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Tag: Light – Reflection and Refraction
CBSE 8 | Science – Study – Free
COMPONENTS OF FOOD | Study
SORTING MATERIALS INTO GROUPS | Study
SEPARATION OF SUBSTANCES | Study
GETTING TO KNOW PLANTS | Study
BODY MOVEMENTS | Study
THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS | Study
MOTION AND MEASUREMENT OF DISTANCES | Study
LIGHT, SHADOWS AND REFLECTIONS | Study
ELECTRICITY AND CIRCUITS | Study
FUN WITH MAGNETS | Study
AIR AROUND US | Study
CBSE 6 | Science – Study – Free
Electric Current and its Effects | Study
Light | Study
Forests: Our Lifeline | Study
Wastewater Story | Study
Motion and Time | Study
Nutrition in Plants | Study
Nutrition in Animals | Study
Heat | Study
Acids, Bases and Salts | Study
Physical and Chemical Changes | Study
Respiration in Organisms | Study
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COMPONENTS OF FOOD | Study
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English Version Components of Food | Speed Notes
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Nutrients: Food substances that provide nourishment to the body are called nutrients.
The major nutrients in our food are carbohydrates, proteins, fats, vitamins and minerals. In addition, food also contains dietary fibres and water. Carbohydrates and fats mainly provide energy to our body. (Scroll down to continue …)
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Carbohydrates: Carbohydrates are energy-giving compounds.
Cellulose, starch and sugar are the examples of carbohydrates.
There may be simple carbohydrates or complex carbohydrates.
Fats: Fats are very high energy-giving compounds. They produce greater amount of energy than carbohydrates.
Sources of fats: animal fats and vegetable fats.
Carbohydrates and fats are Energy giving food.
Minerals: minerals are the elements required by the body in small amounts. Minerals are essential for growth and development of bones, teeth and red blood cells.
Proteins: These are body-building foods. They help in growth of the body.
Vitamins: These are organic substances that protect the body from diseases.
Roughage: It is the dietary fibre present in the food. It facilitates regular movement of the bowels and prevents constipation.
Note: Dietary fibre and water are not food.
Balanced diet: It provides all the nutrients that our body needs, in right quantities, along with adequate amount of roughage and water.
Deficiency Diseases: These are the diseases cause due to the lack of required nutrients for a long period in the diet.
Malnutrition: when a person eats enough of food but his diet is unbalanced, it isknown as malnutrition.
Undernutrition: A person not eating sufficient food to maintain good health suffers from undernutrition.
Some Nutrients Deficiency Diseases:
Protein: Kwashiorkar – Stunted growth, thinning of legs, protruding belly.Protein and Carbohydrates – Marasmus – Complete/partial arrest of growth, lack of energy.
Vitamin D and calcium: Rickets – Bowed legs, bent spine, deformed bones are joints.
Vitamin C: Scurvy – Bleeding and swelling of gums, weakness.
Iodine: Goitre – Enlargement of thyroid gland, retarded growth.
Iron – Anaemia – Fatigue, loss of appetite, pale skin.
Vitamin K: Bleeding disease- delay in blood clotting leads to excess bleeding.
Beri-beri: Vitamin B1 – weakness in muscles, little energy to do work, paralysis
Night blindness – Vitamin A – No vision at night or in dim light.
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SORTING MATERIALS INTO GROUPS | Study
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English Version Sorting Material into Groups | Speed Notes
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Material: A material is a substance which is used for making things.
A given material could be used to make a large number of objects.
It is also possible that an object could be made of a single material or of many different types of materials. (Scroll down to continue …)
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GENERAL PRPERTIES OF MATRIAL
(A) Apearance : Shiny ( luster or luster ) or Roughness ( non-lustrous ) All metals are lustrous , some are more and some are less.
wood, rubber or a piece of rock is non-lustrous.
(B) Hardness: Hard and soft Rocks, iron and many metals are hard.
Hard materials may be:
1. Brittle :- Which break into samller pieces or are powdered when hammered.Example: rock, glass, salt.
Malleable: Which spread into sheets when beaten. metals are malleable.
Ductile:- they can be drawn into thin and long wires. metals are ductile.
Materials like wood, rubber and fibres are soft.
(C) Visibility:-
Transarent :- object through which light passes .
Examples: glass some plastis, sugar and salt solution in water etc.
Transluscent:- object through which light passes partially.
Example: Butter paper, etc.
Opaque: object through which light does not pass.
Examples: wood, metals, rock and wall etc.
(D) Good and bad conductor of electricity:-
Good conductors of electricity:- Material through which electric current can pass easily are the good conductors of electricity.
Examples: metals are good conductors of electricity.
Bad conductors of electricity:- Material through which electric current do not can pass are the bad conductors of electricity.
Examples: wood, plastic, rubber, cork and certain materials are bad conductors of electricity.
(D) Good and bad conductor of heat:- All metals are good conductors of heat.
Examples: wood are bad conductors of heat.
(E) combustible substances:- The materials which catch fire on heating are combustible substance.
wood, plastic, fibre and paper are combustible substance.
(F) SOME MATERIAL MAY FLOAT AND SOME SINK IN WATER.
material which sinks in water is denser than water. material which floats on water is less dense than water.
(G) SOLUBILITY O A SUBSTANCES IN WATER.
The substnces like salt and sugar , which disappear in water , are said to be soluble.
The substances which remain as such and do not disappear in water are said to be
(H) Miscible and Immiscible Liquid:- when two liquids are mixed and they do nort mixed well, they are said to be immiscible.
The liquids which mix well with water are said to be miscible.
GROUPING OF MATERIALS. Things made from wood
Things made from metal
Things made from ceramic
Things made from glass
Things made from plastic
Things made from rubber
things that are liquids such as oil.
Materials are grouped together on the basis of similarities and differences in their properties.
Things are grouped together for convenience and to study their properties.
Advantages of classification:
(a) Helps in identification of objects.(b) Helps in sorting of objects.
(c) Helps in locting things.
(d) Makes study of different objects easy and more meaningful rather than studying each other separately. (e) Helps to understanding similarities and dissimilarties among
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SEPARATION OF SUBSTANCES | Study
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PURE SUBSTANCES: The substances which contain only one kind of particles are called pure substances. Elements and compounds are pure substances.
ELEMENT: A substance made from identical particles of one material.
COMPOUND: A substance formed as a result of chemical combination of two or more elements in a fixed ratio.
Solution: A solution is a homogeneous mixture of two substances.
Solvent: The substance in larger quantity is the solvent.
The substance other than the solvent present in the solution is/are is the solute/solutes.
IMPURE SUBSTANCES: The substances which contain more than one kind of particles are called impure substances.
NEED FOR SEPARATING COMPONENT OF A MIXTURE
Removing harmful or unwanted components, and obtaining useful and desire component in pure form.Methods of separation are Threshing, winnowing, handpicking, sieving, magnetic separation, floating and sinking method, filtration.
separation to immiscible liquids, churning to separate cream from milk, sublimation.
(i) Separation of solid from other solids:
(a) Threshing: The process of separating grain from husk or chaff is called threshing.
Chaff: The waste material of agriculture processes such as pieces of straw are called chaff.
(b) Winnowing: The process of separation of heavier and lighter components of a mixture by wind or blowing air.
(c) Hand-picking: The process of picking the undesirable components from desirable material with hand is called Hand-picking.
(d) Sieving: The process of separating the solid constituents of different sizes in a mixture using a sieve is called sieving.
