Explore NCERT Solutions

Chapter Review:

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• Metals, in their pure state, have a shining surface. This property is
  called metallic lustre.
• Some metals can be beaten into thin sheets. This
  property is called malleability.
• The ability of metals to be drawn into thin wires is called ductility.
• Gold is the most ductile metal a wire
  of about 2 km length can be drawn from one gram of gold.
• The metals that produce a sound on striking a hard surface
  are said to be sonorous.
• The best conductors of heat are silver and
  copper. Lead and mercury are comparatively poor conductors of heat.
• Full Form of PVC is polyvinylchloride.
• Gallium and caesium have very low melting points.
• Iodine is a non-metal but it is lustrous.
• Diamond, an allotrope of carbon, is
  the hardest natural substance known and has a very high melting
  and boiling point.
• Graphite, another allotrope of carbon, is a conductor of electricity.
• Lithium, sodium, potassium are so soft that they can be cut with a knife. They have low densities and low melting points.
• Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open.Therefore they are kept immersed in kerosene oil.
• Anodising is a process of forming a thick oxide layer of aluminium.
• Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1.Aqua regia is a highly corrosive, fuming liquid.
• The metals at the top of the activity series (K, Na, Ca, Mg and Al) are so reactive that they are never found in nature as free elements.
• The metals in the middle of the activity series (Zn, Fe, Pb, etc.) are moderately reactive. They are found in the earth’s crust mainly as oxides, sulphides or carbonates.
• Ores mined from the earth are usually contaminated with large amounts of impurities such as soil, sand, etc., called gangue.
• Cinnabar (HgS) is an ore of mercury.
• The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting.
• The carbonate ores are changed into oxides by heating strongly in limited air. This process is known as calcination.
• Galvanisation is a method of protecting steel and iron from rusting
  by coating them with a thin layer of zinc.
• The rusting of iron can be prevented by painting, oiling, greasing,
  galvanising, chrome plating, anodising or making alloys.
• When iron is mixed with nickel and chromium, we get stainless steel, which is hard and does not rust.
• An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
• Pure gold, known as 24 carat gold, is very soft. It is, therefore, not suitable for making jewellery.
• The alloy of mercury is known as an amalgam.
• The extraction of metals from their ores and then refining them for use is known as metallurgy.

Text-book Questions with Solution:

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NCERT Book Page 40

Q1: 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.

Answer: 

(i) Metal that exists in liquid state at room temperature is Mercury. 

(ii) Metals that can be easily cut with a knife are Sodium and Potassium

(iii) Metals that are the best conductor of heat are Silver and Gold

(iv) Metals that are poor conductors of heat are Mercury and lead.

Q2. Explain the meanings of malleable and ductile.

Answer: 

Meliable: Some metals can be beaten into thin sheets by beating such substances are called malleable.

Ductile: Some substances can be drawn into thin wires such substances are called ductile. 

Page No. 46

Q1. Why is sodium kept immersed in kerosene oil?

Answer: Sodium and potassium are highly reactive metals, they react with air and catch fire easily, so sodium is kept immersed in kerosene.

Q2. Write equation for the reactions of

(i) iron with steam

(ii) calcium and potassium with water

Answer: 

(i) 3Fe(s)+ 4H2O(g)→ Fe3O4+4H2(g) |

(ii) Ca(s)+2H2O(I)→ Ca(OH)2 (aq)+H2(g) |  

Q3. Samples of four metals A, B, C, and D were taken and added to the following solution one by one. The results obtained have been tabulated as follow: 

Use the table above to answer the following questions about meals A,B,C and D. 

(i) Which is the most relative metal?

(ii) What would you observe of B is added to a solution of copper (II) sulphate.

(iii) Arrange the metals A,B,C and D in the order of decreasing reactivity.

Answer: (i) Metal B is more reactive metal.

(ii) displacement reaction will take place.

(iii) Metal B > Metal A > Metal C > Metal D

Q4. Which gas is produced when dilute hydrochlroic acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₄. 

Answer: Hydrogen gas is released.

  Fe (s) + H2SO4  → FeSO4 (aq) + H2 (g) 

Q5. What would you observe when zinc is added to a solution of Iron(II) sulphate? write the chemical reaction that takes place?

Answer: Zinc displaces iron from iron sulphate solution.

Zn + FeSO4   → ZnSO4 + Fe 

Page no. 49 

Q1. (i) Write the electric-dot structure for sodium, oxygen and magnesium.

(ii) Show the formation of Na2O and MgO by the transfer of electrons.

(iii) What are the ions present in these compound?

Q2. Why do  ionic compound have high melting points?

Answer: The mutual ionic attraction is very strong in an ionic compound. It takes a lot of energy to break this powerful bond. Hence their melting point is high.

