Adaptation is the ability of plant and animal to cope means to live and survive with the conditions of their habitats. Adaptation can be physical feature or special behaviour. On basis of habitats organisms divided into five main groups: o Terrestrial o Aquatic o Amphibians o Arboreal o Aerial Adaptation of plants animals with respect to their habitats. (A) Structural adaptation: The special body parts of an organism helps in survive. Change in skin colour, shape are examples of structural adaptation (B) Physiological adaptation: The special system found in organism which helps in survival. Ability to maintain a constant body temperature, making venom comes under physiological changes (C) Behavioural adaptation: Taking a certain posture, being active at night are behaviour adaptations. Aquatic Habitat: Hydrophytes are the plants found in fresh water bodies. As they are light in weight and spongy, and having air chambers make them float in water. Poor development of root system.Eg. water lily Some plants are submerged in water, as they have narrow leaves, lack in stomata as they breathe to their surface and makes the water clean Eg. Tapegrass With developed root system plants termed as fixed plants such as lotus. Adaptation in Fish:
Fish have streamline and smooth body having gills for respiration. Whereas dolphins and whale do possess the blowholes at upper parts of their head by which they perform breathing above water surface.
Presence of scales on their bodies protect them and make easy to swim.
Flat fins and tails help the fish to change their direction in water.
In salty water as well as in fresh water fish can survive.
Adaptation for Deserts: Plant Life:
Xerophytes are the plants which live in hot and dry climates of deserts. Example: cactus, babul.
Roots are long to penetrate deep into soil in search of water easily. Adaptation in Cactus: For storage of water cactus possess fleshy and swollen stem The stem is green to store food. Waxy coat help in retention of water. Photosynthesis is carried out by leaves Leaves are converted into spikes as to reduce loss of water from transpiration. Animal Life: Animals have fewer pores and thick skin and they excrete less urine and minimal amount of sweat in order to retain more water. Adaptation in Camel:
Have long eyelashes and ear hairs , theses variation protect eyes and ears from sand .
Long legs to stay away from heat
Hump on camel store fat as stored food.
Broad feet helps them to walk on sand
Ability to drink large amount of water at a time
Nostrils can be closed to keep out sand Adaptation for Mountains: Plant life:
Plants grow near the land, which prevent uprooting due to harsh and strong wind. Examples pine and fir.
Plant cope up with extreme cold temperature.
Leaves are needle shaped to prevent water loss
Some plants grow under snow layer. Animal life: Animal mainly found in mountain region are goat, sheep snow leopards, polar bear. They have thick coat of hair from prevention of chilling cold.
White thick and long fur that keeps the body warm found in case of goat
Strong hooves to walk on cliff and on uneven slope.
They can jump very far
Adaptation for Air:
Adaptation for flight in Birds
Feathers are provide insulation.
Feathers protect them from cold and rain and keep the body warm as well
Feather are act as water proofing with reflection of UV rays as well
Body is light weighted and in streamline to overcome resistance Plant Life: Aerial plant have root system above ground.
Plants evolved with aerial root system in order to absorb more sunlight as in evergreen rain forest lack in direct fall of sunlight on ground
They may grow on the trunks, leave and branches of host plant.
Epiphytes are orchids and bromeliads
Epiphytes absorbs moisture from air or moisture laden pockets of the host plant.
They are autotrophic in nature. Acclimatization: This includes the certain changes occur in organism for shorter period of time to help them to adjust with periodic changes. Example include the growth of thick wool during winter season only in case of sheep. o Adaptation refers to the changes in organism for longer period of time o Acclimation refers to the changes occur in an organism a short period of time.
There are different types of plants in our surroundings. They are of different sizes varying from microscopic forms to complex tall trees. They are different in shape, size and colour of flowers. Some common features seen in all plants are root, stem and leaf. We know that a plant mainly consist of two systems –
Root system – It is the underground part of the plant which develops from the radicle body. Radicle is the embryonic root contained in the seed of the plant. Roots grow towards the ground and absorb water and minerals from the soil.
Shoot System – It consists of a stem, the part which is above the ground. It bears braches, leaves, flowers, buds, and fruits. LEAF – It is thin, flat and green part of the shoot system. It is also known as food factory of a plant. It arises from nodes of stem and grows up to a certain size. External Structure of a leaf – The leaf constitutes of following parts –
Lea Lamina – The green, flat and expanded part of the leaf is known as leaf lamina or leaf blade. The tip of lamina is called apex.
Leaf Stalk (Petiole) – The basal by which the leaf is attached to the node of stem is called petiole.
Midrib – The petiole enters the lamina forming the midrib. The midrib branches out to form veins which bear branches to form veinlets. Vein provides supportive framework to the leaves
Functions of leaf –
The primary function is to perform photosynthesis which means to prepare food with the help of carbon dioxide and water in the presence of sunlight and chlorophyll.
It also helps in transpiration i.e. loss of water through stomata.
It also stores food like in spinach.
Leaves give rise to new plants like in Bryophyllum.
Leaves get modified into spines in desert plants which help the plant to reduce water loss by transpiration. Kinds of leaves – There is a variety of leaves around us. They can be rectangular, circular, needle-shaped, tapered in shape. They may differ in terms of leaf margin which may be complete (Peepal), toothed (rose), wavy (mango), spinous (prickly poppy). These leaves can be classified into two categories.
Simple leaf – In this type of leaf lamina of leaf has a single blade without cuts or incisions. If present, do not reach the midrib. Example – mango, radish etc.
Compound leaf – In this type of leaf lamina has divided into a number of leaflets. In this, the margin has incisions which reach down to the midrib leading to formation of small leaflets. Therefore, the leaf appears as a group of leaflets. Example – rose and neem. To differentiate between leaf and leaflet, we must locate the axillary bud. It is always present at the base of the leaf petiole but not at the base of laflet. Types of venation – The fine lines running through within the lamina forming different patterns are called veins. Veins distribute water and minerals to various parts of leaf blade. The arrangement of veins and their veinlets within a leaf bade is called venation. There are two types of venation.
Parallel venation – In this type of venation, the veins run parallel to each other and join the midrib. This type of venation can be seen in the leaves of monocotyledonous plants like maize, rice and sugarcane etc.
Reticulate venation – In reticulate venation, the veins divide and redivide into a number of veinlets. This pattern can be observed in the leaves of dicotyledonous plants such as mango and peepal. Arrangement of leaves – The arrangement of leaves on branches or stem is called phyllotaxy. This prevents the leaves from overlapping so that every leaf may get sufficient sunlight. There are three types of leaf arrangements.
Alternate – In this arrangement, only one leaf is arises from at a node. The next arising on the following node is opposite to the previous. Example – mustard and sunflower.
Opposite – In this arrangement, two leaves are arranged one node but these are opposite to each other. Example – jasmine and guava. But in some plants, leaves show opposite arrangement with each pair of leaves arising at right angle to each other. Example – calotropis.
