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Asked: 2025-07-31T04:58:31+00:00 In:

Aanandi took two test tubes and marked them A and B. She put two spoonfuls of sugar solution in each of the test tubes. In test tube B, she added a spoonful of yeast. Then she attached two incompletely inflated balloons to the mouth of each test tube. She kept the set-up in a warm place, away from sunlight. (i) What do you predict will happen after 3–4 days? She observed that the balloon attached to test tube B was inflated. What can be a possible explanation for this? (a) Water evaporated in test tube B and filled the balloon with the water vapour. (b) The warm atmosphere expanded the air inside the test tube B, which inflated the balloon. (c) Yeast produced a gas inside the test tube B which inflated the balloon. (d) Sugar reacted with warm air, which produced gas, eventually inflating 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 attached the balloon to the test tube with lime water and shook it well. What do you think she wants to find out?

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Aanandi took two test tubes and marked them A and B. She put two spoonfuls of sugar solution in each of the test tubes. In test tube B, she added a spoonful of yeast. Then she attached two incompletely inflated balloons to the mouth of each test tube. She kept the set-up in a warm place, away from sunlight. (i) What do you predict will happen after 3–4 days? She observed that the balloon attached to test tube B was inflated. What can be a possible explanation for this? (a) Water evaporated in test tube B and filled the balloon with the water vapour. (b) The warm atmosphere expanded the air inside the test tube B, which inflated the balloon. (c) Yeast produced a gas inside the test tube B which inflated the balloon. (d) Sugar reacted with warm air, which produced gas, eventually inflating 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 attached the balloon to the test tube with lime water and shook it well. What do you think she wants to find out?

(i) After 3–4 days, the balloon on test tube B inflates. Yeast feeds on sugar and produces carbon dioxide gas. This gas collects in the balloon, causing it to expand. That’s why balloon B is inflated. Correct answer: (c) Yeast produced a gas inside test tube B which inflated the balloon.

Class 8 Science Grade 8 Chapter 2 The Invisible Living World: Beyond Our Naked Eye question answer

Class 8 NCERT Science Curiosity Chapter 2 The Invisible Living World: Beyond Our Naked Eye solutions

the invisible living world: beyond our naked eye question answer chapter 2the invisible living world: beyond our naked eye question answer class 8 pdf downloadtwo spoonfuls of sugar solution in each of the test tubesyeast produced a gas inside the test tube b which inflated the balloon
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    2 Answers

    1. (i) In test tube B, yeast breaks down the sugar and produces carbon dioxide as a result of fermentation. This gas rises and inflates the balloon. Since test tube A doesn’t contain yeast, no gas is formed and the balloon remains flat. This experiment clearly shows how living microorganisms like yeast can produce gases during metabolic activity, proving their role in fermentation.

      (ii) By attaching the balloon to the lime water test tube, Aanandi is checking whether the gas inside the balloon is carbon dioxide. If lime water turns milky, it proves the presence of CO₂, confirming that yeast produced it during fermentation. This is a classic test for carbon dioxide and helps link microbial activity with chemical changes that can be observed through simple experiments.

       

      For more NCERT Solutions for Class 8 Science Curiosity Chapter 2 The Invisible Living World: Beyond Our Naked Eye Extra Questions & Answer:

      https://www.tiwariacademy.com/ncert-solutions/class-8/science/

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    2. Aanandi checks if the balloon contains carbon dioxide by passing the gas through lime water. If it turns milky, it confirms CO₂ from yeast fermentation.

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