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BasicScienceEnglish (2)_1_1 Flipbook PDF
BasicScienceEnglish (2)_1_1
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BASIC SCIENCE Part - 1
Standard VIII
Government of Kerala Department of Education
State Council of Educational Research and Training (SCERT), KERALA 2015
The National Anthem Jana-gana-mana adhinayaka, jaya he Bharatha-bhagya-vidhata. Punjab-Sindh-Gujarat-Maratha Dravida-Utkala-Banga Vindhya-Himachala-Yamuna-Ganga Uchchala-Jaladhi-taranga Tava subha name jage, Tava subha asisa mage, Gahe tava jaya gatha. Jana-gana-mangala-dayaka jaya he Bharatha-bhagya-vidhata. Jaya he, jaya he, jaya he, Jaya jaya jaya, jaya he!
PLEDGE India is my country. All Indians are my brothers and sisters. I love my country, and I am proud of its rich and varied heritage. I shall always strive to be worthy of it. I shall give respect to my parents, teachers and all elders and treat everyone with courtesy. I pledge my devotion to my country and my people. In their well-being and prosperity alone lies my happiness. State Council of Educational Research and Training (SCERT) Poojappura, Thiruvananthapuram 695012, Kerala Website : www.scertkerala.gov.in, e-mail : [email protected] Phone : 0471 - 2341883, Fax : 0471 - 2341869 Typesetting and Layout : SCERT Printed at : KBPS, Kakkanad, Kochi - 30 © Department of Education, Government of Kerala
Dear students, You were provided with opportunities to observe your surroundings and engage in simple experiments and investigative activities in earlier classes. The classroom experience, undoubtedly, might have helped you to record the information systematically and assimilate ideas through discussion and analysis. While understanding the scientific approach, there should also be the attitude to take forward the skills to apply them in day-today life. Moreover, an eco-friendly perspective must be adopted too. All these, through direct experiences, enquiry and understanding preferably. This textbook presents ideas in accordance with this. There are experiments, illustrations and explanatory details that enable the comprehension of these ideas. There are opportunities appropriate to the situation to make learning more enjoyable. Go ahead, thinking, asking questions, approaching ideas critically and quizzing with teachers and friends. Make learning a joyful experience. Regards,
Dr. S. Raveendran Nair Director, SCERT
TEXTBOOK DEVELOPMENT TEAM Emerson F GGHS, Chavara, Kollam Satheesh R GHSS Anchal West, Kollam Shajil U K GGHSS, Balussery, Kozhikode Nisar Ahamed M GHSS Venjarammood, Trivandrum Rasheed Odakkal GVHSS Kondotti, Malappuram Vineesh T V GHS Chenad, Wayanad P D Baby St. Antony's HSS, Mutholi, Pala Gopalan N K HSA (Rtd.), KKMGVHSS Vadakara Unnikrishnan T I Headmaster (Rtd.), AKKRHS for Boys, Kozhkode Pradeepkumar K V Moothedath HSS, Taliparamba, Kannur Premachandran K V GHSS Maniyoor, Vadakara, Kozhikode Sajikumar K G GV & HSS for Girls, Manacaud, Trivandrum Sureshkumar K AMHSS, Thirumala, Trivandrum Babu Payyath BPO, BRC, Kozhikode Muhammed Abdul Nazar Master Trainer, IT @ School Santhoshkumar V G BYKVHSS, Valavanoor, Malappuram Dr. Vishnu V S Asst. Prof., College of Engineering, Trivandrum Sadanandan C Pantheerankave HSS, Kozhikode Muhammed Rafi C Govt. Technical HS, Naruvambram, Kannur Shabu Ismail PMSAVHSS Chappanangadi, Malappuram K T Manoj CBHSS Vallikkunnu, Malappuram Hassan C C MMVHSS Parappil, Kozhikode Preethi K A SHS Mannarkadu, Palakkad
EXPERTS Prof. Sivasankara Pillai Head (Rtd.), Dept. of Physics, Women's College, Trivandrum Dr. S Mohanan Reader & Head (Rtd.), Dept. of Physics, University College, Trivandrum Paul P I Associate Prof., Dept. of Zoology, Mar Ivanios College, Trivandrum Dr. Alaudeen M Principal (Rtd.) Govt. College, Elerithattu Sebastian Lukose T J Sel. Grade Lecturer (Rtd.), University College, Trivandrum Dr. N Ratheesh Asst. Professor, SN College, Kollam ENGLISH VERSION Dr. Sushil Kumar R Associate Professor of English, D B College, Sasthamcotta Dr. Saji Mathew Asst. Professor, School of Letters, M G University Famila E R HSST, GHSS, Karunagappally K Suresh Kumar AMHSS, Thirumala, Trivandrum ARTISTS Musthajib E C MMETHS, Melmuri Noushad Vellalasseri Ganapath AUPS, Keezhisseri Muhammed Shameem VAUPS, Kavanoor Lohithakshan K Assisi School for the Deaf, Malapparambu Viswanathan P DDE Office, Malappuram
Academic Co-ordinator Dr. Ancey Varughese Research Officer, SCERT
1.
