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

Stars form inside relatively dense concentrations of interstellar gas and dust known as molecular clouds. These regions are extremely cold (temperature about 10 to 20K, just above absolute zero). At these temperatures, gases become molecular meaning that atoms bind together. CO and H₂ are the most common molecules in interstellar gas clouds. The deep cold also causes the gas to clump to high densities. When the density reaches a certain point, stars form.

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What role does dark coloured leaves of trees play in nature???

Posted by Aryan Raj 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 6 months ago

It takes a lot of energy to make chlorophyll. If the plants break down the chlorophyll and move it out of their leaves before the leaves fall, plants save energy. ... So the different colors in leaves are caused by changes in the pigments. When the weather changes, some plants break down all the green pigment. Tree species are adapted to their local sunlight regime by producing leaves with varying degrees of reflectiveness; i.e., dark colored leaves absorb the most energy from sunlight, while light colored leaves reflect excess sunlight.

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Why some tree shed their leaves in winter season?

Posted by Aryan Raj 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 4 months ago

Since deciduous plants lose their leaves to conserve water or to better survive winter weather conditions, they must regrow new foliage during the next suitable growing season; this uses resources which evergreens do not need to expend.

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How needle like leaves minimise water loss??

Posted by Aryan Raj 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 10 months ago

Xerophytic plants found in arid regions have needle like leaves covered with thick waxy layer called cuticle and sunken stomata to prevent loss of water from their surface. Their stems are modified to perform the function of photosynthesis.

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What is animal cell and plant cell

Posted by Neetu Pareek 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 5 months ago

Plant Cell	Animal Cell
Cell wall is present.	Cell wall is absent.
Plastids are found in plant cell.	Plastids are absent in animal cell.
A mature plant cell has a large central vacuole.	An animal cell has many small vacuoles.

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Ch 11 force

Posted by Tamanna Kharbanda 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Lawanya Chandrakar? 6 years, 5 months ago

Search on google

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How ro make cude

Posted by Vinayak Mulik 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 4 months ago

Milk is converted into curd or yogurt by the process of fermentation. Milk consists of globular proteins called casein. The curd forms because of the chemical reaction between the lactic acid bacteria and casein. During fermentation, the bacteria use enzymes to produce energy (ATP) from lactose. The byproduct of ATP production is lactic acid. Lactic acid acts on the globular proteins present in the milk and denatures them. This denaturation destroys the tertiary and quaternary structures of proteins and the globular proteins are converted into fibrous proteins thus giving a thick texture to the milk due to coagulation of the proteins.

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Explain harmful effect of microorganisms

Posted by Venkatesh Kane 6 years, 5 months ago

CBSE > Class 08 > Science

4 answers

Lalit Lalit 6 years, 5 months ago

Microorganisms are also very harmful to us. They cause a no.of disease in human as well as in other animals. Common cold, T.B.,chicken pox, polio, typhoid, malaria are some common human disease caused by microorganisms. Anthrax is a disease in animals caused by microbes.

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Vinayak Mulik 6 years, 5 months ago

Because of bacteria we gate feaver

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Yogita Ingle 6 years, 5 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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C Goyat 6 years, 5 months ago

They can damage our cloths They can spoil our food Many bacteria cause many disease and many more bad effects of the micro organisms

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How many cells are there in a human body

Posted by Yug Patel 6 years, 5 months ago

CBSE > Class 08 > Science

2 answers

Mohit Kumari 6 years, 5 months ago

There are 30 to 40 cell in hunan body

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Anirudh Singh 6 years, 5 months ago

Billions

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Give example to show that friction is both friend and a foe

Posted by Ćhánďäñ Singh Rajput 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 10 months ago

Frictional force plays an important role in our life. In some cases it is useful whereas if it is harmful and we need to reduce it.

