2014 results here
2014 photos:
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| Reaction Flask - Initial |
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| Control Flask - Initial |
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| Reaction Flask - Final |
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| Control Flask - Final |
Photos of the experiment (2012) below.
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| Set up of the reaction vessel and limewater airlock system |
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| Set up of the control and limewater airlock system |
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| Reaction vessel vs control flask after 6 hours |
Summary Feedback
A) The hypothesis needs to be a full statement (ie similar to a ‘full sentence’). In addition we are NOT testing whether the glucoses loses mass, we are testing whether the reaction mixture loses mass.
Similarly your discussion answers need to be full sentences.
B) While we do a risk assessment for each experiment, a written risk assessment is not needed on this summary.
C) Don’t try and explain complex set-up details in the method. Refer to the diagram, ie “Set up the apparatus as shown in the diagram.
D) In Science mass and weight mean different things. Weight is a force (measured in newtons), mass is a quantity of matter (measured in grams or kilograms). We should always say ‘…record the mass of…’ whenever we are recording data in grams. Perhaps rather than ‘weighing’ we should be ‘measuring the mass’.
E) When explaining why there was mass loss in the flask it is not enough to say that carbon dioxide was produced – you MUST say that the mass decreased because the carbon dioxide gas ESCAPED the ‘open’ flask (via the airlock).
F) The control does allow us to calculate the mass lost to evaporation but you are justifying these steps. So think about WHY we needed to know the mass lost to evaporation (in order to validly determine the...).
G) The yeast is needed to ferment BECAUSE it produces enzymes (biological catalysts) that catalyse the fermentation reaction. These enzymes operate at maximum efficiency at 36oC (too much above that they are ‘denatured’ and no longer work).
H) The airlock had two roles – one to keep air (oxygen) out of the reaction flask (but you need to say why). The second minor role was to keep air (atmospheric CO2) out of the limewater flask (but you need to say why).
I) It is expected that in HSC Chemistry you have a thorough understanding of intermolecular bonding. You need to know that alkanols have a hydroxyl (OH) functional group. You need to know that the extreme polarity of the O-H bond means that strong intermolecular bonds called hydrogen bonds can form between alkanol molecules. In addition, because water can also form intermolecular hydrogen bonds there are strong hydrogen bonds formed between water and alkanols when they mix. Because these bonds are strong lots of energy is needed to separate these molecules…
J) Straight lines in diagrams need to be drawn with a ruler. You need to use correct scientific diagrams for glassware (not fancy 3D pics). You should label what is in the flask and test tubes. You need to draw diagrams, not use photos (though you can use photos for the results if you wish). You MUST show the correct level of liquids in relation to the airlock tubes and where the tubes come from and go to. The whole point of the diagram is to explain the airlock system so if this is incorrect it means your method is incomplete. The limewater flask was stoppered.
K) Conclusions need to address the aim and hypothesis. Remember, experiments can NEVER prove a hypothesis but they can SUPPORT a hypothesis.
L) Methods need to be in chronological, numbered point-form.
M) All diagrams involving alkenes (addition, dehydration etc) should use full structural diagrams (with states). Remember that dehydration needs concentrated sulfuric acid.
N) When you get to 15% ethanol the yeast dies. Once the yeast dies…
O) You must include observations of the reaction vessel and control.
P) There must have been an error o the spread sheet for one group - BUT - if the mass loss of the sample was 7.15g and there was a mass loss of 0.6g in the control. The real CO2 mass loss in the sample would be... The other group did not use exactly 90ml of water - check the results table!
Q) When calculating the wt% ethanol - assume the mixture mass is the mass of the WATER we used at the start of the experiment - check the spread sheet if not sure.
R) Summaries must be typed!
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