CHAPTER 3
Metals and Non-Metals
Objective Questions
Multiple Choice Questionsent
1 Which of the following pairs will give displacement reactions
(a) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
- Which of the following methods is suitable for preventing an iron frying pan from rusting?
(a) Applying grease
(b) Applying paint
(c) Applying a coating of zinc
(d) All of these.
- An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
(a) Calcium
(b) Carbon
(c) Silicon
(d) Iron.
- Food cans are coated with tin and not with zine because
(a) Zinc is costlier than tin
(b) Zinc has a higher melting point than tin.
(c) Zinc is more reactive than tin.
(d) Zine is less reactive than tin.
- Which of the following non-metal is a good conductor of electricity?
(b) Hydrogen
(a) Phosphorus
(d) Graphite.
(c) Bromine
- Metal exist in liquid state
(a) Mercury (c) Aluminium
(b) Sodium. (d) Zinc.
- In the thermite process, the reducing agent used is
(a) Calcium
(b) Sodium
(c) Coke
(d) Aluminium powder
.8. Which among the following is present in human blood ?
(a) Titanium (c) Gold
(b) Mercury (d) Iron.
- The border line elements, which neither fit with metals nor with non-metal are known as
(a) Allotropes (c) Isotopes
(b) Alloys. (d) Metalloids.
- The metals which can displace hydrogen from water at room temperature appear in the activity series
(a) Below Hydrogen. (c) At the bottom
(b) In the middle. (d) Near the top.
- Which of the following is the lightest metals ?
(a) Silver (c) Lithium
(b) Mercury. (d) Lead.
- Which of these metals does not liberate hydrogen from dilute acids ?
(a) Leads does not
(b) Copper
(c) Aluminium
(d) Iron.
- Rusting of iron takes place in
(a) ordinary water
(b) distilled water
(c) both ordinary and distilled water
(d) none of these.
- Silver articles become black on prolonged exposure to air. This is due to the formation of
(a) Ag₂O
(b) Ag₂S (d) AgSO4
(c) Ag₂CO3
Ans. 1. (d), 2. (c), 3. (a), 4. (c), 5.(d), 6. (a), 7. (d), 8. (d), 9. (d), 10. (d). 11. (c), 12. (b), 13. (c), 14. (b).
Fill in the Blanks
- The ability of metals to be drawn into thin wires is called………….
2 …………. is a non-metal, but it is lustrous.
3 ……. .…..is the most ductile metal.
- Chemical formula of rust is …………
- Metals can be beaten into thin sheets. This property is called……………
6…………. is a liquid metal.
- Metal oxides which react with both acids and bases to produce salt and water are called ………… oxides.
8………….can dissolve gold and platinum.
- The green substance formed on the surface of copper when exposed to air is ………….
- ………..is an ore of mercury.
Ans. 1. ductility. 2. Iodine, 3. Gold, 4. Fe₂O3.nH₂O 5. Malleability, 6. Mercury, 7. amphoteric, 8. Aqua regia, 9. Copper Carbonate, 10. Cinnabar (HgS).
True/False
- Stainless steel is an alloy of nickel and chromium.
- Hydrogen is the lightest non-metal.
- Solder is an alloy of lead and zinc.
- Ionic compounds have high melting and boiling points.
- Bronze is a good conductor of electricity.
Ans. 1. True, 2. True, 3. False, 4. True, 5. False.
Match the Columns
Column ‘A’. Column ‘B’
- Solder. (a) Low Melting Point
- Gallium. (b) Quick Silver
- Mercury. (c) Welding
- Gold. (d) Allotrope of Carbon
- Diamond. (e) Free state
- Sodium. (f)(Highly reactive metal
Ans. 1. (c), 2. (a), 3. (b), 4. (e), 5. (d), 6. → (f).
Answer in one Word/Sentence
- Which metal melts on keeping on palm ?
Ans. Gallium.
- Term used to express the purity of gold.
Ans. Carat.
- Bronze is an alloy of which elements ?
Ans. Copper and Tin (Cu and Sn).
- What is added to Gold to increase its strength?
Ans. Silver or Copper.
- Name two metals which float on water.
Ans. Calcium and Magnesium.
Very Short Answer Type Questions
- I. Give an example of a metal which :
(i) is a liquid at room temperature.
(ii) can be easily cut with a knife.
(iii) is the best conductor of heat.
(iv) is a poor conductor of heat.
Ans. (i) Mercury, (ii) Sodium, (iii) Silver and copper, (iv) Lead.
- 2. Which metals do not corrode easily?
Ans. Metals which have low reactivity such silver, gold do not corrode easily.
- 3. Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Ans. Iron and aluminium will displace hydrogen from dilute acids as they are more reactive than hydrogen.
Mercury and copper cannot displace hydrogen from dilute acids as they are less reactive than hydrogen.
Q.4. Write equations for the reactions of:
(1) Iron with steam.
(2)Calcium and potassium with water.
Ans
- 5. What are amphoteric oxides? Give two examples of amphoteric oxides.
Ans. Those oxides that behave as both acidic and basic oxides are called amphoterie oxides.
Examples-Aluminium oxide (Al₂O3), Zinc oxide (ZnO).
- 6. What type of oxides are formed when non-metals combine with oxygen?
Ans. When non-metals combine with oxygen then neutral or acidic oxides are formed Examples of acidic oxides are NO₂, SO₂ and examples of neutral oxides are NO, CO.
- 7. Define corrosion.
Ans. Corrosion “Some metals get reacted with atmospheric oxygen in presence of moisture forming their oxides or hydroxides and are decayed slowly. This is called corrosion.”
Short Answer Type Questions
- 1. Explain the meanings of malleable and ductile.
