This book is a part of a series of six books written to provide complete coverage of the NCERT science syllabus for Classes 9 and 10 prescribed by the Central Board of Secondary Education (CBSE). The six books in this series are: Science for Ninth Class (Part-1) : PHYSICS, Science for Ninth Class (Part-2) : CHEMISTRY, Science for Ninth Class (Part-3) : BIOLOGY; Science for Tenth Class (Part-1) : PHYSICS, Science for Tenth Class (Part-2) : CHEMISTRY, and Science for Tenth Class (Part-3) : BIOLOGY. The most important feature of the revised editions of these books is that a large variety of solved and unsolved questions has been included to assess the learning abilities of the students.