CBSE > Class 08 > Science | CBSE Board | Homework Help

Hi shreyash singh i know the answer , The plastics which are moulded once and can't be moulded again and again is called thermosettinf plastic .example- bakelite is also an example of thermosetting plastics and are used as insulators .

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How microorganisms harm us??

Posted by Mehak Palak 6 years, 7 months ago

CBSE > Class 08 > Science

3 answers

Mehak Palak 6 years, 6 months ago

Yogita great well played

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Yogita Ingle 6 years, 7 months ago

Harmful effects of microorganisms:

Bacteria: Causes various diseases such as typhoid, diarrhea, and cholera.
Fungi: Causes a large number of diseases in plants and in animals such as rust diseases in plants, fruit rot in apple, red rot in sugar cane and ring worm disease in human beings.
Algae: Algal boom in water (rapid growth of algae) causes poisonous effect after they die, which in turn results in the death of aquatic organisms.
Protozoa: Causes Amoebic dysentery, pyorrhoea and sleeping sickness etc.
Virus: Cause small fox, common cold, influenza, herpes, hepatitis, polio and rabies.

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Dharmendra Kushwaha 6 years, 7 months ago

Micro organism are harmful for us because they caused food poisoning and affect us my many diseases like chloera.

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What are all the base and metals materials

Posted by [email protected] Kannan @ Gmail. Com 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

A metal is a material when freshly prepared, polished and fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. And base material is a parent material to which painting and coating is applied.

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Chapter 4 science page number 48 table 4.4 answer

Posted by [email protected] Kannan @ Gmail. Com 6 years, 7 months ago

CBSE > Class 08 > Science

0 answers

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Name any two parts which are present in plant cell but not in animal cell.

Posted by Priyanka Jalan 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 7 months ago

Cell Membrane : A selectively permeable wall that surrounds and protects the contents of the cell.
Cytoplasm: The fluid which fills the cell and keeps the organelles in place.
Nucleus :The command center of the cell that controls the various processes of the cell. The nucleus also contains most of the cell's genetic material.
Mitochondria : The powerhouse of the cell. Here, food is converted into energy.
Ribosomes: Ribosomes generate proteins from amino acids.

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Write 10 lines on the usefulness of microorganisms in our lives.

Posted by Shejinah Christoe 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 7 months ago

Microorganisms are very useful to us. They help us in following ways:
(i) Microorganisms help us in food sector. They are used for curdling of milk, preparation of bread, cake, etc.
(ii) Microorganisms are used to produce alcohol at large scale.
(iii) They are also used to produce wine.
(iv) Yeast is used in bakeries.
(v) They are also used as preservatives for food items.
(vi) They are used to make different medicines, especially the antibiotics.
(vii) Microorganisms are used to prepare vaccines for various diseases.
(viii) They are useful for agriculture sector, as they enhance the fertility of soil by fixing nitrogen.
(ix) They work as natural cleaners, as they decompose the dead bodies of plants and animals.
(x) Microorganisms prepare manures by decomposing dead bodies of plants and animals.

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A brick is 32cm long 10cm wide and 10 cm thick.its weight 16n and is lying on the ground.find pressure exerted by the brick on the ground

Posted by Aasim Jamal 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Shivansh Prajapati 6 years, 7 months ago

Gravitational force is exerting it

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What is the formula of water

Posted by Naved Khan 6 years, 7 months ago

CBSE > Class 08 > Science

2 answers

Gaurav Seth 6 years, 7 months ago

Its chemical formula is H2O, meaning that its molecule contains one oxygen and two hydrogen atoms.

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Yogita Ingle 6 years, 7 months ago

Formula of water is H₂O.

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What is virtical image

Posted by Satyam Dubey 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

The image which cannot formed on the mirror is called virtual image.

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List and explain the various useses of microbes

Posted by Yuvraj Singh 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 7 months ago

1. Production of dairy products: Bacteria help in fermentation which helps in making different forms of dairy products from milk like curd, buttermilk, butter, cheese.
2. Bread Baking: A species of Streptococcus is added to the dough before making bread to bring about the required fermentation.
3. Alcoholic Drinks: Alcoholic drinks are prepared or manufactured by the process of fermentation.
4. Organic acids: Organic acids are commercially prepared using fungi.
5. Enzymes: Many microbes are used in the derivation of enzymes such as lipase, lactase, protease, peptidase to name a few.

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Define fossil fuels

Posted by Manishi Lohiya 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

The natural fule which is made from dead animals, plants or human in mīllíöñ of years is called fossil fuels. Eg :- coal, petroleum

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S chand solution

Posted by Subhajit Das 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

What I can't understand what are you asking

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How will the pressure vary if : a. Force is doubled while keeping the area constant? b. Force and area both are tripled? c. Area is doubled while keeping the force constant?

Posted by Naman Aggarwal 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 6 months ago

(a) If the area is doubled keeping the force constant, then pressure will be halved.
(b) If force is doubled keeping area constant, then pressure will also be doubled.

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What are charomozons and where they are found

Posted by Harsh Sharma 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

A part of cell in living bodies which decided the character,*** of the plants, animals and human beings is called chromosome. It is found in the nucleus of the cell.

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How is rayon chemically prepared in laboratory ?

Posted by Mukesh Prachi 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 6 months ago

Rayon is made from purified cellulose, harvested primarily from wood pulp, which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments which are chemically solidified, resulting in fibers of nearly pure cellulose. Sulfuric acid reacts with complex compound of copper and dissolves it. Thin blue fibers of rayon are formed. After some time, sulfuric acid reacts with the complex compound and washes out the copper salts from the fibers. Fibers become colorless.