Sieve: A sieve is a device with many small holes in it , which allow the smaller particles to pass through and stops the bigger particles in it is called a sieve.
(e) Magnetic separation: Process of seperating the magnetic material by moving a magnet over a mixture of magnetic and non-magnetic substances is called magnetic seperation. In this process the magnetic material sticks to the magnet are removed.
(ii) Separation of water soluble solids or separating solute dissolved in solvent:
(a) Evaporation: Process of converting a liquid into its gaseous state by placing in open air without heating is called evaporation.
(b) Condensation: Process of converting a gaseous material into its liquid state by cooling it is called condensation.
(iii) Separation of insoluble solids from Liquids:
(a) Sedimentation: The process of settling down of heavier and insoluble component from mixture is called sedimentation.
Examples: sand, water.
(b) Decantation: The process of transferring clean liquid without disturbing the sediment, is called decantation
(c) Loading: The methods by which finer particles are made to settle faster by dissolving a small quantity of alum.
(d) Filtration: In this process the impurities are passed through a filter.
Filter: The filter has pores in it that allow only liquids to pass through the pores but stops the suspended particles or solid particles.
Therefore, the filter separates the suspended particles or solid particles.
The clear liquid so obtained in filtration is called the filtrate.
residue: The left over material on the filter paper due to filtration is known as residue.
(iv) Separation of Immiscible Liquids:
IMMISCIBLE: The liquids which donot mix well with one another are called immiscible liquids.
Example: Mixture of oil and water are immiscible liquids.
immiscible liquids are sepreated by centrifugation, churning etc. methods.
(b) Centrifugation: The method in which mixture containing suspended particles is rotated at a high speed in a centrifuge and heavier particles settle down.
Example: Cream is separated from milk, using centrifugation method.
(c) Churning: The method which is used for separating lighter particles of solid suspended in.
SEPARATING SOLUTE NOT SOLUBLE IN A SOLVENT
Flotation and sinking methods:- This method is used when the components are not soluble in water and one of the component of a mixture is lighter than water and the other is heavier than water.SUBLIMATION:- The changing of a solid directly to vapour, without coming to liquid state is called sublimation.
Husk and stones could be separated from grains by handpicking.
· Husk is separated from heavier seeds of grain by winnowing.
· A saturated solution is a solution in which no more solute could be dissolved.
· More of a substance can be dissolved in a solution by heating it.
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GETTING TO KNOW PLANTS | Study
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English Version Getting to know Plants | Speed Notes
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Plants are usually grouped into herbs, shrubs, trees, creepers and climbers.
From where does a plant come?
A plant comes from a seed. A seed is covered with seed coats.,The seed coats protect the seed. The seed has a baby plant inside. (Scroll down to continue …)Study Tools
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The baby plant has a tiny root towards the outer side. The tiny root is termed as radicle.
The baby plant has a tiny shoot towards the inner side. The tiny shoot is termed as plumule.
Classification of Plants Based On The of Growth Habit:
(a) Herbs: Have soft, green and weak stems.Example: rice, wheat, maize, sunflower, mint,etc.
(b) Shrubs: They are bushy and have hard stems that do not bend easily.
These are plants with the stem branching out near the base. Example: lemon, China rose, jasmine, Nerium, etc.
(c) Trees: These are big plants which have a tall and strong stem (trunk).
Stems have branches in the upper part, much above the ground. Live for many years. Example: mango,neem, banyan, coconut, etc.
(d) Climbers: Have weak stems and cannot stand erect. They take the support of other treesand climb on them. Example: pea, grape, vine, etc.
(e) Creepers: Plants which creep on the ground and spread out. Example: pumpkin and watermelon.
Classification of plants on the basis of their Life Cycle:
(a) Annuals: Plants whose life cycle is completed in the one season. These are generallyherbs.
Example: wheat and mustard.
(b) Biennials: Plants whose life cycle requires two seasons for completion. They aregenerally
herbs and rarely shrubs.Example: carrot, radish, and potato.
(c) Perennials: Plants whose life cycle runs for more than two seasons example: guava, Babul, and palm trees. Parts of a Plants:
(a) Root system: The root and its branches make up the root system of a plant. Root is the underground art of a plant body.It is non-green. The root grows into the soil and away from the light.(i) Tap Root: It is formed by the baby root (radicle) which comes out from a germinating seed.
It is the main primary root arises from the lower end of the stem.
A number of tiny branches called secondary roots. Example: mustard, neem, rose, etc.
(ii) Fibrous Root: A bunch of roots arises from the base of the stem. Example: wheat, maize, etc. Functions of root system:
(i) Roots absorb water and nutrients from the soil.(ii) Roots help the plant to stand erect.
(iii) Roots check soil erosion.
(iv) Roots store food.
(v) Prop roots offer extra support.
MODIFIED ROOTS:
Roots may show certain changes in their shape, size or structure for performing special functions. These roots are called the modified root.1. Roots modified for the storage of food: – We find such roots in carrots, radish, turnip, beetroot, sweet potato and some other plants.
2. Roots modified to provide support to the plant: – In a banyan tree, you might have noted root like roots coming out from the branches and hanging downwards.
These roots give support to the branches. They are called the supporting roots or the prop roots.
3. Root modified to bear nodules: On the roots of the gram and other pulses.
Rhizobium, a nitrogen-fixing bacteria makes its home in the form of small are termed as nodules.
(b) Shoot system: The part of the plant which grows above the soil.
It includes The stem, The leaves,The buds, The branches,The flower, The fruits, The seeds.
(ii) Leaf: A leaf is a flat and green structure on a plant, coming out from a node on the stemand always bearing a bud in its axil. Parts of leaf:
(a) Petiole: Stalk of the leaf with which it joined to the stem.(b) Leaf lamina: The flat green portion of the leaf. (c) Veins: These are the network of small, narrow, tube-like structures on both sides The function of Leaf:
(i) Transpiration: Process of losing water by the leaves of a plant.(ii) Preparation of food by the process of photosynthesis.
(iii) Flower: It is the reproductive organ of the plant.
The function of Flowers:
(i) Help in reproduction.
(ii) These become fruits that store food and seeds.
(iii) Modified flowers like cauliflower, broccoli are rich sources of vitamins. ·
Parts of Flower:
(i) Pedicel: Stalk of the flower through which the flower is joined to the branch. It has joinedto the branch.
(ii) Sepal: Small green leaf-like structures on the thalamus. They protect the flower.
(iii) Petals: Brightly colored leaf-like structures present inside the sepals. Petals attract the insects and help in the process of reproduction.
(iv) Stamens: These are long, thin and needle-like structures. These are male organs of the flower. It consists of two parts: Anther, Filament.
(a) Anther: The swollen tip of each stamen that encloses in it a small powdery
(b) Filament: Long stalk-like structure that joins the anther with thalamus.(v) Carpel: It is a flask-shaped organ in the center of the flower. It is the female organ of the flower. It consists three parts: Style, Stigma, and Ovary.
(a) Style: a Long thin tube-like structure which is swollen at the base.
(b) Stigma: Small, round and sticky part of the carpel at the top of the style the
traps thepollen grains.(c) Ovary: Swollen part of carpel that contains ovules. The Bud : A bud is a compact or a condensed shoot. It encloses future stem, nodes and leaves. Axillary bud Terminal bud floral bud
(i) Stem: Stem forms the central axis of the plant body.Gives rise to a number of branches that bear leaves. The stem bears leaves, flowers, and fruits.
The function of Stem:
(i) It provides support to plant.(ii) It bears important plant parts.
