6th Standard Science Term I PDF

www.tntextbooks.in GOVERNMENT OF TAMILNADU STANDARD SIX TERM - I VOLUME - 3 SCIENCE SOCIAL SCIENCE A publication under Free Textbook Programme of Government of Tamil...

www.tntextbooks.in GOVERNMENT OF TAMILNADU STANDARD SIX TERM - I VOLUME - 3 SCIENCE SOCIAL SCIENCE A publication under Free Textbook Programme of Government of Tamil Nadu Department Of School Education Untouchability is Inhuman and a Crime  www.tntextbooks.in Government of Tamil Nadu First Edition - 2018 Revised Edition - 2019, 2020, 2022 (Published under New syllabus in Trimester Pattern) NOT FOR SALE Content Creation The wise possess all State Council of Educational Research and Training © SCERT 2018 Printing & Publishing Tamil NaduTextbook and Educational Services Corporation www.textbooksonline.tn.nic.in II  www.tntextbooks.in The Science textbook for standard six has been prepared following the guidelines given in the National Curriculum Framework 2005. The book is designed to maintain the paradigm shift from the primary General PREFACE Science to branches as Physics, Chemistry, Botany and Zoology. The book enables the reader to read the text, comprehend and perform the learning experiences with the help of teacher. The Students explore the concepts through activities and by the teacher demonstration. Thus the book is learner centric with simple activities that can be performed by the students under the supervision of teachers.  The first term VI science book has seven units. HOW  Two units planned for every month TO USE including computer science chapter THE BOOK? has been introduced.  Each unit comprises of simple activities and experiments that can be done by the teacher through demonstration if necessary student’s can perform them.  Colorful info-graphics and info-bits enhance the visual learning.  Glossary has been introduced to learn scientific terms.  The “Do you know?” box can be used to enrich the knowledge of general science around the world.  ICT Corner and QR code has been introduced in each unit for the first time to enhance digital science skills. Lets use the QR code in the text books ! How ?  Download the QR code scanner from the Google play store/ Apple App Store into your Smart phone.  Open the QR code scanner application  Once the scanner button in the application is clicked, camera opens and then bring it closer to the QR code in the text book.  Once the camera detects the QR code, a URL appears in the screen.  Click the URL and go to the content page. III  www.tntextbooks.in SCIENCE (Term - Ⅰ) Table of Contents Unit Topic Page No. Month 1 Measurements.................. 1 June 2 Force and Motion.............. 14 July 3 Matter around Us.............. 34 August 4 The World of Plants............ 55 June 5 The World of Animals........... 68 July 6 Health and Hygiene............ 80 August 7 Computer - An Introduction...... 96 August E - book Assessment IV  www.tntextbooks.in Unit 1 Measurements metre Learning Objectives  To understand the need for measurement in daily life.  To define length, mass and time.  To evaluate the values of some physical quantities in terms of their units and sub-units.  To identify zero error and parallax error.  To construct measuring tools (models).  To solve problems based on conversion of units. 1  www.tntextbooks.in Introduction && How does the shopkeeper measure kerosene while selling it? && Your brother asks you what your height is. How will you measure it and tell him? To do the tasks given above, we && Your friends decide to play kabbadi. need to know about measurement. The How will you measure and draw the comparison of unknown quantities with border lines? some known quantities is known as && Your father gives you a bag and asks measurement. Measurement of a quantity you to get potatoes. How will you ask has two parts: a number and a unit. the shopkeeper? To measure the quantities we need && Your mother gets milk from the milkman measuring tools. What are the measuring daily. How much does she get? tools that you know? Which of those tools && How long will it take to reach your you will use to do the tasks listed above school from your house? and the similar ones? Measuring Tools 2  www.tntextbooks.in We hear the terms related to length of a banner or height of a lamp post measurement like weight, kilogram, litres, are all measured in metre. How to express millilitres, kilometre, length, distance etc. still longer lengths say, distance between In this chapter let’s study in detail about two cities or villages or distance between length, mass and time and the necessity your school and home? It is expressed in to measure them. kilometre (km). 1.1 Length Know the unit of length 1 km (kilometre) = 1000 m (metre) What is length? The distance between 1 m (metre) = 100 cm (centimetre) one point and the other desired point is 1 cm (centimetre) = 10 mm (millimetre) known as length. It may be the distance Think: Can you express 1 km in cm? between the edges of your book or the Let us measure the length of your corners of the football ground in your pencil. school or even from your home to school. 1. Take the meter scale The standard unit of length is 2. Notice the lines with marking 1,2,3,4... 'metre'. It is represented by the letter till 15 (for smaller scales) or 30 (bigger ‘m’. Very small lengths can be measured scales). The distance between two in millimetre (mm) and centimetre (cm). numbers (say between 1 and 2) denotes Larger measures, say height of a building, a centimetre (written as ‘cm’). 3  www.tntextbooks.in 3. Notice, in between 1 and 2 there will From the activity 1, you see that be smaller markings. If you count, your measurement is different from there will be 9 such lines. The distance that of your friends. Similarly different between any two consecutive smaller measuring units are used in different markings within a ‘cm’ denotes a countries. millimetre (written as ‘mm’). For the sake of uniformity, scientists Why do we need SI Units? all over the world have adopted a common Activity 1 set of units to express measurements. This system is called as the International Form a group of 5 members. Select System of Units or SI Units. one person and let others measure her/ his height individually using hand span SI unit for length is metre and cubit. Compare your answers with SI unit for mass is kilogram others. Do you find any difference? Why? SI unit for time is second Now you all stand in SI unit for area is m2 front of a wall and SI unit for volume is m3 mark your height on the wall. Measure your Prefix height with a scale. Multiples and sub-multiples of SI What differences do units are given as prefixes. Some prefixes you infer? are given in the table. 