Page no. 53

Q1. Define the following terms.

(i) Mineral       (ii) Ore     (iii) Gangue

Answer: (i) Minerals are those substances in which metals are found in the form of their compounds.

(ii) Such minerals in which the extraction of metals is very easy and suitable are called ores.

(iii) Minerals are not found pure in nature, the impurities present in them are called gangue.

Q2. Name two metals which are found in nature in the free state.

Answer: Gold and Platinum.

Page no. 55

Q1.Metalic oxides of zinc, magnesium and copper were heated with the following metals.

Metal	zinc	magnesium	copper
zinc oxides
magnesium oxides
copper oxides

In which case will you find displacement reactions taking place?

Answer:

Metal	zinc	magnesium	copper
zinc oxides	no	yes	no
magnesium oxides	no	no	no
copper oxides	yes	no

Q2. In which metal do not corrode easily?

Answer: Gold, Platinum and Silver.

Q3. What are alloys?

Answer: A homogeneous mixture of two or more metals is called an alloy.

Additional Questions With Solutions:

Q1: What is malleability?

Ans: Some metals can be beaten into thin sheets. This property is called malleability.  Ex. – gold , Silver.

Q2: What is ductility?

Ans:  The ability of metals to be drawn into thin wires is called ductility.  Such a metal is called ductile metal. Ex. – gold and silver.

Q3: What is sonorous?

Ans: The metals that produce a sound on striking a hard surface are said to be sonorous.

Q4: Why are school bells made of metals?

Ans: The metals have a property of sonorous; they produce sound on striking a hard surface, so the school bells are made of metals.

Q6: Name two metals which melt to keep them on your palm.

Ans: Gallium and caesium.

Q7: Name a allotrope of carbon which is good conductor of electricity.

Ans: Graphite.

Q8: What do non metals produce when dissolve in water.

Ans: They produce acidic oxides.

Q11:  What is anodising?

Ans: Anodising is a process of forming a thick oxide layer of aluminium.

Q13: What is done with the article to protect the further corrosion?

Ans: Anodising.

Q18: Name the metals which float in water.

Ans: Calcium and magnesium.

Q19: Why do Calcium and magnesium float in water?

Ans: Calcium and magnesium start floating because the bubbles of hydrogen gas formed stick to the surface of the metals.

Q20: Name two metals which do not react with hot or cold water but react with steam.

Ans: Aluminium and Iron.

Q21: What is the nature of metallic oxide?

Ans: Basic.

Q22: What is the nature of non-metallic oxide?

Ans: Acidic. 

Additional Questions With Solutions:

 

Q1: Write three chemical properties of metals.

Ans: Three chemical properties of metals.

(i)All metals combine with oxygen to form metal oxides.

(ii)Metals react with water and produce a metal oxide and hydrogen gas.

(iii)Metals reacts with acids to give a salt and hydrogen gas.

Q2: Write three physical properties of metals.

Ans: Three physical properties of metals.

(i)Metals are ductile.

(ii)Metals are malleable.

(iii)Metals are sonorous.

Q3: What is amphoteric oxides? Give to examples.

Ans: The metals oxides which react with both acids as well as bases to produce salt and water and show both acids as well as basic behaviour are known as amphoteric oxides. Ex.- aluminium oxide and zinc oxide etc. q

Q4: Why are sodium or potassium kept immersed in kerosene oil?

Ans: Sodium or potassium reacts so vigorously that they catch fire if kept in open. Hence to protect them and to prevent to accidental fire they are kept immersed in kerosene oil.

Q5: The reaction metal X and Fe₂ O₃ is highly exothermic and is used to join railway.

 (a) Identify metal X and name the reaction.

(b) Write the chemical equation of its reaction with fe₂ O_3.

Ans:

(a)X is (Al) Aluminium. Thermit Reaction.

(b)Fe₂O₃ (s) + 2Al(s) 2Fe(l) + Al₂O₃(s) + (Heat) 

Q6: A metal X react with oxygen to form a blackish thin layer of oxide coat which protects itself to further corrosion.

(i)Identify the metal X.

(ii)What is called such a metal oxide.

(iii)What does it give to react with sodium hydroxide write its chemical equation.

Ans:

(i)Metal X is aluminium.

(ii)Aluminium oxide is called amphoteric oxides.

(iii)It react with sodium hydroxide gives sodium aluminate and water.

Q7: What is aqua regia?

Ans: Aqua regia is freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3: 1. It is used to dissolve gold and clean the ornaments.

Q8: Why are the ornaments made of gold, silver and platinum?

Ans: Gold, silver and platinum have less reactivity so they don’t react with water and oxygen that cause corrosion. Hence the ornaments are made of gold, silver and platinum.