(iii) It helps in transportation of water and food.
(iv) Underground stems store food.
(v) Thick and fleshy stems make food.
(vi) Stem modified into tendrils give extra support for Some Extra Points:
The pattern of veins on the leaf is called venation. It can be reticulate or parallel.Leaves give out water vapor through the process of transpiration.
Green leaves make their food by the process of photosynthesis using carbon dioxide and water in the presence of sunlight.
Roots absorb water and minerals from the soil and anchor the plant firmly in the soil.
Roots are mainly of two types: taproot and fibrous roots.
Plants having leaves with reticulate venation have tap roots while plants having leaves with parallel venation have fibrous roots.
The stem conducts water from roots to the leaves (and other parts) and food from leaves to other parts of the plant.
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BODY MOVEMENTS | Study
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English Version Body Movements | Speed Notes
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Locomotion in the human body:
(i) Human skeleton:It forms a framework that gives shape and support to the body.
It consists of 206 bones.
It protects internal organs. (Scroll down to Continue …)
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Locomotion:
Movement of organisms from place to place.
The human skeleton has two parts: They are The axial skeleton system and Appendicular skeleton system.
- The axial skeleton system: It includes the skull, vertebral column and the chest
bones or the rib-cage. - Appendicular skeleton system: – It includes shoulder and hip girdles and the limbs
( two hands and two legs ). - Bones: – Bone is the unique combination of flexibility and stiffness. Cartilages: – It is a flexible bone which gives support to body parts like ears and nose.
- It also connects bones together. Tough fibers, the tendons: – Tendons are strong, white cords made from collagen.
- They attach to bones.
- Collagen: – Bones in a just born baby are made from soft fibres of a protein
called ‘ collagen ‘. - Ligaments: – Ligaments may be in the form of cords or sheets.
The human skeleton is made of:
(a) Skull: It protects the brain. It is a rigid box made up of plates of bone firmly
joined together. The skull is bony, forming cranium or the brain-case and the face. Twenty-two small flat big bones join to form the skull. Eight flat bones are fitted together forming a protective box for the brain. Fourteen bones of different shapes fuse together to form the face.(b) Rib cage: It is a flexible case of ribs. Each rib curves round the side of the chest from the backbone and is joined in front to a plate of bone called sternum.
Ribs are connected to one another by the muscles. Two lowermost pairs of ribs are called
‘floating ribs’.(c) Backbone or the vertebral column: It is also called the spine or vertebral column. Backbone is made from 33 rings like pieces.
Each piece is called a vertebra. It is a chain of small bones called vertebrae. It protects the spinal cord, which carries messages between the brain and body.
It also supports the skull, ribs and limbs. (d) Limbs: It is made up of long bones with joints that allow them to move. They are mainly for support.
(i) Arms: fore-arms is made up of two bones and hands have several small bones. Shoulder
bones have a pair of collarbones in front and a pair of shoulder blades.(ii) Legs: Lower leg is made up of two bones and feet have several small bones. Hip
bones or griddles bear the weight of the body and are attached to thigh bones.(iii) Joints: The point where two bones meet. Allow movement to take place. Bones
are held together by ligaments.(a) Movable Joints: It allows movement between bones and has cartilage between
them. Type of movable joints are:
(i) Hinge Joints: It allows movement only in one plane backwards and forwards. Example:
elbow joints, knee joints and the joint between phalanges of fingers and toes. (ii) Ball and Socket Joints: It permits a circular movement.Example: the shoulder.
(iii) Gliding Joints: It allows bones to slide a little. Example: bones inside wrists and
feet.(iv) Pivotal Joints: Joint where the neck joins the head. It allows the head to move
backwards and forward and turn to the right and left.(b) Immovable or Fixed Joints: The bones cannot move at these joints. Example:
bones in skull, joint between upper jaw and rest of skull. Locomotion in other animals:
(i) Fish: Locomotion achieved by lateral contractions of the muscular body with a
final thrust by the tail. Fish swim by forming loops alternately on two sides of the
(ii) Birds: When the large flight muscles contract, they pull the wings
down.(iii) Snails: The muscular foot helps in locomotion.
(iv) Earthworms: Move by stretching out the body in front and keeping the hind end
fixed to the ground.The bones are moved by alternate contractions and relaxation of two sets of
muscles.The bone joints are of various kinds depending on the nature of joints
and direction ofmovement they allow. Strong muscles and light bones work together to help the birds fly. They fly by flapping their wings. Snakes slither on the ground by looping sideways. A large number of bones and associated muscles push the body forward.The body and legs of cockroaches have hard coverings forming an outer skeleton. Themuscles of the breast connected with three pairs of legs and two pairs of wings help the cockroach to walk and fly.
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- The axial skeleton system: It includes the skull, vertebral column and the chest
THE LIVING ORGANISMS — CHARACTERISTICS AND HABITATS | Study
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English Version The Living Organisms and Their Surroundings | Speed Notes
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The surroundings where plants and animals live are called their habitat. Several kinds of plants and animals may share the same habitat.
The presence of specific features and habits, which enable a plant or an animal to live in a particular habitat, is called adaptation. (Scroll down to continue …)
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There are many types of habitats, however, these may be broadly grouped as terrestrial (on the land) and aquatic (in water). There is a wide variety of organisms present in different habitats.
Characteristics of living things:
The living things need food, air and water to grow and for the other ife processes.
The young ones grow into adults.
They respire.
Animals breathe in oxygen and breathe out carbon dioxide.
Plants take incarbon dioxide and give out oxygen.
They respond to changes in the surrounding (stimuli).
They all get rid of wastes produced in the body (excretion).
They reproduce their own kind.
They have a definite life span.
Habitat: Habitat is the place where an organism finds comfort, safety, food, water, air, shelter and suitable conditions for breeding and survival.
It has two components biotic (living things like plants and animals) and abiotic (non-living things like rocks, soil, air and water).
BIOTIC COMPONENTS
AUTOTROPHS
AUTOTROPHS MAKE THEIR OWN FOOD ( AUTO MEANS SELF; TROPH MEANS NUTRITION.)
green plants are autotrophs.HETEROTROPHS ( HETERO MEANS DIFFERENT OR OTHERS; TROPH MEANS NUTRITION ) .
Herbivores: Plants and grass eating animals.
Carnivores: flesh or meat eating animals
Omnivores: eat both, plants and flesh or meat of animals.
Habitat provides almost everything to an organism which is needed by it.
ABIOTIC COMPONENTS
Light, temperature, water, humidity and rain, soil, air and wind, height of a place-plains or hills.
Type of Habitat:
(a) Terrestrial Habitat: Plants and animals live on land.
some terrestrial habitats are seashore or the coastal area.
Examples: lants like mangroove and coconut palm are common on the bank of Ponds and lakes.
Examples: Frog, turtle, alligator, crocodile, duck etc.
Life on land.
Examples: cat, deer, lion,tiger, cow.
Plants growing on land under normal conditions of moderate temperature and availability of water are the mesophytes desert habitat on land.
Examples: cactus, euphorbia, aloe, lizards, snake, camel.
Underground habitats:
Examples: moles, beetle, cricket, termite, milliped, ant.
Plants and animals living on hills and mountains.
Example: yak, bear, hill goat, flying fox.
Plants in hills are mostly conical in shape and evergreen.
They bear deep growing roots.
The stem is woody, bearing needle-like leaves.
Plants are mostly xerophytes.
Examples: Apple, pear, plum, apricot, walnut, almond.