4  www.tntextbooks.in Multiples and Sub-multiples of SI Units Prefix Abbreviation Submultiple/ Multiple For Metre Deci d Submultiple: 1/10 10 decimetre = 1 metre Centi c Submultiple: 1/100 100 centimetre = 1 metre Milli m Submultiple: 1/1000 1000 millimetre = 1 metre Nano n Submultiple: 1/1000000000 1000000000 nano metre = 1 metre Kilo k Multiple: 1000 1000 metre = 1 kilometre Measure the objects/event given in the table using suitable measuring units and express them with suitable multiple and submultiples. Measuring Unit Multiple / Picture Activity m/kg/s Submultiple Length of tip of pencil. metre millimetre Length of the pen. Distance between two cities. Mass of dry fruits in table. Mass of ornaments. Time taken to finish 100 m race. 5  www.tntextbooks.in Corrective measures for ­Measurement Activity 2 Measurement has to be accurate and Aim: To find the length of the approach has to be correct always. a curved line using a string. In our day to day life approximation may not have much impact. But it has a Materials needed: A meter scale, large impact in scientific calculations. For a measuring tape, a string and example, if the curvature of key (lock and a sketch pen key) is changed even by 1 mm, the lock Method: would not open. So, measurements have Draw a curved line AB on a piece to be accurate in scientific calculations. of paper Let us look at some common mistakes Place a string along the curved that occur while using a scale. line. Make sure that the string To measure the length of a pin covers every bit of the curved line. Mark the points where the curved 0 cm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 line begins and ends on the string. Now, stretch the string along the The head of the pin has to coincide length of a meter scale and measure with ‘0’ of the scale. the distance between the two Count the number of centimetre and markings of the string and note it. from there count the number of finer This will give you the length of a divisions. The count of the division is curved line. in ‘mm’ In the above example the length of pin is 2 cm and 6 mm. Write the correct submultiple completely. Find the length of a banana. Parallax Error Parallax is a displacement or difference in the apparent position of an object viewed Note: along two different lines of sight. Always keep the object parallel to the Correct position of the eye is also scale. important for taking measurement. Start the measurement from ‘0’ of the Your eye must be vertically above the scale. point where the measurement has to be 6  www.tntextbooks.in A B C 1.2 Mass Mass is the measure of the amount of matter in an object. The SI unit of mass is kilogram. It is represented by ‘kg’. Weight is the gravitational pull experienced by matter. The weight is directly proportional to the mass on the Earth's surface. taken. In the above representation, to Hold a sheet of paper in one hand avoid parallax error, reading from B will and a book in other hand. Which hand be correct. From positions ‘A’ and ‘C’, the feels the heaviness? The mass of the readings will be different and erroneous. book is more than that of a single sheet of paper. Therefore, the pull on the book Activity 3 is more than that is on the paper. Hence, Aim: Measuring the length of our hand needs more force to hold a book a curved line using a divider. than a piece of paper. The force what we experience is called as ‘heaviness’. On the moon where the gravitational force is less than that is on the A earth, the weight will B reduce but the mass will remain same. Draw a curved line AB on a piece of paper. The moon’s gravitational pull is one Separate the legs of the divider by 0.5 cm sixth of the earth’s pull. Thus objects or 1 cm using a ruler. weigh six times lighter on the Moon Place it on the curved line starting than on the Earth. from one end. Mark the position of the other end. Move it along the line What is your mass? If you measure it again and again cutting the line into in grams, that would be a huge number. number of segments of equal lengths. Is it not? So, it is expressed in kilogram. The remaining parts of the line can Bigger weights are measured in tonne or be measured using a scale. Count the metric tonne. number of segments. 1000 milligram = 1 gram Therefore, the length of the line = 1000 gram = 1 kilogram (Number of segments × Length of each 1000 kilogram = 1 tonne segment) + Length of the left over part. 7  www.tntextbooks.in Beam Balance laboratories for weighing chemicals to ensure a precise measurement of We use beam balance to measure those chemicals for using in various mass. A beam balance works by comparing experiments. Electronic balances may the mass of an object to that of known also be used to weigh food, other grocery mass (called a standard mass). items, as well as jewellery. Activity 4 Construct your own beam balance using two scrapped coconut shells, strings or twines, thick cardboard as 1.3 Time frame and a little sharpened pencil as index needle. Day changes into night and night in to day. Seasons also change. We know What can you achieve? time also changes. How do we measure 1. Find which object is heavier. change of time? Clocks are used to 2. Find the approximate weight of measure time. You know how to read a lighter things like leaves, piece of clock face and note the time. You can papers etc. also use your pulse to measure the time roughly. Count the number of pulses. That can tell you the time elapsed. Activity 5 : Ask four or five of your friends to run a race from one end of the school to the other end. Mark the starting point and the ending point. Using your pulse (or counting by Electronic Balance counting 1,2,3,.....) count the time An electronic balance is a device taken by each of them to complete used to find the accurate measurements the race. Check who is fast? of weight. It is used very commonly in 8  www.tntextbooks.in In the earlier days, Fast Facts people used sand An odometer is a device used for clock and sundial to indicating distance travelled by an measure the passage automobile. of time during day time. The shadow cast by a stick can be used The metric system or standard set of to estimate time. A vessel having a units was created by the French in small hole is filled with sand and it 1790. is used as a clock. The sand in the A ruler or scale, used now a days vessel is allowed to come down and to measure length, was invented by it is used to estimate the time. William Bedwell in the 16th century. A standard metre rod made of an alloy of platinum and iridium is placed at the Bureau of Weights and Measures in Paris. National Physical Laboratory in Delhi has a copy of this metre rod. One kilogram is equal to the mass of a certain bar of platinum-iridium alloy that has been kept at the International Bureau of Weights and Measures in Sèvres, France since 1889. Numerical Problems Look at a meter scale carefully and answer the following. How many millimieter divisions are there in a centimeter? How many centimeter divisions are there in a meter? Sand Clock Complete the following. ¾¾ 7875 cm =     m     cm These are rough methods for counting ¾¾ 1195 m =     km     m passage of time. We can use electronic ¾¾ 15 cm 10 mm =     mm clock, stopwatch and other instruments to count even smaller durations of time. ¾¾ 45 km 33 m =     m. 9  www.tntextbooks.in Some open ended questions Points to Remember During your school sport day, it is The comparison of an unknown planned to conduct a mini marathon quantity with some known quantity is race within the school campus. They known as measurement. decided that the running distance All physical quantities have standard be 2 kilometres. Is it