scholar study guide sqa cfe higher chemistry unit 4: researching chemistry€¦ · information...

SCHOLAR Study Guide

SQA CfE Higher ChemistryUnit 4: Researching Chemistry

Authored by:

Emma Maclean

Reviewed by:

Diane Oldershaw

Previously authored by:Peter Johnson

Brian T McKerchar

Arthur A Sandison

Heriot-Watt University

Edinburgh EH14 4AS, United Kingdom.

First published 2014 by Heriot-Watt University.

This edition published in 2014 by Heriot-Watt University SCHOLAR.

Copyright © 2014 Heriot-Watt University.

Members of the SCHOLAR Forum may reproduce this publication in whole or in part foreducational purposes within their establishment providing that no profit accrues at any stage,Any other use of the materials is governed by the general copyright statement that follows.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval systemor transmitted in any form or by any means, without written permission from the publisher.

Heriot-Watt University accepts no responsibility or liability whatsoever with regard to theinformation contained in this study guide.

Distributed by Heriot-Watt University.

SCHOLAR Study Guide Unit 4: SQA CfE Higher Chemistry

1. SQA CfE Higher Chemistry

ISBN 978-1-909633-23-0

Printed and bound in Great Britain by Graphic and Printing Services, Heriot-Watt University,Edinburgh.

AcknowledgementsThanks are due to the members of Heriot-Watt University's SCHOLAR team who planned andcreated these materials, and to the many colleagues who reviewed the content.

We would like to acknowledge the assistance of the education authorities, colleges, teachersand students who contributed to the SCHOLAR programme and who evaluated these materials.

Grateful acknowledgement is made for permission to use the following material in theSCHOLAR programme:

The Scottish Qualifications Authority for permission to use Past Papers assessments.

The Scottish Government for financial support.

All brand names, product names, logos and related devices are used for identification purposesonly and are trademarks, registered trademarks or service marks of their respective holders.

i

Contents

1 Web-based research 11.1 Test your prior knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 Chemical research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Carrying out web-based research . . . . . . . . . . . . . . . . . . . . . . 51.4 Evaluating websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.5 Referencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81.6 Practice research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.8 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2 Planning an investigation 132.1 Test your prior knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . 152.2 Planning an investigation . . . . . . . . . . . . . . . . . . . . . . . . . . 162.3 Identifying the key stages . . . . . . . . . . . . . . . . . . . . . . . . . . 162.4 Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182.5 Practical techniques and apparatus . . . . . . . . . . . . . . . . . . . . . 212.6 Planning ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272.8 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3 Carrying out an investigation 313.1 Test your prior knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . 333.2 Carrying out an investigation . . . . . . . . . . . . . . . . . . . . . . . . 343.3 Identifying the key stages . . . . . . . . . . . . . . . . . . . . . . . . . . 343.4 Practical techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.6 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4 Processing & analysing results 434.1 Test your prior knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . 454.2 Representing experimental data using a scatter graph . . . . . . . . . . 464.3 Replicate measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 484.4 Calculating the mean value for experimental data . . . . . . . . . . . . . 494.5 Identification and elimination of 'rogue' points . . . . . . . . . . . . . . . 494.6 Qualitative appreciation of the relative accuracy of volume apparatus . . 514.7 Qualitative understanding of uncertainty associated with a measurement 52

ii CONTENTS

4.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.9 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

5 Evaluating & drawing conclusions 575.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595.2 Evaluating procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605.3 Evaluating results and drawing conclusions . . . . . . . . . . . . . . . . 645.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 685.5 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 695.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6 Scientific communication 716.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736.2 The passive voice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 736.3 Chemical grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 746.4 Formal language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 756.5 Formats of scientific communication . . . . . . . . . . . . . . . . . . . . 766.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 796.7 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 806.8 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

7 End of unit test 837.1 End of unit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 877.2 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Answers to questions and activities 1031 Web-based research . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032 Planning an investigation . . . . . . . . . . . . . . . . . . . . . . . . . . 1053 Carrying out an investigation . . . . . . . . . . . . . . . . . . . . . . . . 1084 Processing & analysing results . . . . . . . . . . . . . . . . . . . . . . . 1105 Evaluating & drawing conclusions . . . . . . . . . . . . . . . . . . . . . 1126 Scientific communication . . . . . . . . . . . . . . . . . . . . . . . . . . 1147 End of unit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

