Friday, May 30, 2014

Rules for Rechecking and Revaluation for CBSE Class 12 Result

Picture
As per the new rule applicable from 2014 on wards the rechecking (verification of marks), getting photocopy of answer book and applying revaluation is now three step process. No one is allowed to jump steps or skip any step. All the steps have to be completed online. No offline application will be accepted.

First Step : Apply for rechecking (Verification of Marks i.e. re-totaling only) within a weeks from the date of declaration of result (this year 30.5.2014 to 05.06. 2014). If not satisfied with marks go to step two else exit process.

Second Step : Apply for Photocopy of answer sheet within 21 days (this year from 20.6. 2014 to 23.06.2014). If not satisfied go to step three else exit process.

Third Step : Apply for Revaluation of Marks (max 10 questions) within five weeks of declaration of result (this year 28.06.2014 to 04.7.2014).

NOTE : No one can apply for revaluation directly or can get photocopy ofanswer sheet without applying for verification of marks.

<<Click Here to Apply online>>

<Now understand the process for each step : Click Here

Thursday, May 29, 2014

Tissues in Plants and Animals biology notes for 9

1. Tissue is a group of cells having similar origin, structure& function. Study of tissues is called Histology

2. In unicellular organism (Amoeba) single cell performs all basic functions, whereas in multi-cellular organisms (Plants and Animals) shows division of labor as Plant tissue & Animal tissues.

3. Plant tissues are two types: Meristems & Permanent tissues.

4. Meristems: The Meristems are the tissues having the power of cell division. It is found on those region of the plant which grows.

5. Types of Meristems;

1. The Apical meristems – It is present at the growing tip of the stem and roots and increases the length.

2. The lateral meristems - present at the lateral side of stem anf root (cambium) and increases the girth.

3. The intercalary meristems - present at internodes or base of the leaves and increases the length between the nodes.

( Please refer to Fig. 6.2: location of meristems in plant body , NCERT Book Page- 69).

26. Permanent tissues: Two types such as Simple permanent tissues & Complex permanent tissues.

a) Simple permanent tissues: subdivided as

(i): Parenchyma: Tissues provide the support to plants.They are loosly packed and has large intracellular space.

- Parenchyma with chlorophyll which performs photosynthesis is called as chlorenchyma.

- The parenchyma with large air spaces to give buoyancy is called as aerenchyma .
    Parenchyma also stores food and water.

(ii) Collenchyma: Tissue provides mechanical support, thickened at the corners, have very little intercellular space. It allows easy bending of various parts of a plants without breaking

(iii) Sclerenchyma: Tissue makes the plant hard and stiff, thickened due to lignin and no inter cellular space.


Cells of this tissue are dead and commonly seen in the husk of coconut.

(iv) Guard cells and  Epidermal tissue: The tissue aids in protection and exchange of gases. Guard cells kidney shaped in dicots, dumb bell shaped in monocots to guard the stomata.

The epidermal tissues of roots aid in absorption of water and minerals.

The epidermal tissues in desert plants have a thick waxy coating of Cutin with waterproof quality.

The epidermal tissues form the several layer thick Cork or the Bark of the tree.

Epidermis :
Epidermis forms one cell thick outermost layer of various body organs of plants such as leaves, flowers, stems and roots. 

Epidermis is covered outside by cuticle. Cuticle is a water proof layer of waxy substance called as cutin which is  secreted by the epidermal cells. Cuticle is very thick in xerophytes. 

Cells of epidermis of leaves are not continuous at some places due to the presence of small pores called as stomata. Each stomata is guarded by a pair of bean shaped cells called as guard cells. These are the only epidermal cells which possess chloplasts, the rest being colorless.
Functions :
(i) The main function of epidermis is to protect the plant from desiccation and infection.

(ii) Cuticle of epidermis cuts the rate of transpiration and evaporation of water and prevents wilting.

(iii) Stomata in epidermis allow gaseous exchange to occur during photosynthesis respiration.

(iv) Stomata also helps in transpiration.

Cork or phellem : in older roots and stems, tissues at the periphery become cork cells or phellem cells. 

Cork is made up to dead cells with thick walls and do not have any intercellular spaces. The cell walls in cork deposit waxy substance called as suberin. 

The cells of cork become impermeable to water and gasses due to the deposition of suberin. The cork cells are without any protoplasm but are filled with resins or tannins.

