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Page Items
* The Problem
* The Method
* Personal Investigation
Research Assistant Wanted

Brother Gregory wants you to help him find the molecular weight of various molecules. In this investigation you will be provided samples of molecules that have different molecular weights, and you will be provided with a semipermiable membrane.

You will then use this semipermiable membrane and other simple tools, such as a beaker of water, to find out the answers you need.

Assistants

You are to become Brother Gregory's research assistant. You must carry out the experiment, gather data, analyze your results and give Brother Gregory the answer you have found.

First, print out your personal investigation page (below) and find out which solutes (molecules) you are supposed to investigate and. Carry out the experiment, gather and record your data, analyze your results and write down the appropriate numbers on your personal investigation page.

This is important. Bring your completed investigation page to the examination.



Page Items
* Research Assistants
* The Method
* Personal Investigation
The Problem

Specimens of unknown materials have been provided for you. It is hoped that you will be able to use the phenomenon of Osmosis to examine the properties of these molecules, in particular a property known as molecular weight.

Before you begin your investigation, you should read this short story about Brother Gregory, his friends, and learn the background information you need.

Sausage Skins and Molecular Weight



Page Items
* Research Assistants
* The Problem
* Personal Investigation
The Method

In these investigations you observe what happens when two different solutions of two different molecules are placed on either side of a semipermiable membrane.

Osmosis is the movement of water across such a membrane (like a sausage skin), and the rate at which osmosis takes place depends on the nature and molecular weights of the molecules in each solution.

Before you begin, take this opportunity to read about Avagadro (and his number!), Molar solutions, Osmotic pressure differences, and how to calculate your results.

How to use the Osmometer


Start the Investigation

Use the Osmometer to find your molecular weights

Print out your
personal investigation page

Page Items
* Research Assistants
* The Problem
* The Method
Carefully enter your Seat Number or PCIN number
(e.g.
MM34, or MA56, or WA41)
in the box below, click, and print out the page that appears.

Find the answers to the questions, write your answers on the investigation page, and bring the completed assignment to the exam for grading purposes.

Personal Investigation Page

Enter your seat number or PCIN number here: -


Science@a Distance
© 2001, Professor John Blamire