\n(j) A lustrous non metal<\/td>\n | Graphite<\/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\nType<\/strong><\/td>\nSubstances<\/strong><\/td>\nReason<\/strong><\/td>\n<\/tr>\n\nElement<\/strong><\/td>\nChlorine,\u00a0Sulphur<\/td>\n | They cannot be split up into any simpler substance.<\/td>\n<\/tr>\n | \nCompound<\/strong><\/td>\nCarbon dioxide<\/td>\n | It can be produces by chemical analysis of two or more simpler substances with different properties.<\/td>\n<\/tr>\n | \nMixture<\/strong><\/td>\nHoney, milk, sea water, gun powder, apple juice, brine, syrup and bronze<\/td>\n | These 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\nElement<\/strong><\/td>\nCompund<\/strong><\/td>\n<\/tr>\n\n1.\u00a0It is a pure substance which cannot be converted into simpler substances by any physical or chemical means.<\/td>\n | 1.\u00a0It is a pure substance made up two or more elements combined chemically in a fixed ratio.<\/td>\n<\/tr>\n | \n2.\u00a0It is made up of only one kind of atoms.<\/td>\n | 2.\u00a0It is made up of two or more different kinds of atoms.<\/td>\n<\/tr>\n | \n3.\u00a0The molecules are made up of one or more atoms.<\/td>\n | 3.\u00a0The molecules are made up of two or more atoms.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Solution 9.<\/strong><\/span><\/p>\nIt 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>\nSolution 10.<\/strong><\/span><\/p>\nCharacteristics of a compound<\/strong><\/p>\n\n- A compound is made up of one or more atoms of the same or different elements.<\/li>\n
- It has a homogeneous composition.<\/li>\n
- In a compound the elements are present in a fixed ratio by mass.<\/li>\n
- The properties of a compound are different from those of its Constituent elements.<\/li>\n<\/ol>\n
Solution 11.<\/strong><\/span><\/p>\nThe 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- H2<\/sub>O:\u00a0<\/strong>Water is a liquid, while constituent elements, Hydrogen and Oxygen are gases.<\/li>\n
- 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
- 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>\nA 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- H2<\/sub>O:\u00a0<\/strong>Water is a liquid, while constituent elements, Hydrogen and Oxygen are gases.<\/li>\n
- 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
- 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>\nA 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\nElements<\/strong><\/td>\nCompounds<\/strong><\/td>\nMixtures<\/strong><\/td>\n<\/tr>\n\nMercury<\/td>\n | Sugar, Distilled water, Alcohol,\u00a0Nitre, Washing soda, Rust, Marble<\/td>\n | Air, Milk, Wax, Sea-water, Paint, Brass, Bread, Soap, Tap water<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Solution 16.<\/strong><\/span><\/p>\nOn adding\u00a0sulphuric\u00a0acid to water we will get a\u00a0Homogeneous Mixture<\/strong>\u00a0(true solution).<\/p>\nThis 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>\nIron and\u00a0sulphur\u00a0when mixed, forms a mixture. It can be identified as follows:<\/p>\n | | | | | | | | | | | | | | |