Beatty 14.1 METALS (W1) 2023 Answers

1 Beatty Secondary School Science Department (Chemistry Unit) Chemistry 6092 Name: ___________________________________ ( ) Date: ________________ Class: 3E___ TOPIC: PROPERTIES AND USES OF METALS AND ALLOYS (WORKSHEET 1) Learning Objectives: (a) Describe the general physical properties of metals as solids having high melting and boiling points, malleable, good conductors of heat and electricity in terms of their structure. (b) Describe alloys as a mixture of a metal with another element, e.g. brass; stainless steel. (c) Identify representations of metals and alloys from diagrams of structures. (d) Explain why alloys have different physical properties to their constituent elements. (e) Describe steels as alloys which are a mixture of iron with carbon or other metals and how controlled use of these additives changes the properties of the iron, e.g. high carbon steels are strong but brittle whereas low carbon steels are softer and more easily shaped. (f) State the uses of mild steel, e.g. car bodies; machinery, and stainless steel, e.g. chemical plants; cutlery; surgical instruments. Multiple-Choice Questions 1 Layers of metal atoms can slide over each other. Which property is explained by this fact? A Most metals have high melting points. B Metals conduct electricity. C Most metals have high densities. D Metals are malleable. ( D ) 2 Which diagram best shows the structure of an alloy? ( B ) 3 Which alloy of iron is used in surgical instruments? A high carbon steel B low carbon steel C mild steel D stainless steel ( D ) 4 Which pair of elements cannot be used to form an alloy? A aluminium and magnesium B chlorine and sodium C copper and zinc D lead and tin ( B )

2 5 Which row correctly lists the uses of metals? stainless steel mild steel aluminium A galvanising car bodies soft can drinks B car bodies soft can drinks galvanising C soft can drinks aircraft bodies pipes in chemical plants D cutlery machinery aircraft bodies ( D ) 6 The composition of stainless steel is as shown below. What is element X? A carbon B copper C iron D zinc ( C ) 7 High carbon steel is used in manufacturing processes. 1 It is brittle. 2 It is malleable. 3 It is soft. 4 It is strong. Which properties does high carbon steel have? A 1 and 2 B 1 and 4 C 2 and 3 D 3 and 4 ( B ) 8 Magnalium is an alloy of aluminium (8 5 %) and magnesium (15 %). Some properties of magnalium are listed below. Which property of magnalium is not a reason for its use in the construction of aircraft? A It conducts electricity. B It is less dense than aluminium. C It is stronger than aluminium or magnesium. D The surface of the alloy is covered by a layer of aluminium oxide. ( A ) 9 Duralumin is an aluminium alloy that contains copper. Which statement about duralumin is correct? A It contains aluminium and copper that are chemically combined. B It contains mobile electrons. C It has a lattice of oppositely charged aluminium and copper ions. D It has the same melting point as copper. ( B )

3 10 Which statement about alloys is correct? A They are good conductors of electricity as they have mobile ions. B They are formed by a chemical reaction between two metals. C They can be all represented by a molecular formula. D Their structures contain a ‘sea of electrons’. ( D ) 11 A student thinks that element Q is a metal because it has a high melting point and a high boiling point. What other properties could element Q have if it is a metal? 1 Q conducts electricity when solid. 2 Q forms an acidic oxide, QO2. 3 Q is malleable. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only ( C ) Structured questions 12 Over 90% of all the metal used in the world contains the element iron. Most iron is used in the form of the alloy steel. (a) Explain what is meant by the term element. An element is a pure substance that cannot be broken down into 2 or more simpler substances by chemical methods. (b) Trains are mainly made up of steel. Some parts of trains are made of aluminium. (i) Why is steel used in the train rather than pure iron? Steel is an alloy and is stronger and harder than pure iron. (ii) Suggest why some parts of a train are made of aluminium, rather than steel. Aluminium has a lower density than steel, making it lighter for train parts. Aluminium forms a non-porous layer of oxide, which is resistant to corrosion. (iii) Suggest why a train is not made completely out of aluminium. Pure aluminium is soft and malleable as the layers of aluminium atoms can slide over each other easily when a force is applied. This causes the train to be easily damaged. (c) The properties of steel depend on the percentage of carbon in the steel. Give one use for steel containing a small amount of carbon and state one difference in properties between this type of steel and steel containing a large amount of carbon. use car bodies / machinery difference in properties Low carbon steel is softer and more easily shaped / malleable as compared to high carbon steel which is harder, stronger but brittle.

4 13 Most soft drink cans are made from an alloy of aluminium. (a) What is an alloy? A mixture of a metal with one or a few elements (b) Name an alloy and state the elements it is composed of. Brass – zinc and copper. Steel – iron and carbon (c) Sketch a diagram to show how the atoms are arranged in the alloy and explain how the alloy is more desirable than that of a pure metal. An alloy is stronger and harder than a pure metal. As atoms of different sizes are added for alloying, the orderly arrangement is disrupted, making it harder for the layer of atoms to slide over each other. On the other hand, the layer of the same -sized atoms in a pure metal can slide over easily which is soft and malleable, making the pure metal easier to be damaged. 14 Chemists have designed a wide variety of steels to suit particular uses. Some steels simply contain iron and carbon only, whereas others contain one or more other metals. The table shows the content and properties of some steels. type of steel content of steel properties mild steel iron + 0.25 % carbon only easily shaped, not brittle high carbon steel iron + 1.5 % carbon only hard and brittle cast iron iron + 4 % carbon only very hard and very brittle stainless steel iron + 18 % chromium + 8 % nickel tough and does not corrode (a) Give two effects of increasing the percentage of carbon in steel. As the percentage of carbon in steel increases from 0.25 % in mild steel to 4 % in cast iron, the steel becomes harder, less easily shaped and more brittle. (b) Explain the type of steel you would choose to make hip replacement joints. choice stainless steel reason Hip replacement joints should be durable, lightweight, tough and resistant to corrosion to allow patients to be continue wit h daily activities without worrying about fractures and immobilities.

5 15 The table below lists some of the properties and composition of a selection of alloys. alloy composition strength (MPa) density (g/cm3) properties mild steel 99.75 % iron 0.25 % carbon 841 7.85 easily pressed into shape brass 67 % copper 33 % zinc 550 8.55 soft, easy to cast bronze 88 % copper 12 % tin 500 8.70 weather resistant, durable stainless steel ……….. iron 18 % chromium 8 % nickel 860 7.86 resists corrosion duralumin 95 % aluminium 4 % copper 1 % magnesium 483 2.79 strong, hard, lightweight (a) (i) State which all