(a) Write the name given to bases that are highly soluble in water. Give an example.
(b) Why does bee using cause pain and irritation ? Rubbing of baking soda on the sting area gives relief. How ?

(a) Write the name given to bases that are highly soluble in water. Give an ezample. (b) Why does bee using cause pain and irritation ? Rubbing of baking soda on the stinf area gives relief. How ?

Why does Honey bee sting cause pain and irritation? Give a method to get relief from the discomfort

If a person is stung by a bee, it causes burning pain and irritation. Application of which of the following on the stung area can give relief from the pain?

Reshma is the student of class X in a city school. One day she was sitting in the school garden with her friends during the recess. There was a tall tree at the edge of the garden having a large honeycomb attached to it. Some students were playing cricket in te school playground. Suddenly the cricket ball hit the honeycomb due to which a large numbr of honey-bees started flying here and there. Reshma was stung on her face by a honey-bee. The sting was so painful that Reshma started crying. She was immediately rushed to the science laboratory. One of her classmates Shanta gave her vinegar solution to rub on the stung area to get relief from pain. Another clasmate Amarjit, howerver, asked Reshma to rub baking soda solution on the stung area of face. On rubbing baking soda solution, Reshma felt a lot of relief from pain. (a) What kind of liquid is injected into the skin when a honey-bee stings a person? (b) Why did rubbing baking soda solution on the stung area of skin give relief from pain? (c) What type of chemical reaction takes place when baking soda solution is rubbed on the honey-bee sting area? (d) Why do you think rubbing the honey-bee sting area with vinegar could not give relief from pain? (e) Name one plant whose stinging hair on leaves inject a similar liquid to that injected by honey-bee sting and can be treated by rubbing baking soda solution? (f) What vaues are displayed by Amarjit in this episode?

Answer the following questions based on Meselson and Stahl's experiment of E. coli : (a) Write the name of the chemical substance used as the only source of nitrogen in the experiment. (b) Why did they allow the synthesis of the light and the heavy DNA molecules in the organism ? (c ) How did they distinguish the heavy DNA molecules from the light DNA molecules? Explain. (d) Write the conclusion the scientists arrived at, at the end of the experiment.

Write the names given to the vertical columns and horizontal rows in the Modern Periodic Table. How does the metallic charcter of elements very on moving down a vertical column ? How does the size of atomic radius vary on moving left to right in a horizontal row ? Give reason in pupport of your answer in the above two cases.

(a) The recovery of silver nitrate solution involves displacement by copper metal. Write the equation of the reaction that takes place. Give the states of all the substances. (b) Under what soil conditions do you think a farmer would treat the soil in his fields with quicklime ? Why? (c) Name one sodium compound which is used for softening hard water and another which is used in fire extinguishers.