CBSE > Class 07 > Science | CBSE Board | Homework Help

Aeration brings water and air in close contact in order to remove dissolved gases (such as carbon dioxide) and oxidizes dissolved metals such as iron, hydrogen sulfide, and volatile organic chemicals (VOCs). Aeration is often the first major process at the treatment plant.

There are three methods for aeration in activated sludge process.

Diffused air aeration.
Mechanical aeration.
Combine aerator.

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What is the difference between physical and chemical change

Posted by Tridev Senapati 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Khushi Lodhiya 6 years, 10 months ago

Physical change is reversible change where chemical change is irreversible change

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Ritika Artani 6 years, 10 months ago

Physical change 1. It is mostly reversible change. Eg- Melting of wax, Melting of ice

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Name any two decomposer

Posted by Om Dubey Dubey 6 years, 10 months ago

CBSE > Class 07 > Science

3 answers

Shami Rukhsar Ali 6 years, 10 months ago

Bacteria fungi

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Saanvi Tripathi 6 years, 10 months ago

Bacteria and mushrooms .

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Gaurav Seth 6 years, 10 months ago

Decomposers are the organisms which convert dead and decaying matter into organic matter of the soil. They break down the complex organic compounds present in dead animals and plants, which are then used by other members of the ecosystem.
*Decomposers like bacteria and fungi are known as saprobes. Bacteria and Fungi are considered to be decomposers as they clean up the environment by performing the process of decomposition. Decomposers like bacteria and fungi are known as saprobes.

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How much fresh water is available in earth ?

Posted by Amrut Dani 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Yogita Ingle 6 years, 10 months ago

About 71% of the earth’s surface is filled with water. But out of this, a very small amount is available for the human use.
2% fresh water available in earth but only 1% available for human use .

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Contaminants means

Posted by Bhagwat Hajare 6 years, 10 months ago

CBSE > Class 07 > Science

3 answers

Khushi Lodhiya 6 years, 10 months ago

Impurities present in water is called contaminants

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Shami Rukhsar Ali 6 years, 10 months ago

Inpurites in water like can,plastic bags,packets etc

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Payal 16 6 years, 10 months ago

Adulterator

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The SI unit of electric current

Posted by Subha Lakshmi 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Prabhat Kumar 6 years, 10 months ago

Ampere

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Amrut Dani 6 years, 10 months ago

ampere (A)

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What is sexcual reproduction and assxcual reproduction

Posted by Kammy Kaur 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Aditi Dixit 6 years, 10 months ago

One more i am giving... Sexual reproduction:- Sexcual reproduction rise a new young one by involving seeds and spores..and two parents are involved... Asexual reproduction:- Asexual reproduction rise a new young one with out the seeds and spores... And only one parent is involved...

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Amrut Dani 6 years, 10 months ago

Asexual reproduction : when single parent is involved in this process is asexual reproduction Sexual reproduction : when two parents are involed in this process it is called sexual reproduction

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Acid is change blue litmus_____________

Posted by Parvez Iqbal 6 years, 10 months ago

CBSE > Class 07 > Science

3 answers

Khushi Lodhiya 6 years, 10 months ago

Avid change blue litmus into red

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Prabhat Kumar 6 years, 10 months ago

Acid changes blue litmus into red.

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Saanvi Tripathi 6 years, 10 months ago

To red

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What is understorey

Posted by Shami Rukhsar Ali 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Aditi Dixit 6 years, 10 months ago

The layer of vegetation in a forest which is just below the canopy is called understorey..The understorey layer consists of smaller trees and trees saplings. The understorey layer of forest has comparatively much less sunlight...

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Payal 16 6 years, 10 months ago

A layer of vegetation beneath theain canopy of a forest

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What is the function. Of pulmonary artery and pulmonary vein in celectriction in human beings

Posted by Shivam Yadav 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Khushi Lodhiya 6 years, 10 months ago

It carry oxygen to different part of the body to heart &pulmonary carry carbondioxide from heart to different part of the body

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explain heating and magnetic effect of electric current with two examples

Posted by Raviraj Ghatage 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Aryan Prajapati 6 years, 10 months ago

Example are electric heater ,toaster Electric motor,fan

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Aditi Dixit 5 years, 9 months ago

Heating effect of electric current:- When electric current is passed through a conductor,some amount of electrical energy is converted in to heat energy. This is called heating effect of electric current.. Magnetic effect of electric current:- The term magnetic effect of current means that an electic current flowing in a wire produces a magnetic field around it... Sorry i don't know examples??

