NCERT CLASS 10 CHAPTER 3 METALS AND NON METALS
NCERT CLASS 10 SCIENCE
CHAPTER 3 – METALS AND NON-METALS
COMPLETE QUESTIONS AND ANSWERS
PART A: IN-TEXT QUESTIONS AND ANSWERS
1. Physical Properties of Metals and Non-Metals
Q1. Give an example of a metal which is liquid at room temperature.
Answer: Mercury is a metal that is liquid at room temperature.
Q2. Give an example of a metal which can be easily cut with a knife.
Answer: Sodium and potassium are soft metals that can be easily cut with a knife.
Q3. Which non-metal is a good conductor of electricity?
Answer: Graphite, an allotrope of carbon, is a good conductor of electricity.
Q4. Which metal is the best conductor of heat?
Answer: Silver is the best conductor of heat among metals.
Q5. What are malleable and ductile materials?
Answer:
Malleable materials can be beaten into thin sheets.
Ductile materials can be drawn into thin wires.
Gold and silver are examples of highly malleable and ductile metals.
2. Chemical Properties of Metals
Q6. Why is sodium kept immersed in kerosene oil?
Answer: Sodium is a highly reactive metal. It reacts vigorously with oxygen and moisture present in the air and may catch fire. Therefore, it is stored under kerosene oil to prevent contact with air and water.
Q7. Write the equations for the reactions of iron with steam.
Answer:
3Fe + 4H₂O → Fe₃O₄ + 4H₂
Iron reacts with steam to form iron oxide and hydrogen gas.
Q8. What happens when calcium reacts with water?
Answer: Calcium reacts with water to form calcium hydroxide and hydrogen gas.
Ca + 2H₂O → Ca(OH)₂ + H₂
Q9. What happens when metals react with oxygen?
Answer: Metals generally react with oxygen to form metal oxides.
Example:
2Mg + O₂ → 2MgO
Q10. Why do ionic compounds have high melting and boiling points?
Answer: Ionic compounds contain positively and negatively charged ions held together by strong electrostatic forces of attraction. A large amount of energy is required to break these forces. Therefore, ionic compounds have high melting and boiling points.
3. Reactions of Metals with Acids
Q11. What happens when metals react with dilute acids?
Answer: Metals generally react with dilute acids to form a salt and hydrogen gas.
Metal + Dilute acid → Salt + Hydrogen
Example:
Zn + 2HCl → ZnCl₂ + H₂
Q12. What happens when copper reacts with dilute hydrochloric acid?
Answer: Copper does not react with dilute hydrochloric acid because it is less reactive than hydrogen and cannot displace hydrogen from dilute hydrochloric acid.
Q13. Why does nitric acid generally not produce hydrogen gas when it reacts with metals?
Answer: Nitric acid is a strong oxidising agent. It oxidises the hydrogen gas produced into water and is itself reduced to nitrogen oxides. Therefore, hydrogen gas is generally not evolved.
An exception is that very dilute nitric acid may produce hydrogen with metals such as magnesium and manganese.
4. Reactions of Metals with Solutions of Other Metal Salts
Q14. What happens when an iron nail is dipped in copper sulphate solution?
Answer: Iron is more reactive than copper. Therefore, iron displaces copper from copper sulphate solution.
Fe + CuSO₄ → FeSO₄ + Cu
Observations:
The blue colour of copper sulphate solution changes to pale green.
A reddish-brown coating of copper forms on the iron nail.
Q15. What is a displacement reaction?
Answer: A displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.
Example:
Zn + CuSO₄ → ZnSO₄ + Cu
5. The Reactivity Series
Q16. Arrange the following metals in decreasing order of reactivity: Al, Cu, Fe, Mg and Zn.
Answer:
Decreasing order of reactivity:
Mg > Al > Zn > Fe > Cu
Q17. What is the reactivity series?
Answer: The arrangement of metals in decreasing order of their chemical reactivity is called the reactivity series.
6. Ionic Compounds
Q18. What are ionic compounds?
Answer: Ionic compounds are compounds formed by the transfer of electrons from one atom to another, resulting in the formation of positively and negatively charged ions held together by electrostatic forces.