possible to units for the sake of uniformity. have a school campus with the Length, mass and time are some of circumference of 2km? Discuss with the fundamental physical quantities. your friends, how big the campus should be. Give other options if it is The SI units are: not a big campus. Length - metre Is the distance in the sea also Mass - kilogram calculated in kilometres? How is it Time - second possible to calculate the distance in While using a ruler, the accurate sea water? Explore! measurement can be arrived by We know that the distance between avoiding three types of possible errors. celestial bodies is calculated in terms Electronic balance is an instrument of light year. Light year is the distance which provides accurate measurement travelled by light in one year. Now of mass correct upto milligram. without calculator find how many kilometres light would have travelled in a year. Get the speed of light from your teacher. Evaluation We see that the distances between Chennai and Madurai is written as I. Choose the correct answer. ‘462’   kms. But from which point to which point is this distance calculated?. 1. The height of a tree can be measured As we are science students we need by to know it with the precision. Is it a) metre scale c) plastic ruler between the two bus stands? Or b) metre rod d) measuring tape between the two railway stations? Discuss and figure it out. Check your 2. Conversion of 7 m into cm gives _____ answers with your teacher. a) 70 cm c) 700 cm A person needs to drink two litres of b) 7 cm d) 7000 cm water a day. Note down how much 3. Quantity that can be measured is water you drink each day? Make a called ____ rough calculation and check if you are drinking the required amount a) physical quantity c) unit of water. b) measurement d) motion 10  www.tntextbooks.in 4. Choose the correct one IV.  Complete the analogy. a) km > mm > cm > m 1. Sugar : Beam balance :: Lime juice b) km > mm > m > cm :___? c) km > m > cm > mm 2. Height of a person : cm :: Length of d) km > cm > m > mm your sharpened pencil lead :___? 5. While measuring the length of an 3. Milk : Volume :: Vegetables :___? object using a ruler, the position of your eye should be V. Match the following. a) left side of the point. 1. Length of the fore arm a. metre b) vertically above the point where 2. SI unit of length b. second the measurement is to be taken. 3. Nano c. 103 c) right side of the point 4. SI Unit of time d. 10–9 d) a ny where according to one’s 5. Kilo e. Cubit convenience. VI.  Arrange the following in the II.  Fill in the blanks. increasing order of unit. 1. SI Unit of length is . 1 Metre, 1 centimetre, 1 kilometre, and 2. 500 gm =       kilogram. 1 millimetre. 3. The distance between Delhi and Chennai can be measured in . VII.  Answer in a word or two. 4. 1 m =       cm. 1. What is the full form of SI system? 5. 5 km =       m. 2. Name any one instrument used for measuring mass. III.  State True or False. If false, correct the statement. 3. Find the odd one out. kilogram, millimetre, centimetre, 1. We can say that mass of an object is nanometre 126 kg. 4. What is the SI Unit of mass? 2. Length of one’s chest can be measured 5. What are the two parts present in a using metre scale. measurement? 3. Ten millimetre makes one centimetre. 4. A hand span is a reliable measure of VIII. Find the answer for the ­following length. questions within the grid. 5. The SI system of units is accepted 1. 10-3 is one        everywhere in the world. 2. SI Unit of time is        11  www.tntextbooks.in 3. Cross view of reading a measurement IX. Answer briefly. leads to        1. Define measurement. 4.        is the one what a clock 2. Define mass. reads. 3. The distance between two places is 43.65 km. Convert it into metre and cm. 5.        is the amount of substance present in an object. 4. What are the rules to be followed to make accurate measurement with scale? 6.        can be taken to get the final reading of the recordings X. Solve the following. of different students for a single 1. The distance between your school and measurement. your house is 2250 m. Express this distance in kilometre. 7.         is a fundamental 2. While measuring the length of a quantity. sharpened pencil, reading of the scale 8.        shows the distance at one end is 2.0 cm and at the other covered by an automobile end is 12.1 cm. What is the length of the pencil? 9. A tailor uses        to take measurements to stitch the cloth. XI. Answer in detail. 10. Liquids are measured with this 1. Explain two methods that you can use physical quantity. to measure the length of a curved line. A P L R K C O E O S M K N R I P R G R T R H E S T E D L L I T R E D A L T H D H P O E O N K E A M S O R V V I E C T O E L K E S S R L I S T K H A I T I V P G M X M N U E Z D E S K P G I W M F Z T D K H O D O M E T E R 12  www.tntextbooks.in 2. Fill in the following chart. Property Definition Basic Unit Instrument used for measuring Length Mass Volume Time ICT CORNER AREA & PERIMETER Lets play with Area N Perimeter Steps: Access the application by typing Area N Perimeter or install with the help of the link given below or the given QR code  pen the Application and click START button. O Y  ou can see the field whose area is to be measured. Drag and put the tiles on field. U  se the (+) and (-) to find out the area of the given field.  lick the CHECK button to check your answer. C  ou can view your whole results by clicking the RESULT button. Y Step1 Step2 Step3 Step4 URL: https://play.google.com/store/apps/details?id=com.bodhaguru.AreaNPerimeter *Pictures are indicative only 13  www.tntextbooks.in Unit 2 Force and Motion Learning Objectives ™™ To identify that push or pull or both are involved when there is a motion. ™™ To understand that some forces are contact forces and some are non-contact forces. ™™ To know that when a force is applied, it can make things move, change the direction or change its shape and size. ™™ To distinguish between rest and motion and understand that they are relative. ™™ To infer motion is caused by application of force. ™™ To classify different types of motion. ™™ To deduce the definition of speed. ™™ To understand and use the unit of speed. ™™ To distinguish uniform and non-uniform motion. ™™ To compute time, distance and speed. 