ions of metals and non-metals from the number of the element, limited to the metals in 1 Draw a dot and cross diagram for ionic compounds formed by magnesium and oxygen. Draw a flow diagram to explain the reaction of magnesium and oxygen into magnesium oxide in terms of ions and electron structure. Use magnesium ribbon to produce magnesium Video clips: YouTube: YouTube:
5.2.1.3 An ionic compound is a giant structure of ions. Ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice and this is called ionic bonding. The structure of sodium chloride can be represented in the following forms: Be familiar with the structure of sodium chloride but do not need to know the structures of other ionic compounds. Deduce that a compound is ionic from a diagram of its structure in one of the specified forms Describe the limitations of using dot and cross, ball and stick, two and three dimensional diagrams to represent a giant ionic structure. Work out the empirical formula of an ionic compound from a given model or diagram that shows the ions in the structure. WS 1.2 Visualise and represent 2D and 3D forms including two dimensional representations of 3D objects. 1 Describe an ionic compound. Draw a diagram of sodium chloride. Draw a dot and cross diagram for the ionic compound formed by sodium and chlorine. Ask students to work out the empirical formula of ionic compounds from various models of elements with their valence electrons. Demo the formation of sodium chloride in a fume cupboard. Assign students to groups representing different elements. Each group identifies the atomic number and valence electrons for their element. Give each element a different colour balloon reflecting the number of valence electrons. One pupil becomes the element, with an atomic number and symbol and valence electrons stuck on them. Students then move around the room locating their match (some examples include MgCl2, NaF, MgS, NaCl, CaO and Ne). Once a group has formed a compound they label their compound name
MS 4a, 1a, 1c. and describe the movement of electrons. 5.2.1.4 When atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong. Covalently bonded substances may consist of small molecules. Some covalently bonded substances have very large molecules, such as polymers. Some covalently bonded substances have giant covalent structures, such as diamond and silicon dioxide. Recognise substances as molecules, polymers or giant structures from diagrams showing their bonding. Recognise common substances that consist of small molecules from their chemical formula. Draw dot and cross diagrams for the molecules of hydrogen, chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane. 1 Draw dot and cross diagrams for the molecules H2, Cl2, O2, N2, HCl, H2O, NH3 and CH4. Draw these molecules using the other forms described in the Learning outcomes. Ask students to predict the formula of covalent substances using a variety of different diagram formats. Demo the formation of hydrogen chloride. Ask students to draw the dot and cross diagram for this reaction and explain the results of the demonstration in terms of electrons and atoms. Give students a diagram of the dot and cross diagram for a covalent substance and ask them to write out the formula. Model simple covalent substance using molecular model kits. Video clip:
arranged in a regular pattern. The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds. The bonding in metals may be represented in the following form: from diagrams showing their bonding. WS 1.2 Visualise and represent 2D and 3D forms including two dimensional representations of 3D objects. MS 5b Draw a diagram to illustrate the different forms that bonding in metals can be represented by. Label the delocalised electrons. silver crystals. Write an explanation to describe the reaction in terms of metallic bonding. Students label themselves as a positive metal ion. Use balloons marked with a negative symbol to represent the electrons. Each pupil is a metal atom; each balloon is an electron belonging to that atom. The balloons are gently tossed from hand to hand and every balloon must stay in the air. The electrons are then transferred freely between atoms. YouTube: 5.2.2 How bonding and structure are related to the properties of substances
5.2.2.2 In chemical equations, the three states of matter are shown as (s), (l) and (g), with (aq) for aqueous solutions. Include appropriate state symbols in chemical equations for the reactions in this specification. 0.5 5.2.2.3 Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions. compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds. When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow Knowledge of the structures of specific ionic compounds other than sodium chloride is not required. 1 Write up the results from the circus of experiments. Students should describe how the ions lead to the behaviours of each of the materials. Use sodium chloride, copper (II) sulfate and potassium chloride. Examine the crystalline of structure under a microscope. Test the conductivity of the solid ionic compounds. Use flame tests to determine the colours of the compounds. Test the solubility by timing how long it takes each to dissolve. Test the conductivity of the ionic compounds in solution. Video clip YouTube: 5.2.2.4 Substances that consist of small molecules are usually gases or liquids that have relatively low melting points and boiling points. These substances have only weak forces between the Use the idea that intermolecular forces are weak compared with covalent bonds to explain the bulk properties of molecular substances. 1 Describe the properties of small molecules. Describe how soluble salt and salicylic acid are in the different liquids. Give students the size, structure, boiling and melting points of ethanol, acetone, and hexane. Test solubility of NaCl in water, ethanol, acetone, and hexane. Video clip YouTube:
flavouring, leaving behind the polymer). Mass can be measured before and after. 5.2.2.6 Substances that consist of giant covalent structures are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome to melt or boil these substances. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures. Recognise giant covalent structures from diagrams showing their bonding and structure. WS 1.2 MS 5b 1 Use the results of experiments to determine whether the sugar (covalent), table salt (ionic) and paraffin wax (covalent) are covalent or ionic compounds. Compare the properties of table salt, sugar and paraffin wax. Test the melting point of the three substances by heating on an aluminium foil boat. Test the solubility by dissolving each material in distilled water. Test the conductivity of the compounds from the solubility test. 5.2.2.7 Metals have giant structures of atoms with strong metallic bonding. This means that most metals have high melting and boiling points. In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped. Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.. Explain why alloys are harder than pure metals in terms of distortion of the layers of atoms in the structure of a pure metal. WS 1.2 1 Describe the structure of metals. Describe melting points and boiling points of metals and why they are high. Describe the structure of metal alloys. Model alloys using plasticine and various amounts of sand and test how ductile it is (pull a cylinder of sand-plasticine mix apart). Video clips: