{"id":16615,"date":"2017-07-28T11:46:34","date_gmt":"2017-07-28T11:46:34","guid":{"rendered":"https:\/\/www.aplustopper.com\/?p=16615"},"modified":"2020-12-03T15:29:01","modified_gmt":"2020-12-03T09:59:01","slug":"selina-icse-solutions-class-9-chemistry-elements-compounds-mixtures","status":"publish","type":"post","link":"https:\/\/www.aplustopper.com\/selina-icse-solutions-class-9-chemistry-elements-compounds-mixtures\/","title":{"rendered":"Selina ICSE Solutions for Class 9 Chemistry – Elements, Compounds and Mixtures"},"content":{"rendered":"

Selina ICSE Solutions for Class 9 Chemistry – Elements, Compounds and Mixtures<\/span><\/strong><\/h2>\n

ICSE Solutions<\/a>Selina ICSE Solutions<\/a><\/p>\n

Download Formulae Handbook For ICSE Class 9 and 10<\/a><\/p>\n

Selina ICSE Solutions for Class 9 Chemistry Chapter 3 Elements, Compounds and Mixtures<\/strong><\/p>\n

Exercise 3(A)<\/strong><\/span><\/p>\n

Solution 1.<\/strong><\/span><\/p>\n

An element is a pure substance composed of only one kind of atom. Example: C, H, O, Na, Ca, N etc.<\/p>\n

Characteristics of an element:<\/strong><\/p>\n

    \n
  1. An element is made up of only one kind of atoms.<\/li>\n
  2. An element is pure and homogeneous substance.<\/li>\n
  3. An element has fixed melting and boiling points.<\/li>\n
  4. An atom is the smallest particle of an element which takes part in a chemical reaction.<\/li>\n
  5. An element may chemically react with another elements or compounds.<\/li>\n
  6. An element can occur in solid, liquid or gaseous state.<\/li>\n
  7. The molecules are made up of one or more atoms of the same or different elements.<\/li>\n<\/ol>\n

    Solution 2.<\/strong><\/span>
    \n\"Selina<\/p>\n

    Solution 3.<\/strong><\/span><\/p>\n

    Two elements which show exception to the properties of:<\/p>\n

    Metals :-<\/strong><\/p>\n

      \n
    1. Mercury (Hg) is liquid at room temperature.<\/li>\n
    2. Tungsten (W) is a poor conductor of electricity.<\/li>\n<\/ol>\n

      Non-metals:-<\/strong><\/p>\n

        \n
      1. Iodine is lustrous.<\/li>\n
      2. Carbon is ductile.<\/li>\n<\/ol>\n

        Solution 4.<\/strong><\/span><\/p>\n

        (a)\u00a0Molecule:<\/strong>\u00a0A molecule is the smallest particle of a pure substance (element or compound), and it has all the properties of that substance. It is composed of atoms. It is capable of existing in a free state.
        \nExample: O2<\/sub>, H2<\/sub>, Cl2<\/sub>\u00a0are molecules.<\/p>\n

        (b)\u00a0Atomicity:<\/strong>\u00a0Atomicity is the number of atoms present in a molecule of an element.<\/p>\n

        (c)\u00a0Compound:<\/strong>\u00a0A compound is a pure substance composed of two or more elements combined chemically in a fixed proportion by mass. The properties of compounds are different from the properties of their constituent elements. Example: H2<\/sub>O, CO2<\/sub>\u00a0etc.<\/p>\n

        Solution 5.<\/strong><\/span><\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
        (a) A diatomic element<\/td>\nNitrogen (N2<\/sub>)<\/td>\n<\/tr>\n
        (b) A\u00a0tetratomic\u00a0element<\/td>\nPhosphorus (P)<\/td>\n<\/tr>\n
        (c)\u00a0Monoatornic\u00a0element<\/td>\nHelium (He)<\/td>\n<\/tr>\n
        (d) Lustrous non-metal<\/td>\nIodine<\/td>\n<\/tr>\n
        (e) Liquid non-metal<\/td>\nBromine (Br2<\/sub>)<\/td>\n<\/tr>\n
        (f) A gas filled in electric bulbs<\/td>\nArgon (Ar)<\/td>\n<\/tr>\n
        (g) A liquid metal<\/td>\nMercury (Hg)<\/td>\n<\/tr>\n
        (h) A non metal conductor of electricity<\/td>\nGraphite<\/td>\n<\/tr>\n
        (i) A metal non malleable and non ductile<\/td>\nZinc (Zn)<\/td>\n<\/tr>\n
        (j) A lustrous non metal<\/td>\nGraphite<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Solution 6.<\/strong><\/span><\/p>\n

        (i) Sodium chloride is obtained when sodium chemically combines with chlorine in ratio of 23:355 by weight.
        \n(ii) When molten sodium chloride is subjected to electrolysis, the ratio by weight of sodium and chlorine librated at electrodes is 2:3.<\/p>\n

        Solution 7.<\/strong><\/span><\/p>\n\n\n\n\n\n\n
        Type<\/strong><\/td>\nSubstances<\/strong><\/td>\nReason<\/strong><\/td>\n<\/tr>\n
        Element<\/strong><\/td>\nChlorine,\u00a0Sulphur<\/td>\nThey cannot be split up into any simpler substance.<\/td>\n<\/tr>\n
        Compound<\/strong><\/td>\nCarbon dioxide<\/td>\nIt can be produces by chemical analysis of two or more simpler substances with different properties.<\/td>\n<\/tr>\n
        Mixture<\/strong><\/td>\nHoney, milk, sea water, gun powder, apple juice, brine, syrup and bronze<\/td>\nThese are produced by mere mixing of two or more substances in any proportions by weight.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Solution 8.<\/strong><\/span><\/p>\n

        (a)<\/strong>\u00a0This is because molecules have all the\u00a0properites\u00a0of that substance and is capable of existing in a free state, molecules are composed of atoms.<\/p>\n

        (b)<\/strong><\/p>\n\n\n\n\n\n\n
        Element<\/strong><\/td>\nCompund<\/strong><\/td>\n<\/tr>\n
        1.\u00a0It is a pure substance which cannot be converted into simpler substances by any physical or chemical means.<\/td>\n1.\u00a0It is a pure substance made up two or more elements combined chemically in a fixed ratio.<\/td>\n<\/tr>\n
        2.\u00a0It is made up of only one kind of atoms.<\/td>\n2.\u00a0It is made up of two or more different kinds of atoms.<\/td>\n<\/tr>\n
        3.\u00a0The molecules are made up of one or more atoms.<\/td>\n3.\u00a0The molecules are made up of two or more atoms.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Solution 9.<\/strong><\/span><\/p>\n

        It is true that the elements can form different compounds.
        \nExample: Hydrogen and oxygen combine to give two different compounds, water (H2<\/sub>O) and hydrogen peroxide (H2<\/sub>O2<\/sub>) under different conditions.<\/p>\n

        Solution 10.<\/strong><\/span><\/p>\n

        Characteristics of a compound<\/strong><\/p>\n

          \n
        1. A compound is made up of one or more atoms of the same or different elements.<\/li>\n
        2. It has a homogeneous composition.<\/li>\n
        3. In a compound the elements are present in a fixed ratio by mass.<\/li>\n
        4. The properties of a compound are different from those of its Constituent elements.<\/li>\n<\/ol>\n

          Solution 11.<\/strong><\/span><\/p>\n

          The properties of compounds are different from the properties of their constituent elements. Example: H2<\/sub>O,\u00a0FeS, C12<\/sub>H22<\/sub>O11<\/sub><\/p>\n

            \n
          1. H2<\/sub>O:\u00a0<\/strong>Water is a liquid, while constituent elements, Hydrogen and Oxygen are gases.<\/li>\n
          2. FeS<\/strong>:\u00a0<\/strong>Iron\u00a0sulphide\u00a0is a black substance, not attracted by a magnet and insoluble in carbon disulphide. While constituent elements, Iron is grey colored, attracted by a magnet.\u00a0Sulphur\u00a0is a yellow colored, soluble in carbon disulphide.<\/li>\n
          3. C12<\/sub>H22<\/sub>O11<\/sub>:\u00a0<\/strong>Sugar is a crystalline solid, sweet to taste and soluble in water. But,\u00a0its constituent elements, Carbon, is\u00a0black insoluble solid. Hydrogen and Oxygen are invisible and odorless gases.<\/li>\n<\/ol>\n

            Solution 12.<\/strong><\/span><\/p>\n

            A compound is a pure substance composed of two or more elements combined chemically in fixed proportions by mass. The properties of a compound are different from\u00a0the\u00a0properties\u00a0of their constituent elements.<\/p>\n

              \n
            1. H2<\/sub>O:\u00a0<\/strong>Water is a liquid, while constituent elements, Hydrogen and Oxygen are gases.<\/li>\n
            2. FeS<\/strong>:\u00a0<\/strong>Iron\u00a0sulphide\u00a0is a black substance, not attracted by a magnet and insoluble in carbon disulphide. While constituent elements, Iron is grey colored, attracted by a magnet.\u00a0Sulphur\u00a0is a yellow colored, soluble in carbon disulphide.<\/li>\n
            3. C12<\/sub>H22<\/sub>O11<\/sub>:\u00a0<\/strong>Sugar is a crystalline solid, sweet to taste and soluble in water. But,\u00a0its constituent elements, Carbon, is\u00a0black insoluble solid. Hydrogen and Oxygen are invisible and odorless gases.<\/li>\n<\/ol>\n

              Solution 13.<\/strong><\/span><\/p>\n

              A mixture cannot be represented by a chemical formula because constituents present in a mixture are in any ratio and they are not chemically united.<\/p>\n

              Solution 14.<\/strong><\/span><\/p>\n

              (a) Air
              \n(b) Concrete
              \n(c) Milk<\/p>\n

              Solution 15.<\/strong><\/span><\/p>\n\n\n\n\n
              Elements<\/strong><\/td>\nCompounds<\/strong><\/td>\nMixtures<\/strong><\/td>\n<\/tr>\n
              Mercury<\/td>\nSugar, Distilled water, Alcohol,\u00a0Nitre, Washing soda, Rust, Marble<\/td>\nAir, Milk, Wax, Sea-water, Paint, Brass, Bread, Soap, Tap water<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

              Solution 16.<\/strong><\/span><\/p>\n

              On adding\u00a0sulphuric\u00a0acid to water we will get a\u00a0Homogeneous Mixture<\/strong>\u00a0(true solution).<\/p>\n

              This mixture will have different densities and boiling points depending upon the amounts of acid and water. The properties of acid and water will remain same even after mixing.<\/p>\n

              Solution 17.<\/strong><\/span><\/p>\n

              Iron and\u00a0sulphur\u00a0when mixed, forms a mixture. It can be identified as follows:<\/p>\n