Functions :

(i) Cork is protective in function. Cork cells prevent desiccation, infection and mechanical injury.

(ii) Imperviousness, lightness, toughness, compressibility and elasticity make the cork commercially valuable.

(iii) Cork is used for insulation, as shock absorber in linoleum. 

(iv) Cork is used in the making of a variety of sport goods such as cricket balls, table tennis, shuttle cocks, wooden paddles etc.
(Please refer to Fig. 6.3- 6.6, NCERT Book Page-70-73).

b) Complex permanent tissues: The complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function.

They are subdivided as;

Xylem: It consists of tracheids, vessels, xylem parenchyma and xylem fibers. The cells have thick walls,

Function - aids in conduction of water and minerals.

Phloem: It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers.

Function - Phloem transports food material to other parts of the plants.

(Please refer to Fig. 6.7, NCERT Book Page-73).

6. Animal tissues: Sub divided as epithelial tissue, connective tissue, muscular tissue and nervous tissue.

i. Epithelial tissue: It is a protective covering forming a continuous sheet. Simple epithelium is the one which is extremely thin in one layer, whereas stratified epithelium are arranged in pattern of layers.

Depending on shape and function they are classified as:

a) Squamous epithelium in the lining of mouth and esophagus.

b) Cuboidal epithelium in the lining of kidney tubules and salivary glands.

c) Columnar epithelium in the intestine &Columnar epithelium with cilia in the lining of respiratory tract.

d) Glandular epithelium in the Glands aids in a special function as gland cells, which can secrete at the epithelial surface.

Extra: 
Epithelial tissue lines the surface of a body and forms a protective covering. Epithelium cells are packed tightly together with little intercellular matrix. Epithelial tissue in the body is of two types.

(a) Simple epithelium: It consists of a single layer of cells where cells are in direct contact with the basement membrane. It is further sub-divided into the following types:

(i) Simple squamous epithelium: It consists of a single layer of flat cells with irregular boundaries. It is found in the walls of the blood vessels and in the lining of alveoli.

(ii) Simple cuboidal epithelium: It consists of a single layer of cube-like cells. It is present in regions where secretion and absorption of substances takes place such as the proximal convoluted tubule region of the nephron.

(iii) Simple columnar epithelium: It consists of a single layer of tall, slender cells with their nuclei present at the base of the cells. They may bear micro-villi on the free surfaces. Columnar epithelium forms the lining of the stomach and intestines, and is involved in the function of secretion and absorption.

(iv) Ciliated epithelium: It consists of columnar or cuboidal cells with cilia on their free surfaces. They are present in bronchioles and oviducts from where they direct mucus and eggs in specific directions.

(v) Glandular epithelium:It consists of columnar or cuboidal cells involved in the secretion of substances. Glands are of two types, unicellular glands (goblet cells of the alimentary canal) and multicellular glands (salivary glands). They can be classified as exocrine (ductless glands) and endocrine glands (duct glands) by the method through which they release enzymes.

(b) Compound epithelium: It consists of many layers of cells. It is involved mainly in the function of providing protection and has a limited role in secretion and absorption.

Examples of compound epithelium include the dry surface of the skin or moist inner lining of the buccal cavity, pharynx, pancreatic ducts, and the inner lining of ducts of salivary glands.(Please refer to Fig. 6.9, NCERT Book Page-75).

ii) Connective Tissue: Five Types, such as;

a) Blood: The Blood is a fluid connective tissue. Blood plasma has RBCs (Red Blood Cells) WBCs (White Blood Cells) and platelets. Blood plasma contains proteins, salts and hormones. Blood flows and transports gases, digested food, hormones and waste materials.

b) Bone: The bone is a connective tissue with hard matrix, composed of calcium and phosphorus. A bone is connected by another bone with another connective tissue called ligaments. A bone is connected by muscle with another connective tissue called tendon.

c) Cartilage: The cartilage is a connective tissue with solid matrix composed of proteins and sugars. It is commonly seen in nose, ear, trachea, and larynx.

d) Areolar Connective Tissue: It is found between the skin and muscles, around the blood vessels. It supports internal organs and aids in repair of tissues.

e)Adipose Connective Tissue: It is filled with fat globules for the storage of fat. It acts as insulator. (Please refer to Fig. 6.10, NCERT Book Page-76).

