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10" Kannada Science (Part 1), , First Edition, March 2018, , © National Council of Educational, Research and Training., , Publication / Translation Rights, Karnataka Textbook Society, Bengaluru, , Copyright Certificate No., , IN-KA-89413760 2221839, Date: 17 August - 2017, , , , , , , , , , OFFICES OF THE PUBLICATION, KARNATAKA TEXTBOOK SOCIETY, #4, DSERT Building,, , 100 Feet Ring Road, Hosakerehalli,, Banashankari III Stage,, , Benguluru - 560 085, , Website: http:/ www.ktbs.kar.nic.in, , , , , , , , ALL RIGHTS RESERVED, , No part of this publication may be reproduced, stored, in a retrieval system or transmitted, in any form or by, any means, electronic, mechanical, photocopying,, recording or otherwise without the prior permission of, the publisher,, , , , O This book is sold subject to the condition that it shall, not, by way of trade, be lent, re-sold, hired out or, otherwise disposed of without the publisher's, consent, in any form of binding or cover other than, thatin which itis published., , The correct price of this publication is the price printed, on this page, Any revised price indicated by a rubber, stamp or by a sticker or by any other means is, incorrect and should be unacceptable., , , , Education., , , , Acknowledgements, , KARNATAKA TEXTBOOK SOCIETY wholeheartedly acknowledges the, valuable contribution of officials of publication division, NCERT, Chairperson, Members of Textbook preparation Committee, Review Committee, Computer, Officials and all officers of NCERT., , We are also thankful to NCERT Officials for providing copyright for publication /, translation to regional medium for Government of Karnataka, Department of

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FoREWORD, , The National Curriculum Framework, (NCF), 2005, recommends that children’s life at school must be, linked to their life outside the school. This principle marks a departure from the legacy of bookish learning, which continues to shape our system and causes a gap between the school, home and community. The, syllabi and textbooks developed on the basis of NCF signify an attempt to implement this basic idea., They also attempt to discourage rote learning and the maintenance of sharp boundaries between different, subject areas. We hope these measures will take us significantly further in the direction of a child-centred, system of education outlined in the National Policy on Education (1986)., , The success of this effort depends on the steps that school principals and teachers will take to encourage, children to reflect on their own learning and to pursue imaginative activities and questions. We must, recognise that, given space, time and freedom, children generate new knowledge by engaging with the, information passed on to them by adults. Treating the prescribed textbook as the sole basis of examination, is one of the key reasons why other resources and sites of learning are ignored. Inculcating creativity, and initiative is possible if we perceive and treat children as participants in learning, not as receivers of, a fixed body of knowledge., , These aims imply considerable change in school routines and mode of functioning. Flexibility in the daily, time-table is as necessary as rigour in implementing the annual calendar so that the required number of, teaching days are actually devoted to teaching. The methods used for teaching and evaluation will also, determine how effective this textbook proves for making children’s life at school a happy experience,, rather than a source of stress or boredom. Syllabus designers have tried to address the problem of curricular, burden by restructuring and reorienting knowledge at different stages with greater consideration for child, psychology and the time available for teaching. The textbook attempts to enhance this endeavour by, giving higher priority and space to opportunities for contemplation and wondering, discussion in small, groups, and activities requiring hands-on experience., , The National Council of Educational Research and Training (NCERT) appreciates the hard work done, by the textbook development team responsible for this book. We wish to thank the Chairman of the, advisory group in science and mathematics, Professor J.V. Narlikar and the Chief Advisor for this book,, Professor Rupamanjari Ghosh, School of Physical Sciences, Jawaharlal Nehru University, New Delhi,, for guiding the work of this committee. Several teachers contributed to the development of this textbook;, we are grateful to them and their principals for making this possible. We are indebted to the institutions, and organisations which have generously permitted us to draw upon their resources, material and, personnel. We are especially grateful to the members of the National Monitoring Committee, appointed, by the Department of Secondary and Higher Education, Ministry of Human Resource Development, under the Chairmanship of Professor Mrinal Miri and Professor G.P. Deshpande, for their valuable time, and contribution. As an organisation committed to systemic reform and continuous improvement in the, quality of its products, NCERT welcomes comments and suggestions which will enable us to undertake, further revision and refinement., , Director, New Delhi National Council of Educational, 20 November 2006 Research and Training

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PREFACE, , This textbook of Science for Class X is a continuation of our attempt in the Class IX Science textbook, to comply with the guidelines of the National Curriculum Framework-2005. We had to work within, a limited time frame and also had our own constraints coming in the way of this radical change. The, revised and re-structured syllabus for Class X covers selected topics in the broad themes of — Materials,, The World of the Living, How Things Work, Natural Phenomena and Natural Resources. We have, interpreted the syllabus to present a coherent coverage of scientific concepts related to our daily life on the, select topics. It is an integrated approach to science at this level, with no sharp divisions into disciplines, such as Physics, Chemistry, Biology and Environmental Science., There has been a conscious attempt to address the relevant social concerns in this science textbook, wherever possible — the concerns for people with special needs, the issues of gender discrimination,, energy and environment have found their natural place in this book. Students have been encouraged to, get into the debates on some of the management concerns (for sustainable development, for example) so, that they can arrive at their own decisions after a scientific analysis of all the facts., This book has some features which are meant to enhance its effectiveness. The theme of each chapter, has been introduced with examples from daily life, and if possible, by a relevant activity that the students, have to perform. The entire approach of the book is, in fact, activity-based, i.e., the students are required, to construct knowledge themselves from these activities. The emphasis is not on definitions and technical, terms, but on the concepts involved. Special care has been taken so that the rigour of science is not lost, while simplifying the language. Difficult and challenging ideas, which are not to be covered at this stage,, have often been placed as extra material in the boxes in light orange. The excitement of doing science, comes from pursuing the unknown — the students would have the opportunity to think and explore, somewhat beyond the syllabus and may feel the urge to continue their scientific expedition at higher, levels. All such box items, including brief biography of scientists, are, of course, non-evaluative., Solved examples are provided, wherever felt necessary, to clarify a concept. The in-text questions after, a main section are for the students to check their understanding of the topic. At the end of each chapter,, there is a quick review of the important points covered in the chapter. We have introduced some multiple, choice questions in the exercises. There are problems of different difficulty levels answers to the multiplechoice questions and numericals, and hints for the difficult questions are included at the end of the book., This book has been made possible because of the active participation of many people. I wish to thank, Professor Krishna Kumar, Director, NCERT, Prof. G. Ravindra, Joint Director, NCERT, and Professor, Hukum Singh, Head, Department of Education in Science and Mathematics, NCERT, specially for their, keen interest in the development of the book and for all the administrative support. I wish to put on, record my sincere appreciation for Dr Anjni Koul, the member-coordinator of the textbook development, committee, for her extraordinary commitment and efficiency. It has been a real pleasure working with, my textbook development team and the review committee. The chosen editorial team worked extremely, hard, on tight deadlines, to bring the book close to the shape that we dreamt of. Fruitful discussions with, some members of the MHRD Monitoring Committee helped in providing the final touches to the book., I do not have the words to acknowledge the professional and personal inputs I received from some of, my close friends during the preparation of this book. We warmly welcome comments and suggestions, for improvement from our readers., , Rupamanjari Ghosh, , Professor of Physics, School of Physical Sciences, Jawaharlal Nehru University, , New Delhi