Class 9 Chemistry Chapter 8 Question Answer

Important Notes of Class 9 Chemistry Chapter 8 Question Answer English Medium written by Professor M. Shahid Suib. These notes are very helpful in the preparation of Chemical Reactivity Class 9 for students of the Class 9 Chemistry Chapter 8 Question Answer English Medium and these are according to the paper patterns of all Punjab boards.

Summary and Contents:
Topics which are discussed in the notes are given below:
  • Complete Exercise MCQs of Chapter No.8: Chemical Reactivity
  • Complete Exercise Short Questions with Answers of Chapter No.8: Chemical Reactivity
  • Why the reactivity of metals increase down the group?
  • Write the names of any four least reactive metals.
  • State two physical properties of the metals. (Also A long Question).
  • Write any two chemical properties of metals. (Also A long Question).
  • Write any two physical properties of non-metals. (Also A long Question).
  • Write any two chemical properties of non-metals. (Also A long Question).
  • Define metallic character. OR Define electropositive character. Write its trend.
  • Name a metal that exists in liquid form.
  • What is the nature of metal oxide?
  • Why ionization energies of alkaline earth metals are higher than alkali metals?
  • Why magnesium is harder than sodium?
  • Why the ionization energy of Na is more than K?
  • Why sodium metal is more reactive than magnesium metal?
  • Name the best ductile and malleable metal.
  • Why is gold used to make jewelry?
  • Why silver & gold are least reactive?
  • Why is platinum used for making jewelry? OR What are the unique characteristics of platinum? OR Write uses of platinum.
  • What do you mean by 24-carat gold?
  • What do you mean by 22-carat gold?
  • Give the applications (uses) of silver.
  • Write the two uses of Magnesium. 
  • Write two uses of calcium.
  • Write two uses of sodium metal. 
  • Write two properties of silver metals. 
  • Give the reaction of magnesium with O2 and N2. 
  • Give a chemical reaction of methane with chlorine in bright light.
  • Write a detail note on the significance of non-metals.
  • Write four physical properties of metals.
  • Write four Chemical properties of metals.
  • Write four physical properties of non-metals.
  • Write four chemical properties of non-metals 
  • Important physical properties of non-metals are as follows: Physical properties of non-metals change gradually but uniquely in a group of non-metals. Non-metals usually exist in all three physical states of matter. The non-metals at the top of the group are usually gases while others are either liquids or solids.
  • Solids non-metals are brittle (break easily)
  • Non-metals are bad conductors of heat and electricity (except graphite).
  • They are not shiny, they are dull except iodine (it is lustrous like metals).
  • They are generally soft (except diamond).
  • They have low melting and boiling points (except silicon, graphite and diamond).
  • They have low densities.
  • Important chemical properties of non-metals are as follows: Their valence shells are deficient of electrons, therefore, they readily accept electrons to complete their valence shells and become stable.
  • They form ionic compounds with metals and covalent compounds by reacting with other non-metals e.g. CO2, NO2, etc.
  • Non-metals usually do not react with water.
  • They do not react with dilute acids because non-metals are itself electron acceptors. 
  • Comparison of Reactivity of the Halogens: Elements of Group-17 of the periodic table consist of fluorine, chlorine, bromine, iodine and astatine. They are collectively called halogens. Fluorine and chlorine exist as diatomic gases at room temperature. Interestingly, the intermolecular forces of attraction increase downward in the group due to the increase in the size of atom. Due to this reason bromine exists as a liquid and iodine as solid. Some physical properties of halogens.
  • Important Reactions of Halogens: Oxidizing properties:  All halogens are oxidizing agents. Fluorine is the strongest oxidizing element while iodine is the least i.e is mild oxidizing agent. Fluorine will oxidize any of halide ion (X^-) in solution and changes itself to F^- ion. Similarly, chlorine will displace Br^- and I^- ion s from their salt solutions and oxidize them to bromine and iodine.

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