CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class IX > 2009 > Science > Science By : Mr M. p. Keshri

CBSE CLASS I X

Matter In Our Sourroundings (Solved)

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Q. 91. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why ?


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Q. 92. Show that the three states of matter are interchangeable.


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Q. 93. Three substances A, B and C melts at 0ºC, 56ºC and -140ºC, respectively and their boiling points are 100ºC, 158ºC and 15ºC. What will be the physical states of A, B and C at room temperature.


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Q. 94. When ice at -5ºC is heated, temperature increases to 0ºC and remains constant till the ice is changed to water. On further heating temperature again rises. Why ?


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Q. 95. Define latent heat of fusion and latent heat of vaporization.


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Q. 96. Explain the relation between boiling point of a liquid and intermolecular force of attraction between the particles of the liquid.


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Q. 97.Change the following temperature to Kelvin scale :

40ºC, 78ºC, 227ºC.


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Q. 98.  At 80ºC, liquid benzene is in equilibrium with its vapours. Why particles of benzene vapours are more energetic than particles of liquid benzene?


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Q. 99. Why ice at 273 K is less energetic than water at the same temperature ?


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Q. 100. Define sublimation and give examples.


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Q. 101. Choose the substances from the following that shows the phenomenon of sublimation :

Ice, salt, ghee, coconut oil, ammonium chloride, naphthalene, camphor.


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Q. 102. Choose the substances which shows the process of sublimation :

Solid water, solid oxygen, solid carbon dioxide, solid alcohol.


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Q. 103. In winter, ghee freezes at room temperature and mustered oil does not. Which of these has a higher melting point and lower intermolecular force ?


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Q. 104. Explain the effect of temperature and pressure on a gas.


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Q. 105. Differentiate between a gas and a vapour.


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Q.106. Define pressure.


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Q. 107. What is atmospheric pressure ?


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Q. 108. Ice at 273 K is more effective than water at 273 K. Explain.


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Q. 109. Explain the effect of pressure on the boiling point of liquid.


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Q. 110. Convert the following temperature to Celsius scale.

(a) 300 K

(b) 573 K


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Q. 111. What is the physical state of water at ?

  (a) 250ºC 

(b) 100ºC


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Q. 112. For any substance, why does the temperature remain constant during the change of state ?


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Q. 113. Suggest a method to liquefy atmospheric gases.

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Q. 114. Liquids are converted both by boiling and evaporation. What is the basic difference between the two process ?


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Q. 115. Define the term evaporation.


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Q. 116. State and explain the factors affecting evaporation.


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Q. 117. Evaporation cause cooling of a liquid system. Why ?


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Q. 118. Wet clothes kept in shade dry slowly in a rainy day even in summer. Why ?


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Q.119. How does human body maintain its temperature during summer ?


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Q. 120. How will you show that evaporation increases with the increase in surface area ?


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Q. 121. How will you show that evaporation increases with the increase in wind speed ?


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Q. 122. Give reason for the following :

Solid carbon dioxide (dry ice) is kept under high pressure.


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Q. 123. Why after rain in summer, heat becomes unbearable ?


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Q. 124. How does the water kept in an earthen pot (matka or kalsi) become cool during summer ?


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Q. 125. Why are we able to sip hot tea or milk faster from a saucer rather than a cup ?


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Q. 126. What type of clothes should we wear in summer ? 


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Q. 127. What is a plasma ?


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Q. 128. Does fluorescent tube contains plasma ?


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Q. 129. Why do the sun or the stars glow ?


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Q. 130. Do all particles or plasma glow in a similar way ?


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Q. 131. Differentiate between a gas and plasma.


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Q. 132. Convert the following temperature to the Celsius scale :

 (a) 300 K

(b) 573 K


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Q. 133. Convert the following temperatures to Kelvin scale :

(a) 25ºC

(b)  373ºC


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Q. 134. Give reasons for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.

(b) We can get the smell of perfume sitting several metres away.


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Q. 135. Arrange the following substances in increasing order of forces of attraction between the particles – water, sugar, oxygen.


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Q. 136. What is the physical state of water at :

( a)  25ºC

(b)   0ºC

(c)   100ºC


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Q. 137. Give two reasons to justify :

(a) Water at room temperature is liquid.

(b) An iron almirah is a solid at room temperature.


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Q. 138. What produces more severe burns, boiling water or steam ?


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Paper By Mr. M. P. Keshari [ For Further Enquiry 09434150289]