Muscular tissues: They have special contractile proteins responsible for movements. Three types, such as; Striated muscles/skeletal muscles/voluntary muscles :

They are cylindrical, un-branched and multinucleated.They have dark bands and light bands.

Unstriated muscles/smooth muscles/involuntary muscles:

They are commonly called as Smooth muscles, having no striations (dark bands/ light bands are absent). Commonly found alimentary canal, uterus, Iris of an Eye. They are spindle shaped. Involuntary in nature

Cardiac Muscles: They are commonly called as Heart muscles, cylindrical, branched and uni-nucleate. Involuntary in nature.(Please refer to Fig. 6.11, NCERT Book Page-77).

Nervous Tissue: The tissue responds to stimuli. The brain, spinal cord and nerves are composed of nervous tissue or neurons.

A neuron consists of Cell Body, cytoplasm, Nucleus, Dendrite, Axon, nerve ending. The neuron impulse allow us to move our muscles when we want to respond to stimuli.

Related Post: 9th Biology Tissues in Plants and Animals

CBSE Biology - CH6 - Tissues MCQs Solved
Download
CBSE 9th Biology - Chapter: 06 - Tissues Solved Questions
Download 
9th Biology Chapter Tissue Study Notes
Download 
Biology assignment Chapter: Tissues

Tuesday, May 27, 2014

8th Microorganisms Trend Setter Quick Revision

Microorganisms
Definition
The organisms which cannot be observed with the naked eye and can be seen only through a microscope are called microorganisms or microbes.

Food and water become unsafe for consumption due to the presence of harmful organisms, commonly referred to as germs. These germs are so small that they are invisible to the naked eye, but can often cause dangerous diseases.

Since these organisms can be seen only through a microscope, they are called microorganisms or microbes.

When the body is attacked by germs or pathogens, medicines called antibiotics are given. Antibiotics act against the bacteria within the body, without harming the person.
Microorganisms
Microorganisms are present in the air, water, food and even inside our bodies. While a majority of the microbes are harmless, some of them have the capability of causing dangerous diseases.




Microorganisms

Bacteria
Algae
Fungi
Protozoa
Viruses

Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases. 

Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.

Whenever we fall ill the doctor may give us some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is microorganisms. These medicines kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics. These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases. 

When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected from the disease causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.
Some microorganisms live inside our body. They help in certain functions of our bdoy systems. For example some bacteria in our gastrointestinal tract help in digestion. These type of organisms which reside in our body and are beneficial as well are called commensals. 

Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.

Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.

Disease— causing Microorganisms in Animals

Several microorganisms not only cause diseases in humans and plants, but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.

Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops. They can be controlled by the use of certain chemicals which kill the microbes.

Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. So, it is very important that we preserve food to prevent it from being spoilt.
Microorganisms spoil our food. Spoiled food emits bad smell and has a bad taste and changed colour.

Chemical Method: Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives. We add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in the jams and squashes to check their spoilage.

Our atmosphere has 78% nitrogen gas. Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins. Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Once nitrogen is converted into these usable compounds, it can be utilised by plants from the soil through their root system. Nitrogen is then used for the synthesis of plant proteins and other compounds. Animals feeding on plants get these proteins and other nitrogen compounds.
                                                                    
Classification of Microorganism
Microbes are mainly classified into five major groups :

Bacteria :

Bacteria (singular: bacterium) are single-called organisms that vary in shape and size. Some bacteria are  round or oval (coccus), others are rod-shaped (bacillus) or spiral. Some bacteria are autotrophic as they contain chlorophyll, but most of them are heterotrophic, showing saprophytic or parasitic mode of nutrition.

Algae :
Autotrophic organisms having undifferentiated plant bodies are called algae (singular: alga). Algae occur abundantly, like grass in aquatic habitats and are also called 'grass of water'.

Fungi :
Fungi (singular: fungus) are a group of plant-like organisms exhibiting heterophic (saprophytic or parasitic) nutrition. They are commonly found on bread, leather, cotton, paper, etc. Fungi grow vigorously in damp, warm, dark places, Yeast, moulds and mushrooms are forms of fungi. Yeast, moulds and mushrooms are forms of fungi. Yeast is commonly used for baking breaed, cakes, etc. The yeast ferments sugar present in the wheat and converts it to carbon dioxide and alcohol. The gas expands, so that the dough (kneaded atta) rises, giving shape and flavour to the preparation.

