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But again it will be back. This process of circulation of water to water vapour then clouds and again rain is called water cycle Fig. The water you drink today may have been drunk by someone thousands of years ago! Nature has been crumbling the rock into tiny fragments called soil. This is done in many ways. The frequent change in heat and cold, cracks off surfaces of rock. Blow of wind converts rocks into sand. Glaciers scrape rock surfaces.
Waves beating against a shore converts rocks into smaller and smaller pieces. The soil in which plants grow is a complex substance which contains mineral salts, decayed organic materials and decayed living organisms. The value of the soil depends on its power to supply plant food, air and water to the root of plants. Water rises in soil just as water rises in a sponge. The rising of this water keeps the plants growing.
Soil is the shelter to a number of insects, reptiles and other animals. There must be a right temperature. All living things must remain with certain limits of temperature. Another condition is water. All living things require water. Light is essential for green plants. Animals need a source of food. They cannot exist in places where the food is not available.
Plants use carbon-di-oxide present in the air and sunlight in preparing their food. We cannot live without breathing. We get oxygen from the air.
Animals living in water like the fish get the oxygen from water. The oxygen is dissolved in water. Hence, for plants carbon di oxide and for animals oxygen are essential. So atmosphere must have oxygen and carbon-di-oxide. Water, atmosphere with oxygen and carbon dioxide, suitable temperature and food are available.
Hence, life exists only on the Earth. In the other planets the above said things are not available. So life is not possible in other planets. Choose the correct answer. How many planets are in the solar system? Write the name of the planets. Day and night changes alternately in the Earth.
Give the reason. What is the time taken by the Earth to complete one rotation? If the day is longer than night, then is it summer or winter? If the night is longer than day, then is it summer or winter? Is our Earth like a solid cricket ball or hollow foot ball? What are three layers of Earth? What is called atmosphere? Give the composition of air. What is the use of Ozone layer? Which gas is essential for burning? Name the useful important materials available in the ocean.
What is called water cycle? How is soil formed? State the requirements that are essential for the existence of life on Earth. In which layer of the Earth do you expect to find petroleum?
If you breathe out over a glass plate, why the glass plate appears misty for some time? What happens to water when wet clothes dry? List out the uses of soil. From where do the fish get oxygen? Measurement Measurement is necessary in everyday life. If we go to the textile shop to download the cloth for stitching shirt, we do not ask the seller to give one cloth. If we go to the vegetable shop, we do not ask to give a little amount of potato. If we go to the provision store, we do not ask to give a little amount of sugar.
What is the journey time of the bus from your village to town? In the textile shop, we ask for 1 metre cloth and the seller measures it using a scale. In the provision store, we ask for 1 kilogram or 2 kilograms sugar and the seller measures it using a balance. The journey time of the bus is 30 minutes. In the above cases, we measure the quantities like length, mass and time using a metre scale, a balance and the time watch. Hence measuring quantities with units like metre, kilogram and hour or minute plays an important role in our daily life.
What is the size of your science book? At what distance your school How much milk do you want? What is the area of your class room? What is your mass?
What is the time taken by you to complete metre running race? Measurements are necessary to answer such questions. Without measurement we cannot make a correct judgement. A guess or a rough estimate may give a wrong answer. Science is concerned with finding out about the world, Why things happen?
How things work? Early scientists, the ancient Greeks relied almost entirely on their senses. They were good at observing and at suggesting explanations of what they saw, but without doing experiments. For example, Aristotle believed that heavy objects fall faster than lighter objects. But we know it is wrong. Measurements have helped scientists and engineers to understand motion, how aeroplanes fly, how satellites behave, how machines work. Measurements make it easier to describe observations.
Careful measurement is an important work of any scientist. What is measurement? See the blackboard in your class room. What is its length? Let your answer be 2 metres. Here 2 is the number and metre is the unit of length. That is the length of the blackboard is two times the length of the fixed quantity metre called unit. Let your answer be 30 kilograms. Here 30 is the number and kilogram is the unit of mass.
That is, your mass is 30 times the mass of the fixed quantity, kilogram, called unit. Thus, every measurement consists of a number and a unit. The comparison of an unknown quantity with some known fixed quantity of the same kind is called measurement. The known fixed quantity is called unit. Different units. Long ago, the lengths are measured with the units derived from some parts of the human body. For example, width of four fingers, handspan, a cubit, a pace or a footstep and yard Fig.
But these units were not reliable because the lengths of body parts are different for different people. For example, your teacher measures the length of the classroom in cubits. Let the answer be 15 cubits.
