Page 26 - Innovator's Science-8

a. Water evaporated in test tube B and filled the balloon with the water vapour.
b. The warm atmosphere expanded the air inside test tube B, which inflated the balloon.
c. Yeast produced a gas inside test tube B, which inflated the balloon.
d. Sugar reacted with warm air, which produced gas, eventually infla ng the balloon.
ii. She took another test tube, 1/4 filled with lime water. She removed the balloon from test tube B in
such a manner that the gas inside the balloon did not escape. She a ached the balloon to the test
tube with lime water and shook it well. What do you think she wants to find out?
Ans. c. Yeast produced a gas inside the test tube B, which inflated the balloon.
Explana on: The yeast used the sugar to produce energy and gave off a gas called carbon dioxide, which
made the balloon fill up. To check if the gas is really carbon dioxide, you can pass it through lime water. If
the lime water turns milky, it shows that carbon dioxide is present because it reacts with the lime water
to form a white substance called calcium carbonate.

3. A farmer was plan ng wheat crops in his field. He added nitrogen-rich fer liser to the soil to get a good
yield of crops. In the neighbouring field, another farmer was growing bean crops, but she preferred
not to add nitrogen fer liser to get healthy crops. Can you think of the reasons?

Ans. Beans have a special partnership with certain bacteria called Rhizobium, which live in small bumps on
their roots. These bacteria take nitrogen from the air and turn it into a form that plants can use. Because
of this, the soil already gets enough nitrogen naturally, so the farmer doesn't need to use extra nitrogen
fer liser.

4. Snehal dug two pits, A and B, in her garden. In pit A, she put fruit and vegetable peels and mixed them
with dried leaves. In pit B, she dumped the same kind of waste without mixing it with dried leaves. She
covered both the pits with soil and observed a er 3 weeks. What is she trying to test?
Ans. She is tes ng how well compos ng works. In Pit A, the mix of fruit and vegetable peels (which have
nitrogen) and dry leaves (which have carbon) creates the right balance for things to break down quickly.
Pit B doesn't have this balance, so it will rot more slowly and might smell bad. This shows that ny
organisms that cause decomposi on work best when both carbon-rich and nitrogen-rich materials are
present.

5. Iden fy the following micro-organisms:
i. I live in every kind of environment, and inside your gut.
ii. I make bread and cakes so and fluffy.
iii. I live in the roots of pulse crops and provide nutrients for their growth.
Ans. i. Bacteria ii. Yeast iii. Rhizobium

6. Devise an experiment to test that microorganisms need op mal temperature, air, and moisture for
their growth.
Ans. Set up 3 bread slices:
• Slice A: Warm, moist environment (near sink)
• Slice B: Dry environment (sealed container)
• Slice C: Cold environment (refrigerator)
A er 3 days, observe: Slice A will have maximum microbial (fungal) growth.

Conclusion: Microorganisms grow best when temperature, moisture, and air are op mal.
7. Take 2 slices of bread. Place one slice on a plate near the sink. Place the other slice in the refrigerator.
Compare a er three days. Note your observa ons. Give reasons for your observa ons.

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Science-8