Protozoa :
Unicellular organisms that exhibit animal-like characteristics are called protozoa (singular: protozoan). The word protozoan literally means 'the first animal'. Most protozoa are heterotrophic.

Viruses :
A virus is a microorganism which exhibits characteristics of living as well as non-living things. Viruses exhibit a variety of shapes, having simple structure. Reproducing only inside a living organism, viruses can cause many diseases.

Useful Microorganisms
Humans have many microorganism in their in their digestive system that contribute to overall health. The microbial community in humans not only protects us from disease, but also provides necessary vitamins.
Bacteria also help in nitrogen fixation in production of antibiotics, etc. Algae are also useful in a number of industries. Therefore, even through microbes are responsible for food spoilage and many diseases, they can also be very helpful.

Yoghurt or curd (dahi) is the commonest example of beneficial use of microbes. Youghurt is a part of our daily diet and we eat it in various forms, with different flavour. This dahi is made from milk by the action of a bacterium called lactobacillus or latic acid bacteria. It converts the sugar in milk (lactose) to lactic acid, giving curd its sour taste. This process was initially used as a way to preserved milk.

Lactose  ------Lactobacillus----------> Lactic Acid (Yoghurt)

Curdling of milk takes places naturally, due to heat (specially in summer).

Curding of milk also takes place due to addition of any of the acid products such as sour curd, lemon juice and even tomato juice.
Microorganisms and we

Microorganisms play an important role in our lives. Some of them are beneficial in many ways whereas some others are harmful and cause diseases.

Commercial Use of Microorganisms

Microorganisms are used for the large scale production of alcohol, wine and acetic acid (vinegar). Yeast is used for commercial production of alcohol and wine. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice and crushed fruit juices, etc.

Medicinal Use of Microorganisms

Whenever we fall ill the doctor may give us some antibiotic tablets, capsules or injections such as of penicillin. The source of these medicines is microorganisms. These medicines kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics. These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases.

Vaccine

When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected from the disease causing microbes. This is how a vaccine works. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.

Increasing Soil Fertility
Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers.

Commensals:

Some microorganisms live inside our body. They help in certain functions of our bdoy systems. For example some bacteria in our gastrointestinal tract help in digestion. These type of organisms which reside in our body and are beneficial as well are called commensals.

Apart from them certain food like curd, contain beneficial bacteria.

Harmful Microorganisms

Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.

Disease— causing Microorganisms in Humans

Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried through an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.

There are some insects and animals which act as carriers of disease causing microbes. Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. Another example of a carrier is the female Anopheles mosquito, which carries the parasite of malaria. Female Aedes mosquito acts as carrier of dengue virus.

Some Common Human Diseases caused by Microorganisms

Disease— causing Microorganisms in Animals

Several microorganisms not only cause diseases in humans and plants, but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.

Disease— causing Microorganisms in Plants

Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops. They can be controlled by the use of certain chemicals which kill the microbes.

Food Poisoning

Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. So, it is very important that we preserve food to prevent it from being spoilt.

Food Preservation

Microorganisms spoil our food. Spoiled food emits bad smell and has a bad taste and changed colour.

Common methods to preserve food in our homes.

Chemical Method: Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives. We add salt or acid preservatives to pickles to prevent the attack of microbes. Sodium benzoate and sodium metabisulphite are common preservatives. These are also used in the jams and squashes to check their spoilage.

Preservation by Common Salt: Common salt has been used to preserve meat and fish for ages. Meat and fish are covered with dry salt to check the growth of bacteria. Salting is also used to preserve amla, raw mangoes, tamarind, etc.

Preservation by Sugar: Jams, jellies and squashes are preserved by sugar. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.

Preservation by Oil and Vinegar: Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment. Vegetables, fruits, fish and meat are often preserved by this method.

Heat and Cold Treatments: You must have observed your mother boiling milk before it is stored or used. Boiling kills many microorganisms.

Similarly, we keep our food in the refrigerator. Low temperature inhibits the growth of microbes. Pasteurized milk can be consumed without boiling as it is free from harmful microbes. The milk is heated to about 700C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur. It is called pasteurization.

Storage and Packing: These days dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.

Nitrogen Fixation: Rhizobium is involved in the fixation of nitrogen in leguminous plants (pulses). Sometimes nitrogen gets fixed through the action of lightning. But the amount of nitrogen in the atmosphere remains constant.

