Chapter 9 manufactured substances

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  • 1. Rossita Radzak SASER MANUFACTURED SUBSTANCES IN INDUSTRY 1. The composition , properties and uses of some alloy Alloy Composition Properties Uses Bronze Cu -Hard and strong -in building of statue or monuments. Tin -does not corrode easily -in making of medals -has shiny surface -swords and artistic material Brass Cu -harder than copper -in making of musical instruments and Zinc kitchenware Steel Iron Hard and strong -in construction of buildings and Carbon bridges -in building of the body of cars and railway tracks Stainless Iron -shiny -in making of cutlery steel Carbon -strong -in making of surgical Chromium -does not rust instrument Duralumin Aluminium -light -in building of the body of aeroplane Copper -strong and bullet trains Magnesium manganese Pewter Tin, Copper -lustre, shiny In making of sourvenirs antimony -strong Paper 3 1. The copper wire in an electric cable can be easily bent by hand. A one-cent coin made an alloy of copper with tin and zinc cannot be bent easily. Referring to situation above, plan a laboratory experiment to investigate the effect of alloy formation on the hardness of a metal. Statement of problem Copper atom Does the formation of alloy increase the hardness of a metal? Hypothesis Bronze is harder than copper Stanum atom Zinc atom Variable Manipulated: Metal block (copper) and its alloys Responding: Size of the dent (made by the metal ball on the block) Constant variable: mass of the weight / the height of the thread / type of metal of the ball List of apparatus Metal block, alloy block, steel ball bearing, weight, ruler, rope, retort stand 1
  • 2. Rossita Radzak SASER Procedure: 1. Put the steel ball bearing on the metal block / copper 2. Pull the rope that tied to the weight until the weight is 60 cm high on the metal block / copper 3. Drop the weight onto the steel ball bearing 4. Measure the diameter of the dent made on the metal block and records it 5. Repeat the activity 3/5 times 6. Repeat step 1 to 5 by using the alloy block, replacing the metal block. Tabulation of data Name of metal Diameter of the dent (cm) Average , 1 2 3 4 5 cm Metal/ copper Alloy / bronze Paper 2 Conclusion: the diameter of the dent on the copper metal is bigger Reason: 1. The presence of atoms of other metals / tin that are different sizes 2. Disturb the orderly arrangement of copper atoms 3. Tin atoms reduce the layers of copper atoms from sliding 4. Alloy is stronger and harder than pure metal. 2. You have learnt the steel is an alloy of iron. Steel is harder than pure iron. Both iron and steel can rust when exposed to air and water. Do they rust at the same rate? To compare the rate of rusting between iron, steel and stainless steel Problem Statement How does the rate of rusting between iron, steel and stainless steel differ Hypothesis Iron rust faster than steel and steel rust faster than stainless steel. Variables Manipulated : Iron, steel and stainless steel. Responding : intensity / amount of dark blue colour / rate of rusting Fixed : size of nail, concentration of solution, duration of rusting Procedure: 1. Clean the nails with sand paper (to removed the rust from all the nails) 2. Place the iron nail, steel nail and stainless steel nail into the test tube A, B and C respectively. 3. Prepare a 5 % jelly solution by adding 5 g jelly to 100 cm3 of boiling water. Add a few drop of potassium hexacyanoferrate (III) solution. 4. Pour the hot jelly into the test tubes until all the nails are fully immersed. 5. Leave the nails for 3 days. 6. Observe and record the intensity of the dark blue colour. 2
  • 3. Rossita Radzak SASER Tabulation of data Test tube The intensity of the dark blue colour A B C Conclusion 1. The concentration of Fe2+ ions in the test tube A is higher than in test tube B. No Fe2+ ions are present in test tube C. 2. The rate of rusting in test tube A is higher than that in test tube B. No rusting takes place in test tube C. Alloy slow down the rate of rusting. Describe how toxic waste product from factory affects the quality of the environment. Your description should include the following aspects. Source, process and effect. Sample answer: 1. [Source] sulphur dioxide gas produced by factory or burning of fossil fuels 2. [process ] sulphur dioxide gas dissolves in rain water / water to form acid rain, SO2 + H2O  H2SO3] 3. [effect ] toxic waste / acid flows to into lakes and rivers, acid rain lowers the pH value of water, soil and air. 4. fish and other aquatic organisms die. 5. acid rain corrodes concrete buildings and metal structures 6. acid destroys trees in forest 7. acid rain reacts with minerals in soil to produces salt which are leached out the top soil. 8. plants die of malnutrition and diseases. 9. soil becomes acidic, unsuitable for growth of plants and destroys the roots of plants. 10. sulphur dioxide causes respiratory problems in humans. Properties, composition and uses different type of glass Type Properties Chemical Uses composition Fused glass -Very high softening point SiO2 Lenses, telescope -Highly heat resistant mirrors, optical -Does not crack when temperature changes fibres. -very resistant to chemical reactions -difficult to be shaped Soda lime -low softening point SiO2 Flat glass, light glass -does not withstand heating CaCO3 / bulb, mirrors, glass -break easily Na2CO3 containers. -less resistant to chemical reactions -easy to be shaped - cracks easily with sudden change in temperature Borosilicate -lower thermal coefficient SiO2 Laboratory 3
  • 4. Rossita Radzak SASER -heat resistant B2O3 glassware, cooking - Does not crack when temperature changes Na2O utensils. -very resistant to chemical reactions Automobile -does not break easily headlights. Lead glass -low softening point SiO2 Decorative items, -high density PbO crystal glass ware, -High refractive index CaO lens, prism, chandelier Composite Materials is a structural material that is formed by combining two or more different substances such as metal, alloys, glass, ceramics and polymers. Composite Component Properties of Properties of Uses of material component composite components Reinforced Concrete Hard but brittle, Stronger, high Construction of concrete low tensile strength tensile strength framework for Steel Hard with high does not corrode highway, bridges tensile strength but easily, can and high-rise expensive and can withstand higher building corrode. applied forces and loads, cheaper. Super- Copper(II)oxide, Insulators of Conducts Generators, conductor barium oxide electricity electricity transformers, electric cable, amplifiers, computer parts MRI Fibre optics Glass of low Transparent, does reflect light rays Transmit data in the refractive index reflect light rays. and allow light form of light in Glass of high rays to travel along telecommunications refractive index the the fibre Fibre glass Glass Heavy, strong but Light, strong, Water storage brittle and non- tough, resilient and tanks, small boat, flexible flexible wit high helmet Polyester plastic Light, flexible, tensile strength not elastic but weak inflammable, low and inflammable density, easily coloured, shaped and moulded. Photo- Glass Transparent, does Sensitive to light : Photochromic chromic reflect light rays. darkens when light optical lens, camera glass intensity is high, lens, car Silver chloride Sensitive to light becomes clear windshields, optical or silver when light switches, light bromide intensity is low. intensity meters. 4