© HERIOT-WATT UNIVERSITY

1

Topic 1

Web-based research

Contents

1.1 Test your prior knowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Chemical research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 Carrying out web-based research . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.4 Evaluating websites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.4.1 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.4.2 Assessing level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.4.3 Assessing bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.5 Referencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.6 Practice research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.8 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Prerequisite knowledge

You should already:

• have carried out a variety of practical experiments throughout the course (Higher);

• be familiar with researching a chemical issue and collating this information into ashort presentation (National 5, Outcome 2.2 & 2.3);

• be familiar with the following from your National 5 Assignment:

– applying knowledge of chemistry to new situations and interpretinginformation;

– selecting and presenting information appropriately in a variety of forms;

– processing the information/data collected (using calculations and units,where appropriate);

– drawing valid conclusions and giving explanations supported byevidence/justification;

– communicating findings/information (National 5, Assignment);

• be familiar with applying your knowledge of experimental techniques to unfamiliarsituations (National 5, Outcome 2.4).

2 TOPIC 1. WEB-BASED RESEARCH

Learning Objectives

By the end of this topic, you should have:

• developed the key skills necessary to undertake research in chemistry;

• demonstrated the relevance of chemical theory to everyday life by exploring thechemistry behind a topical issue;

• investigated the chemistry underlying an issue or story featured in broadcast andpublishing media;

• experienced carrying out literature based research;

– In particular, candidates carrying out web-based research, should be familiarwith issues of reliability and they should be able to clearly state the source ofthe information they find;

• developed the skills to allow you to reference websites to allow another person tofind the same information;

• the ability to carry out research in order to answer an individual focus question setby your teacher.


TOPIC 1. WEB-BASED RESEARCH 3

1.1 Test your prior knowledge

Test your prior knowledge

Q1: Where might chemists look up information if they were to research a topic?

a) Booksb) Websitesc) Journalsd) All of the above

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q2: Name a practical technique which could be used to increase the alcoholpercentage in a mixture.

a) Precipitationb) Titrationc) Fermentationd) Distillation

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q3: Which of the following could be the correct way to write up an experiment?

a) Aim, Results, Conclusionb) Aim, Method, Resultsc) Aim, Method Results, Conclusiond) Aim, Method, Conclusion, Results

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 Chemical research

Key Point

An explanation of the importance and availability of chemical research.

The aim of the Researching Chemistry unit of the course is to help you to develop thekey skills necessary to undertake research in chemistry.

The first step in any research activity involves finding out about a particular topic bycarrying out a literature search.

You will be provided with a focus question on a topical issue (this will be given to you byyour teacher) and will be expected to research the underlying chemistry associated withthis issue.

The brief you might be given can contain a number of focus questions related to thetopic. You will be expected to provide a clear and accurate answer to one focus question.



In order to do this, you will have to carry out a number of tasks including:

• obtaining and recording information from suitable sources relating to a focusquestion;

• recording the sources of information selected.

To avoid wasting time and resources it is essential that scientists check the literature tofind out what is already known about their area of research.

Scientists use different methods to communicate their findings. These include:

• writing books;

• presenting at conferences;

• publishing articles in scientific journals and magazines;

• appearing on TV programmes;

• publishing their findings on the internet.

You may be able to use books, scientific journals, videos, TV programmes etc, to accessthe information you need. However, as the internet can provide information within hoursof the completion of an experiment or report, websites offer some of the most up-to-dateinformation on new areas of science. The internet also offers free access to a far greatervolume of information than is likely to be found in school or college libraries.

http://www.sciencedirect.com, one of the largest scientific databases


http://www.sciencedirect.com


1.3 Carrying out web-based research

Key Point

An introduction to the concept of a focus question.

The aim of this topic is to help you undertake effective web-based research. It is easyto simply look up a single fact on the internet, but harder to know whether or not theinformation found is accurate and reliable.

A few simple checks will allow you to evaluate web-based resources to decide howtrustworthy they are.