Whorled – In this arrangement, three or more leaves arise from a node and form a whorl around it. Example – oleander.
Modification in leaves – It means a structural change is required to perform specific functions. Some of the modifications are –
Leaf tendrils – The modification of leaves in thin thread-like coiled strand is called leaf tendrils. They are sensitive to touch. They coil around a support in order to give support to weaker stems. Thus, help in climbing.
Leaf spines – The modification of leaved of desert plant into pointed spines, it is called leaf spines. They help to reduce water loss. They also perform defensive role as they keep away grazing animals.
Scale leaves – In this leaves get modified into scale leaves. They help to protect buds. They also store food and water. They may be dry (garlic) or fleshy (onion). Modification of leaves in insectivorous plants – Insectivorous plants are also known as carnivorous plants as they feed on insects. As most of these plants are green, they can prepare their food by photosynthesis. Poor environmental soil supplements their diet by carnivorous habits. These plants are adapted to trap, capture and digest insects. These traps are mostly the modification of leaves.
Pitcher plant – The leaf is modified in pitcher shape to trap and capture insects. The front part of petiole is coiled like a tendril that holds the pitcher in erect position. The leaf tip forms the lid. Its leaf is filled with a liquid to collect and digest insects.
Bladderwort – In this plant, the leaves are highly segmented and modified into sacs called bladders. The bladder has a trap door in which the minute organisms can only go but cannot come out. It can be observed in aquatic plants.
Venus flytrap – In this plant, the edge of leaf has long pointed stiff hair. The leaf blade is divided into two parts and the midrib acts as hinge of the door. When any insects touch the leaf, the edge of leaf interlocks and prevents the escape of insect. Vegetative Propagation – It is an asexual method of reproduction in plants. In this method, new plants are produced from the parts of a plant like roots, stems, and leaves. This process is known as vegetative propagation. It usually involves the growth and development of one or more buds on the vegetative parts of an old plant. After providing suitable conditions to the bud, it grows to form a new plant. Example – rose and champa. Vegetative propagation in leaves – In this method, plant grows from leaves. Leaves of some plants develop buds on them. Such leaves having buds are used for vegetative reproduction. Example – Bryophyllum.
Artificial Vegetative Propagation – The methods of vegetative propagation which are developed by man are called artificial vegetative propagation. Some of the methods are –
Cutting – In this method, the stems of the plants are cut into small pieces. Each stem is kept in moist soil. After some time, roots develop at the base and new plant develops. Example – rose and sugarcane.
Grafting – This method is used to obtain a plant by combining two different plants. Thus, it produces a variety with the features of two different plants. In this method, a stem cutting called scion (without roots) from one plant is attached to the other stem cutting part of stock (with roots). After few days, both fuses and new cells develop having characteristics of both plants. Example – mango and lemon.
Layering – In this method, a branch of a plant is pulled and its part is covered with moist soil leaving the top part outside in the air. After some time, new roots develop from buried part and it grows to become a new plant. Example – layering is done in jasmine.
Tissue culture – It involves growing of plants in test tubes. A small piece of plant is grown in suitable conditions in the test tube. An organized mass of cell is called callus develops from it. It is put in hormone containing medium which include cell differentiation and formation of plantlets. These plantlets grow into an independent plant when transferred to the soil. Example – orchid. Advantages of Vegetative propagation –
It is faster method to grow new plants.
There is no difference between produced plant and parent plant.
It is very useful for production of seedless plants.
The plants produced by this method bear flowers and fruits earlier than the plants produced by seeds. Disadvantages of Vegetative propagation –
All the plants produced by this method have same features. Thus, they are likely to be infected by the same infections.
It can results in destruction of entire crop. As there is no dispersal of plants, there are chances of overcrowding
Health- Physical and mental fitness is must for healthy mind of an individual. WHO has defined health as state of complete physical, mental social well being and not merely the absence of disease or infirmity. A disease may occur due to following reasons: viruses, bacteria, fungi.
TYPES OF DISEASES:
▪ CONGENITAL DISEASES: Diseases which are already present in the body since birth are called congenital diseases. Causes- genetic abnormality or when organ in the body is not fully developed. Eg- colour blindness, haemophilia , thalassaemia. Colour blindnessColour blindness is due to vision problem. This is because person lacks certain pigments in eyes therefore it is called colour vision deficiency. Most common colour blindness is red green colour deficiency.
Haemophilia: In this disease blood loses its ability to clot.
Thalassaemia: In this disease body makes haemoglobin and red blood cells lesser than normal value. It ultimately causes amaemia.
Acquired diseases: Two categories- 1- communicable 2-Non communicable 1- Communicable or infectious diseasesDirectly or indirectly infection is paased from infected person to healty person. Eg. Viruses ,bacteria. 2- Non communicable or non infectious diseasesDirectly or indirectly the diseases is spread from person to person or by microorganisms.
COMMUNICABLE DISEASES :This diseases are classified on the basis of oraganisms that cause diseases. Mode of spread- air, water, food from infectef persons Diseases caused by bacteria
1- Tuberculosis- • Causative organism- mycobacterium tuberculosis • Incubation period: 2-10 weeks It is period between exposure to the infection and appearance of first symptom • Symptoms- Cough, sputum with blood, pain in chest, loss of weight,etc 2- Cholera- • Causative organism- vibrio cholera • Incubation period- few hours to 5 days • Symtoms- acute diaarhoea, vomiting dehydration, extreme thirst and muscle cramp. 3- Typhoid- • Causative organism- Salmonella thyphi • Incubation period- 7-12 days • Symptoms- high fever in afternoon, acute headache, reddish eruptin on chest. 4- Leprosy- • Causative organism- mycobacterium leprae • Incubation period- several years • Symptoms- loss of sensation, skin eruptions and deformation of skin and toes. 5- Tetanus- • Causative organism- clostridium tetani • Incubation period- 4-20 days • Symptoms- painful contraction of muscles, neck amd jaw followed by paralysis.
Diseases caused by virusesCommon colddroplet infection spreads through moisture. Incubation period- 1-3 days Symptoms- running nose, headache , fatigue InfluenzaDroplet infection Upper respiratory tract infection symptoms- fever, cold , chill, body ache . Measles Mode of transmission– direct contact through infected saliva and mucous Symptoms- nasal discharge, redness of eyes and coughing. ChickenpoxTransmission– contact with skin sores and clothes of patient Incubation time- 14-16 days. Symptoms– fever, head ache, small watery sores on skin PolioAffects liver Types- Hepatitis A,B,C,D,E,G,H
Causative organism- Human deficiency virus Spread- sexual contact Incubation period- 15 months- 5 years Transmission- can transmit virus from mother to child Precaution- Avoid sexual contact with infected person
DISEASE CAUSED BY PROTOZOA- • AMOEBIASIS- ✓ caused by entamoeba histolytica ✓ Transmission- contaminated food and water ✓ Symptoms- diarrhoea, gripping pain, discharge of mucous ✓ Incubation period- one week • Malaria- ✓ Caused by- Plasmodium ✓ Transmission- bite of female anopheles mosquit0 ✓ Symptom- chillness, sever head ache, rising temperature Diseases caused by worms
AIDS
Elephantiasis {Filaria} ▪ Causative organism- Wucheria bancrofti ▪ Spread-female culex mosquito ▪ Symptom- lympnodes in limbs, scotrum in males and breast in females.
