

* Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons * Personal Investigation 
Research Assistant Wanted
Brother Gregory wants you to help him find out how many carbon atoms there are in various samples and specimens. In these investigations you will be provided with samples of biological substances and molecules taken from unknown materials. You will be asked to find out how many carbon atoms there are in the molecular structure of these molecules. First, print out your personal investigation page (below) and find out which specimens you are supposed to investigate. 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.


* Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons * Personal Investigation 
The Problem
Brother Gregory has provided you with a number of biological molecules. He wants you to use methods devised by Herr Doktor Liebig to determine how many carbon atoms there are in each one of these molecules.


* Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons * Personal Investigation 
The Method
The method you are going to use was devised by Herr Doktor von Liebig. In this procedure a sample of the unknown substance is carefully burnt in oxygen. This destroys the original molecule and produces two new molecules; water and carbon dioxide, thus ... The carbon dioxide produced as the unknown substance burns is collected and weighed. The molecular weight of the carbon dioxide is known (or can be worked out from its formula), the molecular weight of the unknown substance is also known, so a simple calculation can be used to relate the amount of CO_{2} produced to the amount of carbon in the original molecule. 

Step One: * Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons * Personal Investigation 
Burn the Sample
As the first step in this investigation, it is necessary to burn at least two samples of each unknown substance in oxygen, then collect and weigh the amount of CO_{2} given off in each case. Procedure


Step Two: * Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons * Personal Investigation 
Calculate the Slope
As the second step in this investigation you now have to find the relationship between the amount of sample burnt, and the amount of CO_{2} produced. Procedure


Step Three: * Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * Calculate the Carbons * Personal Investigation 
Calculate the Number of Carbon Atoms
You now have two important pieces of information for each of your substances or specimens: (a) its molecular weight and (b) its relationship to the amount of CO_{2} produced when a sample is burnt in oxygen.
You must now calculate the molecular weight of carbon dioxide, and use a formula to determine the number of carbon atoms in the unknown substance or specimen.
 
Print out your personal investigation page * Research Assistants * The Problem * The Method * Burn the Sample * Calculate the Slope * How many Carbons 
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


Science@a Distance © 2003, Professor John Blamire 