Example: Sodium chloride (NaCl).
Q19. Why are ionic compounds generally soluble in water?
Answer: Water is a polar solvent. Its molecules attract positive and negative ions and help separate them from the ionic crystal. Therefore, many ionic compounds dissolve in water.
Q20. Why do ionic compounds conduct electricity in the molten state but not in the solid state?
Answer: In the solid state, ions are fixed in their positions and cannot move freely. In the molten state, ions become free to move and carry electric charge. Therefore, molten ionic compounds conduct electricity.
PART B: NCERT EXERCISE QUESTIONS AND ANSWERS
Q1. 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
Answer: Option (d) AgNO₃ solution and copper metal.
Copper is more reactive than silver and can displace it from silver nitrate solution.
Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
Q2. 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 the above
Answer: Option (d) All of the above.
These methods prevent iron from coming into contact with air and moisture.
Q3. 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
Answer: Option (a) Calcium.
Calcium reacts with oxygen to form calcium oxide, which has a high melting point and reacts with water to form calcium hydroxide.
Q4. Food cans are coated with tin and not with zinc because:
(a) Zinc is more reactive than tin.
(b) Zinc is less reactive than tin.
(c) Tin is cheaper than zinc.
(d) Zinc has a higher melting point than tin.
Answer: Option (a) Zinc is more reactive than tin.
Tin is less reactive than zinc and does not react easily with food materials. Therefore, tin is used for coating food cans.
Q5. 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.
Answer:
(a) The following tests can be performed:
Hammer test: Metals can generally be beaten into sheets, while solid non-metals are usually brittle.
Electrical conductivity test: Connect the sample in an electric circuit containing a battery, bulb and switch. Metals generally allow electricity to pass through them and the bulb glows. Most non-metals do not conduct electricity.
(b) These tests are useful for identifying many metals and non-metals, but they are not universal. For example, graphite is a non-metal that conducts electricity, and some metals are brittle.
Q6. What are amphoteric oxides? Give two examples.
Answer: Oxides that react with both acids and bases to produce salt and water are called amphoteric oxides.
Examples:
Aluminium oxide (Al₂O₃)
Zinc oxide (ZnO)
Q7. Name two metals which will displace hydrogen from dilute acids and two metals which will not.
Answer:
Metals that displace hydrogen:
Zinc
Magnesium
Metals that do not displace hydrogen:
Copper
Silver
Metals above hydrogen in the reactivity series can generally displace hydrogen from dilute acids.
Q8. In the electrolytic refining of a metal, what would you take as the anode, the cathode and the electrolyte?
Answer:
Anode: Impure metal
Cathode: Thin sheet of pure metal
Electrolyte: A solution of a suitable salt of the same metal
During electrolysis, pure metal from the anode dissolves into the electrolyte and gets deposited on the cathode. Insoluble impurities settle below the anode as anode mud.
Q9. Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved in an inverted test tube. How will he identify the gas?
Answer:
Sulphur burns in air to form sulphur dioxide gas.
S + O₂ → SO₂
The gas can be tested using moist blue litmus paper. It turns red because sulphur dioxide dissolves in water to form sulphurous acid.
Q10. State two ways to prevent the rusting of iron.
Answer:
Painting: A layer of paint prevents iron from coming into contact with air and moisture.
Galvanisation: Coating iron with zinc protects it from rusting.
Other methods include oiling, greasing and electroplating.
Q11. What type of oxides are formed when non-metals combine with oxygen?
Answer: Non-metals generally form acidic or neutral oxides when they react with oxygen.
Examples:
Carbon dioxide (CO₂) is an acidic oxide.
Sulphur dioxide (SO₂) is an acidic oxide.
Carbon monoxide (CO) is a neutral oxide.
Q12. 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.
Answer:
(a) Platinum, gold and silver are used to make jewellery because they are lustrous, malleable, ductile and comparatively unreactive.
(b) Sodium, potassium and lithium are highly reactive metals. They react with air and moisture. Therefore, they are stored under oil.