14  www.tntextbooks.in Introduction 2.1 Motion and Rest We have studied in our earlier classes What is rest? What is motion? that push or pull results in some motion of Suppose there is a book on your table the object. When we open the door or kick right in the middle. Is the book moving? a football or lift our school bag, motion is You will say it is not moving; it is at rest. involved and there is some push or pull. If you push the book to one side of the table to clear the space for keeping your notebook, then you will say the book is moving. When the book was at the same place with respect to the table, it was at rest; but when it was pushed from one place on the table to another place, it was moving. Activity 1 Can you identify whether it is push or pull that results in motion in the following cases? Push / Pull Push / Pull Push / Pull Push / Pull Push / Pull Push / Pull 15  www.tntextbooks.in When there is a change in the position of an object with respect to time, then it is called motion. If it remains stationary it is called rest. Is Mohan in motion? Observe the following pictures and say whether Mohan is in motion or at rest Hey Babu! would you say that Mohan is in motion? Yes, of course. Anitha and Babu are standing under a tree at the bus stand waiting for a bus How can you say that? to Madurai. Two of their friends, Reka I can see he’s just sitting and Mohan, get into a bus to go to in the bus! Thanjavur. The bus starts. Reka, do you think mohan is moving? Yes, but the bus is moving isn’t it? You never No, Mohan is not. He is So what? believe me. just sitting in one place! Ask Reka. But I am also in the bus! To me it does not look as if Mohan is moving. He isn’t moving towards me or away from me. Hi! Am I moving or at rest? Can’t you see Anitha tells this to that the bus has Babu. He snatches moved away from the phone from the tree? Mohan is her and says in the bus hence irritably to Reka, Mohan is moving along with the bus. 16  www.tntextbooks.in Discuss: Who is correct? Is Mohan Event 3: Nisha really in motion? is going to her We can clearly say that both Reka and grandmother's Babu are correct. From the point of view house by bicycle. of Babu, Mohan along with the bus is in Sitting on the motion; but for Reka who is sitting beside bicycle, Nisha is him, he is at one place; therefore stationary.  So, according to Babu, Mohan is in motion; with respect to the road. Mohan is at rest from Reka's observation. She is _____________ with respect to Can you think any other examples? the bicycle. Take the case of a book on a table at rest. Is it really without any motion? We know that Earth is rotating on its axis; therefore the table along with the book must be rotating. Is it not? We are also moving along with the earth. Therefore, from the point of view of the ground on which we stand, the book is at ‘rest’. Similarly, while travelling in a bus, we feel Answer by observing the situation in that the poles and trees seem to move the picture backwards, and the things inside the bus Event 1: The man in the boat is moving are stationary. with respect to the bank of river. He is at rest with respect to the boat. Am I at rest or in motion? Event 2: The girl on the An object may appear to be swing is  stationary for one observer and appear with respect to the to be moving for another. An object is at seat of the swing. rest in relation to a certain set of objects She is      with and moving in relation to another set of respect to the objects. This implies that rest and garden. motion are relative. 17  www.tntextbooks.in How things move? Activity 2 When we kick a ball it moves. When Moon or Cloud? we push the book on the table, it moves. Observe the moon on a windy night When a bullock pulls, the cart moves. with a fair bit of cloud cover in the sky. Motion occurs when an object is pulled or As the cloud passes in front of the moon pushed by an agency. you sometimes think it is the moon which is moving behind the cloud. Why don’t we What would you think if you were to try any inanimate observe a tree at the same time? agency? In our daily life, we pull out water from the well using bucket. Animals pull a bullock cart. It is a person or animal, that is an animate agency that does the pushing or pulling. Sometimes we see a tall grass in the meadow dancing in the wind or a Aryabatta, an ancient piece of wood moving down a stream. Indian astronomer, What pushes or pulls them? We know said, "As the banks that blowing wind and flowing water of the river appear is the cause. Sometimes the push to move back or pull can be due to the inanimate to a person in agency. a boat floating gently in a river, the night sky Forces are push or pull by an animate studded with or inanimate agency. stars appear to move from the Contact, Non-contact Forces east to the west and so the Earth Forces can be classified into two major rotates from the west to the east." types; contact and non-contact forces. 18  www.tntextbooks.in Wind making a flag flutter, a bullock pulling Animate Inanimate a cart are contact forces. Magnetism, Factors Factors gravity are some examples of non-contact Agencies forces. In all the above cases, the force Force is executed by touching the body. So, this type of forces are called contact forces. Types on the basis of contact Mysteriously, ripen coconut falls to the Contact Non-Contact ground. What pulls it to the ground? We Forces Forces would have heard about ‘force of gravity’ of Earth. Gravity pulls the ripen coconut What happens when we apply a from the tree to the ground. force on an object? What happens when you apply a force on an object? Say, you push a book on the table. The book moves. Application of force in an object results in motion from a state of rest. What happens when a batsman hit a Hey! Who is ball? The ball is already in motion, but with pulling me? the strike, the speed of the ball increases. Moreover the direction of the ball changes. Application of force on an object results in a change in its speed and change in its direction. When we crush a balloon or press roti dough or pull a rubber band, the shape of the object changes on application of When we bring a magnet near a small force. Application of force in object results iron nail, the nail jumps into the air and in expansion or contraction. sticks with the magnet. Observe that the magnet and the nail did not touch each other. Still, there was a pulling force that made the nail to jump towards the magnet. In these two examples, the force is applied without touching the object. Such forces are known as non-contact forces. 19  www.tntextbooks.in In a nutshell, we can say that the applied force is an interaction of one object on another that causes the second object to move from rest, speed up, slow down, stop the motion, change the direction, compress or expand. Look at this picture. The person is Forces can applying force to stop the cart from 1. Change the states of a body from moving. When the force is applied against rest to motion or motion to rest. the direction of the motion, the speed can be reduced, or even the motion is stopped 2. Either change the speed or direction or completely. Discuss what happens when both of the body. you apply break in a speeding bicycle. 