Chemistry : Elements, Compounds & Mixtures
Elements An element is defined as a pure substance made up of one type of atoms and cannot be further subdivided into simpler substances by any physical or chemical means. An element can be represented by using a symbol. Examples of Elements The symbols H2 and Fe represent the elements Hydrogen and Iron respectively. Compounds A compound is defined as a pure substance made up of two or more types of elements (atoms) chemically combined in a fixed proportion, and it can be further subdivided into simpler substances by chemical means only. A molecule is the smallest part of a compound, whose properties are the same as those of the compound. A compound can be represented by using a chemical formula. Examples of Compounds The chemical formulae H2O and FeS represent the compounds water and Ferrous sulfide (Iron [I] sulfide) respectively. Mixtures A mixture is defined as an impure substance made up of two or more types of elements (atoms) or compounds or both mechanically mixed in any proportion, and it can be further subdivided into simpler substances by physical (mechanical) means. The constituents of a mixture retain their original properties. The constituents of a homogenous mixture are uniformly mixed thoroughout the mixture. The properties and composition of a homogenous mixture are the same throughout the mixture. The constituents of a heterogenous mixture are not uniformly mixed thoroughout the mixture. The properties and composition of a heterogenous mixture are not the same throughout the mixture. Examples of Mixtures Stainless steel is a mixture (alloy) of iron, carbon, chromium, and nickel. Carbon gives hardness to the mixture. Chromium and nickel give a silvery look to the mixture. Potassium sulfide solution is a homogenous mixture. A mixture of water and oil is heterogenous in nature. |
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