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Chemistry and Our Earth

Assignment 2: How Physical Properties of Substances Determine Their Uses

Scenario:

As a junior quality control officer for a chocolate manufacturer you have been asked to investigate a complaint from a newsagents Birmingham. Customers have complained that some chocolate bars have an unusual taste and texture and is discoloured. You must test various chocolates, one of the manufacturing ingredients and some samples of the shelves they were stored on in the shop.

If you wish to make a comment about this assignment or reply to the postings please use the comment box at the bottom of this page.

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1 How Physical Properties of Substances Determine Their Uses
  • Assignment Resources 3 resources

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    1 Worksheet U1 2.1
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    2 Worksheet U1 2.2
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    3 Viscosity Measurement Template
  • Supporting Resources 4 resources

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    1 Chocolate and Structure
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    2 The Melting Point of Stearic Acid
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    3 The Thermal Properties of Water
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    4 Measuring Melting Points
  • Technician's Notes 1 resource

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    1 Assignment U1 2 Technicians Notes

6 Responses to “How Physical Properties of Substances Determine Their Uses”

  1. r.wilkes@greatbarr.bham.sch.uk says:

    We appear to be having issues with the melting point of chocolate. The temperature (starting from 50/60 degrees) appears to just steadily decrease (about 1-2 degrees every 30 seconds), with the rate slowing as the temperature aproaches the temperature of the room . The pupils have then found it really difficult to suggest what the melting point actually is. Does anyone have any advice?

    Also, the viscosity of the syrup experiment is causing issues as alot of staff have concerns over how messy it is. Can anyone suggest other less sticky materials or is anyone using any alternative method?

  2. sandy says:

    Sorry to hear about your concerns but here a few suggestions. The exact melting point of the chocolate is not really an issue as long as students get an idea of the melting point. Instead of doing a heating curve try the following:

    Prepare boiling tubes by dding chocolate (enought to be 1cm deep when melted). Melt on a water bath and add a thermometer. Freeze the chocolate and these can be the ‘retuned samlples’ (they should have melting points well below the usual 35 degrees). Once these have been prepared they can be used repeatedly with different clsses cutting costs.

    The students can then add the samples to a 40 degree (ish) water bath and ‘judge’ when it is melted recording the temperature it does so. This can then be compared with the figure (you give) of ‘fresh’ chocolate. What ever the difference, as long as it rers to the types of chocolate vs melting point list should be good enough.

    For the syrup the contained method (in a boiling tube with marble) will help to prevent mess. The method where the syrup is run down a laminated card does not use much syrup and can be cleaned up quickly. Batches (% concentration and a sample) can be made in bulk and should last for a few months.

    Hope this helps.

  3. j.mcgillicuddy@sellyprk.bham.sch.uk says:

    You will recall you came to discuss chemistry P2 and M2 with us in December, esp with regard to merit work.
    We have finished the Chemistry topic and as Lead IV I am checking what we have done against the spec.
    For P2 it specifically says…
    To achieve P2, the learners would have
    to relate the uses of the chemicals to their physical properties. At least three chemicals should be studied. The
    tutor will have to select the substances carefully so that the unit is delivered efficiently in terms of time. The
    examples should be straightforward. To achieve M2, learners would have to explain the uses of the chemicals
    in terms of their physical properties.
    We have not studied three chemicals and I don’t even know if chocolate will count as a chemical. Are Edexcel happy with the chocolate study and are you certain it will meet the criteria?
    Jackie McGillicuddy

  4. sandy says:

    Jackie. The substances that are mentioned in the suggested assignments cover elements (the aluminium block), mixtures (the syrup and the chocolate as well as a compound (the polymer block) and so this could be seen to cover a range of substances. Furthermore the examples that EDEXCEL suggest in their own delivery amplification are copper wire (element), PVC (compound) and bricks (mixture). When this assignment was shown to the exam board’s lead verifier she felt that the examples we suggested were appropriate to the task however (as is always the case) centres need to make sure that any assignments are internally verified to make sure they are fit for purpose and can comfortably meet the criteria. The Science Team

  5. c.lange@parkview.bham.sch.uk says:

    re – melting point –
    As with any mixture of more than one compound the chocolate does not have a sharp melting point, but a range

    I therefore had my students record 2 temperatures
    1 – the temperature where the sample starts to melt
    2 – the temperature where the sample is completely melted.

    The students found it reasonably simple to follow these instructions and the results show a clear temperature difference between the 2 samples.

  6. sandy says:

    Note: There is now a resource for the measurement of electrical conductivity (Worksheet U1 2.2).

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