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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Chemistry    Class : Class 6

Case Study : Substances expand when we heat them and contract on cooling. Solids, liquids and gases, all the three states of matter expands on heating. Gases expands the most while solid expands the least. Liquid mercury also expands on heating and this process is used in thermometer.
Which of the following materials does not expand on heating?

A Iron
B Wood
C Glass
D Ghee


I attempted B but it is showing that I attempted A.

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Daanish Nagpuria   from The HDFC School , Gurgaon
Subject :Chemistry    Class : Class 6

Case Study : Most of the physical changes are temporary and reversible. However, there are few exceptions like sharpening a pencil. Evaporation and boiling both are examples of physical changes and both the processes are reversible also.
Which of the given changes is not reversible while burning of a candle?

A Melting of solid wax.
B Liquid wax changes into vapours.
C Wax vapour burns into flame.
D All of these.


I attempted C but it is showing that I attempted D.

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Aaradhay Awasthi   from DPS Vasant Kunj, Delhi
Subject :Chemistry    Class : Class 6

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swar shastri   from DPS Gandhinagar , Ahmedabad
Subject :Chemistry    Class : Class 9

The molecules of a gas are free to move about in any direction. Because of large intermolecular spaces, the gases are easily compressible. The kinetic energy of the molecules of gases is maximum and they move about randomly at a high speed. The randomly moving high speed molecules hit against the sides of containing vessel. The pressure exerted by any gas is due to the force exerted by its molecules on the sides of containing vessel.
The force per unit area exerted by the particles of the gas on the walls of container is called

A atmospheric pressure
B pressure of the gas
C kinetic energy of the gas
D density of the gas.


Ans 1:

swar shastri from DPS Gandhinagar , Ahmedabad
Class : Class 9
20

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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

Ans 1:

RITVIK AGRAWAL from CMRNPS , Bangalore
Class : Class 6

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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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