Question

life processes activity 6.2 How is the air inside the bell jar in fig. (a), different from the air outside it?

Answer 1

Answer:

Leaf of plant kept without potassium hydroxide turn blue with iodine solution.The plant with potassium hydroxide does not turn blue.

Explanation:

Potassium hydroxide is a highly reactive compound. It reacts with the carbon dioxide of the bell and forms its carbonate.

KOH + CO2 —————>K2CO3 + H2O

As a result, no carbon dioxide is available for the plant. In the absence of Carbon dioxide plant is unable to do photosynthesize and form starch. So, iodine does not turn the leaf blue.

The plant kept in bell without Potassium hydroxide can do photosynthesis and form starch. So, iodine solution here turns the leaf blue.

Answer 2

Let us take a bell jar and suspend an electric bell in it and connect it to a battery outside the jar When the circuit is closed (switch is on) we can hear the bell ringing as the jar contains air and sound travels through this air.

Explanation:

• We then remove the air from the jar with the help of a vacuum pump connected to the bell jar now as we close the circuit we can hardly hear any sound even though the hammer of the bell is seen striking the gong.
• So we can conclude that sound cannot propagate in the absence of the material medium.
• The experiment is done by placing an electrical bell in the bell jar.
• As the air is pumped out of the sealed bell jar, the sound from the bell jar fades.
• However the sound is not audible to our ears because of the vacuum inside the jar. This demonstrates that the sound wave cannot travel through vacuum.
• An alarm clock is placed in a special jar. As the air inside the jar is pumped out, the alarm bell becomes quieter and quieter. When the air has been completely emptied from the jar the bell can't be heard at all, although it is still ringing.