If you measure the same length, the answer may be 20 cubits. For the same length of class room, two different answers are given, if we use the unit cubit. Hence, cubit cannot be a standard one. Each measurement must mean the samething to every one. Therefore, everyone must use the common units of measurement called standard units like metre, kilogram and second.
SI is the abbreviation of The system International D units. In the S I system i the unit of length is metre The unit of force is newton The unit of work is joule. Symbol for 30 kilograms is 30 Kg It should not be written as 30 Kgs Symbol for 2 metres is 2 m It should not be written as 2 ms Symbol for 10 newtons force is 10 N It should not be as 10 Ns.
Symbol for metre is m It should not be as m. Symbol for second is s It should not be as s. Let the answer be 2 Km. Eventhough the distance, that is length is measured by the unit metre, we do not use metres. What is the length of your pencil? Let the answer be 15 cm. What is the thickness of the coin? Let the answer be 2 mm. Eventhough the length is measured in metre, it is convenient for us to express in millimetre.
Hence greater distances are expressed in kilometres and smaller distances are expressed in centimetres and in millimetres. That is, in multiples and submultiples of metre. Hence the mass is also expressed conveniently in terms of ton, and quintol, gram and milligram, which are respectively the multiples and submultiples of kilogram.
Table 2. For example, in Fig 2. Therefore, the length of the object is 6. To measure the length we use a metre scale or a measuring tape. In these devices, the two successive divisions are separated by a millimetre. To measure anything, we have to use the scale carefully. Otherwise, the measurements may not be accurate. The important precautions are: In some scales, the ends may be broken. Hence, zero mark may not be seen. In such cases, you should use any other mark of the scale say 1 cm Fig 2.
Then you have to subtract this mark from the reading at other end. Position of eye A is correct. Position of eye B and C are wrong. The reading corresponding to B and C will give parallox error. We can measure the length of a curved line using a thread Fig 2.
Activity 2. How is it possible? Take your text book. By pressing it, measure the total thickness of the book using a scale. Divide that value by the total number of papers in the book. You can get the thickness of a paper. Distance km Arrange 10 coins one above another as shown in the Fig. All the coins must be similar 25 paise coins. Measure the height of 10 coins using a metre scale. In what way this reading is useful in measuring the thickness of one coin?
It is simple. If you divide the value by it gives the Fig 2. Now arrange the same 25 paise coins, but this time use 20 coins. Can you confirm the thickness of one coin? What exactly are we trying to compare? We compare the surface of the class room and the playground. That is about the area. Area is the measure of a surface of an object. Each little square in the graph is 1 square millimetre.
How many little squares are there? Mark the boundary of the surface in the graph using pencil. Remove the object. Count the number of little squares within the boundary. Do not count the square, if it is less than half.
You know, that each little square is 1 mm2. Hence you can calculate the total area by multiplying number of squares with 1 mm2.
Like this, you can measure the area of a leaf also. The area of smaller objects can be expressed in the unit of mm2 or cm2. The area of bigger objects can be expressed in the unit of m2 or km2. The space occupied by a football is more than a cricket ball.
The space occupied by an object is called volume. An object like a match box or book or The volume of cuboid is calculated if you know its length, breadth and height. The volume of liquid is expressed in litre L.
How much is one litre? Let us find out. You might have seen a one litre pack of milk or one litre pack of edible oil or one litre water bottle. Take a glass vessel of length 10 cm, breath 10 cm and height 10 cm. Pour any one of the liquid mentioned above into the vessel. You can see, that the vessel is completely filled by the liquid. Hence one litre milk can occupy a space of cm3.
We call this cm3 as cubic centimetre, simply cc. You must have seen some of the vessels used for measuring volume of liquids as shown in the Fig. As in the Fig 2. Brick Geometry box Science book Class room Almirah length breadth height volume. But many solids are irregular, for example, a stone.
How to find its volume? One way to find the volume of a stone is shown in the Fig. Pour water into a measuring cylinder, so that it is about half full and read the volume. Then put the stone into the water. The water level will rise. Read the new volume. The difference between the two readings gives the volume of the stone. They do not have a definite length, breadth and height, but take the shape of the container in which they are poured.
Pour the liquid, whose volume you want to know, into a container as shown in the Fig 2. Measure the internal length, breadth and height. Multiply all three together and you have the volume of liquid. It is because the quantity of matter in brick is more than that of sponge. The quantity which measures the amount of matter in an object is called mass and it is measured in kilograms kg.
Mass and weight are It is unfortunate that people use the word weight when they mean mass. You might have seen a packet of sugar marked as net weight g. It is wrong. It has to be marked as net mass g. Mass is the quantity of matter inside the body. Weight is the pull of gravity on the object.