Life's Mysteries in Little Chambers ......................... 07
2. Cell Clusters ..................... 22 3. Let's Regain our Fields .... 35 4. Properties of Matter ......... 53 5. Basic Constituents of Matter .............................. 68 6. Chemical Changes ............ 80 7. Metals .............................. 91 8. Measurements and units ..103 9. Motion ............................117 10. Force...............................132 11. Magnetism ......................145
Certain icons are used in this textbook for convenience For further reading (Evaluation not required) ICT possibilities for making concepts clear Significant learning outcomes
Let us assess
Extended activities
The bell rang.. It is the Biology period now. Manu, the class leader, peeped out to the verandah and said, “Teacher is coming. She has something in her hand too”. It is her usual way. She always carries some materials in her hand. What is she bringing today? Everyone became anxious. When the teacher entered the class, Rahna said in a loud voice, “I know it. Isn’t it a microscope? And what is in your other hand, Madam?” “I’ll tell you……” The teacher placed the microscope on the table and gave the other materials to Meenu. “Madam, isn’t it the root of a plantain?”
“Well, don’t you know that the body of all organisms are made up of cells? Let's observe the cells in the root of plantain through this microscope. Don’t you remember having observed onion cells? Similarly arrangements should be made to observe the cells in the root of plantain. All required materials are there in this box. Who will do this?” “I’ll do Madam”, Manu came forward enthusiastically. He took the section of the root using a blade, placed it on a slide and observed it through the microscope... Nothing could be seen! Then he turned the knob of the microscope. Feeling disappointed he said, “No Teacher. Nothing is visible”. Why were Manu’s attempts a failure? Can you help him? For this, you must know how to operate a microscope and prepare materials for observation. Let's familiarise ourselves with the microscope. Observe the microscope with the help of your teacher and identify the following parts and their use. z Eyepiece z Knob z Objective lens z
Stage and clip
z
Condenser
Fig. 1.1 Compound microscope
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z
Mirror
The function of a microscope is to magnify objects, isn’t it? Lenses are fixed in the microscope for this purpose. Name the parts where lenses are fixed. z z
Microscopes in which more than one lens is used are called compound microscopes (Fig 1.1). Analyse the given description on the basis of indicators and note down your inferences in the science diary.
Arrangement of light in a microscope In the microscope, the part fixed below the stage is to reflect light on the material to be observed. This arrangement which is fixed in a metal ring has two planes, a plane mirror to reflect sunlight and a concave mirror to reflect artificial light. The lens in the condenser that is fixed on the lower side of the stage focuses light on the material to be observed. Diaphragm, a part of the condenser, helps to regulate the intensity of light.
Magnification power
Indicators z
Why is a mirror fixed in a microscope?
The magnification power of Why do we use a slide made of glass to place the objective lenses are marked material to be observed? as 10x and 45x. Such markings Have you understood the basic concepts of a microscope? can be seen in eyepiece too. Accuracy in using a microscope can be attained only The magnification power of a through practice. Learn to operate a microscope using the microscope is the result of multiplying the numbers seen permanent slides available in your science lab. in the objective lens and the Let's prepare the observation material eyepiece. z
Preparation of observation material requires much accuracy and patience. Observe the illustration that shows the stages for the preparation of the slide to observe plant cells. Then prepare a slide by taking the cross section of the root of plantain.
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Preparation of observation material
Stage 1
Stage 2
Stage 3
Put the material to be Take thin cross sections With a brush, shift the observed in the petridish of the material to be sections to a watch glass containing water to observed. containing water. prevent dehydration.
Stage 5
Stage 6
Add one or two drops of glycerin to the slide to prevent drying up of the material.
Wash the stained section in clean water and place it in the glycerin on the slide.
Stage 4 Put the thinnest and complete sections to a watch glass containing stain.
Stage 7
Stage 8
Place a cover glass over Wipe out the excess the material using a glycerin using tissue needle in such a way that paper. air bubbles do not pass.
Illustration 1.1
Observe the slide you have prepared through a microscope. Try to understand the difference in the magnification when lenses 10x and 45x are used.
Sample of practical recording Aim Materials required Procedure Observation Inference
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10x Fig. 1.2
45x
Recording the findings is as important as conducting practicals in science. Record each stage of the experiment following the sample given, in your science diary.