How to extract copper from Malachite

Malachite is a copper ore consisting mainly of basic copper(II) carbonate, CuCO3.Cu(OH)2. This experiment involves producing copper from copper(II) carbonate. The copper carbonate is first heated to produce copper(II) oxide, which is then reduced to the metal using carbon as areducing agent. Lesson organisation If possible, show the class a genuine sample of malachite ore and artefacts, such as paperweights or polished ‘eggs’ made from malachite, noting the green colour characteristic of many copper compounds. It contains copper, but how can copper metal be obtained from it? Heating will probably be suggested. This forms the first part of the experiment. While the copper(II) oxide produced by heating cools down, discuss how to get the oxygen out of the oxide, leaving the metal itself. The discussion can be worked around to the idea of providing some element, carbon, which is ‘better’ at combining with oxygen than copper is. The ‘competition’ idea is illustrated by the second part of the experiment. Explain that the green powder they start from is effectively powdered malachite, basic copper(II) carbonate. The experiment should take about 20 minutes. Apparatus and chemicals Eye protection Each student or pair of students will require: Crucible, preferably metal, eg nickel (see note 1) Crucible tongs Tripod Gauze or pipeclay triangle (see note 2) Beaker (250 cm3 or larger) Spatula Access to: Copper(II) carbonate (Harmful), about 1 g Powdered wood charcoal (Low Hazard), about 2 g Technical notes Copper(II) carbonate (Harmful) Refer to CLEAPSS Hazcard 26. Powdered wood charcoal (Low Hazard) Refert to CLEAPSS Hazcard 21. 1 A metal crucible is best for this experiment as it is less likely to crack than a porcelain crucible. 2 The gauze should preferably be one without a ceramic centre. Such centres tend to prevent the crucible from getting hot enough. A pipeclay triangle may be used if the metal crucible fits snugly into it; pipeclay (or silica) triangles are intended for use with porcelain crucibles, metal crucibles tend to be larger and fit the triangles badly. Procedure HEALTH &SAFETY: Wear eye protection throughout. Part 1 a Put one spatula measure of powdered malachite, copper(II) carbonate, into a crucible. b Heat the crucible and contents, slowly at first, then strongly until there is no further change in appearance of the mixture. c Allow the crucible and contents to cool for a few minutes. Part 2 d Add two spatula measures of powdered charcoal (carbon) to the contents of the crucible. Mix with the spatula whilst holding the crucible with tongs. CARE: Grip the edge of the crucible with the tongs; do not attempt to grip around the body of the crucible because it is likely to slip out. Finally, add a thin layer of powdered charcoal over the surface of the mixture. e Heat the crucible and its contents strongly on the tripod and gauze for a few minutes. Beware of sparks. f Allow the mixture to cool for a couple of minutes. g Half fill the beaker with water and then use tongs to tip the powder from the crucible into the water. h Swirl the contents of the beaker around so that any copper falls to the bottom, and then pour off the water and charcoal suspension. i Add more water and keep on pouring and swirling so only the heavy material is left at the bottom of the beaker. Teaching notes It should be clear from the outcome of Part 1 that heating alone brings about some change but does not produce copper metal: CuCO3(s) = CuO(s) + CO2(g) (This is a simplification as copper(II) carbonate is, as mentioned above, actually a basic carbonate: CuCO3.Cu(OH)2. On heating the copper(II) hydroxide also decomposes, losing water, and ending up as copper(II) oxide as well). Discussion of the nature of this change and the thinking behind the use of carbon also gives time for the crucible to cool somewhat so that manipulation at the beginning of Part 2 is safer. The purpose of the thin layer of charcoal on the surface of the mixture is to minimize the chance of the hot copper metal re-oxidising during the pouring-out process.