Advantages of friction:

We are able to walk on ground because friction between the sole of our shoes and ground prevents us from slipping over the ground.
Friction between tyres of a car and the road enables a car to move forward on road without skidding.
The brakes of a car or a bicycle work by friction.
We are able to write and make drawings on paper because there is friction between the tip of pencil and paper.
We can hold a glass tumbler in our hands because of friction between the glass tumbler and our hands.
We are able to fix nails in a wall due to friction.

Disadvantages of friction:

Friction wears away the soles of our shoes.
The tyres of vehicles wear out gradually due to friction.
Friction wears out the rubbing machine parts.
Friction wears out the brake pads of vehicles gradually.
Friction wears out steps of staircases in buildings and foot over-bridges.
Friction produces heat which may damage machines.

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What is the power house of cell?

Posted by Lakshita Nagpal 6 years, 5 months ago

CBSE > Class 08 > Science

3 answers

Yogita Ingle 6 years, 5 months ago

Mitochondria is called power house of the cell .

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Sanjeev Naphriya 6 years, 5 months ago

Mitochondria

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Lakshita Nagpal 6 years, 5 months ago

Mitochondria

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What is friction? Define types of friction.

Posted by Madiha Fatima 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Yogita Ingle 6 years, 5 months ago

Friction is a force that opposes the relative motion between two surfaces of objects in contact.
There are three types of friction that exist between solid surfaces. They are static friction, sliding friction and rolling friction. Frictional force that comes into action before the start of the motion of an object is called static friction. Example: a box placed on the floor. When an object slides over another surface, the frictional force that comes into action is sliding friction. Example: a boy sliding on a slide. The frictional force exerted when an object rolls over a surface is called rolling friction. Example: rolling ball on the ground.

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Fourceis100nuten areais10whatispreature

Posted by Bhimjibhai.M Kariyavra 6 years, 5 months ago

CBSE > Class 08 > Science

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Which organelle is called suicide bag of cell

Posted by Gaurav Kumar 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Renuka Seiwal 6 years, 5 months ago

Lysosomes

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What is the reaction between O2&S ? Give the equation respectively.

Posted by Aditya Kumar 6 years, 5 months ago

CBSE > Class 08 > Science

1 answers

Meghna Thapar 5 years, 6 months ago

Combination Reaction: When two or more substances combine to form a single product, the reaction is known as a combination reaction. These reactions are also called addition reactions. For example: sulphur (S) combines with oxygen (O2) to form sulphur dioxide, SO2.

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Excessive use of fertilizers damage the soil quality and fertility and also create some kind of pollution. Justify this statement.

Posted by Naina Pathak 6 years, 5 months ago

CBSE > Class 08 > Science

5 answers

Lakshita Nagpal 6 years, 5 months ago

Fertilisers are made in factories so obviously they are made up of chemicals . They are relatively less rich in plants nutrients. They don't provide any humus to soil. So fertilizer make pollution in soil

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Sujith Kumar Vaithilingam 6 years, 5 months ago

Fertilizer it was made of chemicals so its make pollution

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??? ?? 6 years, 5 months ago

I don't know

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Sriya? Ghosh 6 years, 5 months ago

Excessive use of fertilizers damage the soil quality and fertility and also create soil pollution because: 1. They do not provide humus to the soil. 2. They add chemical to the soil.

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Swati Bokka 5 years, 8 months ago

I dont know but download ncert class8 book solution free in your mobile

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Tom wants to practice crop rotation in his field.Suggest a rabi crop and a kharif crop which will replenish in his field with nitrogen. Which crop replenish nitrogen and why?

