Introduction
All the objects that we see around us is called material. Materials are made up of matter. For example, animals, insects, birds, plants, trees, houses, machines, tools, tables, chairs, clothes etc. are the materials made up of matter. Matter has mass and it occupies space. Mass is used to measure the amount of matter present in an object and volume is used to measure the amount of space occupied by the object.
Due to the huge quantity and large variety of materials, it is very difficult to study each one of them separately. Therefore, materials are classified into groups, so that we can study and understand them better.
Classification of Materials
The process of grouping objects according to their shared characteristics is called classification. In other words, the materials having similar properties are kept in the same group.
For example: Classification of the following objects into living and non-living things: Plants, books, tables, animals, water, air, birds, fishes, insects, houses, buses, machines.
Living: Plants, animals, birds, fishes, insects.
Non –living: Books, tablets, water, air, houses, buses, and machines.
Basis of Classification
The characteristics or properties, which are taken as the base for the classification of given objects, are called the basis of classification.
There are a number characteristics which are taken as the base for classification.
For example, 'living and non-living', 'natural and artificial', 'solid, liquid and gas', 'shape', 'colour' etc.
Note: You can also classify the materials by selecting the characteristics as per your own choice.. 
Silk
Silk is also a natural fibre. It is obtained from cocoons of silkworm. Silk is a fine, strong, soft and shiny fibre. The rearing of silkworms for obtaining silk is called sericulture.
Production of Silk
Eggs from the adult silk moth are kept at suitable temperature and humid conditions. During the hatching, silkworms come out in the form of larvae or caterpillar. After 25 to 30 days, they get ready to spin cocoons.
Processing of cocoons for fibres
Reeling machine is used for unwinding the silk fibre from cocoons. Silk fibres are twisted to make silk yarn for waving the silk cloth. There are many varieties of silk obtained from different silk moth. A most common type of silk is mulberry silk which is soft, lustrous, elastic and can be dyed in different colours.
Look at the following picture to obtain silk from silk moth:
Eggs from female adult silk moth Caterpillar form cocoons Caterpillar covers themselves form silk
Natural and Artificial Fibre
Silk and wool are natural fiber. A type of fibre which is neither natural nor artificial is called rayon. Rayon is obtained from wood pulp (cellulose) which is a natural fibre. Some artificial or synthetic fibres are : nylon, polyester, acrylic, polyolefin, etc. The first artificial fibre known as viscose was produced in 1894.
Rayon came into being in the year of 1924.
The following are the method by which, we can find out whether the fibre is artificial or natural.
(i) Take a piece of fibre and burn it. If burning smell is same as the burning smell of hair then the taken piece of fibre is a natural fibre.
(ii) If the burning smell is same as the burning smell of paper then the taken piece of fibre is an artificial fibre.
Consider the following statements:
Statement 1: Silk is obtained from silk worm.
Statement 2: Silk is obtained from plants.
Which one of the following is correct about the above statements?
(a) Statement 1 is true and 2 is false
(b) Statement 1 is false and 2 is true
(c) Both statements are false
(d) Both statements are true
(e) None of these
Answer: (a)
Explanation
Silk is obtained from silkworm. Therefore option (A) is correct and rest of the options is incorrect.
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Introduction
Clothes, which protect us from rain, cold etc. are made of fibres. Fibres are obtained from plants and animals. Fibre from plants is called plant fibre and fibre from animal is called animal fibre. Both plant and animal fibres are called natural fibre. First silk fibre was discovered accidently in China. Synthetic fibre is the composition of chemicals hence called manmade fibre. In this chapter we will study about the source of fibre and its use.
Note: China is the leading producer of silk products in the world.
Animal Fibre
We need warm or woolen dresses during winter to protect ourselves from cold. Thread of wool used to make the sweater, is obtained from animal fibre. Another animal fibre is silk. Silk is used for making sarees and other wearable dresses which is obtained from cocoons of silk moth therefore, called animal fibre.
Wool
Wool is an important and commonly used animal fibre which is mainly obtained from sheep. It is soft and wavy (curly). Wool is widely used for knitting sweaters. It traps air more than that of cotton fibre hence keep our body warm.