Weight of a given object is variable from place to place and planet to planet. Let us discuss, further about this idea in the chapter 'force and motion.
It is commonly measured with the help of a beam balance. Fig 2. Shopkeepers use many types of balances for weighing vegetables and provisions. You can see it in your school physics laboratory. Long ago, people did not have clocks. They used various events that occurred at regular intervals to count time intervals. One such event was occurrence of day and night. Our Earth rotates about its own axis and it takes a time of 24 hours to complete one rotation, we call it as one day.
The Earth also revolves around the Sun; it takes days to complete one revolution, we call it as one year. The moon revolves around the Earth and it takes The In the provision stores, we can see the balance as shown in the Fig 2. In the jewellory shops, to measure the mass of jewels we are using the electronic balance Fig 2. To measure the accurate mass. A simple sundial is made of a horizontal circular board with a triangular plate of metal fixed vertically on it.
The plate is fixed along North-South direction. The shadow of the plate falls on the board. The edge of the shadow falls at different angles at different times of the day. The position of the shadow was used to note the time of the day. It cannot be used after sunset.
In a sand clock, sand flows from one glass container to other through a small hole connecting them as Fig. In a fixed interval of time, one hour, the entire sand in the top container flows down to the container at the bottom. A can of water helps to measure time.
Make a tiny hole at the bottom of the can. The can is filled with water and placed at certain height Fig 2. The water flows out and collected in another can. Everytime you fill the can, it will take the same time to empty. Around B. Sumerian people, living in what is now Iraq, made the first shadow clock as shown in the Fig. Each swing always took the same length of time. That is, the time interval is fixed. Later, the boy, whose name was Galileo Galilei became one of the greatest scientists.
He used this principle to measure time and made a pendulum clock. In this type of clock, a pendulum makes oscillations. The movement of the pendulum is connected with the movement of second, minute and hour hands of the clock.
Nowadays, to measure the short time intervals accurately, stop clocks and stop watches are used Fig 2. See the clock in the Fig 2. That clock does not have hour, minute and second hands. These clocks display time directly in digits called as digital clocks. Tie a solid ball metal with a hook to a thread and hang it as shown in the Fig 2.
Now, pull the ball to one side and leave it to go.
It will come to its original position and continue to move to the other side. It will stop and start its return journey. This back and forth motion is called oscillation. The time taken by the pendulum to complete one oscillation is fixed. In a pendulum clock In the modern clocks most accurate one is atomic clock. Based on the time interval of an energy change in a caesium atom second is second.
Name the unit of length, which you would like to use while expressing the distance between Chennai and Madurai. How many Kilograms are there in one metric ton? Name the unit of length, which should be used to express the thickness of a paper. What is the circumference of a one rupee coin? What is meant by volume of an object?
State the unit in which volume of liquids is expressed. How many millilitres are there in one litre? What is mass? Name the two types of clocks used in earlier days. Draw the diagrams of the vessels used to measure the volume of liquids. What kind of watch is used to measure the time in metre race?
Why a cubit or handspan cannot be used as a standard unit of length? Arrange the following in the decreasing order. Kilometre, millimetre, centimetre, metre. The value of one division of a measuring cylinder is one ml.
Water is poured into it, so that its level is at 50th division. When a stone is put in the cylinder, the level of water rises to 75th division.
What is the volume of the stone? Identify the mistake and correct it. State True or False a Hand span is a standard unit for measuring length. What is the area of a rectangular field m long by 60 m wide? What is the volume of a block of metal 6 cm long, 5 cm wide and 4cm high? What is the volume of the metal cube with side 5 cm?
Name the balance used in science laboratory. State two examples for periodic motion. What is the necessity of standard units in measurement? What are the conventions used in writing the unit and their symbols of SI system? State two precautions, which should be taken while using a metre scale.
How will you measure the thickness of a coin? How will you measure the volume of a stone? The milkman gives you a half litre pack milk. How will you verify the volume of milk?
Find out the area of your science book? Find out the volume of your science book. Estimate the area of the blackboard in your class room in square metres. Estimate the floor area of your class room in square metres. Estimate the volume of your class room in cubic metre. Nature of matter We see many living and nonliving matter around us in this Earth. You will study about living things in Chapter In this chapter you are going to learn about non-living matter.
In our day-to-day life we see and use many non-living things like stone, sand, table, iron rod, water, milk, air etc. So learning about these things is quite necessary. Fill it with dry sand and lift it again. You feel it heavier now. Don't you? From this you understand that sand has mass Fig. Now try to add more amount of sand into the bucket. The sand begins to fall out.