Nitrogen cycle

Our atmosphere has 78% nitrogen gas. Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins. Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Once nitrogen is converted into these usable compounds, it can be utilised by plants from the soil through their root system. Nitrogen is then used for the synthesis of plant proteins and other compounds. Animals feeding on plants get these proteins and other nitrogen compounds.

When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again. Certain other bacteria convert some part of them to nitrogen gas which goes back into the atmosphere. As a result, the percentage of nitrogen in the atmosphere remains more or less constant.

Steps Involved in Nitrogen Cycle

 The atomspheric nitrogen is fixed into nitrogen compounds like nitrates hy Rhizobium bacteria, bluegreen
algae, lightning or industrial method.

 The plants absorb nitrate compounds from the soil and water and convert them into plant proteins.

 The plants are eaten up by animals and thus plant protiens are used for making animal proteins.

 When the plants and animals die, the putrefying bacteria and fungi present in the soil decompose the
protiens of dead plants and animal into ammonia. This process is called ammonification.

 Ammonia thus formed is converted first into nitrites and then into nitrates by the action of Nitrosomonas
and Nitrobacter bacteria respectively. The process is called nitrification. These nitrates are again
absorbed by plants and the cycle is repreated.

 The soil contians denirifying bacteria called Pseudomonas which convert nitrate form of nitrogen into
free nitrogen which goes back into the atmosphere. The process is called denitrification.


VIII Microorganisms-Friend and Foe Solved Questions            Read     Download
Microorganisms-Friend and Foe
Microorganisms: Solved Questions
Microorganisms: Objective Questions:
Microorganisms- Notes       
Microorganisms- : MCQ 's
Microorganisms- : Test Paper-1
Microorganisms- : Test Paper -2

Wednesday, May 21, 2014

Improvement of Performance examination CBSE 2014 on July 16, 2014

CBSE Class 10 Compartment Exam on July 16, 2014
Improvement of Performance examination (Improvement or Compartment exam) will be taken on July 16, 2014 for CBSE class-10. The Improvement examination for class 10 will be conducted by CBSE for all candidates who scored E grade or scored D (or higher) but wish to improve the grades. All students who appeared in 2014 examination will get only and only ONE CHANCE to appear in improvement examination in the month of July 2014.
The number of attempts for Improvement of Performance for Class X has been reduced to one from five w.e.f. 2013 examination. The candidates shall appear for the Improvement of  Performance conducted by the Board in July/ School by July, as per the option exercised for the Main examination held in March the same year. However, for candidates who have appeared in the 2012 examination and placed in the category ‘IMPROVEMENT OF PERFORMANCE’ shall get upto five chances.
The first chance Improvement of Performance Test under Scheme-II will commence from 16th July, 2014. Regular candidates will route their requests through the Head of institution. The Heads of Institutions will ensure that the list of Improvement of Performance candidate reaches the respective regional offices without late fee upto 21.06.2014 or with late fee of Rs. 10/- per day upto 30.06.2014.
Improvement of Performance (IOP) under Scheme-I (school based examination) will be held by July and conducted by the schools.
Application forms for private / Improvement of Performance candidates for Delhi region will be issued to the candidates along with Mark Statements from their respective Schools/Examination Centers.

Apply for Rechecking or Verification of Grades in CBSE Class 10


If you are not satisfied with the grades you received in class 10 examination, you can apply for rechecking or verification of grades in class-10. There are two schemes for applying the same :

(1) Students who gave school based examination that is Scheme-I
(2) Students who gave board based examination that is Scheme-II

Scheme-I
Students who have appeared under Scheme-I would apply for verification of grades to the schools only and schools would verify their answer book and communicate the result.
Scheme-II
(1) For urgent verification, applications should be made online within 5 days from the date of declaration of result. The fee will be Rs.300/- per subject.
(2) Applications can also be made online within 21 days from the date of declaration of result, with fee of Rs.200/- per subject.
(3) The past practice of applying for verification of Grades at designated schools in case of Regional Office Delhi and respective Regional Offices (in other cases) has been done away with. The applications for verification of marks will now be received online only.
(4) For 2014 examination, the fee will be received only through E-challan. The candidates will have to deposit the same by visiting the identified Bank branch.
(5) For details, the candidates are advised to see the Notice on the CBSE website www.cbse.nic.in.
The result of verification of grades will be available on the Board’s website. The candidates whose result gets revised after verification of grades will be intimated through letter also by the Regional office concerned.