Ascariasis- ▪ Occurs in small intestine ▪ Causation- Ascaris lumbricoides Spread- unsafe food and water
Taeniasis- ▪ Caused by tapeworm ▪ Symptom- pain, weight loss, digestive problems. TRANSMISSION OF COMMUNICABLE DISEASES Airborne diseases or droplet infectionBacteria, spores of fungi and viruses enter our body through inspiration and attack our throat, wind pipe and lungs. Microbes are present in saliva and blood When person sneezes in public places droplets are spread in air and transmitted to healthy person
WATER BORNE AND FOOD BORNE DISEASES • Water is polluted in so many ways. • Dumping of sewage water in water bodies is cause of disease. • Uncleansed food contains bacteria and eggs of parasite; if not washed properly than diseases like diarrhoea and vomiting occur. • Botulism is serious food poisoning due to special bacterium. INSECT BORNE OR VECTOR BORNE o Organisms which carry disease containing pathogens to a healthy person without getting affected. o Contact diseases: spreads from one person to anothe directly or indirectly. o Unsanitary toilet habits should be avoided. Eg; conjunctivitis, chicken pox, common cold, etc. WAYS TO PREVENT COMMUNICABLE DISEASES o We should be very much careful regarding our personal cleanliness by taking a regular bath with good soap and shampoo. o Cove your nose and mouth with a tissue or handkerchief while coughing or sneezing. Do not forget to throw the tissue. o We should avoid using bathrooms and lavatories of railway station and cinema hall. o We should dustbins. o Food items exposed to flies should not be used. NON COMMUNICABLE DISEASES Nutritional deficiency diseases When all nutrients are done in right amount and ratio according to need its called balanced diet. A.PROTEIN ENERGY MALNUTRITION Deficiency of protein, fats and carbohydrates is called protein energy malnutrition. Eg- Kwashiorkor and marasmus Kwashiorkor- results due to diet poor in protein. Symptoms- protruding belly, mental retardation, bulging eyes, etc.
Marasmus- Deficiency of proteins and carbohydrates. Child may suffer mental retardation. No change in skin colour and ribs look prominent and becomes thin. B. VITAMIN DEFICIENCY DISEASES Vitamins are vital though they are required in small quantities. 1- Night blindness is caused by vitamin A 2- Rickets are caused by vitamin D 3- Haemolysis and sterility are caused by vitamin E. C. MINERAL DEFICIENCY DISEASES Metals and non-metals and their salts are called minerals. They do not supply energy to body. 1- Muscle cramps is caused by deficiency of sodium 2- Weakness of muscles or paralysis is caused by potassium 3- Rickets is caused by deficiency of calcium DISEASES DUE TO MALFUNCTIONING OF ORGANISMS: • Diabetes mellitusIt is a hereditary disease When insulin secreted by pancreas is not in enough amounts than it can neither use the sugar nor store in liver in form of glycogen. Than sugar level becomes high. This is called diabetes mellitus. • Heart diseasesCoronary artery diseases and atherosclerosis are common. The blood vessels that supply blood to heart muscles are called coronary arteries. And arteries become hard its called atherosclerosis. The blood supply is reduced due to which heart muscles don’t get proper supply its called coronary artery disease. • Arthritis :It is joint disease. Found as two types – rheumatoid arthritis and osteoarthritis.
• CANCER :It is characteristic by uncontrolled cell division. Malignancy refers to growing mass of cancerous cells. Renal disease or malfunctioning of kidney Due to some reason if kidney is malfunctioning and waste material accumulating in body is called uraemia. Due to head ache and extreme fatigue patient may go into coma. • ALLERGY :Unusual hypersensitivity of body tissues. Substances causing it are called allergens. • Asthma: Respiratory passage become swollen and constricted. Symptoms include coughing at night and shortness of breath, etc. BITES AND STINGS It needs immediate medical attention and is dangerous. Bite of snake may be dangerous and that of mosquito may be serious sometimes in case of carrier. BURNS AND FIRST AID First degree of burns is superficial burned Second degree of burns is called serious burns. Third degree of burn is called severe burns. CUTS AND THEIR FIRST AID If the cut is not deep is called superficial cut. If the cut is deep a cloth or pad should be kept on cut Bruises are injuries under the skin. Ways to prevent communicable diseases ❖ Diet and exercise play an important role ❖ Regular health screening and doctor check-up ❖ One should avoid fast food
CLEANLINESS, HYGIENE, EXERCISE • Always eat clean and healthy food. • Always wash hands after and before meal • Never split in public places • Always cover your mouth and nose while sneezing. • Always take a balanced and healthy diet. BAD HABITS LEAD TO ILL HEALTH • Tobacco addiction- chewing of tobacco may lead to cancer of mouth • Drug addiction- symptoms like nausea, vomiting and pain in stomach may occur’ • Addiction of fast food- they have dangerous effect on health • Alcohol consumption- it retards mental health and driving under influence of alcohol may cause accident • Unhealthy lifestyle- absence of physical activity and workout than unhealthy lifestyle increase the risk of heart ailments, blood pressure, and obesity and also makes us feel stressed
Map – A map is a representation or a drawing of the earth’s surface or a part of it drawn on a flat surface according to a scale.
Atlas – When many maps are put together we get an Atlas. Atlases are of various sizes, measurements drawn on different scales.
They are of different types of maps. Some of them are described below.
Physical Maps
Maps showing natural features of the earth such as mountains, plateaus, plains, rivers, oceans etc., are called physical or relief maps.
Political Maps
Maps showing cities, towns and villages, and different countries and states of the world with their boundaries are called political maps.
Thematic Maps
Some maps that focus on specific information; such as road maps, rainfall maps, maps showing distribution of forests, industries etc., are known as thematic maps.
There are three Components of Maps – distance, direction and symbol
Distance
Scale is the ratio between the actual distance on the ground and the distance shown on the map. Scale is very important on any map. If you know the scale, you will be able to calculate the distance between any two places on a map. When large areas like continents or countries are to be shown on paper, then we use a small scale. It is called a small scale map. When a small area like your village or town is to be shown on paper, then we use a large scale that is 5 cm. It is called a large scale map.
Direction
There are four major directions, North, South, East and West. They are called cardinal points. Other four intermediate directions are north-east (NE), southeast (SE), south-west (SW) and north-west (NW). We can find out the direction of a place with the help of a compass. It is an instrument used to find out main directions. Its magnetic needle always points towards north-south direction.
