Topic outline

    • Sorting Materials into Groups

      Q14. Write any two objects made up of opaque materials.

      Ans. wooden doors and steel plate


      Q15. What is common between oil and water?

      Ans. Both are in liquid state.


      Q16. Write two things made from leather.

      Ans. belt and hand-bag


      Q17. Write name of any three metals.

      Ans. Iron, Aluminium and Copper


      Q18. Name few things made up of plastic.

      Ans. cups, plates, toys, buckets, baskets

      Q19. Why water is considered as a universal solvent?

      Ans. Water is capable of dissolving most of the substances in it. That is why it is known as universal solvent.

      Q20. Why does a coin sink in water?

      Ans. Object with higher density than water will sink. A coin is made up of metal. Density of metal is higher than water. That’s why coin sinks in water.


      Q21. Why are cooking utensils made of metal but their handles of plastic or wood?

      Ans. Cooking utensils have wood or plastic handles to prevent us from burning our hands when utensils are hot.


      Q22. Why oil does not dissolve in water?

      Ans. Oil does not dissolve in water because the space between the molecules of water is not occupied by the oil.


      Q23. Why some material loses their shine and appears dull?

      Ans. Due to the action of air and moisture on them, a dull layer of some other compound appears on them. Thus material loses their shine and appears dull.


      Q24. We can group things in more than one way. Explain.

      Ans.  We can group things in more than one way because one object can have more than one property.


      Q25. Oxygen and carbon dioxide are slightly soluble in water. What is the importance of each of these gases in nature?

      Ans. Oxygen and carbon dioxide gas dissolved in water are needed for the survival of animals and plants that live in water.


      Q26. Define density. How is it related to floating and sinking in water?

      Ans. The degree of compactness of a substance is called density. The object which is denser than water will sink whereas object which is less dense than water will float.

      Q27. Why does sugar dissolve in water?

      Ans. Water molecules surround the tiny sugar cubes and hit them. This weakens the attractive forces of the surrounding molecules and pulls them into the solution.


      Q28. Why in departmental stores all brands of shampoos and soaps are kept together while all pulses and kitchen items are kept at one place?

      Ans.  This is done, so that customer can easily pick the things needed and compare values of different brands available.


      Q29. What is classification?

      Ans. The process of grouping things together on the bases of some similar characteristics is called classification.


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