(c) Aluminium forms a thin, protective layer of aluminium oxide on its surface. This layer prevents further corrosion. Aluminium is also a good conductor of heat and is lightweight.
(d) Metal oxides can generally be reduced to metals more easily than metal carbonates and sulphides. Therefore, carbonate and sulphide ores are converted into oxides before reduction.
Q13. 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.
Answer: Copper vessels develop a green coating of basic copper carbonate or a dark coating of copper oxide. Lemon and tamarind contain acids that react with these coatings and help remove them.
Q14. Differentiate between metal and non-metal on the basis of their chemical properties.
Answer:
Metals:
Metals generally form basic oxides.
Many metals react with dilute acids to release hydrogen gas.
Metals generally lose electrons to form positive ions.
Metals can displace less reactive metals from their salt solutions.
Non-metals:
Non-metals generally form acidic or neutral oxides.
Non-metals generally do not release hydrogen gas by reacting with dilute acids.
Non-metals generally gain or share electrons.
Non-metals generally do not displace metals from their salt solutions.
Q15. A man went door to door posing as a goldsmith. He promised to bring back the glitter of old gold ornaments. An unsuspecting lady gave him a set of gold bangles, which he dipped in a particular solution. The bangles became new-looking but lost weight considerably. What was the solution he used?
Answer: He most likely used aqua regia, a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1 by volume.
Aqua regia can dissolve gold. Therefore, some gold was lost from the bangles.
Q16. What are the constituent metals of brass and bronze?
Answer:
Brass: Copper and zinc.
Bronze: Copper and tin.
Q17. Which of the following metals will melt at body temperature?
Gallium, caesium, aluminium, copper.
Answer: Gallium and caesium have melting points close to or below normal human body temperature and can melt at body temperature under suitable conditions.
Q18. Why is iron used in the construction of bridges and buildings?
Answer: Iron is strong, hard and has high tensile strength. It can withstand heavy loads, making it useful in construction. In many structures, iron is used in the form of steel.
PART C: ADDITIONAL IMPORTANT QUESTIONS AND ANSWERS
Q1. Define metals.
Answer: Metals are elements that generally have a shiny appearance, are hard, malleable, ductile and good conductors of heat and electricity. They usually lose electrons to form positive ions.
Q2. Define non-metals.
Answer: Non-metals are elements that generally lack metallic properties. They are usually poor conductors of heat and electricity, brittle in the solid state and tend to gain or share electrons.
Q3. What is corrosion?
Answer: Corrosion is the gradual destruction of a metal due to its reaction with substances present in the environment, such as oxygen and moisture.
Example: Rusting of iron.
Q4. What is rust?
Answer: Rust is a reddish-brown substance formed when iron reacts with oxygen and moisture. It is mainly hydrated iron(III) oxide.
Q5. What is galvanisation?
Answer: Galvanisation is the process of coating iron or steel with a thin layer of zinc to prevent rusting.
Q6. What is an alloy?
Answer: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
Examples:
Brass: Copper and zinc.
Bronze: Copper and tin.
Steel: Iron and carbon.
Q7. Why are alloys generally preferred over pure metals?
Answer: Alloys are often harder, stronger and more resistant to corrosion than pure metals. Their properties can be modified according to their uses.
Q8. What is aqua regia?
Answer: Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio 3:1 by volume. It can dissolve noble metals such as gold and platinum.
Q9. What is an ore?
Answer: Minerals from which metals can be extracted conveniently and profitably are called ores.
Q10. What is mineral?
Answer: Naturally occurring substances in the Earth's crust containing metals or their compounds are called minerals.
Q11. What is roasting?
Answer: Roasting is the process of heating a sulphide ore strongly in the presence of excess air to convert it into an oxide.
Example:
2ZnS + 3O₂ → 2ZnO + 2SO₂
Q12. What is calcination?
Answer: Calcination is the process of heating a carbonate ore strongly in limited or no air to convert it into an oxide.
Example:
ZnCO₃ → ZnO + CO₂
Q13. What is electrolytic refining?
Answer: Electrolytic refining is the process of purifying a metal by using electricity. The impure metal is made the anode, a thin sheet of pure metal is the cathode, and a solution of a suitable salt of the metal is used as the electrolyte.
