fermentation (1 Viewer)

[rooeys2]

ok im so pist now cuz i cant find my fermentation of ethanol prac >=[ and i need some help please

i tried to write one again, and i looked at the textbook and it said you measure the change in mass over like a week, but the one we did in class was only in a double period, so does it really matter?
i wrote up my procedure again for the prac, please feel free to correct me

equipments:
-yeast (how many grams was it...book said 1g but im not sure)
-thermometer
-water
-water bath (the metal bath that looks like a pot, lol wats the proper name)
-conical flask 100mL
-cork with bent glass tube
-small beaker
-limewater
-glucose solution 20mL
-electronic balance
-measuring cylinder
-rubber tube
-retort stand, clamps, bosshead
-bunsen burner, tripod

method:
1. weigh out 1g of dry yeast with the electronic balance in a small beaker and add this in the conical flask
2. measure 20ml of glucose solution with the measuring cylinder and add this in the conical flask
3. connect the cork with bent glass tube on the conical flask and join the rubber tube to it, weigh this on the electronic balance to record initial mass
4. add about 200ml of water to the water bath and insert the thermometer into the water bath
5. i GIVE UP
why is my prac so long?! i was goin to write 'set up the equipment', but i dono, im so lost now, WHERES MY PRAC

anyone's so kind plz help me out *pulls hair*

 

[namburger]

Experiment – Fermentation

Aim To ferment a glucose solution and to monitor the mass changes involved

Equipment
- 100mL Conical Flask with Rubber Stopper and Bent Glass Tube
- 500mL beaker
- 50mL Measuring cylinder
- Large Test Tube
- 20mL Glucose Solution 10%(w/v)
- 1.0g Dried Yeast
- Limewater
- Thermometer
- Electronic Balance
- Cold Water
- Hot Water
- Test Tube Rack
- Rubber Stopper
- Rubber Tubing

Safety
Wear safety glasses throughout this experiment
Be careful when handling hot water

Method
1. Place 1.0g of dried yeast and 20mL of glucose solution inside the sidearm flask and weigh it on the electronic balance.
2. Use the thermometer, hot water and cold water to fill the 500mL beaker, about half-full. Note: the temperature of the water should be about 35oC.
3. Setup the equipment as shown in the diagram.
4. Monitor the equipment for one hour. Make sure the temperature of the water inside the beaker remains constant.
5. Disassemble the equipment and reweigh the sidearm flask and its contents. Note the colour of the limewater.

Results

Characteristics of Limewater
Observations
Before Fermentation: Initially clear and colourless
After Fermentation: Turned milky white and cloudy

Weight of Flask
Mass (grams)
Before Fermentation: 195.6
After Fermentation :195.4

Discussion

Independent Variable:
Amount of glucose solution
Amount of dried yeast
Time for fermentation

Dependent Variable:
Change in limewater colour
Change in weight of flask

Controlled Variable:
Temperature of water

As fermentation occurs, a gas is being produced by the reaction which is evident by the bubbling in the limewater. We are able to identify this gas as carbon dioxide due to limewater’s (Ca(OH)2) tendency to change from a clear and colourless solution to a milky white and cloudy solution in the presence of carbon dioxide.
Ca(OH)2 (aq) + CO2 (g) �* CaCO3 (s) + H2O (l)
The fermentation of glucose itself was catalysed within the presence of yeast, which was working under optimum conditions at 35oC. As a result if caused the glucose to be converted into ethanol and carbon dioxide.
C6H12O6 (aq) --Yeast--> 2.CH3CH2OH (aq) + 2.CO2 (g) + heat
The experiment was not very reliable as only one trial was conducted. Through the use of repetition the reliability of this experiment could be improved. However with the given timeframe this would not have been feasible.
The experiment was rather valid, despite not measuring the mass of the glucose and yeast directly. However since the mass change after fermentation was so minute it was possible that there could have been an inaccuracy of measurement. The validity of the experiment could be further improved by, extending the time for fermentation, hence allowing for a greater change in mass. Another way to improve the validity of the experiment could have been to measure the mass of the test tube to see if it had increased in mass equal to the loss of mass in the flask.

Conclusion

The mass of the glucose solution when undergoing fermentation will drop. This is because the glucose molecule is being split into ethanol and carbon dioxide gas, where the gas escapes the mixture into the surroundings, which in this case was into the limewater solution.

Courtesy of Steven Ngo =D

 

[uberturtle]

In industry fermentation may be carried out over long periods of time but in school laboratories we only do it for a period or so. cause our low grade yeast dies off after a while anyway due to the acidity.

whats the rubber tube for? :S
i only remember using the bent glass tube and placing it in a test tube with limewater in it, i dont remember connecting a rubber tube to it :S
maybe you did it different from my class iuno

5. boil the water bath until it is around 36-37 degrees celcius
6. place conical flask in the water bath and place galss tube into limewater solution.
7. let reaction take place for however long you want, maintaining the temperature at 36-37 degrees. During this time you must observe the limewater to see if the reaction is taking place (it should turn milky since CO2 is released)
8.remove conical flask and dry the outside
9. reweigh all the things again
9. calculate stuff zzz i forgot D:

 

[rooeys2]

thankkkkkss youse rock =)
but i sorta did my prac the same way as uberturtle pedo did
nam dont u have to describe HOW you got the hot water, and how come you used cold water? wats that for? and didnt you use a water bath, becuase i thought the beaker is easier to lose heat =/

IM STILL LOST =(

 

[namburger]

Steven Ngo wrote this prac. His method is kinda short and dodge haha.
This is from Leondios's class
Since in his equipment there is no bunsen burner, im thinking the hot and cold water is used to maintain the temp at 35 degrees.

Im not gona write his method in the exam. Ill write the one with a water bath and bunsen burner which is what Eastment's class did.
I suggest you change the method but i reckon all the other headings of the prac are alrite i.e. discussion

 

[rooeys2]

ok thanks yea i did the one with water bath and bunsen burner, i just said you have to heat it for a bit if the temp drops below 35 degrees

 

[uberturtle]

I think the cold water beaker is used to compare to the hot water beaker?
to measure the difference in yield? :S i'm not sure.

beaker... thats wroooooong.
fermentation has to be under anaerobic conditions + ethanol is volatile so any gravimetric measurements you made should be wrong

 

[undalay]

steven stole all my pracs gg.

 

[namburger]

steven stole all my pracs gg.

Rofl

 

[kooltrainer]

oned

 

[zazzy1234]

hectic perfect ferminatation experiment