3. Change the shape of the body. Activity 3 Fill in the empty spaces move objects at rest Force can change the speed compress or expand Can you give example for contact and non-contact forces? Force Contact Force Non-Contact Force Examples Examples Kick a football Magnet attracts nails 20  www.tntextbooks.in 2.2. Types of motion Activity 4 Play with pencil Do what Shanthi did... (i) Shanthi took a pencil and sharpened it with a sharpener. (ii) Then she drew a circle using the pencil and a compass. (iii) Later she took her ruler (scale) and drew a straight line in another paper. (iv) Then she kept the pencil between her fingers and moved it back and forth. Now, look at the motion of the pencil in all these four cases. How was it? (i) In the first case, the pencil rotated in its axis. (ii) In the second case, it went in a circle. (iii) In the third case, the pencil travelled in a straight line. (iv) In the fourth case, the pencil tip moved back and forth, that is it oscillated like a swing. We can say that the motion of the A fly buzzing around the room is a pencil was rotational, circular, straight combination of all these motions and line or linear and later oscillatory. flight path is zigzag. Throw paper aeroplanes or paper dart. Watch its flight path when you throw it at an angle. The path curves i.e the paper flight is moving ahead but its direction is changing while moving. Such paths are called curvilinear. You can classify the motion according to the path taken by the object. a. Linear motion - Motion in a straight line. Eg. A person walking on a straight path. 21  www.tntextbooks.in b. Curvilinear motion - Motion of a body Oscillations at moving ahead but changing direction. Eg. Motion of a ball thrown. Greater Speed Ask your friend to c. Circular motion - Motion in a circle. Eg. Swirling stone tied to the rope. hold the two ends of a stretched rubber band. Strike it in the d. Rotatory motion - Motion of a body middle. Do you see that it oscillates about its own axis. Eg. Rotating top. very fast? When the oscillation is very e. Oscillatory motion - A body coming back swift, it is called as vibration. to the same position after a fixed time interval. Eg. A pendulum. Fast oscillations are referred f. Zigzag (irregular) - The motion of a to as vibrations. body in different direction. Eg. People walking in a crowded street. Activity 5 Hi! Friends! Tell me what type of motion. I am in. Linear Motion 22  www.tntextbooks.in Activity 6 Classify the following according to the path it takes. Linear, Curvilinear, Circular, Rotatory, Oscillatory, Zigzag (irregular) A sprinter running a 100 m race A coconut falling from a tree Striking a coin in a carom board game Motion of flies and mosquitoes Beating of heart Children playing in a swing The tip of hands of a clock Flapping of elephant’s ears A stone thrown into the air at an angle Movement of people in a bazaar Athlete running around a track Revolution of the moon around the earth The movement of a ball kicked in a football match Motion of a spinning top Revolution of the earth around the sun Swinging of a pendulum Children skidding on a sliding board Skidding down a playground slide Wagging tail of a dog Flapping of a flag in wind A car driving around a curve Woodcutter cutting with a saw Motion of water wave Motion of piston inside a syringe Bouncing ball [Add five motions you observe to this list] 23  www.tntextbooks.in Periodic and non-­periodic motions All oscillatory motions Take the case of the hour-hand of a are periodic, but not all clock. In one day it makes two rounds. periodic motion are Look at a bouncing ball. It bounces a oscillatory motion. certain number of times for a given time interval or period. Look at the water waves. Fast Vs Slow? In a given period that is in a time interval, a fixed number of waves hit the shore. Look at a tall tree. When the wind is Motion repeated in equal intervals of time gentle, its branches are dancing slowly; is called as periodic motion. but if the gentle wind becomes strong, the branches shake violently, and if the speed increases further, the branch may even break and fall. That is the motion can be slow or fast. Can we say a motion is slow or fast without comparing anything? Let us take the example of sapling swing in wind. This motion is not in uniform interval. Such motions are called Compared to walking, cycling is fast, but a bus is faster than a cycle. The non-periodic motion. aeroplane is much faster than a bus. Revolution of the Moon around the So, slow or fast is a relative concept Earth is periodic but not oscillatory. which depends upon the motions we are However, the children playing in a swing comparing. Then how do we say a body is both periodic and oscillatory. moves at a particular speed? Speed. I have travelled 160 km in two hours. I have travelled 200 km in four hours. Taxi Driver I have travelled 300 km in five hours. Can you say who travelled with highest speed? Bus Driver Truck Driver 24  www.tntextbooks.in Let us calculate how long they A bus takes three hours to cover travelled in one hour? a distance of 180 kilometres. Then its Distance travelled by the car in speed is given as: one hour =   80    km (160/2) Speed (s) = Distance travelled (d) / Distance travelled by the bus in Time taken (t) one hour =       km = 180 kilometre/ 3 hour Distance travelled by the truck in = 60 kilometre / hour one hour =       km Have you found out? Say now. Who is fast?      , Who is slow?       Have you noticed that saying who is fast or slow is easy when we calculate the distance they travelled in one hour? In other words, you divide Note that metre/second or kilometre/ the distance travelled by the time taken hour comes next to our answer for to get the speed. speed. What is it? The distance travelled by an object Observe the formula for speed. If in unit time is called speed of the we denote the distance in metre and object. time by second then the unit of speed If an object travelled a distance 'd' in is metre/second. If we denote the time 't' then, its speed is given as: distance in kilometre and time in hour Distance travelled d then the unit of speed is kilometre/ Speed (s) =  = Time taken t hour. Sometimes we use units like centimetre/second. Suppose a car travels 300 km in one In science we generally use SI units. hour. Then we say that the speed of the In SI units the unit of distance is metre car is ‘300 kmph’ (We read it as ‘three and the unit of time is second. So, the SI hundred kilometres per hour’). unit of speed is metre/second. If an object travelled 10 metre in 2 second, then its speed is given as: Let us calculate Speed (s) =D  istance travelled (d) / 1. A  car travelled 150 metre in 10 second. Time taken (t) What is its speed? = 10 metre/ 2 second 2. P  riya rides her bicycle 40 km in two = 5 metre / second hours. What is her speed? 25  www.tntextbooks.in Our speed... Let us play a small game. Go to the playground with your friends. Mark 100 metre distance for a race. Conduct a friendly running race and calculate the time taken by them to complete the distance. Now record the time in the table. Name of the Time taken Distance travelled S. No Distance Speed = Speed (m/s) Student (in seconds)  Time taken 1 Murugesan 100 m 12 S 100 M / 12 S 8.3 m/s 2 100 m 3 100 m 4 100 m 5 100 m If you know the speed of an object If a ship travelled at a speed of 50 and the time taken by it, then we can kmph and it sailed for five hours, how compute how much distance it had much distance it has travelled? travelled. Distance = s × t We know that, = 50 kmph × 5 h = 250 km Distance travelled If we know the speed and distance Speed = travelled we can compute the time taken. Time taken s = d/t or st = d s = d/t or t = d/s Time taken = Distance travelled / Speed Therefore, the distance travelled = speed × time. Suppose a bus travels at a speed of 50 kmph and has to cover a distance of 300 km, how much time will it take? t = d/s = 300 km/50 kmph = 6 h. Compute the following Numerical Problems. 