Symbols
It is the third important component of a map. It is not possible to draw on a map the actual shape and size of different features such as buildings, roads, etc. So, they are shown by using certain letters, shades, colours, pictures and lines. These symbols give a lot of information in a limited space. Maps have a universal language that can be understood by all. There is an international agreement regarding the use of these symbols. These are called conventional symbols.
Various colours are used for the same purpose. For example, generally blue is used for showing water bodies, brown for mountain, yellow for plateau and green is used for plains.
Sketch
A sketch is a drawing mainly based on memory and spot observation and not to scale. Sometimes a rough drawing is required of an area to tell where a particular place is located with respect to other places. Such a rough drawing is drawn without scale and is called a sketch map.
Plan
A plan is a drawing of a small area on a large scale. A large-scale map gives a lot of information, but there are certain things, which we may sometimes want to know, for example the length and breadth of a room, which can’t be shown in a map. At that time, we can refer drawings drawn to scale called a plan
A mountain is any natural elevation of the earth surface.
There are permanently frozen rivers of ice. They are called glaciers.
Mountains may be arranged in a line known as the range.
The Himalaya, the Alps and the Andes are mountain ranges.
There are three types of mountains—Fold Mountains, Block Mountains and Volcanic Mountains.
The Himalayan Mountains and the Alps are young fold mountains.
The Aravalli range in India is one of the oldest fold mountain systems.
Block Mountains are created when large areas are broken and displaced vertically.
Volcanic mountains are formed due to volcanic activity, e.g. Mt. Kilimanjaro in Africa
Plateaus
A plateau is an elevated flat land.
The Deccan plateau in India is one of the oldest plateaus.
The Tibet plateau is the highest plateau in the world.
The African plateau is famous for gold and diamond mining.
The lava plateaus are rich in black soil that are fertile and good for cultivation.
Plains
Plains are large stretches of flat land.
Most of the plains are formed by rivers and their tributaries.
In India, the Indo-Gangetic plains are the most densely populated region of the country
Landforms and the People
Humans have been living in different kinds of landforms in different ways.
Sometimes, natural calamities such as earthquakes, volcanic eruptions, storms and floods cause widespread destruction.
The surface of the earth is not the same everywhere.
Mountains, plateaus and plains are different landforms of the earth.
A mountain is a natural elevation of the earth surface. There are three types of mountains—Fold mountains, Block mountains and Volcanic mountains.
A plateau is an elevated flat land. It is a flat-topped table land standing above the surrounding area. A plateau may have one or more sides with steep slopes.
The Deccan plateau is one of the oldest plateaus.
The Tibet plateau is the highest plateau in the world.
Plains are large stretches of flat land. Some plains are extremely level while others may be slightly rolling and undulating
Plains are generally thickly populated regions of the world
Human habitation is found on different kinds of landforms. But population varies on these landforms. Mountains are generally not thickly populated. But plains are the regions where the thick population is found.
The land is precious. We must not use it in a wasteful manner. Construction work of any type should not be carried on fertile land. Also, we should not throw garbage on land. It is our duty to take care of the land or any other natural gift. If we do this we will be conscious citizens.
Erosion: The wearing away of the earth’s surface is known as erosion.
Mountain: A mountain is a natural elevation of the earth surface.
Glacier: Some mountains have permanently frozen river of ice. They are called glaciers.
Range: When mountains are in an arranged line, it is called a range.
Horsts and graben: The uplifted blocks are known as horsts and the lowered blocks are known as graben.
Storehouse: A building where things are stored or kept.
Terraces: One of the series of flat areas of ground which are cut into the side of a hill like steps in order to grow crops there.
Flora: The plants of a particular area.
Fauna: The animals living in an area.
Plateau: A plateau is an elevated flat land. It is a flat-topped table land standing above the surrounding area.
Plain: A plain is a vast stretch of flat land where the thick population is found.
1. The Aryans were nomadic people who came to India from the north-west.
2. They settled down and gradually took to agriculture.
3. Our knowledge of the Aryans comes from the Vedas.
4. The Rigveda gives information about the Early Vedic Age.
5. The period when the Aryans first settled in India is known as the Early Vedic Age (1500 BCE to 1000 BCE).
6. During this period, the kingdoms were tribal in character.
7. The period between 1000 BCE to 600 BCE is known as the Later Vedic Age.
8. The king now became very powerful and the status of women declined.
9. Megalithic burials have been found in many places in India.
10. Inamgoan is believed to have been occupied from 1600 BCE to 700 BCE.
Have you ever heard or recited the Gayatri Mantra? It is from the oldest text in India called the Rigveda. There are four Vedas. The Rigveda is the oldest among them. The Vedic Age is the period during which the Vedas were composed. This period from 1500 BCE to 600 BCE, is often called the Vedic Age.
Earlier, we have read about the Harappan Civilisation. Slowly it declined and by around 1800 BCE, people again began living a simple life in villages. About this time, some people entered India from the north-west. They called themselves ‘Arya’ meaning ‘noble ones’. A new culture developed in India with the arrival of the Aryans. They did not come to India to invade and plunder and go back. They settled down in the plains and took to agriculture. They first settled in seven places in the Punjab region which they called Sapta Sindhu. These Aryans who settled in India are called Indo-Aryans.
STUDY OF VEDAS
Our knowledge of the Aryans comes from the Vedas. The Vedic Age gets its name from the four Vedas. Historians have studied these texts carefully. They provide an insight into the life of the Vedic Age.
LANGUAGES
The Aryans spoke a language called Indo- European which was the ancestor of Sanskrit, Assamese, Gujarati, Kashmiri and many other foreign languages like Latin, Greek, German and Persian. Similar words exist in all these languages. In India, the languages used in the north-east belong to the Tibeto-Burman family. Tamil, Telugu and other languages of the sout belong to the Dravidian family.
The oldest Veda is the Rigveda. It was composed about 1500 BCE and is a collection of 1028 hymns written by rishis. These hymns are in praise of various gods and goddesses. These hymns were considered sacred. For hundreds of years, the Rigveda was passed down by word of mouth. Finally, it was written down in Sanskrit. The other three Vedas were written later and tell us about the Later Vedic Age.
EARLY VEDIC AGE
The period when the Aryans first entered India is known as the Early Vedic Age (1500 BCE to 1000 BCE). The chief source of information about this period is the Rigveda.
Political Organisation
The kingdom was tribal in character. The tribal chief was called rajan. He ruled over the people (jana) and not over any specific area of land. His position was not hereditary. He did not live in any palace and did not collect regular taxes. His main function was to protect the people and lead the army to victory in battle. Battles were fought for land which was essential for agriculture and for pastures for the cattle. He used to receive a large part of the booty collected in battle. He was also called gopati (Lord of Cattle) indicating that protecting and increasing the cattle was his other major role. He received from the people a voluntary offering called ball. The king did not maintain a standing army. The king’s power as kept in check by assemblies such as sabha and samiti. The king dispensed his duties with the help of the purohita (religious advisor) and senani (army chief).