how Zinc reacts with Copper

The reaction between zinc and copper oxide In this experiment copper(II) oxide and zinc metal are reacted together. The reaction isexothermic and the products can be clearly identified. The experiment illustrates the difference in reactivity between zinc and copper and hence the idea of competition reactions. Lesson organisation This is best done as a demonstration. The reaction itself takes only three or four minutes but the class will almost certainly want to see it a second time. The necessary preparation can usefully be accompanied by a question and answer session. The zinc and copper oxide can be weighed out beforehand but should be mixed in front of the class. If a video camera is available, linked to a TV screen, the ‘action’ can be made more dramatic. Apparatus and chemicals Eye protection Bunsen burner Heat resistant mat Tin lid  Beaker (100 cm3) Circuit tester (battery, bulb and leads) (Optional) Safety screens (Optional) Test-tubes, 2 (Optional – see Procedure g) Test-tube rack Access to a balance weighing to the nearest 0.1 g The quantities given are for one demonstration. Copper(II) oxide powder (Harmful, Dangerous for the environment), 4 g  Zinc powder (Highly flammable, Dangerous for the environment), 1.6 g Dilute hydrochloric acid, approx. 2 mol dm-3 (Irritant), 20 cm3  Zinc oxide (Dangerous for the environment), a few grams Copper powder (Low hazard), a few grams. Concentrated nitric acid (Corrosive, Oxidising), 5 cm3 (Optional – see Procedure g) Technical notes Copper(II) oxide (Harmful, Dangerous for the environment) Refer to CLEAPSS Hazcard 26. Zinc powder (Highly flammable, Dangerous for the environment) Refer to CLEAPSS Hazcard 107 Dilute hydrochloric acid (Irritant at concentration used) Refer to CLEAPSS Hazcard 47A and Recipe Card 31 Concentrated nitric acid (Corrosive, Oxidising) Refer to CLEAPSS Hazcard 67 Copper powder (Low hazard) Refer to CLEAPSS Hazcard 26 Zinc oxide (Dangerous for the environment) Refer to CLEAPSS Hazcard 108. Procedure HEALTH & SAFETY: Wear eye protection throughout. Consider placing safety screens around the experiment (Samples of zinc can vary considerably in reactivity, depending on particle size and the state of surface oxidation.) a Weigh out 2 g (0.025 mol) of copper oxide and 1.6 g (0.025 mol) of zinc powder. b Mix thoroughly to give a uniformly grey powder. c Pour the mixture in the shape of a ‘sausage’ about 5 cm long onto a heat resistant mat or clean tin lid. d Heat one end of the ‘sausage’ from above with a roaring Bunsen flame until it begins to glow, then remove the flame. A glow will spread along the ‘sausage’ until it has all reacted. A white/grey mixture will remain. e Heat this to show that the white powder (zinc oxide) is yellow when hot and white when cool. f Pour the cool residue into a 100 cm3 beaker and add a little dilute hydrochloric acid to dissolve the zinc oxide (and also any unreacted zinc and copper oxide), warming if necessary. Red-brown copper will be left. This can be rinsed with water and passed around the class for observation. Show that the powder conducts electricity using a circuit tester. g If further confirmation of identity is required, treat a small amount of the red-brown powder with a few drops of concentrated nitric acid in a test-tube in a fume cupboard. A brown gas (NO2, Very Toxic) is given off as the copper reacts and dissolves. After the reaction adding a little water makes the blue solution of copper(II) nitrate visible. Teaching notes The depth of discussion depends on the level of the students involved. Essentially it is a competition between metal(1) and metal(2) for oxygen in a reaction represented by: Metal(1) + Metal(2) oxide → Metal(1) oxide + Metal(2) The more reactive metal displaces the less reactive metal from its oxide, as in the case of zinc and copper(II) oxide, for example: Zn(s) + CuO(s) → ZnO(s) + Cu(s) Demonstrate that zinc oxide goes yellow when heated and returns to white when cool to help confirm the identity of this product. (This phenomenon is caused by a change in crystal structure - a genuine example of a 'physical change'.) Where appropriate, it could be pointed out that these reactions are redox reactions, the more reactive metal behaving as a reducing agent, and the metal oxide acting as an oxidising agent. This could be extended to consider these redox reactions in terms of the loss and gain of electrons by the metals. Other metals can be used, but take care to compare like with like. Coarse magnesium powder, for example, gives a less vigorous reaction than powdered zinc. Finely powdered magnesium gives a very vigorous reaction and should only be attempted with great care. The reaction between aluminium powder and copper oxide is almost explosive and must not be attempted. Health & Safety checked, March 2009

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	Is That So? The Zen master Hakuin was praised by his neighbors as one living a pure life. A beautiful Japanese girl whose parents owned a food store lived near him. Suddenly, without any warning, her parents discovered she was with child. This made her parents very angry. She would not confess who the man was, but after much harassment at last named Hakuin. In great anger the parents went to the master. "Is that so?" was all he would say. When the child was born, the parents brought it to the Hakuin, who now was viewed as a pariah by the whole village. They demanded that he take care of the child since it was his responsibility. “Is that so?” Hakuin said calmly as he accepted the child. A year later the girl-mother could stand it no longer. She told her parents the truth – that the real father of the child was a young man who worked in the fishmarket. The mother and father of the girl at once went to Hakuin to ask his forgiveness, to apologize at length, and to get the child back again. Hakuin was willing. In yielding the child, all he said was: "Is that so?"