1. If you travel 10 kilometres in 2 hours, your speed is     km per hour. Usain Bolt crossed 100 metre in 9.58 2. If you travel 15 kilometres in 1/2 hour, seconds and made a world record. If you would travel     km in one hour, you are able to run faster than him, and your speed is     km per hour. then Olympic Gold Medal is waiting for you. 3. If you run fast at 20 kilometres per hour for 2 hours, you will cover     km 26  www.tntextbooks.in moved some distance it will gather speed. FACT FILE After that it may slow down while crossing bridges and stop at intermediate stations for passengers. Finally, as the train approaches A Cheetah is the fastest land animal Madurai, again it will slow and finally will running at a speed of 112 km/h. come to a halt. It means that the speed is not the same all through the journey. That is, the speed is non-uniform. This motion is Uniform and Non-uniform motion said to be non-uniform motion. Suppose a train leaves Thiruchirapalli However, in between the journey, there and arrives at Madurai. Will the train travel may be a stretch where in the train might in an uniform speed? First, the train will go at a constant speed. During that interval be stationary. When the train leaves the the train will be moving at uniform speed. station, the motion will be slow. After it That is, its motion is uniform. MOTION Based on Based on Based on Path Duration Speed Periodic Uniform Motion Linear Motion Motion Non-uniform Curvilinear Non-periodic Motion Motion Motion Circular Motion Rotatory Motion Oscillatory My machine has many of the motions Motion mentioned in the above chart. Can you list Zigzag them? (Irregular) Motion 27  www.tntextbooks.in Many motions we see in our day to day or not. However, in real life, the motions life are non-uniform. We will learn more are combinations of many types of about uniform and non-uniform motion in motion. higher classes. Multiple Motion If an object covers uniform distances in uniform intervals then the motion Look at the bicycle in the picture. What of the object is called uniform motion. type of motion does the wheel perform? Otherwise the motion is called non- What type of motion does the cycle in uniform motion. total perform? In a nutshell, we can classify the The tyres rotate and make a rotatory motion in terms of a) path b) if it is motion, but the cycle as such moves periodic or not c) if the speed is uniform forward in a linear path. Activity 7 Simple Spinner Let us enjoy by making a simple spinner. Make it by the following instruction. Cut a 2cm long piece from an old ball-pen refill and make a hole in its center with a divider point (Fig. 1). Take a thin wire of length 9cm and fold it into a U-shape (Fig. 2). Weave the refill spinner in the U-shaped wire (Fig. 3). Wrap the two ends of the wire on the plastic refill, leaving enough clearance for the spinner to rotate (Fig. 4). On blowing through the refill, the spinner rotates (Fig. 5). For obtaining maximum speed adjust the wires so that air is directed towards the ends of the spinner. Have you enjoyed with simple spinner? Do you observe the motions in the toy? Can you answer the following questions? 1. Motion of the air in tube is         motion. 2. Motion of the refill stick is         motion. 3. The toy converts         motion into         motion. Think In a simple spinner linear motion is converted into rotatory motion. Can you make a toy which converts rotatory motion into linear motion? 28  www.tntextbooks.in Rotational Motion A bipedal humanoid robot. Linear Motion The term 'robot' comes from a czech Multiple motion in a sewing word, ‘robota’ meaning ‘forced labour’. machine Robotics is the science and study of robots. What can Robots do? Robots can sense and respond to their surroundings. They can handle delicate objects or apply great force. For example, they can perform eye operations guided by a human surgeon, or assemble a car. With artificial intelligence, robots will also be able to make decisions for themselves. Motion of the needle How do Robots sense? Electronic sensors function as robot’s _______________________ eyes and ears. Twin video cameras Motion of the wheel give the robot a 3-D view of the world. _______________________ Microphones detect sounds. Pressure Motion of footrest _______________________ 2.3 Science Today - ­Robot Robots are automatic machines. Some robots can perform mechanical and repetitive jobs faster and more accurately than people. Robots can also handle dangerous materials and explore distant The quadrupedal planets. military robot 29  www.tntextbooks.in sensors give the robot a sense of touch, are too delicate or too difficult for standard to judge how to grip an egg or heavy surgery. Imagine if a nanobot could target luggage. Built-in computers send and cancer cells and destroy them without receive information with radio waves. touching healthy cells nearby. Artificial Intelligence Artificial intelligence attempts to create computer programs that think like human brains. Current research has not achieved this, but some computers can be programmed to recognize faces in a crowd. Can Robots think? Future of Nanorobotics Robots can think. They can play complex games, such as chess, better than human beings. But will a robot ever Points to Remember know that it is thinking? Humans are Motion and rest are relative. conscious - we know we are thinking. All things that are at rest may seem to But we do not know how consciousness be in motion from a different point of works. We do not know if Robots can view, and all motion may seem to be ever be conscious. at rest from a different perspective. Application of forces is implemented by a push or pull. Forces can be applied by animate as well as inanimate agency. Application of forces result in motion of an object at rest, increase or decrease its speed, change its direction, and distortion of the shape. Some forces act only when they are in Articulated welding robots contact. There are some forces which (industrial) can even have effect at a distance. Speed = Distance travelled / Time Nanorobotics taken (s= d/t) Nanobots are robots scaled down to The motion can be classified according microscopic size in order to put them into to the path (periodic or non-periodic) very small spaces to perform a function. or according to speed (uniform or Future nanobots could be placed in the blood non-uniform). stream to perform surgical procedures that Unit of speed is m/s. 30  www.tntextbooks.in II. Fill in the blanks. 1. A bike moving on a straight road is an Evaluation example for         motion. 2. Gravitational force is a     force. 3. Motion of a potter’s wheel is an I. Choose the correct answer. example for       motion. 1. Unit of speed is 4. When an object covers equal distances a. m  b. s  c. kg  d. m/s in equal interval of time, it is said to be 2.  hich among the following is an W in     motion. oscillatory motion? III.  State True or False. If false, a.  Rotation of the earth about its correct the statement. axis. b. R  evolution of the moon about the 1.  To and fro motion is called oscillatory earth. motion. c. T  o and fro movement of a vibrating 2. Vibratory motion and rotatory motion string. are periodic motions. d. All of these. 