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www.GOALias.blogspot.com6Physical and ChemicalChangesEvery day you come across manychanges in your surroundings.These changes may involve oneor more substances. For example, yourmother may ask you to dissolve sugarin water to make a cold drink. Making asugar solution is a change. Similarly,setting curd from milk is a change.Sometimes milk becomes sour. Souringof milk is a change. Stretched rubberband also represents a change.Make a list of ten changes you havenoticed around you.In this chapter we shall perform someactivities and study the nature of thesechanges. Broadly, these changes are oftwo kinds, physical and chemical.Fig. 6.1 Paper pieces6.1 P6.1 PHYSICALCHANGESActivity 6.1Cut a piece of paper in four squarepieces. Cut each square piece furtherinto four square pieces. Lay these pieceson the floor or a table so that the piecesacquire the shape of the original pieceof paper (Fig. 6.1).Obviously, you cannot join the piecesback to make the original piece, but isthere a change in the property of thepaper?Activity 6.2Collect the chalk dust lying on the floornear the blackboard in your classroom.Or, crush a small piece of chalk intodust. Add a little water to the dust tomake a paste. Roll it into the shape of apiece of chalk. Let it dry.Did you recover chalk from thedust?Activity 6.3Take some ice in a glass or plastictumbler. Melt a small portion of ice byplacing the tumbler in the sun. You havenow a mixture of ice and water. Nowplace the tumbler in a freezing mixture(ice plus common salt).Does the water become solid ice onceagain?58SCIENCE