Look at the following pictures of wool yielding animals:
Ox Yak
Sheep Lama
How wool is obtained from sheep
Wool from sheep is obtained by different process. The process by which thin skin of sheep along with its dense hair is removed is called shearing After obtaining the fleece of sheep, it is washed and dried because, dust particles are present on the body of the sheep. The process by which fleece from sheep is washed and dried is called scouring. Hairs on the fleece of sheep is not uniformly distributed. Some parts of fleece are dense, some are not Length of hairs, s also not uniform. In the process of sorting, fleece of sheep is separated m sections according to their quality, like separation of dense hair long and short hair, etc. Fleece of sheep cannot be obtained in desired colour hence desired colour of wool is obtained by dyeing the fleece. Combing method is used for spinning the yarns of wool. It removes dust particles which present in fleece. A comb which having metal teeth is used for combing. Long woolen fibre is twisted or spun into thick yarn is called wool and short woolen fibre spun into fine yarns. The process by which long and short woolen fibre is twisted into thick and fine yarn is called spinning.
Look at the following process to more... 
Types of Consumers
Consumers have been classified into the following groups on the basis of their food habits.
Herbivores
The animals that eat only plants or plant products, are called herbivores. Cow, buffalo, goat, elephant, horse, rabbit, camel etc. are the example of herbivores animals.
Carnivores
The animals that eat only other animals are called carnivores. Tiger, lion, cheetah, wolf, snake, etc. are the example of carnivores animals
Omnivores
The animals that eat both plants and animals are called omnivores. Man, bear, dog, crow etc. are the example of omnivores animals.
Scavengers
The animals that eat dead bodies of other animals are called scavengers. Crow, vulture, hyena etc. are the examples of scavengers.
Which one of the following plants store food in its stem?
(a) Turnip
(b) Garlic
(c) Lettuce
(d) Beet
(e) None of these
Answer: (b)
Which one of the following animals is a herbivores?
(a) Giraffe
(b) Hyena
(c) Lion
(d) Bear
(e) None of these
Answer: (a)
Food gives us energy, keep healthy and protects from diseases.
Food like cereals, pulses, fruits etc. are obtained from plants.
Food like milk, eggs and meat we obtain from animals.
Some plants store their food in roots.
Green plants are called producers.
Animals are known as consumers.. 
Producers & Consumers
All living organisms has been broadly classified into two groups, producers and consumers.
Producers: All the green plants make their own food, therefore, green plants are called producers.
Consumers: Animals consume the food prepared by green plants, therefore, animals are called consumers.
Food
Food is a substance eaten by the living organisms in order to remain alive. Fruits, vegetables, eggs, meat and milk etc. are the example of food.
What are the functions of food?
The functions of food are:
It provides energy and enables us to do work
It keeps us fit and healthy
It protects us from the diseases
It gives us strength
It helps our body to grow
Sources of Food
Plants and animals are two prime sources of our food.
Plants
Foods like cereals, pulses, fruits, vegetables etc. are obtained from the plants.
Plant parts as food: Different types of plants store their food in different parts such as roots, leaves, stem etc. So the part, in which food is stored , is used by us as food. Let us know about this in some detail.
Roots as food: Some plants store food in their roots. Therefore roots of such plants are used as food. For example, carrot, beet, radish, sweet potato etc.
Stems as food: Some plants store food in their stems. Therefore stems of such plants are used as food. For example, turmeric, garlic, ginger, potato, onion etc.
Leaves as food: Some plants store food in their leaves. Therefore their leaves are used as food. For example, cabbage, lettuce, spinach etc.
Fruits as food: Some plants store food in their fruits. For example, apple, orange, mango etc.
Flowers as food: Flowers of some plants are also used as food. For example, jasmine, sunflower, dandelion etc.
Seeds as food: Some plants store their food in their seeds. So seeds of such plants are used as food. For example, wheat, rice, pulses, peas etc.
Animals
Food like meat, milk, eggs, honey etc. are obtained from animals.
