Sunday, January 27, 2013


1. An old man and a scientist were talking about a deserted house. The old man was sure that it was haunted by ghosts, but the scientist discarded the view saying no one had ever seen a ghost. The old man was annoyed and challenged the scientist about existence of atoms, sub-atomic particles which also could not be seen.
· Name the three sub-atomic particles and their discoverers.
· Whose viewpoint do you support and why?
2. An activity was conducted in a classroom where students held placards with symbols and valency of the elements separately. Each student held two placards, one with the symbol in the right hand and other with the valency in the left hand.
· Which placards will be required for formation of sodium chloride ( both symbol
as well as valency).
· Which qualities are required in the student to perform such a group activity?
3. Two class IX students, Kaveri and Nalin, were asked to take 5.3 g of sodium carbonate and 6g of ethanoic acid to make 2.2g of carbon dioxide, 0.9g of water and 8.2 g of sodium ethanoate. Kaveri followed the instructions but Nalin took the chemicals without measuring their amounts.
· Whose activity do you think will be in agreement with the law of ``Conservation of mass''?
· State the law of ``Conservation of mass''.
· Whose method do you like and why?
4. Raghu and Vansh were performing an activity related to conservation of mass in chemistry lab of their school. They mixed a solution of barium chloride and sodium sulphate. Raghu suggested that as they already knew the amount of both compounds taken by them, they need not to measure the amount of final solution. On the contrary, Vansh insisted to measure the amount of final solution, which had barium sulphate and sodium chloride. Atomic mass of ions: Ba 2+ = 137 units, Cl - = 35.5
        units, Na + = 23 units, S2 - = 32units, O2 - = 16 units.
Determine the molecular mass of
a) Barium chloride
b) Barium sulphate
c) Sodium sulphate
d) Sodium chloride
· Comment on Vansh's Insistence to complete the activity.
5. Beenu was quite confused when she was taught mole concept in the class. Same evening she went to the market with her mother to buy fruits. Her mother bought one dozen apples, one dozen oranges and one dozen (one dozen=12 piece.) banana, fruits-seller gave the fruit according to their mass in kg. on observing their respective masses, beenu understood the mole concept instantly.
· Can you explain what made Beenu understand mole-concept?
· What is Avogadro's constant.
6. Ayush is not keeping happy and is unable to focus on studies. His friend Udghosh observed the same and inquired Ayush. Udghosh was told by Ayush that his younger brother is not keeping good health. His neck has swollen. The fact that Ayush's family was not including iodized salt in their diet came to light. Udghosh immediately suggested certain measures and insisted that Ayush's brother must
see the doctor without any delay.
· What values are displayed by Udghosh?
· What can be possibly the disease from which Ayush's brother is suffering?
         · Name the element whose isotope is used in the treatment for the disease.

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