The bucket cannot hold any more amount of sand as it is already full. The sand has occupied the entire space. From this you understand that sand occupies space. The space occupied by matter is called as volume. Lift an empty iron bucket and feel its weight. Fill it with water and lift it again. From this you understand that water has mass Fig.
Now pour more amount of water into the bucket. Water overflows. The bucket cannot hold any more amount of water as it is already full.
Water has occupied the entire space. From this you understand that water occupies space. Take a deflated ball and keep it on the left pan of a balance. Add some sand on the right pan gradually till the pointer comes to zero. Now take the ball and inflate it with air. Place it again on the left pan. Now you can see the pointer moving to the left side. Add more amount of sand to the right pan till the pointer again comes to zero Fig.
From this you understand that 'air has mass'. Now allow the air to get out of the ball. Ball shrinks in size. Doesn't it? From this you understand that air occupies space. What is matter made up of? Matter is made up of very tiny uniform fundamental particles. These particles cannot be seen with our eyes.
The particles are held together by an attractive force. The nature of the fundamental particles and the strength of the attractive forces among them vary from one substance to another. These fundamental particles may be atoms, molecules or ions. Solid Book, chair, pen, stone, sand and ice are in the solid state. The particles in a solid are packed very closely to each other and are held together by strong attractive forces Fig. We conclude from the above activities that matter substance like sand, water and air have mass and can occupy space.
Feelings like sorrow, happiness and pain have no mass and cannot occupy space. So these are not considered as matter. Activity 3. Take a glass tumbler and plunge it into the water as shown in the Fig. Water does not enter the glass tumbler beyond a level. Now tilt the tumbler slowly to a slanting position. You can see the air bubbles coming out of the tumbler and Air Air Bubbles. Liquid Milk, water and fuels like petrol and diesel are in the liquid state.
The particles in a liquid are not very close to each other. The distance between them is greater when compared to a solid Fig. The attractive force between them is also weaker. Solids have definite shape and volume. When the temperature remains constant, they do not change their shape or volume. Observe the shape of water. It has the shape of the beaker. Transfer this water into a ml conical flask. Now the water gets the shape of the conical flask Fig.
But the volume of. Gas The air we breathe is a gaseous substance. The fundamental particles in a gas are held together by weak forces of attraction. The distance between them is also greater than that in a liquid Fig.
The stone has a definite shape and volume. Now place the stone on the floor. It has the same volume and shape. Place it in a glass tumbler. Now also you do not find Liquids like water and oil have definite volume.
But they do not have definite shape. They get the shape of the containers in which they are kept. Since the force of attraction between the particles in a liquid is weaker, they are capable of moving. So they can change their shape. The two inflated balloons differ in shape. The air inside the two balloons get the shape of the balloons Fig.
They get the shape and volume of the containers in which they are kept. You feel it hard and rigid. Solids contain particles which are closely packed. The particles have strong forces of attraction between them. So they are rigid and have high density. How do you feel when you touch water or when the gentle breeze touches you?
You feel them softer. The reason is that the particles in a liquid and gas are comparatively far apart. They are held together by weak forces of attraction. So the liquids and gases are highly flexible, soft and have lesser density than solids. Density of gases is less than that of liquids. Does it move on its own? It does not move towards lower level.
Since the particles in a solid are bonded strongly, they do not separate easily and move. Solids do not show the property of fluidity.
Pour some water on an uneven surface. You can see the water running from higher level to a lower level Fig. Fill a ml jar with g of brown nitrogen peroxide gas. The gas jar appears brown all over. The volume of the gas is ml. Fill the same amount of gms of nitrogen peroxide in a ml jar.
Now also you can see the gas jar appearing brown all over. Now the volume of the gas is ml. See Fig. So they can move easily.
Liquids show the property of fluidity. Water flows from mountains down into rivers due to this property. The sugar disappears by completely mixing with water. Solids like sugar and salt dissolve in water. So the sugar particles separate and mix with water. Place an iron ball in a beaker containing water and stir it. What do you observe? Iron ball does not dissolve in water. From this you understand that some solids are soluble and some solids are insoluble in water.
Prick an inflated balloon with a pin. The air inside the balloon comes out with a force and noise Fig.
What is the reason? The particles in a gas are far apart from each other and are held together by very weak forces of attraction. So they move very easily. Gases have the property of fludity. Solubility of liquids Add a small quantity of ethyl alcohol to water.
