If possible in IGCSE format or just explain how to do it....??? Thanks!
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I just gave the IGCSE Edexcel exam with this as the last question and here is what i wrote:
1. Add yeast to a sugar solution and add pH indicator solution in a test tube
2. Place an oil layer on top of mixture (to make medium anaerobic)
3. Place a tube into mixture and attach a syringe to other end
4. Close the test tube with a rubber bung
5. As yeast respires anaerobically it produces Carbon dioxide (CO2) and ethanol
6. The carbon dioxide produced is collected in the syringe and amount is recorded every minute to find rate of reaction
7. The ethanol produced causes the mixture to turn more acidic as will be shown by the change in ph indicator colour
8. Record the amount of CO2 produced and colour of ph indicator solution every minute in a table and plot a graph.
CONTROL: [damn just remembered you need to write this according to CORMS, wish i remembered in exams ): ]
Take another yeast sample and set up apparatus with same conditions and amount of mixture but dont add the oil layer on top of the mixture in the test tube so yeast respires aerobically and there is no ethanol produced and so no pH change.
RESULTS:
Since the pH changes (gets more acidic) the rate of reaction decreases are rate of growth decreases. Eventually the rate of reaction stops as yeast are killed. Compare this to control where rate of reaction is fairly constant until the glucose runs out of course :)
Hope it helps, though i don't know if its all correct. I'm especially not sure if we have to add the indicator but well thats what i wrote :D
1. Add yeast to a sugar solution and add pH indicator solution in a test tube
2. Place an oil layer on top of mixture (to make medium anaerobic)
3. Place a tube into mixture and attach a syringe to other end
4. Close the test tube with a rubber bung
5. As yeast respires anaerobically it produces Carbon dioxide (CO2) and ethanol
6. The carbon dioxide produced is collected in the syringe and amount is recorded every minute to find rate of reaction
7. The ethanol produced causes the mixture to turn more acidic as will be shown by the change in ph indicator colour
8. Record the amount of CO2 produced and colour of ph indicator solution every minute in a table and plot a graph.
CONTROL: [damn just remembered you need to write this according to CORMS, wish i remembered in exams ): ]
Take another yeast sample and set up apparatus with same conditions and amount of mixture but dont add the oil layer on top of the mixture in the test tube so yeast respires aerobically and there is no ethanol produced and so no pH change.
RESULTS:
Since the pH changes (gets more acidic) the rate of reaction decreases are rate of growth decreases. Eventually the rate of reaction stops as yeast are killed. Compare this to control where rate of reaction is fairly constant until the glucose runs out of course :)
Hope it helps, though i don't know if its all correct. I'm especially not sure if we have to add the indicator but well thats what i wrote :D
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If it was me, I'd have 9 specimens. One would be neutral, one would be highly positive and the other would be as low as possible. I'd Triple the samples to show that it happens in every case and that there were no other outside factors.
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1-Read up a specific heat
2-Have a look at research articles that have grown yeast
3-Youd only need a few samples One control at a neutral pH, one at the research articles pH, only alot higher then the other two
2-Have a look at research articles that have grown yeast
3-Youd only need a few samples One control at a neutral pH, one at the research articles pH, only alot higher then the other two
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I would attempt to grow yeast at pH's ranging from 1 to 13. That way, you could create a curve of yeast growth based on pH.