Physical and Chemical Changes PDF
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This document provides a detailed explanation of physical and chemical changes. It includes definitions, classifications, examples, and comparisons. The document covers reversible and irreversible changes, slow and fast changes, and periodic and non-periodic changes. It also includes examples of various chemical and physical changes, like the melting of ice, burning of magnesium, and rusting of iron.
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## Introduction - Changes ### 1. Term - A substance (i.e matter) undergoes a kind of change when subjected to energy changes. - Matter is said to undergo changes when energy is added or removed from the matter. ### 2. Classification #### Physical Changes - Are temporary, easily reversible & the...
## Introduction - Changes ### 1. Term - A substance (i.e matter) undergoes a kind of change when subjected to energy changes. - Matter is said to undergo changes when energy is added or removed from the matter. ### 2. Classification #### Physical Changes - Are temporary, easily reversible & the state of the substance changes without its fundamental nature undergoing any change. #### Chemical Changes - Are permanent, not easily reversible & the identity of the substance is altered which generally results in - formation of new substances. ### 3. Other Changes Include - #### a. Reversible and Irreversible Changes - Irreversible changes which can be reversed - by change in conditions - E.g. Melting of ice and freezing of water. - Reversible changes which cannot be reversed - by change in conditions - E.g. Burning of magnesium. #### b. Slow and Fast Changes - Slow changes occur very slowly - E.g. A seed growing into a tree - Fast changes occur very rapidly - E.g. Occurrence of lightening. #### c. Periodic and Non-Periodic Changes - Periodic changes occur periodically - E.g. Change of seasons - Non-periodic changes do not occur periodically - E.g. Change of weather. #### d. Desirable and Undesirable Changes - Desirable changes produce useful results & are brought about by - man or nature - E.g. Making of glass. - Undesirable changes produce useless results & are brought about by - man or nature - E.g. Breaking of glass. ## B. Physical and Chemical Changes - Term ### 1. Definition #### Physical Change - A change in which the substance - - Retains - its identity & - Changes - in form or state - without altering in composition. - A physical change is - - Temporary - Easily reversible - With no new substance formed & - Composition & properties of - Original substance - not altered #### Chemical Change - A change in which the substance - - Loses - its identity & - Produces - one or more new substances - - By change in its composition. - A chemical change is - - Permanent - Not easily reversible - With a new substance formed & - Composition & properties of - - Original substance - altered ### 2. Example #### Physical Change - Melting of ice. #### Chemical Change - Burning of magnesium. ### 3. Comparison #### Physical change 1. Unaltered composition - of the molecules of the substance is seen. No new products, are formed. 2. Temporary change - reversed by - reversal of conditions. 3. No change in mass of the substance undergoing a - physical change. Reason - No matter is added or removed- during a physical change. 4. Not accompanied by a marked evolution or absorption of heat. #### Chemical Change 1. Altered composition of the molecules of the substance is seen. New products, are formed. 2. Permanent change - not reversed by - reversal of conditions. 3. Change in mass of the substance undergoing a - chemical change. Reason - Matter is added or removed- but total mass is unaltered. 4. Accompanied by - evolution or absorption of heat & sometimes emission of light. ## C. Physical Changes - Examples ### Example - The change of state of matter - Melting - conversion of - a solid into a liquid - on heating. - Vaporization - conversion of - a liquid into vapour (or gas). - Condensation - conversion of - vapour (or gas) into a liquid. - Freezing - conversion of - a liquid into a solid . ### Other Examples - a. Melting of wax - b. Boiling of milk - c. Rain cycle - d. Sublimation of camphor - e. Drying of a fruit - f. Ringing of an electric bell - g. (Addition of salt to water) - h. Heating of a platinum wire - i. Magnetization of iron ## D. Chemical Changes - Examples ### Examples - Chemical reactions taking place - Addition of acids to substances. - Fermentation of substances. - Dehydration of carbohydrates. - Respiration in living organisms. - Burning of substances in air. ### Other Examples - a. Carbon cycle - b. Ripening of a fruit - c. Changes in electro chemical cells - d. Curdling of milk - e. Butter turning rancid - f. Rotting of eggs - g. Addition - of iron to acid - h. Burning - sulphur powder - i. Rusting - of iron