3. Vehicles moving with varying speeds 3. The correct relation among the are said to be in uniform motion. following is 4. Robots will replace human in future. a. Speed = Distance × Time IV. Match the following. b. Speed = Distance / Time c. Speed = Time / Distance 1. a. Circular motion d. Speed = 1 / (Distance × Time) 4. Gita travels with her father in a bike to her uncle’s house which is 40 km away from her home. She takes 40 minutes 2. b. Oscillatory motion to reach there. Statement 1 : She travels at a speed of 1 km / minute. 3. c. Linear motion Statement 2 : She travels at a speed of 1 km/hour. a. Statement 1 alone is correct. 4. d. Rotatory motion b. Statement 2 alone is correct. c. Both statements are correct. 5. e. L inear and d. Neither statement 1 nor statement rotatory motion 2 is correct. 31  www.tntextbooks.in V. Given below is the distance-travelled 4. The motion of an object which covers by an elephant across a forest with equal distances in equal intervals of uniform speed. Complete the data time.  of the table given below with the idea of uniform speed. 5. A machine capable of carrying out a complex series of actions Distance (m) 0 4 12 20 automatically.  Time (s) 0 2 4 8 10 IX. Answer briefly. 1. Define force. VI. Complete the analogy. 2. Name different types of motion based on the path. 1. Kicking a ball : Contact force :: Falling of leaf : ? 3. If you are sitting in a moving car, will you be at rest or motion with respect 2. Distance : metre :: Speed : ? your friend sitting next to you? 3. Circulatory motion : A spinning top :: 4. Rotation of the earth is a periodic Oscillatory motion : ? motion. Justify. 5. Differentiate between rotational and VII. Complete the web chart. curvilinear motion Non- periodic X. Answer in detail. 1. What is motion? Classify different types of motion with examples. Movement repeated after a fixed interval XI. Problems. of time 1. A vehicle covers a distance of 400km in 5 hour. Calculate its speed. XII. Give examples. Linear motion Movement about an axis or a fixed centre Curvilinear motion Motion of the wheel VIII. Answer in a word or two. Self rotatory motion in a cart 1. The force which acts on an object Circular motion without physical contact.  2. A change in the position of an object Oscillatory motion with time.  3. The motion which repeats itself after a Irregular motion fixed interval of time.  32  www.tntextbooks.in ICT CORNER Force and motion Play with force and motion. Steps: Lets learn force and motion on PhET in Google browser. Download and install.  rag any one side and place him in the knot portion of the rope. Now click go. D If placed on the right side then the load will move in that direction. The place of the man and the number of man can be changed. The direction of force and the unit of force will display on the screen. I f we place equal number of men on both the sides the load will not move. By changing the number of men the strength of force can be changed. Step1 Step2 Step3 URL: https://phet.colorado.edu/en/simulation/forces-and-motion-basics *Pictures are indicative only 33  www.tntextbooks.in Unit 3 Matter Around Us Anything which occupies space and has mass is called matter LPG Gas Air Liquid Water OIL Iron Solid Wood Learning Objectives  To define matter and develop an understanding on the particle nature of matter.  To sort the objects on the basis of certain properties.  To differentiate solids, liquids and gases based on the arrangement of their particles.  To differentiate pure substances from mixtures.  To identify the need for separation of mixtures.  To suggest suitable methods for separating given samples of mixtures.  To acquire an awareness on food adulteration and its harmful effects. 34  www.tntextbooks.in Introduction 3.1 Physical Nature of Matter Matter is everywhere around us. The Matter occupies space and has mass. air we breath, water we drink and the What is its nature? Many philosophers material we use are made up of matter. pondered over this question and Matter is defined as anything that occupies came out with ideas. It is known that space and has mass. Matter is found in Indian Philosopher Kanada and Greek three major states: solid, liquid and gas. philosopher Democritus had their ideas Do you know what is matter made of? similar. The Indian philosopher Kanada Matter is made of atoms. Atoms are called it as paramanu and Democritus the smallest particle of matter. They are so called it as atomos. small that you cannot see them with your eyes or even with a standard microscope. Imagine that a piece of thread is A standard sheet of paper is about millions cut endlessly using knife. At one point of atoms thick. Science has come up with it would be like a small piece that it a technology to identify the structure cannot be further cut by a knife. That of atoms by using Atomic resolution small particle may contain millions of Microscope (ARM) and Tunnelling Electron molecules and these molecules are Microscope (TEM) which use electricity to made of atoms. Matter is made of such map atoms. There is more about atoms in smallest particles 'atoms'. These atoms the later classes. But first let's learn about are extremely small even to see under a the three states of matter. powerful microscope. Activity - 1 Take a few crystals of sugar. Observe them carefully with the help of a magnifying lens. A B C D E F Which of the shapes given above resemble a sugar crystal? A B C D E F Now place a few sugar crystals into water. What happens to the sugar crystals? A sugar crystal is also made up of molecules. When sugar dissolves in water, the sugar crystals break down and the molecules of sugar get distributed in water. This makes water sweet in taste. The sugar molecules are extremely small; that is why we are not able to see them. Small amount of matter has many millions of molecules in it (1 million = 10 lakhs). 35  www.tntextbooks.in Characteristics of the particles of 3.2 M  ass, Shape and Volume of matter Solids, Liquids and Gases 1. Particles of matter have a lot of space Let us first take any solid say a stone: in between them. In different forms of Answer the following questions. matter this spacing will be different.  Do you need a container to know the Let us add a spoon full of sugar to a shape of a stone ? Yes / No glass of water. Stir well. Sugar disappears A solid does not need a container. completely. Where has it gone? Will the glass It stays as it is because its particles are of water be now sweet? Water particles have tightly packed and has a definite shape. space between them and sugar particles are now occupying those spaces.  