Diffusion and Osmosis
Design and Measurement Project
The aim of this project is two-fold: 1) to design and conduct an experiment to quantitatively measure
the diffusion of different sized molecules; 2) to design and conduct an experiment to investigate the
relationship between solute concentration and the movement of water through a semi-permeable
membrane. You are to work in pairs. You will be given access to a selection of apparatus and will be
expected to design a set of experiments and controls. Measurements should be quantitative. Anh Ho
will be the laboratory teacher during these sessions.
Objective: It is known that molecules will diffuse at different rates depending on their molecular size.
Investigate the relationship between diffusion and molecular size.
Controls
Control observations are important in the design of any experiment. The purpose of a control
observation is to determine whether the variable that is directly manipulated by the experimenter is the
one that controls the change in response. In the design of your experiments you should include any
necessary controls.
Laboratory Notebook
The laboratory notebook is one of the basic tools for any experimental work, whether it be basic
research, product development or engineering design. Laboratory notebooks, in contrast to project
reports are primarily for the experimenter’s own use but can be used for other reasons such as:
1.
2.
3.
4.
To establish the authenticity of the work
To act as a basis for project reports and journal articles.
To defend patents (assuming you agree with the current patent system).
To avoid erroneous or repetitions work
Laboratory notes should be sufficiently detailed so that the experiment can be repeated at a later time
and that results from different experiments can be compared. Relying on one’s own memory is
extremely unreliable no matter how sure one is at the time. There are certain entries in a laboratory
notebook that are common to all lab work, these include a date and time for the work and a brief
description of the purpose of the work. Nothing in a notebook should ever be erased but a note should
be added to annotate a suspected or known error. The general rule is to write down everything in a
laboratory notebook no matter how inconsequential. The appearance of a note book will not be perfect
but should be sufficiently structured and neat to make it legible. Since a notebook is written during the
experiment, it will invariably be handwritten in ink (or a tablet PC if you have one). It should not be
typed up later; the original should always be kept. Subsequent work such as journal articles and project
report will reply on the notebook and will be formatted for formal publication.
Project Report
The project report will be a formal document describing the work carried out and will draw on material
you recorded in the laboratory notebook. The report should be written up in the form of a journal
paper. Often when manuscripts are submitted to a journal, figures are often included at the end of the
manuscript, this is a historical convention that has little applicability today, I therefore recommend that
for your project reports you place figures, tables etc in the body of the text.
Project reports are often written up in a standard format that includes the following sections:
Cover Page: On the cover page include the title of the laboratory session, the authors' names (including
your team partner), and the dates of the laboratory session.
Abstract: The abstract is a one paragraph summary of the report including the questions investigated,
the methods used, and the principal results and conclusions. Since it summarizes your report, this
section should be written last.
Introduction: The introduction is a brief section (fewer than 350 words) designed to motivate why your
findings are interesting and important. The introduction should offer a rationale for your study. You can
explain how your study fits within a broader context. Citations to previous work are often given in the
introduction.
Methods: Briefly describe the methods that you used to obtain and analyze your results. Avoid "First we
did this, then we did that, then we did yet another thing". Diagrams that illustrate how the experiments
were setup can be included here. If solutions and/or equipment were provided, this should be indicated
here. Also describe any design decisions on the choice of equipment and methodology.
Results: Describe your technical findings and include figures and graphs as appropriate. The text should
lead a reader from results to conclusions. Include any statistical analysis of the data and comment on
the significance of this analysis.
Discussion: Describe the major conclusions from the study and explain the importance of your results. In
particular refer to issues that were brought up in the introduction and any limitations of your results
(e.g. errors in the data). A discussion can include ideas on improving the experiment and any other
speculations.
References: Any citations made in the main text should be provided here.
Appendix: For the purpose of this course work only, you will be expected to include photocopies of your
laboratory notes in an appendix. These will be photocopied at the end of each lab session and the copies
handed in before leaving the lab.
Grading
Laboratory Notebook: 25%
Report Structure: 15%
Technical Content: 25%
Report Clarity: 25%
(e.g use of replicates, statistical analysis, controls)
(Conciseness, readability and spelling)