The Effect of Sugar Level on the Rate of Fermentation
The aim of this experiment is to find out whether the rate of
Fermentation is affected by the amount of sugar.
The equipment used is:
Â· Bunsen burner.
Â· Heat proof mat.
Â· Boiling tube.
Â· Delivery tube
Â· Water bath.
Â· Water flask.
Â· Stop watch.
Â· Yeast and Sugar.
Â· Digital weighing scale.
Â· Measuring cylinder.
Â· Test tube.
Â· Fill the water bath with water (not to the maximum).
Â· Fill the boiling tube with 10ml of water.
Â· Add 2g of yeast to the water and add sugar (1g, 2g, â€¦up to 5g).
Â· Put the Boiling tube into the water bath.
Â· Connect a delivery tube onto the boiling tube.
Â· Fill a test tube with a reasonable amount of water.
Â· Place the other end of the delivery tube into the test tube.
Â· Put the Bunsen burner on a heatproof mat.
Â· Place the water bath on the tripod and heat the water.
Â· Measure the temperature of the water (in the water bath) with the
thermometer. Stop the heating until it reaches 40Â°.
Â· Start the stop watch after the first bubble has appeared in the test
Â· Count the bubbles that appear in 1 minute then stop the stopwatch.
Â· Repeat the process but this time adding another gram of sugar until
Â· Then repeat the whole experiment again starting from 1g to ensure
the reliability of the results obtained.
Planning a fair test:
The factor chosen is the concentration of sugar solution
, so the other
factors are to be kept constant as control factors in order to make
this investigation fair. Here are the control conditions and other
procedures I must take. I should make sure that the test tubes are
thoroughly washed each time I repeat the experiment. This is because
remains of yeast or sugar could affect the results. I must use the
stopwatch rather than counting or guessing the time so that I do not
count the wrong number of bubbles. The yeast which I will use is to
come from the same source so they are at the same age otherwise,
bubbles might not appear as frequently as they should because of
difference in freshness of yeast. The level of water in the boiling
tube must always be exactly 10 ml otherwise; the concentration of the
yeast and sugar mixture might increase of decrease depending on the
amount of water added which will affect the number of bubbles. The
mixture should be gently shaken to blend the solution and the culture
together, as the culture tends to settle at the bottom over a certain
time. The whole experiment should be repeated again to obtain a more
accurate result and to calculate an average result. A thermometer must
be always used when heating the mixture and is to be made sure that
the temperature of the mixture in the boiling tube is at 40Â° so that
there is enough energy and the enzymes do not denature and slow down
the experiment. I must make sure that the Fermentation
lock is not
damaged so that it allows the escape of CO2 gas without the entry of
oxygen, which could oxidize the ethanol produced. All these procedures
must be taken into account in order to produce precise and reliable
evidence. The variables that can be changed are the amount of yeast,
amount of sugar and the temperature of each reaction. The only
variable that will change is the amount of sugar as it goes up by 1
gram each time. The temperature shall remain at 40Â° degrees and the
amount of yeast will always be 2g.
The equipments used in this experiment are quite safe. However, care
is needed in handling glassware, as they are easily broken. I will use
a heat proof mat so that the table doesn't catch fire.
Theoretically, the higher the amount of sugar, the faster Fermentation
should happen. The GCSE chemistry revision guide states that yeast
contains an enzyme which converts sugar into Carbon dioxide and
alcohol (ethanol). So, if we add more sugar, the yeast will have more
to work on. In a brief summary, the more sugar added, the quicker
Fermentation should happen.
I have tried to use the equipment with precision and skill as much as
possible in order to obtain and record reliable data. Here are my
(First Time) (Second Time)
[IMAGE][IMAGE][IMAGE]Amount of Sugar (g): Bubbles per Minute: Bubbles
per Minute: Average:
[IMAGE]1 20 Bubbles 23 Bubbles 21.5
2 19 Bubbles 19 Bubbles 19
3 6 Bubbles 20 Bubbles 13
4 10 Bubbles 9 Bubbles 14.5
5 7 Bubbles 5 Bubbles 6
I have constructed a bar graph and a line graph to represent the data.
The information can now be interpreted in 2 different ways.
(Line of best fit)
The results obtained are sufficient for the conclusion to be drawn
about this topic. As they are plotted on to the graph, they are more
or less on the same lines of accuracy - there is no anomalous result
As the grams of sugar went up, the number of bubbles went down. This
shows that the more sugar you add, the slower the rate of
This conclusion has opposed my prediction. I predicted that the more
sugar you add, the more bubbles that appear (the higher the rate of
Fermentation). The reason that the rate of Fermentation is decreased
as more sugar is added is because if there is too much sugar in the
mixture, some of the enzymes in the yeast (zymase) gradually die. Jams
sugar levels are very high which kills any enzymes that allow
reactions to occur. This is why Jam takes a very long time to mould
The results obtained were fairly reliable. No anomalous results were
obtained confirming precision. I think that the evidence which I have
collected is sufficient enough to support a firm conclusion. I think
that further work could have been useful to propose improvements i.e.
repeat the experiment 3 times rather than twice. I could have also
used a Digital Thermometer in order to obtain more accurate
measurements. The procedure which I took was reasonably suitable. This
is because the results obtained were seemingly precise and consistent.
For the matters concerning the accuracy of the experiment's layout,
there are several inaccuracies - which some can be improved; some
-Carbon dioxide gas is soluble in water; some is not included in the
- Intoxication by ethanol, some yeast cells may be intoxicated and
-The tubes have to be lifted out of the water bath to take
measurements - the environmental temperature could have affected the
rate of Fermentation every time measurements are taken.
If a further investigation is to be carried out, the temperature of
the environment and the types of the sugar used are the interesting
fields to head forth towards.
Background information about Fermentation:
Fermentation is a biological process involving the breakdown of sugars
by bacteria and yeast using a method of respiration without oxygen
(anaerobic respiration). It involves a culture of yeast and a solution
of sugar, producing ethanol and carbon dioxide with the aid of the
enzymes. This process can be slowed down by denaturing of the enzymes
at a certain temperature. As products, ethanol and carbon dioxide are
produced, in form of liquid and gas respectively. The reaction follows
[IMAGE]Glucose solution + Yeast (zymase) Carbon dioxide + Ethanol +
[IMAGE]C6 H12 O6 (aq) 2C2 H5 OH (aq) + 2CO2 (g)
Fermentation is also used for bread-making. The reaction that occurs
in bread making is exactly the same as that in brewing. When bread is
put in the oven, the yeast is killed and the reaction stops.