Q. Why was the king called gopati? Why were cattle so important?
Status of Women
Women were treated equally and were allowed some choice in the selection of their husbands. They received education also. Child marriage and sati1 did not exist and widows were not treated badly. Women participated in the sabha, rituals and even chariot races.
History Reveals
The Rigveda has many hymns composed by women and there are references to women sages.
Economic life
The Aryans did not have any fixed territories and they moved from place to place with their cattle and horses. As they began to settle down, they began to practice agriculture. Cattle were the most-valued possession and chief form of wealth. Besides agriculture and cattle rearing, there were many other professions. People were also engaged in trade.
History Reveals
Ships were also used by the Early Vedic people. The Rigveda speaks of ‘?ships with a hundred oars?.
Religion
People worshipped the forces of nature. Much of the Rigveda is full of prayers for these deities. The important gods were Indra, Varun, Surya, Vishnu, Vayu and Yama. Some goddesses were Usha, Savitri and Prithvi. Their favour could be won by sacrifices. They did not make temples or idols. They worshipped through prayers and chanting Vedic mantras.
LATER VEDIC AGE
The period between 1000-600 BCE is known as the Later Vedic Age. We know about this age through the books that were composed during this period.
Samaveda: It is a collection of musical verses from the Rigveda.
Yajurveda: This contains mantras and rituals for sacrifice.
Atharvaveda: This contains chants to cure diseases and ward off danger. The epics, Mahabharata and Ramayana, were also written during this age. They tell us about the political and social setup of that period and are considered religious texts. This age is also called the Epic Age because these two great epics were written during this period.
Political Organisation
Each tribe now occupied a fixed territory which as named after the tribe. Tribes often fought over territories. The term rashtra which indicates territory first appeared in this period. The king became very powerful and his position became hereditary. He lived a luxurious life in a palace. He received regular taxes in the form of food grains or cattle. He appointed officers to collect taxes. He maintained law and order and all major decisions were taken by him. The sabha and samiti assisted him but did not curtail his power. He performed various sacrifices to prove his strength and power.
Status of Women
There was a drastic change in the position of women. They were not educated or allowed to read the Vedas. They no longer participated in the sabha. Child marriage and sati came into existence and widow remarriage was strongly opposed. The women were supposed to be under the control of her father and later her husband.
Caste System
The caste system developed gradually. The Aryans made the defeated dasas do unpleasant work. Division was created between the dasas and the fair-skinned Aryans. The dasas were given the name shudras and were not allowed to take part in any Aryan ceremony. Hence the caste system consisting of the four castes came into being-the brahmins, kshatriyas, vaishyas and the shudras. We will be learning more about the caste system in the later chapters.
Economic life
Agriculture became very important. Copper, bronze and iron implements were used. The main crops were wheat, rice and barley. Artisans2 produced better goods. Weaving was practiced on a wide scale mostly by women.
Religion
New gods were worshipped. Prajapati, the creator, was most important. He was later called Brahma. Shiva and Vishnu were also worshipped. Idol worship also began. Sacrifices were performed to please the gods who then blessed the people.
Thus, the Aryans brought with them their customs and ways of thinking and influenced the lives of the natives.
MEGALITHS
The word megalith comes from the Greek words megas and lithos meaning ‘great stone”. Megaliths are large slabs of stone used to mark the burial sites. Numerous megaliths have been found in Karnataka, Andhra Pradesh, Maharashtra, Kerala, Kashmir and the north- east.
In a megalithic burial, the bones of a dead person were placed in an urn. This urn was buried and surrounded by a circle of large vertical stones. A large horizontal stone formed the capstone.
If the pit burial has a circle of large stones, it is called a pit circle. If the pit had a heap of stones piled on top, it is called a cairn.
Unlike the Neolithic burials which were in the habitation area, megalithic burials were away from the occupation area. Grave goods like pottery, ornaments and weapons were also found. Pottery was of black and red variety. Weapons consisted of iron axes, spades and daggers. Ornaments were made of carnelian and gold. Some copper objects were also put in the grave. Sometimes horse skeletons and equipment were also found. The number of grave goods probably depended on the status of the person. The presence of these goods is indicative of their belief in afterlife. Some graves have skeletons of more than one person. This is suggestive that probably people from the same family were buried in the same place. The people who died later were got in through portholes.
Megaliths were built with great care and must have been an important part of the lives and beliefs of the people who constructed them.
INAMGAON
Inamgaon is a village in Pune district of Maharashtra. It is located near the River Ghod, a tributary of River Bhima. It is said to have been occupied from 1600 BCE to 700 BCE.
Houses here had fire pits. The pottery was fine, well-baked and designed. A pottery kiln has also been identified. There was an increase in farming and animal domestication. They cultivated grams, beans, peas and lentils apart from wheat, barley and rice. Fruits like berries and dates were also collected.
Bones of animals have been found. These bones have cut marks which are evidence that animals were also used for food.
The adult dead bodies were mostly buried away from the abitation site. Sometimes the burials were in the houses. The dead body was laid out straight, with the head towards the north. A number of burial goods including pots, ornaments and tools were also buried with the dead person. Multiple burials have also been found. In some graves, more than one skeleton and the absence of burial goods indicate that there was probably a large scale killing because of which burial goods were not enough for all the graves. In one large house which had a granary, one man was found buried in a cross legged position in a clay jar.
Q. Why do you think Inamgaon was located near a river?
Around the World
During the Shang Dynasty (1600-1046 BCE) in China, seers4 used bones or shells of tortoises for reading oracles5. They inscribed a question which they wanted to ask on the oracle bone. The bone was then heated. The cracks formed in the bone were studied and interpreted. Archaeologists have found thousands of oracle bones and shells in China. Oracle bones of the Shang Dynasty were ox scapulae and plastrons6 only. They had characters and holes drilled into them.
Palaeolithic: This term refers to the age where we find a large number of stone tools. It extends from 2 million years ago to about 12,000 years ago and is divided into Lower, Middle and Upper Palaeolithic.
Mesolithic: This period extends from 10,000 years ago to about 12,000 years ago. Stone tools found during this period were generally tiny and were called Microliths.
Neolithic: This was the period that dates back to about 10,000 years ago, and is, therefore, known as the New Stone Age.
The Earliest People: They were hunter-gatherers, a name derived from the way they collected food. They hunted animals, collected berries and fruits and gathered nuts, stalks and eggs. To hunt, they needed to move constantly, and to gather plant products, they needed knowledge about the edibility of plants and change of seasons.
Archaeological Evidence of Early Man: How do we know about the early man? This has been possible through an analysis of objects found, which were probably used by the early man. For example, tools made of stones, bones and wood.