High snowy peaks and polar regions.
Examples: Polar bear (white bear), penguin.
(b) Aquatic Habitat: Plants and animals live in water.
Example: ponds, swamps, lakes, rivers and oceans.
Plants growing in water are called hydrophytes.
Adaptations: Plant body is covered with a slippery substance called Adaptations.
Presence of specific features or certain habitats which enable an organism to live in its surrounding.
Adaptation helps an organism in acquiring certain characteristics which helps it in being able to live in the habitat of its choice.
The adaptation may be:
(i) related to the habitat, or
(ii) related to its body structure.
Terrestrial:
(a) Deserts: Small animals stay in burrows deep in sand during the day, and come out at night.
In plants, leaves are either absent or very small as spines;
Stem has a thick waxy coating;
Roots go deep into the soil.
(b) Mountains: Animals have thick skin or fur.
Mountain goat has strong hooves.
Trees are cone shaped having sloping branches.
Leaves are needle like.
(c) Grasslands: Animals are light brown in colour.
Lion: a Long clause in front legs that can be withdrawn inside the toes.
Eyes in front of face.
Deer: Srong teeth, long ears, eyes on the sides of head.
Aquatic:
(a) Ponds:
Plants with roots fixed in soil:Stems are long, hollow and light.
leaves float on water.
Plants with roots submerge: Leaves are narrow and thin ribbon-like.
(b) Oceans: organisms living in sea are called the marine plants and marine animals.
Animals have streamlined body.
Gills to respire (dolphins and whales have blowholes).
Animals like squids and octopus do no have streamlined body and stay deep in the oceans.
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MOTION AND MEASUREMENT OF DISTANCES | Study
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REST: The objects which remain stationary at a place and do not change their position are said to be at rest.
Different modes of transport are used to go from one place to another.
In ancient times, people used the length of a foot, the width of a finger, the distance of a step as units of measurement.
This caused confusion and a need to develop a uniform system of measurement.
We use International System of Unit ( SI unit). This is accepted all over the world.
Meter is the unit of length in SI unit.
Rectilinear motion: Motion in a straight line is called rectilinear motion.
Circular motion: Motion of an object such that its distance from a fixed point is constant.
Periodic motion: Motion that repeats itself after some period of time, is called periodic motion.
Measurement: The comparison of an unknown quantity with some known quantity of the same kind is called measurement.
Measurement of an object consists of:
(i) The unit of measurement.(ii) The number of units the object.
Conventional Methods of Measurement:
Conventional measurements have only been approximate measurement. They differ from person to person and lack precision.Hand span: Length between the tip of the thumb and little finger.
Cubit: Length between the tip of middle finger and elbow.
Arm length: Length from shoulder to the tip of middle finger.
Footstep: It is the distance covered by a step.
Needs for standard units of measurement:- Units such as hand span, foot, footstep, cubit, etc., vary.
They depend upon the size of an individual’s hand, foot,etc., hence such units cause confusion in measurements.
Standard Units of Measurement: Standard Units of Measurement: is a unit to measure any quantity completely and uniformly.
Standard units for measuring, length-metre, mass-kilogram, time-Second.
‘The system International of ‘Units’ or better known as ‘S.I. UNITS.
RULES FOR WRITING SYMBOLS OF UNITS
Symbols for units are usually written in small letters.Symbols is not given in plural form.
Symbols for a unit is not to be followed by a full stop unless it is at the end of a sentence.
Rest: When the position of a body does not change with the passage of time, the body is said to be at rest.
Motion: When the position of a body changes with the passage of time, the body is said to be in motion.
Types of motion:
(a) Linear Motion:
Linear motion is further classified into two types as Straight line motion or Rectilinear Motion and
Curvilinear Motion.
Straight line motion or Rectilinear Motion: Object moves from one position to another along a straight line.
Example: A stone droped from a height.
2. Curvilinear Motion:
Object moving along curved lines.
Example: a car moving along a curve at a turning.
(b) Random Motion: When an object moves from one position to another and changes direction in an irregular manner.Example: butterfly, flies randomly in the
(c) Circular Motion: Object moves in a circular manner in relation to its own axis or arounda fixed centre.
An object remains at the same distance from a fixed point which is the centre of the path of the motion.
Two types of circular motion: (i) Revolution, taking rounds around a fixed point.
Object moves as a whole around a fixed centre.
Example: Earth revolving around the sun in a definite orbit.
(ii) Rotation or spinning motion: Object moves in a circular path in relation to its own fixed axis.
Example: Blades of a moving fan, windmill, etc.
Rotation is restricted to the central axis. The extended parts attached to the rotating axis are in revolutionary motion.
(d) Vibratory Motion: Object moves to and fro very fast. Example: strings of a guitar when plucked.
(e) Oscillatory motion: Object oscillates to and fro along the same path again and again and with the same speed. Time taken by an object to complete one oscillation is same, no matter how many oscillations the object takes. Example: heartbeat, a pendulum of a clock.
(f) periodic motion: – The motion which repeats at regular intervals of time is a periodic motion.
Ex. heartbeat, pendulum o clock, hands of a clock.
(g) Non-periodic Motion: Object does not repeat motion at regular intervals of time.
Ex. Earthquake, the eruption of a volcano, landslide, storm.
(h) Mixed motion: – more than one type of motion at the same time.
Ex. A cricket ball bowled shows linear as well spin motion.
(i) Resultant motion: – one kind of motion resulting in another kind of motion is a resultantmotion.
Ex. wheels of a bicycle rotate about its axis resulting in the linear motion of the bicycle on the road.
(j) Random motion: – The motion without any sequence or direction is random motion.
Ex. A buzzing bee, A player of a football on the field.
(k) Uniform Motion:
When the body covers the equal distance in equal time interval.
Motion of a clock hand.
(l) Non-uniform
Motion: Motion in which the body covers the unequal distance in equal inter of time, the motion of a bus.
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LIGHT, SHADOWS AND REFLECTIONS | Study
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English Version LIGHT | Speed Notes
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Light is the natural agent that stimulates sight and makes things visible.
Its path is only visible when it is scattered by dust particles present in the atmosphere. Light is a form of invisible energy.
Light itsel is not visible .
It makes other objects visible.
Light and the eyes both are necessary to see the things.
The sensation which helps us to see things is called Sight or the Vision.
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SOURCES OF LIGHT
Light is classified into two:
(i) Emission of light: Classifying objects on the basis of emission of light.
LUMINOUS OBJECT: objects which emit their own light are called luminous objcts.
Ex. A candle, electric torch.
NON-LUMINOUS OBJCTS: Objects which do not have their own light and are seen by the light scattered by them are called non-luminous objects.. Example: moon, chair, table, etc.
Optical Media: Any substance which allows ligt to pass through it either partially or wholly is calle an otical media.·
Transparent: All substances that allow light to pass freely through them and through Sun, stars electric torch, candle flame.
Light, Shadows and Reflections
Revision Notes:
which objects can clearly be seen are called transparent substances.
Example: Glass, water, air, etc.
Translucent: A substance that allows light to ass through it only partially is calle a translucent medium or substance.
Example: butter paper, tissue paper, etc.
Opaque: Objects that do not allow light to pass through them.
Example: book, brick, etc.
Shadow: A shadow is the ‘region of absence of light’. Light from a source is cut off by an obstacle and shadow is formed.
Opaque object cast a dark shadow. Translucent objects produce a weak shadow.
Transparent objects do not cast a shadow at all.
Types of shadow:
The kind of shadow depends upon the size of he source of light.
