What do you observe after an hour ? Class 7
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What do you observe after an hour ? Class 7
What do you observe after an hour ? Class 7
Answer:
- The balloon inflates (swells up).
What can you conclude from this experiment?
- Yeast ferments sugar to produce carbon dioxide.
- The carbon dioxide gas inflates the balloon.
- When passed through lime water, the gas turns it milky, confirming it is carbon dioxide gas.
- This demonstrates that yeast causes a chemical change by breaking down sugar into new substances (carbon dioxide and other substance).
Identify all the changes occurring in the experiment and state which of them are physical and chemical changes.
| Step/Change | Type of Change | Explanation |
| Mixing sugar and water | Physical | No new substance formed; just a solution |
| Adding yeast to sugar solution | Physical (initially) | Just mixing; no new substance yet |
| Fermentation (yeast acts on sugar) | Chemical | New substances (carbon dioxide gas and other substance) is formed |
| Balloon inflating | Physical | Gas fills the balloon; no new substance formed |
| Passing carbon dioxide gas into lime water | Chemical | Carbon dioxide gas reacts with lime water to form insoluble substance (milky appearance) |