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Sivaanshi   from Satya prakash, Jabalpur
Subject :Chemistry    Class : Class 7

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Sivaanshi   from Satya prakash, Jabalpur
Subject :Chemistry    Class : Class 7

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aditi   from dps, hyderabad
Subject :Chemistry    Class : Class 6

Match column I with column II and select the correct option from the given codes.

Column I Column II
(i) Ginning (A) Cleaning and
disentangling
the fibres
(ii) Combing (B) Brushing and
straightening of
fibres
(iii) Carding (C) Bolls
(iv) Seed pods (D) Cotton fibres
after being
separated from
seeds
(v) Lint (E) Separating
fibres from seeds

A(i) - (E); (ii) - (B); (iii) - (A); (iv) - (C); (v) - (D)
B(i) - (D); (ii) - (E); (iii) - (B); (iv) - (A); (v) - (C)
C(i) - (E); (ii) - (A); (iii) - (B); (iv) - (C); (v) - (D)
D(i) - (D); (ii) - (A); (iii) - (B); (iv) - (C); (v) - (E)


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Sayan Duary   from Vidyasagar Shishu Niketan, Paschim Medinipur
Subject :Chemistry    Class : Class 7

A change in which a new substance is formed with different properties is called a chemical change. In a chemical change heat is either evolved or absorbed most of the times. The original substances cannot be recovered easily. The change may be accompanied by evolution of light and sound also. Chemical reactions are examples of chemical change. When a matchstick is burnt, it changes forever and it cannot be lighted again.Hence, we say that matchstick has undergone a chemical change.
Which of the following is not involved in a chemical change?

A Change in colour
B Evolution of a gas
C Absorption or release of heat
D All of the above

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Raji   from , Trichy
Subject :Chemistry    Class : Class 10

Directions: In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
Assertion: Calcium sulphate hemihydrate, is called plaster of Paris.
Reason : Plaster of Paris is used for producing moulds for pottery and ceramics and casts of statues.

AIf both assertion and reason are true and reason is the correct explanation of assertion.
BIf both assertion and reason are true but reason is not the correct explanation of assertion.
CIf assertion is true but reason is false.
DIf both assertion and reason are false.


?how

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Krupa   from NES international, Mumbai
Subject :Chemistry    Class : Class 8

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Guest   from ,
Subject :Chemistry    Class : Class 7

Acids which dissociate completely in water to give a large number of hydrogen ions are called strong acids while the acids which do not dissociate completely in water are called weak acids. Acids can also be classified as mineral acids which are prepared from minerals and organic acids which are found in plants and animals. Several fruits like orange, lemon, grapes etc. contain acids.
Which of the following is not correctly matched?

A Citric acid—Lemon
B Lactic acid—Sour milk
C Oxalic acid—Tomatoes
D Acetic acid—Apples

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Guest   from zebar school, ahmedabad
Subject :Chemistry    Class : Class 7

In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as:
Assertion : With some samples of acids and bases turmeric paper turns red.
Reason : Such samples are acidic in nature.

A If both assertion and reason are true and reason is the correct explanation of assertion.
B If both assertion and reason are true but reason is not the correct explanation of assertion.
C If assertion is true but reason is false.
D If both assertion and reason are false.


How do some samples of acids and bases turn red?it’s only base

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Siddhartha Behera   from KENDRIYA VIDYALAYA NO.1 BALASORE, Baleswar
Subject :Chemistry    Class : Class 6

Those substances through which things can be seen, are called transparent. On the other hand there are some materials through which you are not able to see. These materials are called opaque. The materials through which objects can be seen, but not clearly, are known as translucent. We can therefore group materials as opaque, transparent and translucent. Shopkeepers usually prefer to keep eatables in transparent containers of glass or plastic so that buyers can easily see these items. While you cannot tell what is kept in a closed wooden box, a cardboard or a metal container.
Which statement is not true about opaque substances?

A Opaque substances absorb most of the light falling on them.
B We cannot see the objects through opaque substances.
C A mirror is an opaque substance.
D Opaque substances reflect most of the light falling on them.


The answer is showing wrong.

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Urveesh   from VIS, New Delhi
Subject :Chemistry    Class : Class 8

Certain metals have the capacity to displace some metals from their salt solutions. These reactions are known as metal displacement reactions. A metal placed higher in activity series can displace the metal occupying lower position from aqueous solution of its salt or a more reactive metal can displace less reactive metal from its salt solution.
Take aqueous solution of copper sulphate in one test tube and ferrous sulphate in another test tube. Dip an iron nail in copper sulphate and copper wire in ferrous sulphate solution. Mark the correct observation.

A Blue colour in first test tube changes to light green and green in the second test tube changes to blue.
B There is no reaction in both the test tubes.
C Blue colour in first test tube changes to light green and no change in second test tube.
D Blue colour remains as such and green colour in second test tube changes to blue.


why does not copper wire change if it is dipped in ferrous sulphate solution

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