ELEMENTS, MIXTURES AND COMPOUNDS

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Darrell Heath
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big ideas for the topic summary sheet b) a list of

1 Science Revision for Year 7 7C2 ELEMENTS, MIXTURES AND COMPOUNDS In this document you will find: a) a big ideas for the topic summary sheet b) a list of key words c) a ladder setting out the level standards

2 Summary Sheets Elements An element is a simple substance that cannot be split into anything simpler by chemical reactions. Atoms are the smallest particles of an element. Atoms of one element are all the same, and are different from atoms of all the other elements. All the elements are shown in the periodic table. There are 117 known elements. Each element has a chemical symbol, which is usually one or two letters. A symbol is written with the first letter as a capital, and the second letter lower case, for example oxygen O carbon C iron e aluminium Al Compounds Elements can join together to make compounds. The name of the compound tells you the elements that are in it. Compounds made from two elements always have a name that ends in -ide. These elements join together carbon, oxygen sodium, chlorine magnesium, oxygen to make these compounds carbon dioxide sodium chloride magnesium oxide A chemical formula tells you the name and number of atoms in a compound. The smallest particle of many compounds is called a molecule. Molecules are made up of groups of atoms. Some elements are also made of molecules. or example, a molecule of oxygen contains two oxygen atoms joined together. The formula is O 2. Water contains two atoms of hydrogen and one of oxygen. The formula is H 2 O. Elements Compounds Mixtures atoms of helium (He) molecules of carbon dioxide a mixture of helium and oxygen (CO 2 ) molecules of oxygen (O 2 ) molecules of water (H 2 O) a mixture of carbon dioxide and oxygen a lump of iron (e) a lump of sodium chloride (NaCl) a lump of bronze (a mixture of copper and tin) Page 1 of 2 Exploring Science edition 175

3 Summary Sheets (continued) Metals and non-metals The properties of a substance describe the way the substance behaves, or measurements that we can make on it. Metals and non-metals have different properties. Metals good conductors of heat and electricity shiny solids with a high melting point (except for mercury) Mainly found on the left-hand side and in the centre of the periodic table three metals are magnetic flexible Non-Metals poor conductors of heat and electricity dull most are solids or gases found on the right-hand side of the periodic table no non-metals are magnetic brittle (break easily instead of bending) Re-use and recycling Materials can be classified according to their properties. All the different materials in the world are made up of about 90 different elements. Some useful materials occur naturally, but others have to be manufactured using chemical reactions. In many cases, raw materials are non-renewable. If we can recycle these materials, then we reduce the demand for raw materials. There may also be energy savings as well. A process that uses recycled or renewable materials is sustainable. Waste can also be reduced by re-using objects such as glass bottles or plastic bags. Page 2 of 2 Exploring Science edition 176

4 Word Sheets a Sorted!/The material world alchemists al-kem-ists Scientists (originally Arabic) who carried out the first experiments to make a range of new substances. classify Placing things in their groups according to their characteristics. element All the atoms in an element are the same. A substance that cannot be split up into anything simpler by chemical reactions. recycling ree-sy-cling Using a material again, often by melting it and using it to make new objects. b Elementary atom The smallest particle of an element that can exist. mixture Two or more different kinds of particles that are jumbled up with each other but not chemically joined to each other. periodic table peer-ee-od-ick Table that shows all the elements, arranged in a regular order to show patterns in properties. symbol The letter or letters that represent an element. b ocus on: Mendeleev s patience No new words c Metal detecting electrical conductor Something that allows electricity to flow through it easily. heat conductor Something that allows heat to flow through it easily. high melting point Something with a high melting point has to be at a very high temperature before it melts. It is a solid at room temperature. insulator A material which does not let energy flow through it easily. low boiling point Something with a low boiling point will boil and turn into a gas at a relatively low temperature. It can be a solid, a liquid or a gas at room temperature. low melting point Something with a low melting point turns into a liquid at a relatively low temperature. It can be a solid, a liquid or a gas at room temperature. magnetic A material that is attracted to a magnet. metals Elements that are shiny, conduct heat and electricity well, and often have high melting and boiling points. Page 1 of 2 Exploring Science edition 165

5 Word Sheets (continued) c Metal detecting (continued) non-metals properties shiny Elements that are not shiny, and do not conduct heat and electricity well. A description of how a material behaves and what it is like. Hardness is a property of some solids. Reflects light well. d Compound interest chemical formula A combination of symbols and numbers that shows the ratio of the different kinds of atom that are in a particular compound. compounds Substances that can be split up into simpler substances. A compound contains the atoms of two or more elements joined together. molecule Two or more atoms joined together. oxide A compond that includes oxygen. e Re-use, renew, recycle bauxite bork-site Mineral (ore) that contains alumimium oxide-the main source of aluminium. clear See-through or transparent. colourless Something that has no colour. electrolysis e-leck-troll-ee-sis Splitting up a compound by passing an electric current through it. re-use When an object is used again, without being broken up or recycled. renewable A material or energy source that will not run out. sustainable sus-tane-a-bull A process that allows things to continue as they are. Page 2 of 2 Exploring Science edition 166

6 Level Ladder Name Class Date My Target Level is: My final level is: Tick the boxes that apply. Or use traffic lights to show how confident you are (red = I don t know this ; orange = I m not very confident about this ; green = I m confident I know this ). Level At the end of the Unit: I can do this This needs more work Working towards Level 4 Identify some materials that are metals. ollow instructions and work safely during practical work. Recall the names of some metals. Level 4 Explain why we recycle materials. Describe how the periodic table is used to classify the elements. Use secondary sources to select information on materials and their properties. Discuss ideas on resources and recycling. Level 5 Recall that there are only a relatively small number of elements and some of their names. Know the difference between chemical symbols for elements and compounds. Name a variety of common compounds using scientific terminology. Explain that when atoms of different elements combine, compounds are made. Carry out a number of practical methods using a range of apparatus, being aware of the hazards involved. Use practical evidence and/or secondary sources to classify materials as metals and non-metals, or as elements and compounds. Represent elements using chemical symbols. Explain the benefits and drawbacks associated with recycling. Explain how the periodic table is organised. Page 1 of 2 Exploring Science edition 173

7 Level Ladder (continued) Level At the end of the Unit: I can do this This needs more work Level 6 Explain the concept of sustainable development. Plan to collect valid and reliable results. Use word equations for chemical reactions. Level 7 Level Identify some elements whose properties do not fit the general patterns of the periodic table. Use chemical formulae to represent chemical compounds. Work out a chemical formula from a molecular diagram, and vice versa. Evaluate evidence, explaining why or why it is not good evidence. Explain why the periodic table is a more successful classification than some of the preceding attempts Predict the properties of elements by looking at the properties of other elements in the same group Page 2 of 2 Exploring Science edition 174

Elements,Compounds and Mixtures

Elements,Compounds and Mixtures BASIC CONCEPTS: Elements,s and s 1. The smallest fundamental particle of an element that retains the chemical properties of the element is called an atom. 2. A pure substance that cannot be split up into