Due to smaller (point) light source: Only one dark shadow is formed and this is known as Umbra.
Due to larger(extended) light source: Two shadows are formed-a dark one in the centre and a light one on the outside. Dark shadow is called umbra and the faint or lighter shadow is called penumbra.
The size of umbra decreses and penumbra increses as the the screen is moved away from the object.
Colour of shadow: Whatever be the colour of the opaque objcet , the shadow formed is always of the same colour, that is , black.
LENGTH OF THE SHADOW:- The length of the shadow differs depends upon the angle at which light falls on a body.
Eclipse: A shadow formed in space that makes the sun or the moon invisible for some time.Eclips is the overshading of a bright obect.
(ii) Reflection of light: The process of sending back the light rays whichafall on the surface of an object. Silver metal is one of the best reflector of light.
Solar eclipse: The moon comes between the sun and the earth, so that the earth (in the shadow) darkens during the day.
The solar eclips occurs only on a ‘NEW MOON DAY’.
Lunar eclipse: The moon and the sun are in a straight line such that the earth is in the between the sun and the moon, the shadow of the earth falls on moon and the moon cannot be seen.
The lunar eclips occurs on a ‘FULL MOON ‘ NIGHT.
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ELECTRICITY AND CIRCUITS | Study
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English Version Electricity | Speed Notes
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Electric Circuit: Connecting wires, bulb, switch and electric cell is used in Torch, Battery, LED (Light Emitting Diode), etc.
Electric current is carried by Conductor.
Conductor: Materials that allow electic current to pass through them.
All metals are good conductors of electricity. Carbon is the only non-metal which is a good conductor of electricity.
Electric current is stopped by Insulators.
Insulators: Materials which do not allow electric current to pass through them.
Example: Plastic, rubber, wood, glass, polythene, PVC, etc.
Electricity can give us magnetism
Electricity is a form of energy which helps us with, heating effect, light effect , and magnetic effect.
:- It is a flow of electic current.
SOURCES OF ELECTRICAL ENERGY :- Electrical energy is available to us from electric power houses,domestic generators, batteries, and dry cells. (Scroll down to continue …)
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Electric Current :- The Electic current is a flow of elcetric charges ( electron ). Electric current flows in one direction only.
Electric Circuit: The complete ath from one terminal of the cell ( say positive ) through the bulb and back to the other terminal of the cell ( say negative ) is calle an electric circuit .
CLOSED CIRCUIT :- An unbroken path travelled by electrIcity is known as a CLOSED CIRCUIT.
OPEN CIRCUIT :- A broken path is known as an OPEN CIRCUIT.
Circuit Diagram: It is a symbolic representation of the electric circuit and the electrical parts (electrical components).
Component of Electricity:
Connecting wires: Help to conduct the electric current and complete the circuit. A metalic wire used for connections in an circuit is also called a ‘lead’.
Bulb: Lights up when an electric current flows through it. An electric bulb has a filament that is connected to its terminals. An electric bulb glows when electric current passes through it. The filament of an electric bulb is made of a tiny , coiled tungsten wire.
Battery :- A series combination of two or more cells.
Switch: Switch is a simple device that is used to either break the electric circuit or to complete it. When a switch is on, a gap in the circuit is bridge by a conducting material through which the current flows.
Electric cell or dry cell : An electric cell has two terminals; one is called positive (+ ve) while the other is negative (– ve).Inside the electric cell the electric charges flows from
negative (- ive ) terminal to the positive ( + ive ) terminal.
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FUN WITH MAGNETS | Study
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English Version FUN WITH MAGNETS | Speed Notes
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Magnets: Materials that attract iron, nickel and cobalt.
Natural magnet is called Iodestone or magnetite.
Magnetite is a natural magnet.
Magnet attracts materials like iron, nickel, cobalt. These are called magnetic materials.
Materials that are not attracted towards magnet are called non-magnetic
Examples: aer, glass, cloth, lastic, rubber etc. (Scroll down to continue …)
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Magnetic force : The force by means of which a magnet attracts objects towards itself
Poles of a magnet :- The ends of the magnet where maximum iron filings get collected are called the poles.
North pole :- The end pointing towars north is called the north seeking end or the North pole.
South pole :-The end pointing towards south is calle the south seeking or the South pole.
A freely suspended magnet always aligns in N-S direction.
Like poles repel , and unlike poles attract each other.
DIFFERNT TYPES AND SHAPE OF MAGNETS
Bar magnet Ball-ended magnet (Dumb-bell)
Horseshoe magnet
Cylindrical magnet
Magnetic needle Artificial magnet
Loadstone ( natural magnet)
ring or disc shape magnet
Fun with Magnets
Revision Notes
Temporary magnets :- Temporary magnets last or a short time.( Iron bar magnets)
Permanent magnets :- Permanent magnets last for a long time. They are made from a steel
or an alloy known as AlNiCo, a combination of aluminium,nickel an cobalt.
Classification of substances based on attraction to magnets:
Magnetic Substances: Materials which get attracted towards magnets. Example: copper, iron, nickel, etc.
Non-magnetic Substances: Materials which do not get attracted towards magnets.
Example: wood, paper, plastic and most metals.
Single Touch Method: When a magnet is used to rub an iron object along it’s length, the starting from one end to another end like combing one’s hair, the iron object gets magnetised.
Double Touch Method: When an iron bar ( object ) is rubbed by two powerfull bar magnets of equal strength with their opposite poles at the centre, in opposite direction , the bar or the object becomes a magnet.
Using Electric Current: The bar to be magnetized is placed inside the coils of a
conductor and current is passed through these coils of wire.
Properties of Magnet:
A magnet has two poles – north pole and south pole. Similar poles repel each other.
Opposite poles attract each other. Magnetic poles always exist in pairs.
There is no magnet like monopolar magnet. magnet is always bipolar.
Applications of Magnet:
Compass needle: The compasss is a small glass case containing a magnetised neele pivoted on an aluminium nail.
The needle is free to rotate.
It points north-south because the earth is.
Methods to make your own Magnet:
Also a giant magnet.
The compass lines up with the earth’s magnetic field.
Used in factories for lifting heavy masses of iron like scrap iron.
Call bells an door chimes use elctromagnet.
Loudspeaker have parmanent magnet.
Used by surgeons in hospitals to remove steel splinters from the wounds.
Used in the construction of telephones, electric bells, etc.
Used to separate iron and steel from non-magnetic materials.
DEMAGNETISATION, loss of magnetic proprty
A magnet may lose its magnetic property when it is:
hammered heated, or
dropped with a force and it strikes against a hard substance.
When two bar magnets are not stored with their like oles pointing in the same direction, each pole will destroy the other by induction.
TAKING CARE OF MAGNETS
When not in use the magnets should be stored in boxes made from non-magnetic materials like cardboard or wood. magnets should be protected with ‘keepers ‘.
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AIR AROUND US | Study
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English Version Air Around Us | Speed Notes
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Air: The invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and
nitrogen.
The blanket of air that surround the earth is called atmosphere. Air is found everywhere. We cannot see air, but we can feel it. Air in motion is called wind.
Air occupies space. (Scroll down to continue …)
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Air is present in water and soil.
Air is a mixture of nitrogen, oxygen, carbon dioxide, water vapour and a few other gases. Some dust particles may also be present in it.
Atmosphere is essential for life on earth.
Aquatic animals use dissolved air in water for respiration.
Plants and animals depend on each other for exchange of oxygen and carbon dioxide from air.