Uses of Tools: Stone tools were used to cut meat and bones, scrape bark (from trees) and hides (animal skins) as well as to chop fruit and roots.
Making Stone Tools: Two different techniques were used for making stone tools.
Choosing a Place to Live In: Dwellings chosen by the early man were located near sources of water, such as rivers and lakes as well as where the good quality stone was available for their tools.
Painting-Rock paintings: Paintings on a rock shelter.
Finding out about Fire: At Kurnool caves in Andhra Pradesh, evidence and traces of ash have been found suggesting use of fire. The fire might have been used as a source of light, to cook meat and to scare away animals.
A Changing Environment: About 12,000 years ago, there was a major change in the climate of the world. This change led to a shift to warm conditions, leading to the development of grasslands at many places which helped people to start thinking about the herding and rearing animals.
Habitation-cum-Factory Sites: Places where stones were found and early people made their tools. Sometimes, people lived (habitat) here for a longer span of time.
Bhimbetka: This is a place in Madhya Pradesh where we find examples of habitation sites, natural caves and rock shelters.
People who lived in the subcontinent about 2 million years ago were Hunter-gatherers. They hunted wild animals and gathered plant produce to get their food. They moved from place to place, in search of more food, water and resources.
Hunter-gatherers made and used various types of tools—tools of stone, wood and bone
Habitation refers to the place where people lived.
Stone tools were made using different techniques like a stone on stone (using a stone to give required shape to another stone) and pressure flaking.
The fire was used by the early people. They used fire as a source of light, to cook meat and to scare away animals.
Grasslands developed in many areas due to change in climate around 12000 years ago. Herding, and rearing animals and fishing became common.
Several grain-bearing panes of grass, like wheat, barley, rice grew naturally in different parts of the subcontinent. The people also began growing plants on their own.
Many old caves have paintings on their walls. They show wild animals and are drawn with great accuracy and skill. A painting from a rock shelter.
In Hunsgi, a number of early Palaeolithic sites have been found. A large number of tools were also found, most of which were made of limestone.
Factory-Sites: Places where the stone was found and where people made tools are called Factory-sites.
Grasslands: Areas of land with high fertility and thus good for growing crops are called Grasslands.
Habitation-Cum-Factory Sites: Factory-sites, where people lived for some time, have been called Habitation-cum-factory sites.
Hunter-Gatherers: People who lived in the subcontinent about two million years ago and who hunted wild animals, caught fish and birds, gathered food to eat, were the Hunter-gatherers.
Palaeolithic: The part of history extending from 2 million years ago to about 12,000 years ago is called the Palaeolithic period.
Mesolithic: The part of history extending from about 12,000 years ago to about 10,000 years ago is called the Mesolithic period.
Microliths: Stone tools of the Mesolithic period are called Microliths.
There are several things we can know about our past such as:
What people used to eat, the type of clothes they used to wear, the houses in which they lived.
How were the lives of hunters, herders, farmers, rulers, merchants, priests, crafts persons, artists, musicians, and scientists?
The games children used to play, the stories they have heard, the songs they sang.
Where did people live?
People have lived along the banks of the Narmada river for several hundred thousand years. These people stayed on the bank of Narmada river as they knew about the vast wealth of plants in the surrounding forests. They used to collect roots, fruits and other forest produce for their food. Sometimes they also hunted animals.
The areas where women and men first began to grow crops such as wheat and barley was about 8000 years ago.
People also began to look after animals like sheep, goat, and cattle and used to live in villages.
The places where rice was first grown are to the north of the Vindhyas.
About 2500 years ago, cities developed on the banks of the Ganga and its tributaries, and along the sea coasts.
In ancient times, the area along the Ganga and its tributary rivers, to the south of the Ganga was known as Magadha which is now lying in the state of Bihar. Men and women moved in search of livelihood and also to escape from natural disasters like floods or droughts. These movements of people enriched our cultural traditions. People have shared new ways of carving stone, composing music, and even cooking food over several hundreds of years.
Names of the land
Our country is known by both words i.e India and Bharat.
The word India comes from the Indus, called Sindhu in Sanskrit. The Iranians and the Greeks who came through the northwest about 2500 years ago called it the Hindos or the Indos, and the land to the east of the river was called India.
The name Bharata was used for a group of people who lived in the northwest, and who are mentioned in the Rigveda, the earliest composition in Sanskrit (dated to about 3500 years ago). Later it was used for the country.
Finding out about the past
One way through which we can find out about our past is by reading the books that were written long ago. These books are called manuscripts because they were written by hand. These were written on palm leaves, or on the specially prepared bark of a tree known as the birch, which grows in the Himalayas. These books dealt with all kinds of subjects: religious beliefs and practices, the lives of kings, medicine and science. Besides, there were epics, poems, plays as well.
Inscriptions
Inscriptions are writings on relatively hard surfaces such as stone or metal. In the past, when kings wanted their orders inscribed so that people could see, read and obey them, they used inscriptions for this purpose. There are other kinds of inscriptions as well, where men and women (including kings and queens) recorded what they did. For example, records of victories in battle.
Archaeologists
An archaeologist is a person who studies the remains of buildings made of stone and brick, paintings and sculpture. They also explore and excavate to find tools, weapons, pots, pans, ornaments and coins. They also look for bones of animals, birds, and fish to find out what people ate in the past.
Historians use the word source to refer to the information found from manuscripts, inscriptions and archaeology. Once sources are found, learning about the past becomes an adventure. So historians and archaeologists are like detectives, who use all these sources like clues to find out about our pasts.
One past or many?
The title of this book is Our Pasts – I. The word ‘pasts’ in plural is used to draw attention to the fact that the past was different for different groups of people. For example, the lives of herders or farmers were different from those of kings and queens, the lives of merchants were different from those of crafts persons, and so on. It is even true today as people followed different practices and customs in different parts of the country.
Archaeology did not help us to know more about the ordinary people in the past because they did not keep records of what they did. Whereas, kings used to keep the records of their victories and the battles they fought.
What do dates mean?
The years are counted from the date to the birth of Jesus Christ, the founder of Christianity. All dates before the birth of Christ are counted backwards and usually have the letters BC (Before Christ) added on. In this book, we will refer to dates going back from the present, using 2000 as our starting point. 2000 means 2000 years after the birth of Christ.
The name atom comes from the Greek word ‘atomos’, which means uncuttable or indivisible.
An atom is the smallest particle of an element having the same chemical properties of the element.Atoms are the basis for everything in the universe, including us.
Atoms are tiny particles that are too small to see, even with a microscope. They are so tiny that if people were the same size as atoms, the entire population of the world would fit into a small box.
Just like letters are the basic building blocks of any language, atoms are the primary building blocks for things around us. The chair you sit on, the lunch box you carry to school, pizza you eat – just everything is made up of atoms.
When atoms combine together they form molecules.