Components of Food
The food, we eat, are composed of carbohydrates, fats, proteins, vitamins, minerals, water, and roughage. Carbohydrates: Carbohydrates provides energy to the body. Rice, wheat, potato, sugar, bread are rich sources of carbohydrates.
| Nutrient | Source | Function |
| Carbohydrates | Rice, wheat, potato, sugar, honey etc. | It gives energy to the body |
| Nutrient | Source | Function |
| Fats | Butter, ghee, cheese, oil egg yolk etc. | It also gives energy to the body |
| Nutrient | Source | Function | more...
| Deficiency diseases | Causes |
| Kwashiorkor Marasmus Night blindness Beri-beri Scurvey Rickets Goitre Anaemia | Lack of proteins Lack of proteins and carbohydrates Lack of vitamin A Lack of vitamin B1 Lack of vitamin C Lack of vitamin D and calcium Lack of iodine Lack of iron |
Anaemia is caused because of
(a) Lack of calcium
(b) Lack of phosphorus
(c) Lack of iron
(d) Lack of iodine
(e) None of these
Answer: (c)
Which one of the following food is a rich source of fat?
(a) Butter
(b) Ghee
(c) Mustard oil
(d) All of these
(e) None of these
Answer: (d)
Our food is composed of carbohydrates, fats', proteins, vitamins, water roughages minerals.
Carbohydrates and fats provide energy to our body.
Proteins are known as body building material.
A balance diet contains adequate amount of nutrients, roughage and water.
Kwashiorkor is caused by lack of proteins.
Night blindness is caused by lack of vitamin A.. 
Every single day tons of garbage is collected from houses, offices, schools and other organizations. Many things that we use in our day-to-day life can be reused, like you can write on both sides of paper and thus save many trees.
Instead of using disposable plastic bags, you can use cloth bags and save a lot of energy, and also contribute to reducing the amount of garbage. Recycling other materials and then reusing them is a good way to save a lot of landfill space. The process of recycling is a continuous loop that works when collected materials from garbage are turned into products. Then these products are bought and used again. By buying the products made from recycled materials, you will be supporting the industry that manufactures these products, and thus the loop of recycling goes on.
It's fun to buy new electronic gadgets, games, and devices. It's necessary to buy upgraded computers and phones every couple of years to keep up with advancing technology. It's cheaper to buy new devices than fix broken ones.
It's easier to use disposables such as plastic cups or razors or cameras. We must take appropriate actions to manage our production and waste now.
GARBAGE DISPOSAL
A large, low-lying area used to dispose garbage is known as a dump. A garbage dump is also used as landfill. Garbage collectors collect waste and then dispose it at garbage disposals. Garbage dumps have flies, cockroaches and mosquitoes, and later turn into breeding grounds for micro-organisms that may cause diseases. That is why these garbage dumps are usually located on the outskirts of a city. When garbage mixes with soil, it takes a longer time to decay. The soil becomes loose and a building cannot be constructed on such a land fill. Moreover, it takes 20 to 30 years for the soil to get ready for construction.
Types of Waste
There are two types of wastes that we generate depending on their source.
Biodegradable wastes are those that can be decayed easily. The process of decaying is known as composting. Useful garbage components are fruit and vegetable waste, plant and animal waste, tea leaves, coffee grounds and paper.
These useful components of garbage are converted into manure in the soil.
Non - Biodegradable wastes include polythene bags, plastics, glass, metals and aluminium foils. These take longer to decay. When these wastes more... 
About three fourth of Earth's surface is covered with water. Water is found inrivers, seas, oceans, soil, air, plants and animals. Man is dependent on plantsand animals which are in turn dependent on air, water and soil etc. All suchsubstances which are used by man for sustenance of life and his welfare arecalled resources and those that are found in nature are called natural resources.
Importance of water: Water is the most important substances required byus. Without water, we cannot live. Water is used in agriculture, industries, forwashing, bathing, drinking, cooking, cleaning and several other purposes. Ourbody has 70% water by weight while water melon is 99% water.
| Substance | % water |
| Egg | 73% |
| Fish | 67% |
| Tomato | 95% |
| Corn | 70% |
| Cucumber | 95% |
| Milk | 88% |
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Deficiency Diseases
The people, who do not get all the nutrients in required amount, suffer from deficiency diseases.
Look at the following pictures:
These people are suffering from nutrients deficiency diseases.
Look at the following table:
