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Subject:

science-chemistry

Class:

class VIII

Key Concepts

atom, conductor, displacement reaction, ductility, elements, hardness, malleability, metals, metalloids, non metal, sonorous, electrolysis

essential questions

1. What are the properties of metals?
2. How does it help us in everyday life if we know the properties of various elements?
3.What are non metals?

Remembering:

  1. Define malleability.
  2. List 3 properties of metals.
  3. List the various uses of non metals
  4. Define element
  5. The property by which metals can be beaten into sheets is known as: a) ductility  b) sonority  c) lusture   d) malleability
  6. The property of metal by which it can be drawn into wires is called_: a) sonority  b) malleability   c) ductility   d) lusture
  7. What is froth floatation?
  8. Which of the following reactions are possible: i) Mg + CuSO4→ MgSO4 +Cu   ii)  Ca + MgSO4  → CaSO4 + Mg   iii) Cu + ZnSO4 → CuSO4 +Zn   iv) Fe + MgSO4 → FeSO4 +Mg    a) iii and iv only   b) i and iv only   c) ii and iii only   d) i and ii only
  9. Match the following and write the name

Alloy that is used in making of statues, coins and medals & resist corrosion        Al + Cu+ Mn + Mg

Alloy used in aircrafts and light tools has high tensile strength                                 Cu + Sn + Zn

Alloy used for surgical instruments, cutlery                                                                    Cu + Zn + Ni

 

understanding:

  1. Why are temple bells made of metal only?
  2. Write the difference between metals and non metals.
  3. What is displacement reaction. Explain with an example.
  4. What do you understand by a metal being more reactive than the other? Explain with an example.
  5. What is electrolysis? Explain in detail using diagram.
  6. When we use molten sodium chloride for electrolysis, what type of reaction will happen. Explain with diagram and chemical equations.
  7. How is hydrogen as fuel obtained? Why is it called a clean fuel?
  8. What is electroplating?
  9. What is electro refining?
  10. How is the principle of electrolysis used in electro refining?
  11. How are ores extracted from metals?
  12. Write the difference between metals, non metals and metalloids
  13. Why zinc reacts with copper sulphate to form zinc sulphate and copper. Explain with chemical reaction.
  14. How metals are used in our daily life? Give 5 examples
  15. How we use non metals in our daily life? Give 5 examples
  16. What is an alloy? How is it better over metal?
  17. Write the differences between magnetic separation and gravity separation
  18. Study the given table carefully and select the appropriate option:   a) I is copper; II is sulphur   b) II is sulphur; III is coal   c) III is iron; IV is copper  d) II is coal; IV is copper
  19. Which of the following can be beaten into thin sheets:  a) zinc   b) phosphorus   c) sulphur   d) oxygen
  20. A substance is said to be sonorous if it: a) conducts heat   b) beaten into sheets   c) produce ringing sound when beaten  d) conducts electricity
  21. Which of the following is a non metal but is lustrous: a) carbon   b) mercury  c) iodine  d) flourine

Application:

  1. Why is sodium metal stored in kerosene and not in water?
  2. Why is there a pop sound when a burning match stick is brought near test tube that has metals react with acids?
  3. Why are electrodes inert in nature in electrolysis?
  4. Why electrolysis cannot occur in solid salt?
  5. Why is acid added in water to carry electrolysis?
  6. Why copper electrode is used in electrolysis of copper sulphate solution? Explain using the chemical equation?
  7. How does electroplating prevent corrosion?
  8. Why do we use metal to be plated as anode and article to be plated at cathode in the process of electroplating?
  9. Why is diamond a non metal?
  10. Which of the following is false:  a) carbon is most malleable element    b) copper is a good conductor of electricity  c) aluminum is a good conductor of heat   d) bromine is the only  liquid non metal
  11. Metals like zinc and aluminum react with sodium hydroxide to produce_ gas. a) hydrogen  b) hydrogen sulphide   c) oxygen  d) sulphur dioxide
  12. When zinc react with dilute sulphuric acid, a salt is formed with the release of a gas. The gas produced during this puts off a burning candle with a pop sound. The gas evolved during evolved during this reaction is: a) sulphur dioxide   b) oxygen  c) hydrogen  d) hydrogen sulphide
  13. Which of the following order is correct for the reactivity of metals: a) Na> Au> Fe> Mg   b)  Na > Mg> Fe> Au   c) Mg> Fe> Na> Au    d) Mg> Na>  Fe> Au
  14. The oxide of sulphur when dissolved in water gives:  a) H2S   b) H2SO4   c)  H2SO3    d) H2
  15. Fill in the blanks with the most appropriate option: W is a very reactive metal, reacts vigourously with oxygen and water therefore, stored in __1__.  X is a non metal, soft and dull and forms __2__ oxides with oxygen. Y is very reactive __3__ , catched fire if exposed to air therefore stored in water  Z does not react with dilute hydrocholric acid even on heating but it reacts with sulphuric acid. When it is exposed to moist air for long, it acquired a dull_4__ coating. a) 1-water, 2- basic, 3- metal, 4 -reddish brown    b) 1- kerosene, 2 acidic, 3 metal , 4 reddish brown   c) 1- kerosene, 2 acidic, 3 non metal, 4  green   d) 1- water, 2 basic, 3 non metal  4 green
  16. Mr Ramakant, a science teacher stated a few applications of non metals and asked students to guess the names of the non metals. Mark the correct options:

Non metals used in fertilizers                                  K, Cl
Non metal used in water purification process     Br
Non metal used in crackers                                      N
Non metal as an antiseptic                                        I

 

 

 

 

Analysis:

  1. Why do you think all metals when they are exposed to moisture give the resultant as basic?
  2. Why do non metals when react with moisture give the resultant as acidic?
  3. What would happen if sodium is stored in water?
  4. How are metals different from metalloids?
  5. Pick the odd one from the following elements: a) gold   b) potassium   c) carbon   d) sodium
  6. An unknown metal X when places in copper sulphate solution, red brown pieces of copper fall to the bottom of the test tube. When metal X is placed in aluminum sulphate solution, no change is observed. Metal X can be:  a) Sodium   b) Potassium   c) Iron   d) Calcium
  7. Substance X reacts with dilute HCl violently, Y reacts slowly while Z does not react at all. X, Y, Z could be respectively:  a) Cu, Al, Fe      b) Al, Na, Cu    c) Na, Cu, Fe    d) K, Al, Cu
  8. Properties of substances W, X, Y and Z are listed below:  W: a liquid metal   X: a liquid non metal   Y: gaseous non metal   Z: a non metal which conducts electricity   a) Iron, iodine, hydrogen and oxygen   b) gold, sulphur, chlorine and hydrogen   c) copper, phosphorus, nitrogen and carbon   d) mercury, bromine, oxygen and graphite
  9. What will happen if you keep a solution of copper sulphate in an iron container for a few days? What is the reason for your observation: a) the surface of iron container will develop a green layer due to corrosion caused by copper sulphate    b) copper metal will be deposited in iron container since copper is more reactive than iron   c) nothing will happen since no reaction takes place between copper sulphate and iron   d) holes will be formed in the container since iron is more reactive than copper hence iron displaces copper from a solution of copper sulphate
  10. Paheli takes a burning substance and collects the  evolved vapors in a test tube, making sure it does not escape.  She then adds a small amount of water to the test tube. To the solution obtained she adds a few drops of blue litmus paper. The litmus paper turns  red. Which of the following could be the burning substance: a) magnesium   b) copper   c) sodium   d) sulphur
  11. Each beaker contains two metal strips of same size fastened together and immersed in hydrochloric acid. After 5 minutes, which beaker will contain the least amount of zinc ions? a) beaker A contains liquid= hydrochloric acid  metal strip 1= zinc   metal strip 2= magneisum    b) beaker B contains liquid= hydrochloric acid  metal strip 1= lead  metal strip 2= zinc   c) beaker C  contains liquid= hydrochloric acid  metal strip 1= Lead  metal strip 2= zinc d) beaker D  contains liquid= hydrochloric acid  metal strip 1= silver  metal strip 2= zinc

 

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