Let us study about the atoms and molecules in detail.
Dalton’s Atomic Theory:
Matter is made of atoms which cannot be broken down further.
Atoms cannot be created or destroyed in a chemical reaction.
Atoms of the same element are identical to each other while atoms of different elements differ in mass and chemical properties.
Atoms combine in definite ratios of whole numbers to form compounds.
The number and composition of atoms are constant for a given compound.
A few important definitions
Atom: Atom is the smallest unit of matter and is further made up of protons, neutrons, and electrons. Atomic radius is measured in nanometres (10−910−9 m)
Atomic mass: A mass unit equal exactly to 112th112th the mass of one atom of Carbon-12
Gram atomic mass: The atomic mass of an element expressed in grams is called gram atomic mass
Molecule: The smallest unit of an element or a compound which can exist independently and show all its physical and chemical properties is called molecule. A molecule may have atoms of the same kind(element) or of different kinds (compound)
We come across many chemical substances and compounds daily. Everything around us consists of chemical substances. These may be man-made chemical substances and substances extracted from nature
Examples of chemical products at home are dishwashing and cleaning detergents, glue, common salt, baking soda, etc
These chemicals are made up of atoms of a fixed proportion and these atoms are arranged in a certain way. In order to find out what these proportions are and how they are arranged for any given substance, we need to know the chemical formula of the substance or compound.
In order to make it easier to describe elements and molecules, chemical formulae are used. They are used to describe the number of atoms in each element or compound. It contains the symbols of the atoms of the elements present in the compound, as well as how many there are for each element in the form of subscripts.
For example, ‘H’ represents one atom of hydrogen and ‘O’ represents one atom of oxygen. If we want to represent two atoms of hydrogen, instead of writing H H, we write H2. The subscript “2” means that two atoms of the element hydrogen have joined together to form a molecule.
We will study about the formulae in this chapter.
Importance of chemical formulae:
It tells us about the types of elements present in the compound
It tells us the number of atoms of each kind present in the molecule of the compound
It gives us the mass of one molecule of the compound
Chemical Formulae
Every chemical substance is known by a specific name.
Each chemical compound is represented by a chemical formula that gives its composition (constituent elements present) and the number of elements of each type present.
Molecular Formula
A chemical formula that represents the composition of a molecule of the substance in terms of the symbols of the elements present in the molecule is also called molecular formula.
For example, the molecular formula of water is H2O, which means that one molecule of water contains two atoms of hydrogen and one atom of oxygen.
Significance of Molecular Formula
It represents name of the substance
It represents one molecule of substance
It gives the names of all the elements present in one molecule of the substance. It also gives the number of atoms of each element present.
It represents a definite mass and refers to the presence of 6.023 x 1023 molecules (known as the mole concept).
Ancient people like the Greeks, Romans, Indians, the Chinese, knew about elements like iron, copper, gold, silver, lead etc. The first element humans knew was most probably the carbon, in the form of charcoal.
There are about 115 elements out of which there are 92 elements that occur naturally. Most of them were discovered by the late 1800’s.
The modern arrangement of the elements is known as the Periodic Table of Elements and is arranged according to the atomic number of elements. The scientist Dmitri Mendeleev, a Russian chemist, proposed an arrangement of know elements based on their atomic mass.
The periodictable of the chemical elements is a tabular display of the known chemical elements. Each element is listed by its atomic number and chemical symbol.
Symbols are used to represent elements. A symbol is a letter or picture used to represent something. One or two letters are used to represent elements. Example: The symbol for aluminum is Al and the symbol for oxygen is O.
A chemical formula is used as a quick way to show the composition of compounds. Letters, numbers, and symbols are used to represent elements and the number of elements in each compound.
Let us study in detail about elements, compounds, symbols, and formulae in this chapter.
Substances
Substances:
Substances are classified into two types.
Pure Substances – A substance which is made of one kind of particle.
Examples – iron, gold
Impure substances or Mixtures – A substance which contains two or more different particles is known as a mixture.
Example: a salt solution is made up of two components, salt, and water.
On the basis of their chemical composition, pure substances are classified as elements and compounds.
Elements :
A pure substance which is made up of only one kind of atom and cannot be broken into two or more simpler substances by physical or chemical means is referred to as an element. Example: Zinc, Sulphur.
Characteristics of elements:
An element is homogeneous in nature; it is a pure substance, made up of only one kind of atoms. For example, iron and silver are made of only iron and silver atoms.
An element cannot be broken down into simpler substances by any physical or chemical methods such as heat, light electricity, or chemical reactions with other substances. For example, if you were to smash a piece of iron into smaller pieces or heat it, the piece still remains as the element iron.
An atom is the smallest unit that shows all the properties of an element. For example, an atom of iron shows all the properties of that metal.
Elements have sharp melting and boiling points.
Symbols to represent elements:
Each element is represented by a symbol. It is usually derived from the first letter of its name in English or Latin. The first letter of the symbol is always in upper case. Some elements are represented by the starting alphabet of its name. Example: Carbon is represented as C. Symbols of some elements are the first two alphabets, where the second alphabet is in the lower case. Example: Sodium is represented as Na, where Natrium is the Latin name of sodium.
Compounds:
They are made up of one or more elements and are denoted by chemical formulae.
A compound contains atoms of different elements chemically combined in a fixed ratio.The smallest unit of a compound is a molecule
Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds.
A compound can be broken down into simpler substances by chemical methods/reactions
A compound is represented using a formula. Example: Water (H2O), Sodium chloride (NaCl),Magnesium oxide (MgO)
Water is one of the essential element for life on earth. Most of the earth’s surface is covered with water. Any guesses on how much fraction of the earth is covered with water?
About three-fourth of earth’s surface is covered with water.
An interesting fact for you to know is that most part of the human body consists of water.
We need water in daily life for different purposes: drinking, washing clothes and utensils, cooking, watering plants to name a few. As already stated most of the earth’s surface contains water, yet all of it can not be utilised. So how and from where do we get water for daily use?
In this chapter, you will learn about sources of water, different states of water, water cycle, the importance of water, water-borne diseases, and finally purification of water.
Sources of water
Most of the earth’s surface is covered by the oceans.
Sea is the largest source of natural water, but it contains a high amount of dissolved salt and cannot be used directly for irrigation or drinking.
Rivers and lakes contain water that comes from glaciers or rainfall. As rivers flow downhill and through plains, they collect many substances like minerals, organic matter, clay. Sometimes bacteria may also be present in river water.
We meet all our domestic and industrial requirements of water from rivers.
Ground water is a pure form of water because it has no suspended impurities or germs. However, it may have dissolved minerals which give it a distinct taste and even medicinal properties.
We can obtain ground water by digging wells.
Rainwater is the purest form of water.
It will contain dissolved substances like dust, carbon dioxide, oxygen and nitrogen.
States of water
Water exists in all three states of matter: solid, liquid and gas.
