Example Project -- Decaffeinated Coffee

Research Process

  1. Observation

    The topic is decaffeinated coffee. Write down some things you already know about decaffeinated coffee based on everyday observations, experience and general knowledge. A basic observation about decaffeinated coffee could be:
    Caffeine is removed from coffee beans during the decaffeination process.

  2. Towards a Hypothesis

    The next step is to pose questions and speculate about how coffee is decaffeinated. Any speculation about the decaffeination process is a hypothesis (but not necessarily a good one!). Your hypothesis should offer a chemical explanation for the phenomenon that you're investigating.
    As you look over each of the sample hypotheses below, keep in mind the characteristics of a successful hypothesis, as specified by the grading rubric.

    A hypothesis:

    • can be supported or refuted.
    • answers a question you have about the topic.
    • is appropriate for Chem 1A.
    • is appropriate in scope for poster/presentation.
  3. Sample Hypotheses

    Think about how you would assess each of the sample hypotheses.

    Coffee is decaffeinated using a hazardous solvent and therefore is unhealthy.
    Feedback: This has the features of a good hypothesis. It deals with chemical principles salient to Chem 1A and it can be supported or refuted.
    Caffeine is converted from acid to base or vice versa and thus neutralized.
    Feedback: This hypothesis is rather vague. In fact it's two hypotheses. You'd need to decide whether caffeine is an acid or base and specify how it is converted from one to the other. Think about caffeine's molecular structure and what might allow it to be removed from the coffee bean. The word neutralized is also problematic. Does this mean that the pH approaches 7 or that the physiological activity of caffeine is neutralized. You might be better off avoiding "neutralized" and substituting "inactive form."
    Caffeine molecule's bond breaks.
    Feedback: This hypothesis is also too vague.  How do the molecular bonds break? Which bonds and why?
    Caffeine is converted into an inactive form by an enzyme that binds with the caffeine molecule.
    Feedback: What does inactive mean? Does this mean that your body cannot process this new form? Enzyme chemistry may also go beyond the scope of this course. If you can use some of the topics listed on our course syllabus, you are probably on the right track for a Chem 1A project.
    Coffee beans are heated and this causes molecular changes in caffeine.
    Feedback: This is too vague. What molecular changes do you think occur? Why might heating the beans cause molecular changes? And how might these affect the activity of caffeine?
    Caffeine is converted into an indigestible form.
    Feedback: This can be supported or refuted and is a workable hypothesis. It would benefit from some further refinement that would make it clearer what sorts of chemical principles or processes you think might be involved. Solubility is certainly one candidate. Also, you should keep in mind that there may well be multiple ways to decaffeinate coffee. So, even if coffee is commercially decaffeinated in one way, you can't assume that other methods wont work.

    The next step is to choose a hypothesis. You won't be penalized for choosing a hypothesis that is wrong. And perhaps a more important warning is that a correct hypothesis does not guarantee a high mark for the research project.
    Let's choose, Coffee is decaffeinated using a hazardous solvent and therefore is unhealthy.

  4. Supporting Questions

    Now we need to ask ourselves what sort of questions we need to be able to answer in order to support or refute our hypothesis. We'll call these the supporting questions. This is also a way of breaking the hypothesis down into its components. To determine if your hypothesis is correct you might need to know something about a molecular structure, a chemical process, a compound's toxicity, or an industrial technology. For example:

    • What is the molecular structure of caffeine?
    • What solvents are used in the decaffeination process?
    • What are the molecular structures of the solvents used?
    • How do the solubility properties of caffeine affect the choice of solvent for decaffeination?
    • How much, if any, residue remains in the beans after the decaffeination process?
    • Is the solvent toxic/safe/healthy for humans to ingest, and at what level of concentration?
    • Are there methods of decaffeination that do not use solvents?

    To answer these questions you'll need to locate appropriate sources of information. To do this you'll formulate a Research Plan.