Q14. What is the thermite reaction?
Answer: The reaction in which aluminium reduces iron oxide to molten iron is called the thermite reaction.
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + Heat
It is used in welding railway tracks and repairing broken iron parts.
Q15. Why do metals generally form positive ions?
Answer: Metals generally have one, two or three electrons in their outermost shell. They tend to lose these electrons to achieve a stable electronic configuration, forming positive ions.
Example:
Na → Na⁺ + e⁻
Q16. Why do non-metals generally form negative ions?
Answer: Non-metals generally have four to seven electrons in their outermost shell. They tend to gain electrons to achieve a stable electronic configuration, forming negative ions.
Example:
Cl + e⁻ → Cl⁻
Q17. Why is aluminium used for making aircraft?
Answer: Aluminium is lightweight, strong when used in suitable alloys, and resistant to corrosion due to its protective oxide layer. Therefore, it is used in aircraft manufacturing.
Q18. Why is copper used for making electrical wires?
Answer: Copper is a very good conductor of electricity, is ductile and can be drawn into thin wires. Therefore, it is widely used in electrical wiring.
PART D: DIFFERENCES BETWEEN IMPORTANT TERMS
Q1. Differentiate between metals and non-metals.
Answer:
Metals:
Generally have a shiny surface.
Generally are malleable and ductile.
Generally conduct heat and electricity well.
Usually form positive ions.
Their oxides are generally basic or amphoteric.
Non-metals:
Generally have a dull surface.
Solid non-metals are generally brittle.
Generally are poor conductors of heat and electricity.
Usually form negative ions or share electrons.
Their oxides are generally acidic or neutral.
Q2. Differentiate between malleability and ductility.
Answer:
Malleability:
It is the property of being beaten into thin sheets.
Example: Gold can be beaten into thin sheets.
Ductility:
It is the property of being drawn into thin wires.
Example: Copper can be drawn into wires.
Q3. Differentiate between roasting and calcination.
Answer:
Roasting:
Sulphide ores are heated strongly in excess air.
The ore is converted into an oxide.
Sulphur dioxide gas is generally released.
Calcination:
Carbonate ores are heated in limited or no air.
The ore is converted into an oxide.
Carbon dioxide gas is generally released.
Q4. Differentiate between minerals and ores.
Answer:
Minerals:
Minerals are naturally occurring substances found in the Earth's crust.
All minerals containing metals are not suitable for economical extraction.
Ores:
Ores are minerals from which metals can be extracted conveniently and profitably.
All ores are minerals, but all minerals are not ores.
Q5. Differentiate between ionic compounds and covalent compounds.
Answer:
Ionic Compounds:
Formed by transfer of electrons.
Contain positive and negative ions.
Generally have high melting and boiling points.
Conduct electricity in molten or aqueous states when mobile ions are present.
Example: Sodium chloride.
Covalent Compounds:
Formed by sharing of electrons.
Contain atoms held together by covalent bonds.
Generally have lower melting and boiling points than ionic compounds.
Generally do not conduct electricity.
Example: Methane.
PART E: IMPORTANT REACTIVITY SERIES
The reactivity series of metals in decreasing order is:
K – Potassium
Na – Sodium
Ca – Calcium
Mg – Magnesium
Al – Aluminium
Zn – Zinc
Fe – Iron
Pb – Lead
H – Hydrogen
Cu – Copper
Hg – Mercury
Ag – Silver
Au – Gold
Important facts:
Potassium is highly reactive.
Sodium reacts vigorously with water.
Metals above hydrogen can generally displace hydrogen from dilute acids.
Metals above another metal in the series can displace it from its salt solution.
Gold and silver are comparatively unreactive metals.