Different Layers of Atmosphere
Troposphere Stratosphere Mesosphere
Thermosphere
Constituent of Air
Air contains mostly nitrogen and oxygen . Nitrogen is nearly 78% of the air.
Oxygen is nearly 21% of the air.
Rest 1% is carbon dioxide, water vapour, dust particles and some other gases.
The composition of gases in air changes from place to place.
Nitrogen : Plants need nitrogen to grow.
Oxygen : Used by all living things to respire and help to burn things.
Carbon dioxide: Plants and animals consume oxygen and produce carbon dioxide during respiration. It is used by green plants for photosynthesis. It is released on burning.
Water Vapour: Formed due to evaporation of water. Amount of water vapour present in the air is called humidity. Varies from place to place and also in the same place during day and night.
Dust and Smoke: Smoke contains a few gases and fine dust particles. It is very harmful.
Presence of dust particles in air varies from time to time and from place to place.
Importance of Air
Air aids burning.
Air is needed for breathing.
Plants need air to make food.
Birds fly in air.
Aeroplane also go up in the air because of air pressure.
Moving air is called wind.
The wind makes the windmill rotate.
Air help in quick evaporation of sweat that helps in keeping us cool.
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Electric Current and its Effects | Study
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English Version Electric Current | Speed Notes
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Flow of electrons through a conductor.
It is convenient to represent electric components by symbols.
Using these, an electric circuit can be represented by a circuit diagram.
When an electric current flows through a wire, the wire gets heated.
It is the heating effect of current. This effect has many applications. (Scroll down to continue …)
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Wires made from some special materials melt quickly and break when large electric currents are passed through them.
These materials are used for making electric fuses which prevent fires and damage to electric appliances.
When an electric current flows through a wire, it behaves like a magnet.
Electric Circuit: A complete pathway of the flow of electric current.
Component of Electric Circuit: Component of electric circuit are following :
Cell: Provides energy for the current to flow.
Bulb: Lights ups when an electric current flows through it.
Switch: Keeps the circuit off or on.
Connecting wires: Help to conduct the electric current and complete the circuit.
1.Heating Effect: The wire gets hot when an electric current passes through it.
This is the heating effect of the electric current.
Electric heater contains a coil of wire called element which becomes red hot when current passes through it.
The amount of heat produced in a wire depends on its material, length and thickness.
Fuse: It is a safety device which prevents damage to electric circuit.
It is made by inserting a short wire into porcelain or insulating material.
MCB: Stands for Miniature Circuit Breakers. These are switches which automatically turn off when current in a circuit exceeds the safe limit.
Effects of Electric Current:
Electric Current and its Effects
2. Magnetic Effect: When electric current passes through a wire, it behaves like a magnet. This is the magnetic effect of the electric current. This was first observed by Hans Christian Oersted.
A current carrying coil of an insulated wire wrapped around a piece of iron is called an electromagnet.
Electromagnet: An electromagnet is a coil of wire wound on a soft iron core, used to separate magnetic material from the junk. Doctors use tiny electromagnets to take out small pieces of magnetic material that have accidentally fallen in the eye.
Many toys also have electromagnets inside them.
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Light | Study
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English Version Light | Speed Notes
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Light: It is the natural agent that stimulates sight and makes things visible.
Light travels along straight line.
Any polished or a shining surface acts as a mirror.
An image which can be obtained on a screen is called a real image. (Scroll down to continue …).
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It is formed by light rays that actually pass through the screen.
An image which cannot be obtained on a screen is called a virtual image.
It is formed by light rays that seem to pass through the screen.
The image formed by a plane mirror is erect.
It is virtual and is of the same size as the object.
The image is at the same distance behind the mirror as the object is in front of it.
In an image formed by a mirror, the left side of the object is seen on the right side in the image, and right side of the object appears to be on the left side in the image.
A concave mirror can form a real and inverted image.
When the object is placed very close to the mirror, the image formed is virtual, erect and magnified.
A Convex mirror is the mirror that curves out; the reflecting surface is convex.
Image formed is virtual, upright and diminished. Image formed by a convex mirror is erect, virtual and smaller in size than the object.
A Concave lens is the lens that is thinner at the center than at the edges.
It is a diverging lens.
Image formed is virtual, erect and diminished.
A convex lens can form real and inverted image.
When the object is placed very close to the lens, the image formed is virtual, erect and magnified.
When used to see objects magnified, the convex lens is called a magnifying glass.
White light is composed of seven colors.
Properties of Light:
1. Rectilinear Propagation of Light: It is the property of light by which it travels in a straight line in any direction.
The direction of path in which light make a ray.
2. Reflection of Light: It is the bouncing back of light after striking the surface of an object.
Shiny smooth surfaces reflect almost all the light.
3. Dispersion: It is the phenomenon of splitting of white light into its seven colors. White
light is mixture of: Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR) colors.
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Forests: Our Lifeline | Study
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English Version Forests: Our Lifeline | Speed Notes
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Forest: Large area of land thickly covered with trees, bushes, etc.
We get various products from the forests around us.
Forest is a system comprising various plants, animals and micro-organisms.
In a forest, trees from the uppermost layer, followed by shrubs, the herbs to
the lowest layer of vegetation. (Scroll down to continue …).
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Different layers of vegetation provide food and shelter for animals, birds and insects.
The various components of the forest are interdependent on one another.
The forest keeps on growing and changing, and can regenerate.
In the forest, there is interaction between soil, water, air and living organisms.
Forests protect the soil from erosion.
Soil helps forests to grow and regenerate.
Deforestation: Cutting down of trees is known as deforestation.
Importance of Forests:
Forests:Provide timber,
Purify air,
Provide shelter,
Prevent soil,
Absorbs noise.
Independence of Plants and Animals in Forest:
Plants and animals depends on each other to remain alive.All organisms interact with each other and their physical environment to derive and survive.
Effects of deforestation:
Amount of carbon dioxide in air will increase, resulting in the increase of earth’s temperature. (Global Warming) Animals will not get food and shelter.Soil will not hold water, which will cause floods.
Endanger lives and environment.
Conservation of Forests:
Do not allow overgrazing.Promote afforestation.
Protect wildlife.
Food Chain:
Interdependence between producers and consumers studied in form of various linkage that appears as a chain or Interdependence of
organisms which shows who eats whom.Food Web: A system of interdependent food chains used to represent various relationships in organisms.
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Wastewater Story | Study
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English Version Wastewater Story | Speed Notes
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Wastewater: Black-brown water which is rich in lather , mixed with oil that goes down the drains from skins, showers, toilets, laundries is called wastewater.
sewage: Wastewater is generated in homes, industries, agricultural fields and in other human activities. This is called sewage. (Scroll down to continue …).
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Sewage is a liquid waste which causes water and soil pollution.
Wastewater is treated in a sewage treatment plant.
Treatment plants reduce pollutants in wastewater to a level where nature can take care of it.
Where underground sewerage systems and refuse disposal systems are not available, the low cost on-site sanitation system can be adopted.
By-products of wastewater treatment are sludge and bio gas.
Open drain system is a breeding place for flies, mosquitoes and organisms which cause diseases.
We should not defecate in the open. It is possible to have safe disposal of excreta by low cost methods.
Sewage Treatment:
Aeration: Air is bubbled through the wastewater while it is continuously stirred.
Filtration: Aerated water passes through a deep filter of layered sand, fine gravel and medium gravel.
Chlorination: Chlorine is added and mixed to the filtered water until water is clear.
