{"id":153028,"date":"2023-12-28T16:50:05","date_gmt":"2023-12-28T11:20:05","guid":{"rendered":"https:\/\/icsesolutions.com\/?p=153028"},"modified":"2023-12-29T10:11:32","modified_gmt":"2023-12-29T04:41:32","slug":"icse-class-8-chemistry-notes-chapter-3","status":"publish","type":"post","link":"https:\/\/icsesolutions.com\/icse-class-8-chemistry-notes-chapter-3\/","title":{"rendered":"ICSE Class 8 Chemistry Notes Chapter 3 Elements, Compounds and Mixtures"},"content":{"rendered":"
\u2192 \u201cElement is a pure substance made up of one kind of atoms only.\u201d It cannot be broken down into simpler substances by any means, e.g. If we go on breaking a gold piece, however small it be, yet it will be gold.<\/p>\n
\u2192 \u201cCompound is a pure substance made up of two or more different elements in fixed ratio.\u201d Compounds have formula. e.g. Common salt or table salt NaCl.<\/p>\n
\u2192 Atom : \u201cThe smallest particle of element.\u201d It is neutral i.e. has no charge, may or may not exist independently.<\/p>\n
\u2192 All elements have symbol i.e. H for hydrogen, O for oxygen and there are about 118 elements found so far. Elements are in the form of metals, non-metals, metalloids and noble gases.<\/p>\n
\u2192 Molecule : \u201cAtoms of the same element or different elements combine to form a molecule.\u201d<\/p>\n
\u2192 Molecule is smallest particle of substance that can normally exist independently and can retain the physical and chemical properties of the substance, e.g. Cl2<\/sub>, CO2<\/sub>, H2<\/sub>O, O2<\/sub>, H2<\/sub>, Na, K etc.<\/p>\n \u2192 Atomicity : \u201cThe number of atoms present in a molecule.\u201d O2<\/sub> is a molecule of oxygen having 2 atoms of oxygen. Na is a molecule of sodium substance having one atom of sodium.<\/p>\n \u2192\u201cMixture is made up of two or more substances, elements or compounds or both mechanically mixed together in any proportion.\u201d A mixture retains the properties of constituent elements or compound of which it is made up. Mixture has no formula.<\/p>\n \u2192 Compound has new properties different from its constituent from which it is made. i.e. water is a compound (H2<\/sub>O) made up of two element hydrogen (H) and oxygen (O) in fixed ratio combined chemically 2 parts of hydrogen and one part of oxygen by volume and 2 x (1) : 16. \u2192 helps in burning is supporter of combustion but water is a liquid and puts out the fire.<\/p>\n \u2192 \u201cMetalloids are the element whose properties resemble both metals and non-metals.\u201d Boron (B), Arsenic (As), Germanium (Ge), Antimony (Sb), Tellurium (Te), Polonium (Po).<\/p>\n \u2192 Alloys are homogeneous mixtures of (metal, metal) or (metal, non-metals). Sublimable substance are ammonium chloride NH4<\/sub>Cl, Naphthalene balls, iodine, dry ice, camphor, benzoic acid and anthracene.<\/p>\n \u2192 Noble gases or inert gases : occur in traces in the atmosphere are monoatomic. i.e. He, Ne, Ar, Kr, Xe, Rn.<\/p>\n \u2192 Types of mixture and methods to separate :
\ni. e. 2 : 16 or 1 : 8 by mass.
\nHydrogen (gas) is combustible i.e. catches fire and oxygen<\/p>\n
\n<\/p>\n