Pontypridd High School
BTEC 2012-2013
Assignment brief
Qualification
Unit number and title
BTEC Level 3 Certificate in Applied Science
Unit 4: Scientific Practical Techniques
Start date
8th October 2013
Deadline
10th November 2013
Assessor name
Rebecca Cassells
Assignment title
Assignment 4.1: Identifying unknown substances and concentrations
The purpose of this assignment is to: be able to use analytical techniques
Scenario
A number of substances in the laboratory you work in have been mislabelled. You must
conduct a number of tests to identify some unknown substances and the concentrations of
some known substances. (You should identify hazards and necessary control measures to
reduce any risks.)
Task 1
In this first task you need to;
 Produce a suitable volume of a standard solution of 0.1 mol dm-3 sodium carbonate.
 Use standard to identify the concentration of an unknown sample of hydrochloric acid
You could titrate the hydrochloric acid against a standard sodium carbonate solution.
Using the guidance provided in the Student Book, perform the relevant calculations to find
the unknown concentrations of the hydrochloric acid
You can then test your results;
Titrate the hydrochloric acid you have investigated with a known concentration of sodium
hydroxide solution and calculate the concentration using this method.
For each practical you must include a risk assessment
This provides evidence for P1
Task 2
A number of unlabelled jars containing different ions need to be tested.
Conduct flame tests and test tube tests for ions to identify the unknown substances.
Record your results clearly along with the test used to identify the contents.
For each practical you must include a risk assessment
This provides evidence for P1
Task 3
A cupboard in the laboratory contained a number of substances you believe to be food stuffs used
for testing.
Carry out tests to identify proteins, starch and reducing sugars
Record the results to be sure that the cupboard did indeed contain the substances and equipment
you suspected.
For each practical you must include a risk assessment
This provides evidence for P1
Task 4
Write a report explaining how you can be confident that the substances and concentrations
you have identified are true and accurate.
Discuss how you ensure accuracy and prevent any errors in each of the procedures you
carried out.
Specify how you maintained accuracy for each of the following procedures
 titration
 cation test
 flame test
 test for protein
 test for reducing sugar
 test for starch
Comment on equipment used and how accuracy is maintained through their use and aspects of
good volumetric technique should be discussed and the need to avoid contamination in the
spot test explained.
This provides evidence for M1
Task 5
Evaluate each of the procedures you carried out.
Explain the consequence of particular errors in technique.
Suggest improvements of alternatives to the methods used and justify them.
Highlight any features that may have confused you.
You must use multiple sources to reference your information
This provides evidence for D1
Sources of information
Annets F, Foale S, Hartley J, Hocking S, Hudson L, Kelly T, Llewellyn R, Musa I and Sorensen J – BTEC Level 3
National Applied Science Student Book (Pearson, 2010) ISBN 9781846906800
Coyne G S – The Laboratory Companion: A Practical Guide to Materials, Equipment and Technique
(John Wiley & Sons, 2005) ISBN 9780471780861
Dean J R et al – Practical Skills in Chemistry (Prentice Hall, 2001) ISBN 9780130280022
Lawn R and Prichard E – Practical Laboratory Skills Training Guide: Measurement of Mass (The Royal Society of
Chemistry, 2003) ISBN 9780854044634
Prichard E and Lawn R – Practical Laboratory Skills Training Guide: Measurement of Volume (The Royal Society of
Chemistry, 2003) ISBN 9780854044689
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