Wastewater Treatment Plant (WWTP):
Wastewater passes through screens to remove large objects.
To go to a grit and sand removal tank at low speed.
Water is allowed to settle in large tank.
Floating solids are removed with skimmer.
Settled solids (sludge) are removed with scraper.
Clear water is called clarified water.
Water is then decomposed by anaerobic bacteria in a tank and air is passed.
Microbes settled at bottom as activated sludge and water from top is removed.
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Motion and Time | Study
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English Version Motion and Time | Speed Notes
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Motion: The action or process of moving or being moved.
The distance moved by an object in a unit time is called its speed.
Speed of objects help us to decide which one is moving faster than the other.
The speed of an object is the distance travelled divided by the time taken to cover that distance.
Its basic unit is mere per second (m/s). (Scroll down to continue …).
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Periodic events are used for the measurement of time.
Periodic motion of a pendulum has been used to make clocks and watches.
Motion of objects can be presented in pictorial form by their distance-time graphs.
The distance-time graph for the motion of an object moving with a constant speed is a straight line.
Uniform Motion ANd Non – Uniform Motion:
- Uniform motion: An object moving with a constant speed is said to be in uniform motion. The average speed is the same as the actual speed.
- Non-Uniform motion: If the speed of a moving object keeps changing, the object is said to be in non-uniform motion.
Speed: It is the distance covered by an object in a unit time.
Speed = Total distance/ Total Time
Basic unit of speed is m/s.
Distance-Time Graph: Motion of objects can be presented in pictorial form by their distance-time graphs.
The distance-time graph for the motion of an object moving with a constant speed is a straight line.
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Nutrition in Plants | Study
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Nutrition: It is the mode of taking food by an organism and its utilization by the body.
Nutrients: The components of food that provide nourishment to the body.
All organisms take food and utilise it to get energy for the growth and maintenance of their bodies. (Scroll down to continue …)
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Autotrophs: Autotrophs are the green plants which synthesise their food themselves by the process of photosynthesis.
Photosynthesis: the process of preparation of own food by the Green plants with the help of chlorophyll (found in green plants), carbon dioxide and water taken from the environment in presence of sunlight is known as photosynthesis.
Plants use simple chemical substances like carbon dioxide, water and minerals for the synthesis of food.
Chlorophyll and sunlight are the essential requirements for photosynthesis.
Complex chemical substances such as carbohydrates are the products of photosynthesis.
Solar energy is stored in the form of food in the leaves with the help of chlorophyll.
Oxygen is produced during photosynthesis.
Oxygen released in photosynthesis is utilised by living organisms for their survival.
Fungi derive nutrition from dead, decaying matter.
They are saprotrophs.
Plants like Cuscuta are parasites.
They take food from the host plant.
A few plants and all animals are dependent on others for their nutrition and are called heterotrophs.
Parasitic: Organisms that live on the body of other organisms. All parasitic plants feed on other plants as either:
Partial Parasites: Obtain some of their nutrition from the host,
Example: Painted cup
Total Parasites: Dependent completely on the host for nutrition.
Example: Mistletoe.
Nutrition in plants
Saprophytic: Organisms that obtain nutrition from dead and decaying plant and animal matter.
Mushrooms, moulds and certain types of fungi and bacteria.
Insectivorous Plants: Green plants which obtain their nourishment partly from soil and atmosphere and partly from small insects.
Example: pitcher plant, bladderwort, and venus fly trap.
Symbiosis: Mode of nutrition in which two different individuals associate with each other to fulfil their requirement of food.
Lichens found on tree trunks is the association between algae and fungus.
Algae obtains water from fungus and it in turn obtains food from algae.
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Nutrition in Animals | Study
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English Version Nutrition in Animals | Speed Notes
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Classification based on Eating Habits:
Herbivorous: Animals that eat plants or plant products.
Example: Cow, sheep, goat, deer, elephant, kangaroo, giraffe, etc.
Carnivorous: Animals that eat only flesh of other animals. They never eat plants.
Examples: Tiger, lizard, lion, etc.
Omnivorous: Animals consume plants as well as other animals as their food.
Examples: Bear, dog, human being, etc.
Parasites: Organisms that obtain their food from other animals either by living inside (endoparasites) or outside (ectoparasites) their body.
Examples: Tapeworm and roundworm (inside body), tick and lice (outside body).
Scavengers: Animals which feed on the remains of dead animals preyed by predators. Example: vulture, crows, jackal, etc. (Scroll down to continue …)
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The main digestive glands which secrete digestive juices are:
- the salivary glands,
- the liver and
(iii) the pancreas.
The human digestive system consists of the alimentary canal and secretory glands.
It consists of:
- buccal cavity,
- oesophagus,
- stomach,
- small intestine,
- large intestine ending in rectum
- anus.
Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.
The stomach wall and the wall of the small intestine also secrete digestive juices.
The modes of feeding vary in different organisms.
Nutrition is a complex process involving:
- ingestion,
- digestion,
- absorption,
- assimilation and
- egestion.
Digestion of carbohydrates, like starch, begins in the buccal cavity.
The digestion of protein starts in the stomach.
Bile secreted from the liver, the pancreatic juice from the pancreas and the digestive juice from the intestinal wall complete the digestion of all components of food in the small intestine.
The digested food is absorbed in the blood vessels from the small intestine.
The absorbed substances are transported to different parts of the body.
Water and some salts are absorbed from the undigested food in the large intestine.
The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.
The grazing animals like cows, buffaloes and deer are known as ruminants.
They quickly ingest, swallow their leafy food and store it in the rumen.
Later, the food returns to the mouth and the animal chews it peacefully.
Amoeba ingests its food with the help of its false feet or pseudopodia.
The food is digested in the food vacuole.
It pushes out finger-like pseudopodia which engulf the prey.
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Heat | Study
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English Version Heat | Speed Notes
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Heat: It is a form of energy, which makes any object hot or cold.
The materials which allow heat to pass through them easily are conductors of heat.
The materials which do not allow heat to pass through them easily are called insulators.
Temperature: The degree of hotness of an object is called temperature.
Heat is the cause of temperature.
Our sense of touch is not reliable to measure the temperature. (Scroll down to continue …)
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Heat:
It is a form of energy, which makes any object hot or cold.
Temperature: The degree of hotness of an object is called temperature. Our sense of touch is not reliable to measure the temperature.
Thermometer is a device used for measuring temperatures.
Heat is the cause of temperature.
Clinical thermometer is used to measure our body temperature.
Transfer of Heat: Heat flows from a hotter object to a colder object until both objects reach the same temperature.
The heat flows from a body at a higher temperature to a body at a lower temperature.
There are three ways in which heat can flow from one object to another.
These are conduction, convection and radiation.
Conduction: It is the process by which heat is transferred from the hotter end to the colder and end of an object.
Convection: It is the flow of heat through a fluid from places of higher temperature to places of lower temperature by movement of the fluid itself.
Radiation: It is the mode of transfer of heat in which energy is directly transferred from one place to another.
It does not need any material medium.
Dark-coloured objects absorb radiation better than the light-coloured objects.
That is the reason we feel more comfortable in light-coloured clothes in the summer.
Woollen clothes keep us warm during winter.
It is so because wool is a poor conductor of heat and it has air trapped in between the fibres.
Thermometer:
Thermometer is a device used for measuring temperatures.
Clinical thermometer:
Clinical thermometer is used to measure our body temperature.
A thermometer used to measure the temperature of our body is called a clinical thermometer.
For other purposes, we use the laboratory thermometers.
