Chemistry-only: yeast fermentation produces aqueous ethanol
| English | 中文 | Pinyin |
|---|---|---|
| anaerobic conditions | 无氧条件 | wú yǎng tiáo jiàn |
| fermentation/fɜːmənˈteɪʃn/ | 发酵 | fā jiào |
What would explain this observation?
- Bubbles from a yeast/sugar mixture are evidence of gas production. They do not directly measure ethanol concentration or show that every molecule of sugar has fermented.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Yeast enzymes convert sugars in aqueous solution into ethanol and carbon dioxide in anaerobic conditions 无氧条件. A warm temperature, commonly around 30–40 °C in teaching examples, supports fermentation 发酵; low temperature slows activity and excessive heat damages the enzymes or kills yeast. Oxygen is excluded from the fermentation mixture while carbon dioxide can escape through an approved arrangement. The result is an aqueous solution of ethanol, not pure ethanol.
- fermentation: Anaerobic conversion of sugars by yeast to an aqueous ethanol solution and carbon dioxide; anaerobic conditions: Conditions excluding oxygen from the stated biological process.
Which conditions support the taught ethanol fermentation?
Maintain the school-selected temperature and sugar concentration, use the prepared yeast and record actual gas or mass observations over time. An airlock can let gas leave without freely admitting outside air; it is not a licence to tightly seal a gas-producing bottle. The rate can change as substrate runs low or ethanol inhibits yeast. Gas bubbling is qualitative unless quantity is measured, and a silent vessel is not by itself proof that no ethanol is present.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Maintain the school-selected temperature and sugar concentration, use the prepared yeast and record actual gas or mass observations over time. An airlock can let gas leave without freely admitting outside air; it is not a licence to tightly seal a gas-producing bottle. The rate can change as substrate runs low or ethanol inhibits yeast. Gas bubbling is qualitative unless quantity is measured, and a silent vessel is not by itself proof that no ethanol is present.
- For an actual supervised activity, compare matched labelled mixtures with a yeast-free control and the same volumes, sugar concentration and temperature. Retain raw observations and repeat comparisons. Analyse differences cautiously because gas leakage, dissolved carbon dioxide and contamination affect measurements. Any later separation of ethanol requires approved equipment and no flame near flammable vapour. Products of school fermentation must not be consumed.
Which two habits make the investigation or model in this case more defensible?
For an actual supervised activity, compare matched labelled mixtures with a yeast-free control and the same volumes, sugar concentration and temperature. Retain raw observations and repeat comparisons. Analyse differences cautiously because gas leakage, dissolved carbon dioxide and contamination affect measurements. Any later separation of ethanol requires approved equipment and no flame near flammable vapour. Products of school fermentation must not be consumed.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: three illustrative gas readings over the same interval are 18, 21 and 21 cm³. Mean volume=(18+21+21)/3=20 cm³. A yeast-free control gives 2 cm³, so the difference is 18 cm³ under this measurement method. This does not directly determine ethanol volume without an appropriate relation and complete gas accounting. The route differs from adding steam to ethene with an acid catalyst.
Repeat gas volumes over one fixed interval are 24, 27 and 27 cm³. Find their mean. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Repeat gas volumes over one fixed interval are 24, 27 and 27 cm³. Find their mean.
The result is 26 cm³. Known: three illustrative gas readings over the same interval are 18, 21 and 21 cm³. Mean volume=(18+21+21)/3=20 cm³. A yeast-free control gives 2 cm³, so the difference is 18 cm³ under this measurement method. This does not directly determine ethanol volume without an appropriate relation and complete gas accounting. The route differs from adding steam to ethene with an acid catalyst.
Check the conclusion and its limits
- Do not replace yeast with nickel, use the industrial hydration temperature for living yeast or describe fermentation as requiring an oxygen supply. A mass loss can include escaping gas but needs its own controls. No balanced fermentation equation is required by this acquired alcohol section, and the task is preparation for authentic supervised work rather than a replacement written examination.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Fermentation produces pure ethanol without water. This claim is false: Do not replace yeast with nickel, use the industrial hydration temperature for living yeast or describe fermentation as requiring an oxygen supply. A mass loss can include escaping gas but needs its own controls. No balanced fermentation equation is required by this acquired alcohol section, and the task is preparation for authentic supervised work rather than a replacement written examination.
Chemistry-only: yeast fermentation produces aqueous ethanol: Maintain the school-selected temperature and sugar concentration, use the prepared yeast and record actual gas or mass observations over time. An airlock can let gas leave without freely admitting outside air; it is not a licence to tightly seal a gas-producing bottle. The rate can change as substrate runs low or ethanol inhibits yeast. Gas bubbling is qualitative unless quantity is measured, and a silent vessel is not by itself proof that no ethanol is present.
Fermentation produces pure ethanol without water.
Do not replace yeast with nickel, use the industrial hydration temperature for living yeast or describe fermentation as requiring an oxygen supply. A mass loss can include escaping gas but needs its own controls. No balanced fermentation equation is required by this acquired alcohol section, and the task is preparation for authentic supervised work rather than a replacement written examination.
Anaerobic conversion of sugars by yeast to an aqueous ethanol solution and carbon dioxide: write the technical term.
fermentation means Anaerobic conversion of sugars by yeast to an aqueous ethanol solution and carbon dioxide.