Monitering Fermentation of Glucose

Valentina Salloum        

chemistry report

MONITERING FERMENTATION OF GLUCOSE

AIM

To investigate the fermentation of glucose and monitor the mass changes.

Hypothesis

• Monitoring the change in circumference of the balloon at regular intervals will show the conversion of the sugar to ethanol.
• The circumference of the balloon will increase dramatically at first, as there is a sufficient supply of oxygen in order to allow the yeast to respire aerobically producing a large amount of carbon dioxide.
• The circumference of the balloon will stop to increase dramatically and instead slowly increase as there will be an insufficient supply of oxygen, meaning the yeast will then respire anaerobically producing a little amount of carbon dioxide.
• The shift of the circumference increasing dramatically to barely increase means the reaction has shifted from respiring aerobically to anaerobically.
• There should be no change of mass if the experiment is done correctly, as no atoms can be created or destroyed, only rearranged.
• The limewater should turn milky as carbon dioxide should be produced. The loss of mass should equal to the mass of the carbon dioxide.

equipment

• 1x 50mL Erlenmeyer flask
• 5g teaspoon yeast
• 10g glucose
• 40mL warm water
• 1x thermometer
• balloon
• spatula
• 1x scale
• rubber tubing
• 5mL of limewater

Risk assessment

variables

method

1. Place 5g of yeast in Erlenmeyer flask
2. Add 10g of glucose then 40mL of warm water to the 50mL Erlenmeyer flask. Swirl the flask to ensure the contents are mixed
3. Cover the flask tightly with a balloon
4. Record the circumference of the balloon when it is in position
5. Record the circumference again after 5, 10, 15, 20, 25 and 30 minutes

results

Mass changes:

[pic 7]

discussion

QUESTIONS

1. What is the purpose of the glucose in the experiment?

The glucose is needed as it is what ferments, it allows the yeast to respire with it.

1. What happens to the circumference of the balloon as time passes?

The circumference of the balloon increases dramatically at the start, but after 15 minutes it began to increase at a slower rate.

1. What is causing these observations?

The circumference begins to increase dramatically as it is respiring aerobically due to an adequate supply of oxygen allowing for a large amount of carbon dioxide to be produced, however it slowed down after 15 minutes and only increased by little amounts, which is due to the lack of oxygen meaning it was respiring anaerobically and only producing a small amount of gas.

1. A student presented the results shown in the graph below. Discuss the pattern you observe and suggest the type(s) of respiration occurring.

From 0 to 1 hour, the circumference of the balloon increased at a fast rate which would be due to the adequate supply of oxygen allowing a large amount of carbon dioxide to be produced, meaning it was respiring aerobically. However from 1 hour onwards the rate of the circumference increasing slowed down which would have been caused by the insufficient supply of oxygen which would mean only a small amount of carbon dioxide produced indicating that it was respiring anaerobically.