The range of these thermometers is usually from –10°C to 110°C.
The normal temperature of the human body is 37°C.
It consists of a long, narrow, uniform glass tube with a bulb containing mercury at one end.
There is a kink near the bulb.
The range of clinical thermometer is from 35°C to 42°C. (Or from 94°F to 108°F).
Laboratory Thermometer:
Laboratory Thermometer: It is a thermometer used to measure the temperature of objects other than our body.
It consists of a column of mercury enclosed in a glass casing.
The column is continuous without any kink.
It measures a range of temperature from -10˚C to 110˚C.
Sea Breeze:
Sea Breeze: Durign the day, the land heats up faster than the sea.
Warm air above the land rises and cold air from sea takes its place.
Warm air from the land moves towards the sea to compele the cycle.
This produces a sea breeze from the sea to the land.
Land Breeze:
Land Breeze: At night the land cools faster than sea.
The warm air above the sea rises.
This warm air is replaced by colder air from the land producing a land breeze.
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Acids, Bases and Salts | Study
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There are three types of Substances: Acids, Bases and Salts
Acids: Acids are sour in taste. They are corrosive in nature.
A concentrated acid cuts through clothes and eats away the wool.
If it falls on the skin, it can cause burns.
They are good conductors of electricity, as they allow the passage of electric current through them. (Scroll down to continue …)
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Types of Acids:
(i) Mineral Acids: These are acids prepared from minerals present in the earth’s crust.
(ii) Organic Acids: These are acids produced by plants and animals (except hydrochloric acid).
- Weak Acids: These do not dissociate completely in solution.
- Examples: tartaric acid, lactic acid.
- Strong Acids: These dissociate completely in solution. Example: nitric acid, sulphuric acid.
Neutralization: It is the reaction between an acid and a base which results in formation of salt and water.
Acid + Base ———-> Salt + Water
Example: HCl + NaOH ———-> NaCl + H2O
Neutralisation in Everyday Life:
Indigestion: Too much acid in stomach causes indigestion. It is neutralized by taking an antacid like milk of magnesia.
Ant sting: When an ant bites, it injects formic acid into the skin. The effect is neutralized by rubbing moist baking soda (sodium hydrogen carbonate) or calamine (containing zinc carbonate).
(iii) Soil treatment: When the soil is too acidic, it is neutralized by treating with
quicklime (calcium oxide) or slaked lime (calcium hydroxide).
Bases: Bases are bitter in taste and soapy to touch.
Types of Bases:
- Weak Bases: These naturally produce less hydroxide ions in solution. Example: magnesium hydroxide, ammonium hydroxide.
- Strong Bases: These produce more number of hydroxide ions on dissolving in water. Example: Sodium hydroxide(NaOH), Potassium hydroxide (KOH)
Substances which are neither acidic nor basic are called neutral.
An acid and a base neutralise each other and form a salt. A salt may be acidic, basic or neutral in nature.
Solutions of substances that show different colour in acidic, basic and neutral solutions are called indicators.
Indicators: It is special chemical that changes its colour to indicate the presence of a chemical substance.
It is used to confirm the presence of an acid, a base or a neutral solution.
Classification of Indicators:
Natural Indicators:
- Litmus: It is extracted from lichens. It is available in the form of strips of paper or in the form of a solution.· Acid turns blue litmus red. Bases turn red litmus blue.
- Turmeric: It remains yellow in neutral and acidic solutions but turns red in alkaline solutions.
- China rose: It turns acidic solutions to dark pink (magenta) and basic solution to green.
- Red cabbage: It turns acidic solutions to red and basic solutions to blue.
Other Indicators:
- Methyl Orange: It gives pinkish red colour with acidic solutions and yellow colour with bases.
- Phenolphthalein: It is an acid-base indicator. It is colourless in acidic solutions but turns pink in alkali solutions.
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Physical and Chemical Changes | Study
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Changes can be of two types, physical and chemical.
Physical changes are changes in the physical properties of substances.
Due to physical chages new substances are not formed.
Physical changes may be reversible.
Examples: crushing a can, glowing of an electric bulb, tearing of paper, mixing of sand and water. (Scroll down to continue …)
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Chemical Changes are changes in which the composition and chemical properties of the substance get changed.
In chemical changes new substances are produced. The most of the chemical changes are irreversible and permanent.
Note: Some chemical changes are reversible, known as reversible chemical changes.
Example: burning of a candle, formation of curd from milk, ripening of fruits.
Some Chemical Reactions in daily life:
Rusting of Iron: Rusting is the process in which iron turns into iron oxide.
It happens when iron comes into contact with water and oxygen. The process is a type of corrosion that occurs easily under natural conditions.
Prevention of Rusting:
- By Painting
- By Oiling and greasing
- By Chromium plating
- By Galvanizing
- By Alloying
Cooking of food: Cooking causes breakdown of complex molecules of carbohydrates, fats and proteins into smaller molecules.
It is regarded as a decomposition reaction.
Cooked food is easier to digest than uncooked food.
3. Decay of Organic Substances: Microorganisms like fungi and bacteria produce enzymes which break down complex organic compounds into smaller substances.
It is also regarded as a decomposition reaction.
Some substances can be obtained in pure state from their solutions by crystallization.
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Respiration in Organisms | Study
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Respiration is essential for survival of living organisms.
It releases energy from the food.
The oxygen we inhale is used to breakdown glucose into carbon dioxide and water.
Energy is released in this process.
The breakdown of glucose occurs in the cells of an organism (cellular respiration). (ScrollScroll down to continue…)
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During heavy exercise when the supply of oxygen to our muscle cells is insufficient, food breakdown is by anaerobic respiration (without oxygen)
Types of Respiration:
External respiration also known as breathing refers to a process of inhaling oxygen from the air into the lungs and expelling carbon dioxide from the lungs to the air.
Exchange of gases both in and out of the blood occurs simultaneously.
Internal Respiration: Process in which food is broken down in body cells.
Internal respiration is further classified into two types as aerobic respiration and anaerobic respiration
(a) Aerobic Respiration: Aerobic respiration takes place in the presence of oxygen. Carbon dioxide and water are the end products of aerobic respiration. respiration happens in most of the organisms.
(b) Anaerobic Respiration: Anaerobic respiration takes place in the absence of oxygen.
Anaerobic respiration usually happens in most of the microbes.
Alcohol and carbon dioxide are formed at the end of anaerobic respiration.
In some cases, lactic acid is formed at the end of anaerobic respiration.
Respiration in Plants: Leaves have pores called stomata for gaseous exchange by diffusion.
Stems have openings called lenticels for gaseous exchange by diffusion.
Roots have stomatal pores for gaseous exchange of oxygen dissolved in soil water.
Respiration in Animals: Respiration in animals vary according to their character like:
Earthworm: Earthworms respire through their skin.
Insect: Insects respire through entire body surface.
Fish: Fishes respire through their gills.
Frogs: Frogs respire through their thin, moist and smooth skin when in water and by lungs when on the land.
Respiration in Humans: Inhaled air passes through nostrils into nasal cavity and then into lungs through windpipe.
Breathing is a part of the process of respiration during which an organism takes in the oxygen-rich air and gives out air rich in carbon dioxide.
The respiratory organs for the exchange of gases vary in different organisms.
During inhalation, our lungs expand and then come back to the original state as the air moves out during exhalation.
Increased physical activity enhances the rate of breathing.
In animals like cow, buffalo, dog and cat the respiratory organs and the process of breathing are similar to those in humans.
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