Ans. Malleable-Substances that can be beaten into thin sheets are called malleable.This property is called malleability.For example, most of the metals are malleable, gold and silver are the most malleable metals. Ductile Substances that can be drawn into thin wires are called ductile. Most of themetals are ductile. Gold is the most ductile metal.
- 2. Why is sodium kept immersed in kerosene oil ?
Ans. Sodium is a highly reactive metal. If it is kept in open, it can explosively react with oxygen present in air to catch fire. Hence to prevent accidental fires, it is in kerosene oil.
kept immersed
- 3. Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical equation when iron reacts with dilute H₂SO4.
Ans. Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.
When iron reacts with dilute H₂SO4 green coloured solution of iron (II) sulphate is formed with the evolution of hydrogen gas.
Fe(s) + H₂SO4 → FeSO4 (aq) + H₂ (g) Q. 4.
Q 4 What would you observe when zinc is added to a solution of iron II sulphate? Write the chemical reaction that takes place.
Ans. When zine is added to iron (II) sulphate then it will displace iron from iron sulphate solution, as zine is more reactive than iron.
Zn(s) + FeSO4(aq) → ZnSO4(aq) + Fe(s)
- 5. Why do ionic compounds have high melting points?
Ans. lonic compounds have strong electrostatic forces of attraction between the ionsTherefore, a considerable amount of energy is required to break these forces. That is why, ionic compounds have high melting points.
- 6. What are alloys ?
Ans. An alloy is a homogenous mixture of two or more metals or a metal and a non-metal. Example Steel is an alloy of carbon and iron.
- 7. (1) Write the electron-dot structures for sodium, oxygen and magnesium.
(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
(iii) What are the lons present in these compounds ?
Ans.
- 8. You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Ans. Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in lemon or tamarind neutralises basic copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of copper vessel its characteristic lustre.
- 9. Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
Ans. Copper does not react with cold water, hot water, or steam. However, iron reacts with steam. If the hot water tanks are made of steel (an alloy of iron), then iron would react
vigorously with the steam formed from hot water.
3Fe + 4H₂0———Fe₂O4 + H₂O
Long Answer Type / Analytical Questions
- 1. You are given a hammer, a battery, a bulb, wires and a switch.
(a) How could you use them to distinguish between samples of metals and non-metals?
(b) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Ans. (a) We can use the battery, bulbs, wires and a switch to set i a circuit with the sample. If the sample conducts electricity then it is a metal otherwise it is a non-metal. We can also beat the sample with a hammer. If it can be beaten into thin sheets, i.e. it is malleable, then it is a metal otherwise it is a non-metal.
(b) In the above tests, no chemical reactions are involved and they are based on the physical properties of metals and non-metals.
Hence, they are useful in distinguishing between metals and non-metals.
- 2. State two ways to prevent the rusting of iron.
Ans. Two ways to prevent the rusting of iron are
(i) Oiling, greasing or painting-——By applying oil, grease or paint, the surface becomes water proof and the moisture and oxygen present in the air cannot come into direct contact with iron. Hence, rusting is prevented.
(ii) Galvanisation-It is a method of protecting iron from rusting by coating an iron article with a thin layer of zinc. It prevents the iron to come in contact with oxygen and moisture. The galvanised article is protected against rusting even if the zinc coating is broken.
- 3. Give reasons:
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction. are lustrous.
Ans. (a) Platinum, gold and silver are used to make jewellery because they Also, they are very less reactive and do not corrode easily.
(b) Sodium, potassium and lithium are very reactive metals. They react vigorously with air as well as water. Therefore, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.
(c) Aluminium is a highly reactive metal but it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide (Al₂O3). The reaction is 4A1+30₂-2Al2O3. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, aluminium is light in weight and a good conductor of heat. That is why, it is used to make cooking utensils
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their
carbonates and sulphides.
- 4. Differentiate between metal and non-metal on the basis of their physical properties.
Ans. Difference between metals and non-metals on the basis of physical properties
- 5. Differentiate between metals and non-metals on the basis of their chemical properties.
Ans. Difference between metals and non-metals on the basis of chamical properties
- 6. A man went door to door posing as a goldsmith. He promised to bring back. the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of goldbangles to him which he dipped in a particular solution. The bangles sparkled like new but weight was reduced drastically. The lady was upset, but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Ans. The solution he had used was Aqua regia. Aqua regia is a Latin word which means “Royal water’. It is a freshly prepared mixture of conc. hydrochloric acid and conc. nitric acid in the ratio 3: 1. It is capable of dissolving gold and platinum.
- 7. Write any five physical properties of metals.
Ans. Physical properties of metals :
(1) Metals are generally good conductors of heat and electricity.
(2) Metals are generally melleable.
(3) Metals are generally ductile.
(4) In general, metals are hard.
(5) In general, metals are sonorous.
- 8. Write the general properties for ionic compounds.
Ans. General properties for ionic compounds
(1) Physical Nature-Ionic compounds are solids and are somewhat hard because of the strong force of attraction between the positive and negative ions. These compounds are generally brittle and break into pieces when pressure is applied.
(2) Melting and Boiling Points-lonic compounds have high melting and boiling points. This is beacuse a considerable amount of energy is required to break the strong inter-ionic attraction.
(3) Solubility-Electrovalent compounds are generally soluble in water and insoluble in solvents such as kerosene, petrol, etc.
(4) Conduction of Electricity-The conduction of electricity through a solution involves the movement of charged particles. A solution of an ionic compound in water contains ions, which move to the opposite electrodes when electricity is passed through the solution. Ionic compounds in the solid state do not conduct electricity because movement of ions in the solid is not possible due to their rigid structure. But ionic compounds conduct electricity in the molten state. This is possible in the molten state since the electrostatic forces of attraction between the oppositely charged ions are overcome due to the heat. Thus, the ions move freely and conduct electricity.
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