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2 TOPIC 1 WEEK 1 - THE CHEMICAL EARTH CONTEXTUAL OUTLINE ASSUMED KNOWLEDGE Domain: knowledge and understanding The Earth includes a clearly identifiable biosphere, lithosphere, hydrosphere and atmosphere. All of these are mixtures of thousands of substances and the use of this pool of resources requires the separation of useful substances. The processes of separation will be determined by the physical and chemical properties of the substances. In order to use the Earth s resources effectively and efficiently, it is necessary to understand the properties of the elements and compounds found in mixtures that make up earth materials. Applying appropriate models, theories and laws of chemistry to the range of earth materials allows a useful classification of the materials and a better understanding of the properties of substances. This module increases students understanding of the nature, practice, applications and uses of chemistry. Refer to the Science Years 7 10 Syllabus for the following: 5.7.1a) describe features of and the location of protons, neutrons and electrons in the atom 5.7.2a) identify the atom as the smallest unit of an element and distinguish between atoms and molecules 5.7.2b) describe some relationships between elements using the Periodic Table 5.7.3a) identify that a new compound is formed by rearranging atoms rather than by creating matter 5.7.3b) classify compounds into groups based on common chemical characteristics 5.7.3c) construct word equations from observations and written descriptions of a range of chemical reactions 5.7.3d) identify a range of common compounds using their common names and chemical formulae 5.7.3e) qualitatively describe reactants and products in chemical reactions 2

3 SECTION CONSTRUCT WORD AND BALANCED FORMULAE EQUATIONS OF CHEMICAL REACTIONS AS THEY ARE ENCOUNTERED This dot point will be dealt with using questions throughout the course IDENTIFY THE DIFFERENCE BETWEEN ELEMENTS, COMPOUNDS AND MIXTURES IN TERMS OF PARTICLE THEORY Types of Ma+er Elements Only one type of atom Cannot be seperated into parts by physical or chemical means Pure Substances Compounds 2 or more types of atom chemically bonded in a fixed ra8o Can be chemically sperated into the elements present Mixtures Impure substances which may contain many atoms and molecules which are NOT chemically bonded to one another Can be seperated by physical means ELEMENTS Pure substances that contain only one type of matter particle (atom) Most have definite melting and boiling point (carbon diamonds are an exception) The atoms may be separate: Or be bonded in pairs: Or in a 3 dimensional lattice array 3

4 All of these only contain one type of atom COMPOUNDS MIXTURES 4

5 COMPARING THE PROPERTIES Material Bauxite (mixture) Aluminium oxide (compound) Appearance and state Aluminium (element) Red pebbly solid Crystalline white solid Silvery lustrous solid Melting Point No definite melting point Melting point is 2045 C Melting point is 660 C Composition Decomposition Composition varies from mine to mine Can be separated into aluminium oxide, iron (III) oxide and dirt Constant composition by mass (52.9% aluminium) Can be decomposed (by electrolysis) into aluminium and oxygen Pure aluminium Cannot be decomposed into simpler substances Density Density varies with composition Density is 4.0 g/ml Density is 2.7 g/ml Properties Fairly easily ground into a fine powder The small crystals are hard and brittle Fairly soft, but malleable and ductile IDENTIFY THAT THE BIOSPHERE, LITHOSPHERE, HYDROSPHERE AND ATMOSPHERE CONTAIN EXAMPLES OF MIXTURES OF ELEMENTS AND COMPOUNDS This dot point stresses the importance of knowing that mixtures occur everywhere. LITHOSPHERE HYDROSPHERE ATMOSPHERE BIOSPHERE 5

6 Give 3 specific examples of mixtures in the Biosphere: QUESTIONS 1. Consider the following substances: calcium, neon, chlorine, oxygen and carbon dioxide. Which of the above substances exist as molecules in nature? (B) (C) all the substances chlorine, oxygen and carbon dioxide only Neon, chlorine, oxygen and carbon dioxide only Neon, chlorine and oxygen only 2. The diagram below represents the structure of a solid chemical substance Which of the following is the solid most likely to be? (B) (C) Silver Carbon dioxide Graphite Sodium fluoride 6

7 3. What is the name of the product when solid lead is heated with air? (B) (C) Lead (II) oxide Lead (III) oxide Lead(II)hydroxide Hydrogen 4. Which of the diagrams illustrates molecules of an element? i ii iii iv (B) (C) i,ii,iii,iv i,ii and iii only i, ii, only iii and iv only 5. The spheres of the earth contain examples of mixtures of elements and compounds. Which choice places the mixtures in the correct sphere? biosphere lithosphere hydrosphere atmosphere saliva oceans underground water air (B) blood fecal matter opal soot (C) sap limestone ocean car exhaust coal sweat glacier smoke 6. Which of the following is not a molecule? He (B) N 2 (C) NH 3 Al 7

8 FREE RESPONSE 1. Use the particle theory to explain the difference between nitrogen and nitrogen dioxide (2 marks) 2. A variety of chemical equations can be used to describe chemical reactions. (a) Give a word equation for the chemical reaction that occurs when sulfur is strongly heated in oxygen. (1 mark) (b) Give a balanced formulae equation for the reaction of sodium in water. (1 mark) (c) Give the half equations for the reaction of iron metal with hydrochloric acid. (2 marks) 3. This question refers to the chemical composition of the various spheres. (a) Write the chemical formula of an ionic compound abundant in the hydrosphere. (b) Write the chemical formulas of two common ores found in the Australian lithosphere. (c) Identify the element which is abundant in the biosphere, but is rare in the atmosphere, hydrosphere and lithosphere. 8