Posted by Nandini Rajanal 6 years, 5 months ago

CBSE > Class 08 > Science

3 answers

Navneet Modi 6 years, 5 months ago

1st grow wheat and then leguminous plant

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Sujith Kumar Vaithilingam 6 years, 5 months ago

Leguminous plant fix the nitrogen in the field

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Swati Bokka 6 years, 5 months ago

Try in internet or ask your teacher

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Differnce between metal and non metal

Posted by Arihant Jain 6 years, 5 months ago

CBSE > Class 08 > Science

3 answers

Navneet Modi 6 years, 5 months ago

Metals are hard but non-metals are not hard. Metals are lustrous but non metals are not lustrous. Metals are good conductor of heat and electricity but non metal does not. Metals are malleable and ductile whereas non metals are brittle. Metals are sonorous but non metals are not.

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Lakshita Nagpal 6 years, 5 months ago

There is no defination of metal and non metals. It can only be understood by their properties

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Sujith Kumar Vaithilingam 6 years, 5 months ago

metal can can conduct heat and electric . non metal can not conduct heat and eletric.

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What is force WhAt changes can beproduced by force

Posted by Ramesh Goshikonda 6 years, 5 months ago

CBSE > Class 08 > Science

2 answers

Madiha Fatima 6 years, 5 months ago

Force is an external factor which when applied can change an object shape,size, position and direction. 1}it can change it shape,size, position and direction. 2}it may change speed of an object.

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Navneet Modi 6 years, 5 months ago

Force is an external agent that change or tends to change in the position of rest and motion of the body. Effect of force: *Force can move any stationary object. *Force can change the speed of a moving object. *Force can change the direction of the object. *Force can change the speed of the moving object.

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What is full from of PVC

Posted by Mantasha Ansari 6 years, 5 months ago

CBSE > Class 08 > Science

4 answers

Madiha Fatima 6 years, 5 months ago

Polyvinyl chloride

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Aditya Kumar 6 years, 5 months ago

Polivinyl Chloride (C2H3Cl)n

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Abhay Verma 6 years, 5 months ago

Polyvinyl chloride

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Yogita Ingle 6 years, 5 months ago

PVC -Poly Vinyl Chloride
It is polymerised Vinyl Chloride
Uses - CD's,Plumbing materials, Doors, furntitures etc.

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Draw the flow chart for steps involved in agricultural practices?

Posted by Pranav Kawde 6 years, 5 months ago

CBSE > Class 08 > Science

2 answers

Sia ? 6 years, 5 months ago

Following are the activities involved in agricultural practices for crop production

Preparation of soil by tilling and leveling.
Sowing of seeds into prepared soil.
Adding manure and fertilisers for replenishment and enrichment of soil and healthy growth of crops.
The supply of water to crops at appropriate interval called as irrigation.
Protecting from weeds by using weedicides.
Harvesting of crops by machines.
Proper storage of crops to protect them from harmful effects of pests and microorganisms.

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Lalit Lalit 6 years, 5 months ago

1.Prepation of soil 2.Sowing 3.Adding manure and fertiliser 4.Irrigation 5.Protecting from weed 6.Harvesting 7.Storage

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name a soft metal

Posted by Khyati Parmar 6 years, 5 months ago

CBSE > Class 08 > Science

2 answers

Navneet Modi 6 years, 5 months ago

Magnesium is also a soft metal.

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Yogita Ingle 6 years, 5 months ago

Sodium and Poatssium metals are the two metals which are soft and can be cut with a knife.

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What are the advantages of using manure in the field?

Posted by Naina Pathak 6 years, 5 months ago

CBSE > Class 08 > Science

3 answers

Sia ? 6 years, 5 months ago

Advantages of manure:

It enhances the water holding capacity of the soil.
It makes the soil porous due to which the exchange of gases becomes easy.
It increases the number of useful microbes in the soil.
It improves the texture of the soil.

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??? ?? 6 years, 5 months ago

Fsm

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Nanda Nanda 6 years, 5 months ago

It increase the number of microbes It improves the texture of soil It makes the soil porus due to which exchange of gaseous become easy It enhance water holding capacity

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Why sound does not travels in vacum

Posted by Ramya Si 6 years, 5 months ago

CBSE > Class 08 > Science