Alcohol completely mixes with water. Alcohol is completely soluble in water. Add a few drops of coconut oil and stir well. You will understand that oil does not mix with water. Oil is insoluble in water. Solubility of gases How do aquatic living things breathe? Oxygen present in the air is soluble in water. So they breathe the oxygen dissolved in water. The marine plants take the carbon-di-oxide dissolved in sea-water for the photosynthesis. The soda water, we drink, is containing dissolved carbondi-oxide gas.
Generally gases are soluble in water but certain gases like hydrogen and nitrogen are insoluble in water. The substances which are insoluble in water may be soluble in some other solvents.
Paints are insoluble in water. But they are soluble in kerosene. Pour some water in each. Add a small quantity of sand in the first test tube, salt in the second test tube and starch powder in the third one and shake them. Sand does not dissolve in water. Salt completely dissolves. Starch powder is partially soluble.
Do you observe any change in volume? The volume of iron piece does not change. When pressure is applied over liquids their volume does not decrease. Place that end on a table and press the piston of the syringe downwards. The volume of the water does not decrease. When pressure is applied over gases, their volume decrease considerably.
Since the distance between the particles of a gas is more, they come closer when pressure is applied. Air is sucked in. Close the open end with a cork. Keep the closed end on a table and press the piston downwards. The piston moves easily as the air in the syringe gets compressed. Change of state due to heat i Solid liquid Take out some ice cubes from a refrigerator. Place them in a cup and heat it. Solid ice melts into liquid water. The transformation of a solid matter into liquid when heated is called melting.
The ice-deposits in the Himalayas melt due to heat of the Sun and flow as Ganga and Brhamaputra rivers. Water boils and vapours of water steam come out. The transformation of a liquid into vapour by heating is called evaporation. The sea water evaporates due to Sun light and forms clouds in the sky. Steam gas heat Ice solid heat Water Liquid. Certain solids when heated, are converted to vapour state without passing through the liquid state. This is called sublimation.
Substances like naphthalene, benzoic acid, iodine and ammonium chloride have the property of sublimation. Heat it. Stop heating and observe the change. Change of state due to cooling i Gas Liquid We enjoy when it rains. How do we get the rain from the sky? The water vapour in the cloud gets cooled and forms tiny particles of water. These water particles unite and form water drops which fall as rain. It does not melt into a liquid.
But it evaporates into vapour. Observe the outer surface of the tumbler after sometime. What do you see? What do you understand? Water drops get collected on the outer surface of the tumbler. This is due to the condensation of water vapour present in the atmospheric air.
Or you must have seen such deposits of ice in the television pictures.
How does the ice get deposited on the mountains? Water gets cooled due to severe cold climate at high altitude and converted to ice. These ice particles deposit over the mountains and trees during winter Fig. The transformation of a liquid into solid due to cooling is called freezing. The following representation gives you a clear understanding of change of states of matter. Diffusion of a gas in a gas When you return from school in the evening, you must have smelt the nice odour of your mother's spicy tiffin.
How are you able to get the smell of the food being prepared in the kitchen while you are at the entrance of your house? Visit an ice factory and see how ice creams are made. The vapours of the cooked food come out. The forces of attraction between the particles in a gas or vapour is very weak.
So the particles separate and mix with the particles of. When you breathe that air mixed with vapours of cooked food you feel the smell of the food. You will feel the pleasant odour of the agarbathi all over that room. This happens due to the diffusion of the vapours of agarbathi in air. Diffusion of a liquid in a liquid Pour a drop of blue ink into a beaker of water.
The particles of ink diffuse through the particles of water and the whole water in the beaker turns blue. Liquids diffuse slower than gases. Diffusion of solids in liquid Drop a small piece of potassium permanganate carefully into a beaker of water. You can see the pink colour of the crystal slowly diffusing through the water as the crystal dissolves. The attractive force between the particles of potassium permanganate is removed by the particles of water. So the potassium permanganate particles get diffused in water.
Since the particles of a solid have strong forces of attraction, diffusion of a solid in another solid does not take place naturally. This material, capable of leading in the proper direction is called as loadstone. A magnet has two poles namely North pole and South pole. Poles are at the end of the magnet where the power of attraction is more.
Like poles N-N and S-S repel each other. Unlike poles attract each other N-S and S-N. A magnet attracts iron, nickel and cobalt. Magnets have no effect on wood, glass, aluminium, water, paper and plastic. These are known as non-magnetic substances. We are using the magnets in cranes to lift a heavy load See Fig. To remove any iron particle from the eyes, magnets are used. Impurities of iron could be removed from other metals using magnets.
Magnets are available in electric bell, electric fan, telephone and electric motors. We are using the magnets in doors, window catchers, door closers of almirahs and in beds. Notify me of new posts by email.
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