MATERIALS : METAL AND NON-METAL

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1 4 MATERIALS : METAL AND NON-METAL TEXTBOOK QUESTIONS AND THEIR ANIMALS. Q.1. Does copper also get rusted? I have seen a greenish deposit on the surface of copper vessels. Ans. When a copper vessel is exposed to moist air for long, it acquires a dull green coating. The green material is a mixture of copper hydroxide (Cu(OH) 2 ) and copper carbonate (CuCO 3 ). The following is the reaction +H2O + CO 2 + 2Cu O 2 Cu (OH) 2 + CuCO 3 moist air So, copper also get rusted, a greenish deposit on the surface of copper vessels is a mixture of copper hydroxide and copper carbonate. Q.2. The ash obtained on burning magnesium ribbon is dissolved in water and tested for its acidic / basic nature. How will you ascertain that wheather the solution is acidic or basic? 1

2 Ans. The red litmus turns blue. So, oxide of magnesium is also basic in nature. In general, metallic oxides are basic in nature. Q.3. I heard that magnesium is found in plants. In what form is it found in them? Ans. 1. Magnesium is absorbed as Mg ++ ions by plants. It is a constituent of chlorophyll. Magnesium forms the central atom of porphyrin ring. (In chlorophyll). 2. Magnesium also maintains the ribosomes structure for protein synthesis. Q.4. Doctor reported iron deficiency in my body. Where is iron in my body? Ans. Iron flows in our blood in the form of haemoglobin. haem Haemoglobin + globin (Iron) Deficiency of iron leads to anaemia. Q.5. Which of the following can be beaten into thin sheets? (a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen Ans. (a) Zinc 2

3 Q.6. Which of the following statements is correct? (a) All metals are ductile. (b) All non-metals are ductile. (c) Generally metals are ductile. (d) Some non-metals are ductile. Ans. (c) Generally metals are ductile. Q.7. Fill in the blanks : (a) Phosphorus is very non-metal. (b) Metals are conductors of heat and (c) Iron is reactive than copper. (d) Metals react with acids to produce gas. Ans. (a) reactive (b) good, electricity (c) more (d) hydrogen. Q.8. Mark T if the statement is true and F if it is false. (a) Generally, non-metals react with acids. (b) Sodium is very reactive metal. 3

4 (c) Copper displaces zinc from zinc sulphate solution. (d) Coal can be drawn into wires. Ans. (a) F (b) T (c) F (d) F. Q.9. Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of their properties. Properties Metals Non-metals 1. Appearance 2. Hardness 3. Malleability 4. Ductility 5. Heat conduction 6. Conduction of Electricity Ans. Properties Metals Non-metals 1. Appearance Lustrous Non-lustrous 2. Hardness Hard except sodium Generally soft except diamond 4

5 3. Malleability Generally malleable 4. Ductility Generally ductile 5. Heat Conduction Good conductors 6. Conduction of Good Electricity conductors Nonmalleable Non-ductile Poor conductors Poor conductors Q.10. Give reasons for the following : (a) Aluminium foils are used to wrap food items. Ans. (a) Aluminium foil is used to wrap food items because aluminium can be beaten in sheets to form thin wrapping sheets. It is soft and does not react with food items. (b) Immersion rods are made up of metallic substances. Ans. (b) Immersion rods are made up of metallic substances because metals are good conductors of heat and electricity. They get hot very soon on passage of current and warm the water. (c) Copper cannot displace zinc from its salt solution. 5

6 Ans. (c) Copper cannot displace zinc from its salt solution because copper is less reactive than zinc. More reactive metal can replace a less reactive metal but a less reactive metal cannot replace a more reactive metal. (d) Sodium and potassium are stored in kerosene. Ans. (d) Sodium and potassium are stored in kerosene because they are very reactive and quickly react with oxygen and water, as a result a lot of heat is produced. Q.11. Can you store acidic lemon pickles in an aluminium utensils. Explain. Ans. No, we cannot store acidic lemon pickles in aluminium utensils because aluminium is a metal. Metals readily react with acids to produce hydrogen gas. So :- I. When the aluminum metal comes in contact with acidic lemon pickles, it would react to release hydrogen, which would spoil the food and render it unfit to consume. II. Lemon pickles contain weak acid which react with metal to produce toxic and poisonous compound. These poisonous compound may cause food poisoning. 6

7 Q.12. Match the substances given in Column A with their uses given in Column B. Column A Column B (i) Gold (a) Thermometers (ii) Iron (b) Electric wire (iii) Aluminium (c) Wrapping food (iv) Carbon (d) Jewellery (v) Copper (e) Machinery (vi) Mercury (f) Fuel Ans. Column A (i) Gold (ii) Iron (iii) Aluminum (iv) Carbon (v) Copper (vi) Mercury Column B (d) Jewellery (e) Machinery (c) Wrapping food (f) Fuel (b) Electric wire (a) Thermometers Q.13. What happens when (a) Dilute sulphuric acid is poured on a copper plate? Ans. (a) Copper sulphate is formed and hydrogen gas is liberated. 7

8 Copper + Sulphuric acid Copper sulphate + Hydrogen (gas). (b) Iron nails are placed in copper sulphate solution? Write word equations of the reactions involved. Ans. (b) Brown coating is deposited on the iron nails. This is because of the displacement of copper from copper sulphate solution by iron. Iron nails + Copper sulphate (solution) Iron sulphate (solution) + Copper Q.14. Saloni took a piece of burning charcoal and collected the gas evolved in a test tube. (a) How will she find the nature of the gas? (b) Write down word equations of all the reactions taking place in this process. Ans. (a) She will bring a wet litmus paper in contact with the gas. If the gas turns blue litmus paper into red the gas will be acidic. C + O 2 CO 2. 8

9 (b) (i) Carbon + Oxygen Carbon dioxide. (ii) Carbon dioxide + Water Carbonic acid (from wet litmus) CO 2 + H 2 O H 2 CO 3 Q.15. One day Reeta went to a Jeweller s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back they found that there was a loss in its weight. Can you suggest a reason for the loss in weight? Ans. When gold is washed in acidic solution, it being a metal reacts with acid and forms the hydrogen gas with some metallic oxides. This causes the loss of gold in the form of gold oxides. This looses the weight of gold. Q.16. Discuss with your parents / neighbours / goldsmiths why gold is preferred for making jewellery. Ans. Gold is preferred for making jewellery due to many reasons : 1. Gold does not get corroded, while copper, iron, and aluminium get corroded very easily. Silver ornaments also turning black after using some years while gold remain as such year to year. 9

10 2. The shiny appearance of gold makes it attractive for use in jewellery and decorative purposes. 3. Gold is very expensive, so the ornaments made of gold is considered very classic. 10