If you move the stone from the ground to a table or place it on the shelf does it's shape change? Yes / No If you take a stone from the ground and place it on the table or shelf its shape and volume do not change. Activity 2 Sit together in groups of three. Look 2. Particles of matter attract each other. at the objects given below. Are they It is the force of attraction which keeps familiar to you? Are they same or the particles together. This attractive force different? On what basis you can will be different for different forms of matter. group them? Is there only one way of doing it or more ways? Discuss with Grouping of Matter on the ­ basis of your group members and note down Physical states your points. These are the three physical states of matter. Matter can be grouped into solids, Pencil and books are used for liquids and gases based on the above studying. The bucket and the comb are characteristics. made of plastic while the table and ladle 36  www.tntextbooks.in are made of wood. The scrub brush and Try to fill in the following table broom are rough but the toy bear is soft. You can group them according to their Light can pass through a glass of water uses, the materials with which they are and the spectacles but not through apple made of or some other properties. or iron box. The cow and the bird are S.No Things that float Things that sink living things while the rest are not. Water 1. in the glass is liquid but air in the balloon 2. is gas and the rest are solids. The feather 3. and the paper cup can float but not the Try to make more such tables based on apple or the piece of stone. The rubber the properties discussed above. How many band can be stretched but not the comb. tables could you make? Though they have different properties, How did you classify the items in the they are matter. above list as solids, liquids and gases? 37  www.tntextbooks.in You should have done it based on some Now light an incense stick and keep it properties. Brick and door which are hard in one corner of the room. come under solids, things that flow come under liquids and others which are very light and can flow more freely come under gases. Activity 3 Malar was asked to group some items Let us answer the following questions. based on their physical states. The table Did the book move? she made is given below. Do you agree with her? Correct the table if you do Did the ink particles move and spread not agree and submit it to your teacher. itself in the water? How long did it take (Work in a group of two.) for complete mixing? Chalk piece Wind Steam Did you get the smell of the incense Water Rain Lemon stick from where you are standing? Air in a balloon Stone Lemon juice How fast did you get the smell? How River Air Smoke did the smell reach you? Brick Table Door We may conclude that the particles of gases and liquids can move easily 3.3 Diffusion and quickly. This tendency of particles Let us place a book on a table. Let it to spread out in order to occupy the not be disturbed. Observe for five minutes. available space is called diffusion. Solids Now take a glass of water and add a drop are tightly packed and they do not diffuse of ink carefully at the centre. Do not shake like liquids or gases. Hence ink and smoke or stir. spread easily while book stays on the table. Particles in a Solid Particles in a Liquid Particles in a Gas In solid, the particles are Particles in liquids are The particles in the gases tightly packed with very arranged in a random or are arranged far apart. little space between them. irregular way and the space They move freely. Eg. Stone between the particles is Eg. Air greater than that is in solids. Eg. Water 38  www.tntextbooks.in space and also has mass. Let us try to Activity 4 know more about matter. Let us take two sachets of juice. In Test Yourself both the sachets, it is written 100ml. Let us empty two sachets and pour 1 Name an object which is brittle and the juice into the following glasses. transparent. 2. Name an object which can be stretched. 3. Name two objects which can be bent. 3.4 C  ompressibility of gases Does its shape change? compared to liquids and Yes / No solids A liquid needs a container and Let us take three identical syringes. it takes the shape of a container Close the nozzles because the particles slide over tightly with a cork. After one another and keep moving. removing the plunger Does its volume change when it is first let us fill it with poured into a big glass as well as fine chalk powder. Try a small one? Yes / No to press plunger down. The amount of juice is the What do you observe? same in both glasses. Now let us fill the second one with How will you find out whether the water. Press the plunger down. What do volume has changed or not? you observe? Let us now draw the piston The volume of a liquid remains back to suck air into the third one. Press the same whether it is kept in a the plunger down. What do you observe? large container or a small one but Is it easy or hard to press? Record your its shape changes. observations and share among the group members. Activity 5 You would have observed that the Lift an uninflated cycle tube. Inflate it plunger moved freely in syringe with air and now lift it again. Is there a change than in water. It was difficult to press the in the weight? Can we say that air liquids and the piston hardly moved in has mass? chalk powder. Thus, we can conclude that We can say that air is also a matter. gases are highly compressible as compared Though we cannot see it, it occupies to liquids and solids. 39  www.tntextbooks.in Plunger Chalk Water powder Air Solids are not Liquids are hardly Gases are compressible compressible compressible Think to learn Solid Liquid Gas 'Liquefaction of gases' is the process by which substances in their gaseous state are converted to the liquid state. When the pressure on a gas is increased, its molecules come closer together, and the temperature is reduced. This removes enough energy to make it change from the gaseous state to the liquid state. Lets summarize S.no. Solids Liquids Gases 1. Definite shape and No definite shape. Liquids Gases have neither a volume attain the shape of the vessel definite shape nor a in which they are kept. definite volume. 2. Incompressible Compressible to a small extent. Highly compressible 3. There is little space These particles have a greater The space between gas between solid space between them. Particles particles is the greatest. particles. Particles are not tightly packed or Particles are very loosely are tightly packed arranged. They are free to packed or arranged. or arranged. move. 4. These particles The force of attraction between The force of attraction is attract each other liquid particles is less than least between gaseous very strongly. solid particles. particles. 5. Particles of solid These particles move freely. Gaseous particles are in cannot move a continuous, random freely. motion. 40  www.tntextbooks.in 3.5 P  ure Substances and For a Chemist the word ‘pure’ means Mixtures something else! In shops, we find products which are  A pure substance is made up of only sold with label 100% pure! For common one kind of particles. people pure means unadulterated, does  Pure substances may be elements or not contain any cheap or harmful additives. compounds. Are they really pure substances as they claim to be?  An element is made up of same kind of atoms.  A molecule consists of two or more atoms.  Compound is the substance formed by the chemical combination of two or more elements.  Mixture is a physical combination of two are more substances. 0DWWHU 3XUH VXEVWDQFH 0L[WXUH +RPRJHQRXV +HWHURJHQHRXV (OHPHQW &RPSRXQG S PL[WXUH PL[WXUH 41  www.tntextbooks.in Let us consider the following exa