Tuesday, May 13, 2014

Minimum 25 percent Marks Required to pass SA-1 and SA-2 in class-IX

CBSE has issued a circular on 1st May 2014 stating that students who fail to get minimum 25% marks in SA-1 and SA-2 (class-IX) will have to reappear in exam within a month else they will be declared not successful. However, the overall qualifying percentage to go to next class will be 33% as earlier (in each subject out of 100).

It would be mandatory for a student to appear in both the summative assessments in both classes IX and X. In medical cases, the class-IX student have to appear in improvement exam within a month from the date of declaration of result.

To read the complete circular click Here.

Thursday, May 8, 2014

Synthetic Fibres and Plastics CBSE Class Eight Trend setter Study Notes

Picture8th synthetic materials
Þ       Synthetic materials are kinds of materials obtained from the synthesis of chemicals.
Þ     The chemicals used for synthetic materials are obtained from petroleum and natural gas(methane)
Þ     Petroleum and natural gas is compound of hydrogen and oxygen called hydrocarbon.
Þ     Monomers are simple chemical molecules of hydrocarbon.
Þ     When monomers join end to end form a long chain of monomers called polymers. The process of the formation of polymers is called polymerization.
Þ     Cellulose [beet root] is polymers of glucose while Hemoglobin is polymers of amino acid.
Þ     Fibres are thin thread like materials used to prepared cloths.
Þ     Fibres obtained on mixing natural and synthetic fiber are called semi synthetic fibre. e.g. rayon
Rayon
Þ     Rayon is synthetic fibres obtained from cellulose.
Þ     Rayon are of three types: Viscose Cupreammonium (cupro)  and acetate rayons.
Viscose Rayon
Þ     In industry cellulose dissolved in mixture of sodium hydroxide (NaOH) and CS2 (carbon disulphide) to get Viscous liquid [semi solid] called viscose.
Þ     Viscose is forced to spinnerets [an apparatus having small holes like shower] into an acid bath [through solution of acid like H2SO4] . Thus filaments of rayon are obtained which is spun into thread.
Cupro Rayon
Þ     Cupro Rayon are obtained on dissolving cellulose into solution of CuSO4 and NH4 . The dissolve solutions forced to spinnerets into an acid bath to get filaments of cuprammonium rayon are obtained which is spun into thread.
Acetate Rayon
Þ     Acetate Rayon is obtained on dissolving cellulose into solution of Acetate and H2SO4.
Rayon in our daily life
Þ     Rayon mixed with cotton or silk to make smooth and silky cloth in textile industry.
Þ     Rayon mixed with wool to make carpet.
Þ     Rayon are also used for making reinforced tyre, bangles and surgical dressing
Þ     The name Nylon derived from the New York [NY] and London[LON] as Nylon was first produce in both places at same time.
NYLON
Þ     Nylon (polyamides) was first prepared in 1935 chemically.
Þ     Nylon are prepared using cyclic hydrocarbon Benzene(C6H6)
Þ     Nylon has silk like texture and high tensile strength[Drawn into long thin straps]
Nylon in our daily life
Þ     Nylon is mainly used for making ropes, woman’s wear, fishing net, sari socks and tie
Polyster
Þ     Polyster is obtained from polymer of ethene. It has maximum stretchable strength.
Þ     Terylene, Dacron are kinds of Polyster used for dress, cloth and curtain.
Þ     Terylene mixed with cotton and wood to produce terycot and terry wool respectively.
Þ     Polysters are also used for making sail for sail boat and conveyor belts.
 Acrylics
Þ     Acrylics fibres are obtained on dissolving acetylene[C2H2] into suitable solvent like HCN and then forced to spinneret because acetylene decompose without melting.
 Acrylics in our daily life
Þ     They are light and soft like wool. The y are crimpy (wavy) and straight like Polyster thus appear to be bulky and look like wool.
Þ     They are resistant to weather as they are not easily acted upon by moisture.
Advantages of synthetic fibres
Þ     Having long lasting luster and do not turn yellow with age
Þ     Easy to clean and dry up quickly
Þ     Durable and do not shrink on washing
Þ     They are less expensive than cotton
Þ     They do not depend on plants or animal like cotton

Advantages of synthetic fibres
Þ     The get electrically charged in dry weather and cause skin irritation
Þ     The melt and form sticky beads  on heating. There is always a risk of getting burn in kitchen
Þ     They are hydrophilic as do not absorb sweat and moisture thus uncomfortable to wear.
Þ     They are non bio degradable and cause pollution.
Þ     They are good absorber of radiant heat and not fit in summer.
Good to more good
To make make wide spread use of synthetic material it is mixed with natural fibre .There are called blend fibre.
PLASTIC
Þ     Plastic : Any material which can be molded into any desirable shape on heating is called plastic

Þ     Petroleum product such that Ethane, propane, benzene ,toluene etc are used for manufacturing plastic.