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what is meant by vascular tissue

Posted by Basuki Nath Singh 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Khushi Lodhiya 6 years, 10 months ago

It transport water and minerals ,absorb by roots

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What is called sludg

Posted by Tanmay Thomare 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Yogita Ingle 6 years, 10 months ago

The solid waste which settles at the bottom of the sedimentation tank is called sludge. The sludge is further treated by the process of aeration. This helps in growth of bacteria which eat away the human waste.

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explain Newton's disc

Posted by Raviraj Ghatage 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Khushi Lodhiya 6 years, 10 months ago

It contain 7parts of different colours which rotate gives white colour

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Amrut Dani 6 years, 10 months ago

since the Newton was the first make this it is called newtons disc

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What are xylem and phloem

Posted by Suresh Ganesh Prabhakaran 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Aditi Dixit 6 years, 10 months ago

Xylem :- The vascular tissue for the transport of water and nutrients in the plant is called xylem.. Phloem:- The food has be transported to all parts of the plants. This is done by vascular tissue called the phloem..

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What is SI unit?

Posted by Ritesh Yadav 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Tridev Senapati 6 years, 10 months ago

Standard unit....for e.g. metre

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Sadhana Sinha 6 years, 10 months ago

Standard unit

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What is wastewater

Posted by Raviraj Ghatage 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Aryan Prajapati 6 years, 10 months ago

When water is of no use and dirty we call it as wastewater

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How is rainbow formed

Posted by Shivam Singh 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Nishant Chaudhary 6 years, 10 months ago

In atmosphere the water droplets present that's why the reflection make and when the light of sun pass through these tiny water droplets they form rainbow

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How is eaonbow formed

Posted by Shivam Singh 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Meghna Thapar 5 years, 11 months ago

Rainbow is formed by dispersion of sunlight by tiny water droplets, present in the atmosphere. A rainbow is always formed in a direction opposite to that of the Sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.

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Why do you think that a chemical equation should balnce

Posted by Raj Samrat 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Meghna Thapar 5 years, 11 months ago

Chemical equations need to be balanced in order to satisfy the law of conservation of matter, which states that in a closed system matter is neither created nor destroyed.

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Summary of lesson 12

Posted by Avni Sharma 6 years, 10 months ago

CBSE > Class 07 > Science

0 answers

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Which part of digestive is involved in (a) Absorption of food (b) chewing of food (c) killing of bacteria (d) complete digestion of food (e) formation of faeses

Posted by Usha Deka 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Raj Samrat 6 years, 10 months ago

Formation of faeses

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What is stomata? Give two function of stomata

Posted by Verma Family 6 years, 10 months ago

CBSE > Class 07 > Science

2 answers

Khushi Lodhiya 6 years, 10 months ago

Stomata are the tiny pores surrounded by two guard cells

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Aryan Prajapati 6 years, 10 months ago

Stomata are tiny small pores present under leaves Functions exchange of gases in plants and helps in transpiration

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What is the chemical name of nitrate carbon

Posted by Garima Jaiswal 6 years, 10 months ago

CBSE > Class 07 > Science

1 answers

Meghna Thapar 5 years, 6 months ago

Nitrates are inorganic compounds made up of nitrogen and oxygen, NO3 (one nitrogen and three oxygen molecules). These compounds combine with other elements like sodium and potassium to make sodium nitrate or potassium nitrate.

Salts of nitric acid containing the group NO3- are called nitrate salts. Nitrate anions form salts with a wide range of elements in the periodic table. Examples of nitrates are ammonium nitrate (NH4NO3), sodium nitrate (NaNO3) and potassium nitrate (KNO3).

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