Ice, water and steam have different physical properties but same chemical properties.
The interconversion of these three states of water also occurs in nature and it is called the water cycle.
Water cycle
Evaporation:
Heat from the Sun causes water on Earth (in oceans, lakes etc.) to evaporate (turn from the liquid into the gas) and rise into the sky. This water vapour collects in the sky in the form of clouds.
Condensation:
As water vapour in the clouds cools down it becomes water again, this process is called condensation.
Precipitation:
Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called precipitation.
Collection:
Oceans and lakes collect water that has fallen. Water evaporates into the sky again and the cycle continues.
Importance of water
Commercial water use includes fresh water for motels, hotels, restaurants, office buildings, other commercial facilities, and civilian and military institutions. Domestic water use is probably the most important daily use of water for most people.
Domestic use includes water that is used in the home every day, including water for normal household purposes, such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens.
Industrial water use is a valuable resource to the nation's industries for such purposes as processing, cleaning, transportation, dilution, and cooling in manufacturing facilities. Major water-using industries include steel, chemical, paper, and petroleum refining. Industries often reuse the same water over and over for more than one purpose.
Irrigation water use is water artificially applied to farm, orchard, pasture, and horticultural crops, as well as water used to irrigate pastures, for frost and freeze protection, chemical application, crop cooling, harvesting, and for the leaching of salts from the crop root zone.
Nonagricultural activities include self-supplied water to irrigate public and private golf courses, parks.
Potable water:
Potable water is required for human consumption (drinking). It must be:
Clean and transparent.
Free of germs and suspended impurities.
It should contain some amount of gases and minerals so that it does not taste flat.
It should not have harmful chemicals.
Waterborne diseases
Drinking dirty or contaminated water causes water borne diseases.
Some waterborne diseases are:
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Purification of water
Water must be treated or purified to make it fit for human consumption.
Coagulation stage:
Alum and other chemicals are added to the water at this stage.
Suspended particles get stuck to the chemicals to form 'floc'.
Sedimentation Stage:
As particles get stuck they become heavy and sink to the bottom of the chamber.
At this stage, most of the particles are stuck to form sediments, sinking to the bottom.
The water is passed onto the Filtration chamber.
Filtration stage:
As water passes slowly through this chamber, finer particles (sediments) are filtered out over layers of sand, charcoal and gravel.
Disinfection stage:
Chlorination or addition of chlorine to water is used to kill any bacteria and other living organisms that may be in the water.
It is very normal and natural for fresh water to contain living organisms.
Ozonization:
Because of its excellent disinfection and oxidation qualities, ozone is widely used for drinking water treatment.
Ozone can be added at several points throughout the treatment system,
Storage stage:
The water is then passed into large storage tanks and left for a while for the action of disinfection to be complete.
At the tail end of this storage tanks, huge pipes are connected to transport water to our homes and workplaces.
At home, the easiest way to sterilise water is by boiling. Boiling water kills germs and makes it safe for drinking.
Filtering through a cloth also removes soil and other large particles.
Chlorine can be added to overhead tanks to disinfect water.
Apart from this, we can also install RO systems or water purifiers with activated carbon filters to purify water.
Any liquid in which a solid dissolves easily is known as a solvent. Water has this excellent property of dissolving many substances.
Can you name one or two substances which you use every day, which easily dissolves in water?
They are the salt and the sugar.
Similarly, there are many other substances which dissolve in water. Hence, the name universal solvent for the water. In this chapter, you will learn more about water as a solvent and you will also learn step-by-step procedure to prove that tap water and sea water contain dissolved solids and gases.
Water has the ability to dissolve many substances in it. However, water dissolves different amounts of different substances under the same conditions. For e.g., for the same volume of water, we can dissolve more sugar than salt.
Aquatic life depends on the oxygen dissolved in water.
Stirring and heating increase solubility of a substance.
Pure water is transparent, colourless, tasteless and odourless.
Temperature and solubility:
Add a 1/2 cup of lukewarm tap water to a plastic cup.
Weigh about 5 tablespoons of salt and gradually add the salt to the tap water, stirring to mix.
Stop adding salt when it no longer dissolves.
Repeat the mixing steps with 1/2 cup each of ice water and hot water; determine at which temperature more salt dissolves.
This experiment proves that the solubility of some substances is dependent on temperature, and we observe that much more salt dissolves in hot water than in cold.
Experiment to show that tap water and sea water contain dissolved solids and gases
Two round bottom flasks are filled with tap water and sea water respectively and heated. Bubbles of gas will be released from the water and travel into the test-tube. Continue until the contents of the flask are boiling.
About half a test-tube full of gas will be collected in each case, all of which has been displaced from solution by heating.
A glowing splint continues to glow and does not immediately go out when placed in the gas.
If both samples of water are placed in an evaporating dish and allowed to evaporate, the water completely evaporates leaving behind traces of solids in the dish, showing that the samples of water contain dissolved solids.
Water plays a very important role for all of us in daily lives. You might postpone eating food, but you definitely need water to quench your thirst. Even though most of the earth’s surface is covered with water, most of it is unusable.
Have you tasted sea water?
In case you have, it is very salty, right?
So, one of the main sources of water is rain. Rainwater is collected in rivers, tanks, reservoirs which are available for use by all living beings. It is essential to conserve water and make sure that the water is not polluted by industrial waste or any such means, water is not wasted and so on. It is the responsibility of all of us to preserve and conserve water for generations to come. In this chapter, you will learn about the importance of water, water conservation, water pollution and preventing water pollution.
Water is a precious natural resource and we must conserve water.
We can conserve water by using it in a wise manner.
97% of all the water on the earth is salt water, which is not suitable for drinking. Only 3% of all the water is fresh water, and only 1% is available for drinking. That is why we must conserve water.
A few simple ways to reduce usage and wastage of water:
Turn off the tap when you brush your teeth.
Fix a dripping tap and leaking pipes.
Use a bucket instead of the shower.
Water your garden with a watering can rather than a hosepipe.
Rainwater harvesting is used by many people to save and use rainwater.
Use drip irrigation on fields.
Grow more trees to maintain water cycle.
Avoid water pollution.
Build dams to store and conserve water.
Water pollution:
Sewage, kitchen and industrial wastes are dumped into the water.
Chemicals from farms (dissolved fertilisers) and acidic waters from mines and industries pollute the water.
Nuclear and thermal power plants use water for cooling purposes and discharge the hot water into seas and rivers. This causes an increase in temperature of the water and kills fish and plants in the water.
Water pollution can be controlled by:
Treatment of sewage before being released into rivers.
Removal of solid waste and garbage from sewage.
Avoid using detergents, fertilisers, plastics and pesticides which can increase the chemical content of the water.
Treat all effluents from factories to make them harmless.
Avoid using lakes, ponds and rivers for bathing, washing animals and defecating and for disposing of dead bodies.
