answers of books

12. Light and sound Fill in the blanks.  1. Objects which cannot give out their own light are called Non - luminous.  2. Trandparent   object allow light to pass through them completely.  3. Reflection   is bouncing back of light from a smooth shiny surface.  Write true or false.  1. Sound does not require any medium to travel. (F)   2.The sound of loudspeaker is an unpleasant sound. (T)  3.sound travels through air in the form of particles. (F)  Let us practise 1. Fill in the blanks.  a. Noise is produced by irregular    sound waves.  b. Sun is the main source of heat and light on earth.  c. When light hits a surface and cannot pass through it, the surface is called opaque.  d. Sound is produced due to vibration of objects.  2 . Write 'T' for true and 'F' for false.  a. Honking car is an example of a pleasant sound. (F)  b. Light cannot bend around the cornera. (T)   c. Wat...

11.Soil Erosion Time to Answer Full in the blanks.  1.Removal of fertile topsoil is soil erosion.  2.The two natural agents of soil erosion are wind     and water .  3. Large - scale cutting down of forests is known as deforation .  4.plants take nutrients from soil .  Write true or false.  1. Soil conservation is the protection of soil from erosion.  Ans. True 2.Afforestation is large scale cutting down of trees.  Ans. False 3. Power plants are built on rivers to control force of flood water.  Ans. False 4. Overgrazing should be prevented to avoid soil erosion.  Ans. True 5. The practice of terrace farming helps to reduce soil erosion.  Ans. True.    Match the following.  a. Organisms living in soil =soil life b. Earthworm= Farmers friend c. Crop rotation= Improves fertility of soil d. Crop= plants grown by farmers Q4. Short answer type questions a. What is terrace farming?  An...

10 . Solid liquid and gases Q. 5.Read the following two statements and choose the correct option.  Statement1- liquid have definite volume and shape.  Statement 2- The molecules of solid are not very closely packed.  Ans. Both statements 1 and 2 are incorrect.  Q6. Short answer type questions a . Why is melting of butter a physical change?   Ans. Melting of butter is a physical change as no new substance is fromed and there is only change in the state of matter on cooling the melted butter gets solidified.  b. How can we change a matter from its one state to another?  Ans. We can change a matter from its one state to another by heating and cooling.  c. What is a solution? Give an example.  Ans. When solutes ( suger or salt) dissolve in solvent like water, the mixture then formed is known as solution for example ,sugar inbwater salt in water etc.  d. Define a solute and a solvent.  Ans. The liquid in which other substance...