SCIENCE 58 Physical and Chemical Changes 6 E very day you come across manychanges in your surroundings. These changes may involve one or more su bstances. 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 . Souring of milk is a change. Stretched rubberband also represents a chang e. Make a list of ten changes you have noticed around you. In this chapter we shall perform some activities and study the nature of these changes. Broadly, these changes are oftwo kinds, physicaland chemical . Fig. 6.1 Paper pieces6.1 PHYSICALCHANGES Activity 6.1 Cut a piece of paper in four square pieces. Cut each square piece furtherinto four squ are pieces. Lay these pieces on the floor or a table so that the pieces acquire the shape of the original piece of paper (Fig. 6.1). Obviously, you cannot join the pieces back to make the o riginal piece, but is there a change in the property of the paper? Activity 6.2 Collect the chalk dust lying on the floornear the blackboard in your classroom. Or, crush a small piece of chalk into dust. Add a little water to the dust to make a paste. Roll it into the shape of apiece of chalk. Let it dry. Did you recover chalk from the dust? Activity 6.3 Ta ke some ice in a gla ss or pl ast ic tumbler. Melt a small portion of ice byplacing the tumbler in the sun. You have now a mixture of ice and water. Nowplace the tumbler in a freezing mixture (ice plus common salt). Does the water become solid ice once again?