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What is threshing?

Posted by Rammuana Ralte 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Saurav Kumar 6 years, 7 months ago

Threshing is the process of separating The Grain from the cut crop. threshing can be alone manually by making oxen or buffalo trample over the cut crop by using machine is called threashing

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Rana wants to buy shirts for summer should he buy cotton shirts or shirts made from synthetic materials ? Advise rana ,giving your reasons

Posted by Shivangi Jyotsana 6 years, 7 months ago

CBSE > Class 08 > Science

2 answers

Dharmendra Kushwaha 6 years, 7 months ago

He must buy cotton clothes because it absorb the sweat.

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Mukesh Prachi 6 years, 7 months ago

He should buy cotton clothes as cotton is hydrophilic i.e. it absorbs moisture (eg - sweat ) . They also allow the circulation of air. Therefore, clothes made of cotton are comfortable to wear as they allow sweat to evaporate.

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What is windowing?

Posted by Rammuana Ralte 6 years, 7 months ago

CBSE > Class 08 > Science

1 answers

Smriti Banerjee 6 years, 7 months ago

The process of separating of the stuff from its grains by the means of wind is known as windowing

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Some crops are harvested during in summer others are in winters

Posted by Aaditya Tiwari 6 years, 7 months ago

CBSE > Class 08 > Science

3 answers

Neha Mugal 6 years, 7 months ago

Crop have different season to grow so when we grow kharif crop

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Saurav Kumar 6 years, 7 months ago

Sorry crops

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Saurav Kumar 6 years, 7 months ago

Crops have different season to grow so when we grow kharif crop in different season they will distroyed all xrops

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what is sowong

Posted by Divyani Birhade 6 years, 7 months ago

CBSE > Class 08 > Science

2 answers

Dharmendra Kushwaha 6 years, 7 months ago

The process of planting the seeds in the field for their further growth in plant is called sowing.

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Yogita Ingle 6 years, 7 months ago

Scattering seeds on the Earth after soil is prepared for cultivation is termed as Sowing. It is the most important part of agriculture. Plants can’t grow without seeds. The type of seeds sown decides the quality of crops that would come out of it.

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Man made inorganic substances added to the soil to improve its fertility are called ___________.

Posted by Dattatraya Shinde 6 years, 7 months ago

CBSE > Class 08 > Science

3 answers

Mukesh Prachi 6 years, 7 months ago

Chemical fertilizers.

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Dharmendra Kushwaha 6 years, 7 months ago

Manure

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Nishchaya Meena 6 years, 7 months ago

Fertilizer

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Is cutting of wood to meet the need of factories good?

Posted by Sanket Madaan 6 years, 7 months ago

CBSE > Class 08 > Science

5 answers

Vrushab Algond 6 years, 7 months ago

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Dharmendra Kushwaha 6 years, 7 months ago

No, but wood's should be cut in the right proportion, without harming the environment

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Nishchaya Meena 6 years, 7 months ago

Yes it is good for factory but not for human

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Nishchaya Meena 6 years, 7 months ago

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Vivek Roy 6 years, 7 months ago

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Question answer of metal and non metals

Posted by Ranjeet Singh 6 years, 8 months ago

CBSE > Class 08 > Science

1 answers

Somya Kumari 6 years, 7 months ago

Which one

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Natural wool is attacked by moths whereas acrylic wool is not. Explain.

Posted by Miss Madhuri 6 years, 8 months ago

CBSE > Class 08 > Science

1 answers

Mukesh Prachi 6 years, 7 months ago

Because acrylic fibres has a property that it is not easily acted upon by moisture , chemicals or bacteria as it is man-made fibre i.e. it is prepared by chemicals.

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What are disadvantage of using combine machine?

Posted by Kanhaiyalal Mandavi 6 years, 8 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

I think I have not study about the disadvantage of combine machine.

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What is 2 D4

Posted by Kanhaiyalal Mandavi 6 years, 8 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

2,4-Dichlorophenoxyacetic acid is an organic compound with the chemical formula C₈H₆Cl₂O₃.

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Write and describe the various steps involved in preparation of soil

Posted by Rekha Devi 6 years, 8 months ago

CBSE > Class 08 > Science

1 answers

Dharmendra Kushwaha 6 years, 7 months ago

The various steps involved in soil preparation are:- ploughing and levelling. Ploughing:- in this process soil is ploughed,my mean lossen by various machine to airate the soil. & Levelling :- in this process plough soil is level by machine so that when irrigation is done then water will reach all the places in right amount.

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What is the difference between kharif and Rabi crops ?

Posted by Pragya Kashyap 6 years, 8 months ago

CBSE > Class 08 > Science

3 answers

Dharmendra Kushwaha 6 years, 7 months ago

Kharif:- those crops which are grown in the begging of South West monsoon in the month of June and July and Harvest at the end of October and November are called kharif crops. Eg. Rice,maize, soya bean. Rabi:- those crops which are grown the beginning of the winter season from October to November and harvest at the end of March and April are called rabi crops. E.g wheat,pea,gram

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Nishchaya Meena 6 years, 7 months ago

Rabi = rainy Kharif=winter

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Prashant Dilip Choudhary 6 years, 8 months ago

Rabi crops are the crops grown in rainy season and the kharif crops which are grown in winter season.

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