Experiment 13: Preparation of alcohol Flashcards
What is the first step to this experiment?
Boil a beaker of water for 5 minutes
What is done with the boiled water during this experiment?
The water is added to a conical flask and then glucose is added to create a glucose solution
Why is the water boiled during this experiment?
It is boiled to eliminate any oxygen from the water to ensure anaerobic respiration will take place
What is added to the glucose solution once it has cooled?
Dried yeast is added
What is the solution covered with after the yeast has been added?
Oil
Why is the solution covered with oil?
To prevent oxygen from re-entering the solution
Why is an airlock used during this experiment?
To prevent microorganisms and oxygen from entering the solution as well as letting carbon dioxide escape
What is used in the airlock to detect the presence of carbon dioxide?
Limewater
How does limewater detect the presence of carbon dioxide?
Limewater turns milky in the presence of carbon dioxide but remains clear otherwise
After the apparatus, including the airlock, has been set up where is it placed?
The apparatus is placed in a water bath at 30 degrees Celsius
Why is the apparatus placed in the water bath at 30 degrees Celsius?
As this is an ideal temperature for the mesophilic yeast to grow and maximise their rate of respiration
What will be seen in the limewater if fermentation is occurring?
Bubbles will be seen in the milky white limewater
What control should be used for this experiment?
The same experiment should be carried out without the use of yeast cells (no bubbles should form, limewater remains clear)
When is it said that fermentation has ceased?
When bubbles have ceased to be produced