PART F: IMPORTANT CHEMICAL EQUATIONS
Burning of magnesium:
2Mg + O₂ → 2MgO
Sodium reacting with water:
2Na + 2H₂O → 2NaOH + H₂
Calcium reacting with water:
Ca + 2H₂O → Ca(OH)₂ + H₂
Iron reacting with steam:
3Fe + 4H₂O → Fe₃O₄ + 4H₂
Zinc reacting with hydrochloric acid:
Zn + 2HCl → ZnCl₂ + H₂
Iron displacing copper:
Fe + CuSO₄ → FeSO₄ + Cu
Copper displacing silver:
Cu + 2AgNO₃ → Cu(NO₃)₂ + 2Ag
Formation of aluminium oxide:
4Al + 3O₂ → 2Al₂O₃
Formation of zinc oxide by roasting:
2ZnS + 3O₂ → 2ZnO + 2SO₂
Formation of zinc oxide by calcination:
ZnCO₃ → ZnO + CO₂
Thermite reaction:
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe + Heat
Formation of magnesium chloride:
Mg + Cl₂ → MgCl₂
Formation of sodium chloride:
2Na + Cl₂ → 2NaCl
Reaction of aluminium oxide with hydrochloric acid:
Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Reaction of aluminium oxide with sodium hydroxide:
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O
PART G: IMPORTANT ONE-MARK QUESTIONS
Q1. Which metal is liquid at room temperature?
Answer: Mercury.
Q2. Which non-metal is a good conductor of electricity?
Answer: Graphite.
Q3. Which metal is stored under kerosene oil?
Answer: Sodium and potassium.
Q4. Which metal is used for galvanisation?
Answer: Zinc.
Q5. Which metal is the best conductor of electricity?
Answer: Silver.
Q6. What is the chemical formula of rust?
Answer: Hydrated iron(III) oxide, commonly represented as Fe₂O₃·xH₂O.
Q7. What is the main constituent of brass?
Answer: Copper and zinc.
Q8. Which metals are present in bronze?
Answer: Copper and tin.
Q9. Which gas is produced when a metal reacts with dilute hydrochloric acid?
Answer: Hydrogen gas.
Q10. Which metal is used in the thermite reaction?
Answer: Aluminium.
Q11. Name two amphoteric oxides.
Answer: Aluminium oxide and zinc oxide.
Q12. What is the chemical formula of copper sulphate?
Answer: CuSO₄.
Q13. Which metal is used for making electric wires?
Answer: Copper.
Q14. Which metal is used in jewellery because of its low reactivity and lustre?
Answer: Gold.
Q15. What is the main metal present in steel?
Answer: Iron.
Q16. What is the process of coating iron with zinc called?
Answer: Galvanisation.
Q17. Which acid is used in aqua regia along with hydrochloric acid?
Answer: Nitric acid.
Q18. What is the ratio of hydrochloric acid to nitric acid in aqua regia?
Answer: 3:1 by volume.
Q19. Which metal is extracted from bauxite ore?
Answer: Aluminium.
Q20. Which metal is extracted from cinnabar?
Answer: Mercury.
Q21. What is the chemical formula of haematite?
Answer: Fe₂O₃.
Q22. Which metal is present in the ore called zinc blende?
Answer: Zinc.
Q23. What is the chemical formula of sodium chloride?
Answer: NaCl.
Q24. Which process is used to purify copper?
Answer: Electrolytic refining.
Q25. What is the nature of most metal oxides?
Answer: Basic.
PART H: IMPORTANT FACTS FOR QUICK REVISION
Metals are generally hard, malleable, ductile and lustrous.
Non-metals are generally brittle in the solid state.
Mercury is a liquid metal at room temperature.
Bromine is a liquid non-metal at room temperature.
Graphite is a non-metal that conducts electricity.
Sodium and potassium are stored under kerosene oil.
Metals generally form basic oxides.
Aluminium oxide and zinc oxide are amphoteric.
Metals above hydrogen in the reactivity series generally release hydrogen from dilute acids.
Iron displaces copper from copper sulphate solution.
Ionic compounds have high melting and boiling points.
Ionic compounds conduct electricity in molten and aqueous states when their ions are mobile.
Rusting requires oxygen and moisture.
Galvanisation protects iron from rusting.
Roasting is generally used for sulphide ores.
Calcination is generally used for carbonate ores.
Aluminium is used in the thermite reaction.
Gold and silver are comparatively unreactive metals.
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