         Plastic


Thermoplastic
Thermosetting


Thermosetting Plastic
Þ     Thermosetting plastics are kind of plastic which once moulded cannot moulded again by heating.
Þ     Thermosetting plastics are kind of plastic whose polymers form highly cross linked chain on heating.
Þ     Bakellite , melanin, Formaldehyde are some of the examples of Thermosetting Plastic
Thermoplastic Plastic
Þ     Thermoplastic are kind of plastic which can be moulded again and again by heating and easily reused.
Þ     PVS, Polysterine , nylon , polythine are some of the examples of Thermoplastic Plastic
Þ     Polymers of thermoplastic Plastic  have long chain without cross linked to each other.

Characteristics of plastic

Þ     Plastic has much less toughness as compared to metal
Þ     having light weight
Þ     It is not affected by acids and bases.
Þ     Plastic are non bio degradable as it is weather resistant
Þ     Plastic are bad conductor of heat and electricity
Þ     Plastic melts on heating

Some of the  common plastics are

a. Polythene
Þ     it is obtained from polymerization of ethene. it is non bio degradable .
Þ     it is a kind of thermosetting plastic
Þ     it is insoluble in any solvent
Þ     it is light weight
Þ     it is anti corrosion and insulator
Þ     it is used for making bag ,adhesive tap, electric wire cover and can

b. Polyvinyl chloride (PVC)
Þ     it is use for making sole of shoe
Þ     it is use for making covering of electric wire
Þ     it is use for making sanitary fittings
c. Polysterine
Þ     It is a polymer of polythene .
Þ     it is a kind of thermosetting plastic
Þ     it is highly transparent
Þ     it is use for making cups of hot drink , toy etc.
Þ     it is use for safe packaging of expensive items
Þ     it is use for making Styrofoam[themocole]
Þ     it is use as insulating material in refrigerator
d. Teflon
Þ     It is prepared by using tera- fluroethene.
Þ     Heat and chemical are not effective on Teflon
Þ     it is use for making non stick cooking were
Þ     it is use for making corrosive proof coating in industry
e. Bakelite
Þ     it is a kind of thermosetting plastic
Þ     it is use for making electrical switches and plug
Þ     it is use for making gear wheel
Þ      it is use for making table top
Þ     it is use for making comb, pen bodies and photograph records
f. Melanin
Þ     It is hard and highly polished polymers used for making unbreakable kitchen were.

Some of the common synthetic polymers not used in textiles industry


S. No.
Polymers
Use to make
1.
Polythene
Packaging material, carry bag, bottle
2.
Polypropene
Bottles, Crates
3.
PVC
Pipes, Insulation
4.
Teflon
Non stick Kitchen were
5.
Polystyrene
Foam, Thermocol
6.
Bakelite
Electrical insulation, Button]
7.
Lexan
Bulletproof glass
8.
Melanin
Crockery
9.
Perspex
Window of car, train and aircraft
10.
Vinyl rubber
Rubber, eraser
11.
Neoprene
Rubber
12.
Poly[styrene –butadiene]
Rubbers ,Bubble gums

Study in Depth Trend Setter

Synthetic Fibres and Plastics[CBSE 8th Science]               Read and Download 
III Synthetic fiber and Plastic                                                     Read and download
VIII Synthetic fiber and Plastic                                                 Read and download 
VIII Synthetic fiber and Plastic                                                 view video 
8th Synthetic fiber and Plastic [Solved Questions]           
Download File


Searches related to synthetic fibres
synthetic fibres examples
synthetic fibres list
names of synthetic fibres
synthetic fibres ppt
synthetic fibres and plastics
synthetic fibres and plastics class 8
properties of synthetic fibres
advantages of synthetic fibres