1. When you are carrying out your research, keep your focus question in mind andtry not to get sidetracked.

2. Don’t write as you go along. Instead, bookmark the sites that are of interest to youand return to them when you have finished surfing. You will probably decide laterthat some of the sites are of no real use.

3. Answer your focus question after you have gathered all the information that youthink you require.

1.4 Evaluating websites

Key Point

An introduction to the idea that all websites may not be suitable for chemicalresearch.

The internet allows you to access a huge amount of information. However, as this isnot controlled, and anyone can publish almost anything on it, you have to decide if theinformation that you retrieve is reliable.

This activity involves three tasks which address reliability, level, and bias of websites.

1.4.1 Reliability

Key Point

An introduction to the idea of reliability of websites.

How do we know that information that appears on a web page is reliable and accurate?

Well, the simple answer is that we don’t.

However, we can use some key questions to evaluate the accuracy of the sites we find.



The key questions you should ask yourself are:

Who wrote the site?

Check the address, and particularly the domain:

• .ac and .edu are educational sites

• .gov are government sites

• .co and .com are commercial sites

• .org are used by non-profit organisations

What is the purpose of the site?

• Is it to sell something? To inform? To persuade? The domain name should helpyou to determine this.

How current is the site?

• Check the most recent update.

Reliability: Questions

You have been asked to investigate greenhouse gases. Your task is to find out what themain gases are that are thought to contribute to global warming.

Open a new tab or window and type ‘greenhouse gases’ into http://www.google.co.uk/.

Select the Wikipedia and the US-EPA search results:

• http://en.wikipedia.org/wiki/Greenhouse�gas

• http://www.epa.gov/climatechange/emissions/index.html

Within these two sites you will find lists of the principal greenhouse gases, but the listsdiffer.

Q4: Which source do you think should be the most reliable?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q5: Which list do you think is accurate?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

To resolve this particular problem, continue your search to find other listings ofgreenhouse gases.

Q6: Is either of the original listings inaccurate?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


http://www.google.co.uk

http://en.wikipedia.org/wiki/Greenhouse_gas

http://www.epa.gov/climatechange/emissions/index.html


1.4.2 Assessing level

Key Point

An introduction to accessing websites with content at the appropriate level.

As you carry out research from the web, you will find that sites vary in their complexity.

Always bear in mind that you are studying for Higher Chemistry - you need to ensurethat the information you use is at the right level.

As a rule, try to source information that is at an appropriate level. Having said this, it isusually better to use more straightforward information than complex data that you don’tunderstand yourself.

Assessing level: Questions

To illustrate this, suppose you are researching new catalysts and want to find out howcatalysts work.

Go online and visit the following three sites:

• http://www.science.uwaterloo.ca/~cchieh/cact/applychem/heterocat.html

• http://www.chemguide.co.uk/physical/basicrates/catalyst.html

• http://www.chem4kids.com/files/react�catalyst.html

The three sites each describe the mechanism of catalysis.

Q7: Which of the three is too complex for your level?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q8: Which site gives an easily understood definition of catalysts at an appropriate levelfor a Higher Chemistry candidate?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4.3 Assessing bias

Key Point

An introduction to the idea of bias of websites.

Websites are written for a number of different reasons. The information that is presentedon the site will depend on the purpose of the site.

Assessing bias: Questions

The three sites in this activity contain information about a pesticide that contains theactive ingredient glyphosate. Go to the sites and consider the purpose of each one.


http://www.science.uwaterloo.ca/~cchieh/cact/applychem/heterocat.html

http://www.chemguide.co.uk/physical/basicrates/catalyst.html

http://www.chem4kids.com/files/react_catalyst.html


In this task you will notice that the appearance of sites can vary considerably, but don’tlet this affect your opinion too much!

• http://www.clonaid.com/news.php

• http://www.cloninginformation.org/tag/americans-to-ban-cloning/

• http://learn.genetics.utah.edu/content/cloning/whatiscloning/

Q9: Is there a bias to these sites?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q10: Which site(s) would you consider to be the most scientifically accurate?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q11: Which type of website would you use to obtain an unbiased report about thesepesticides?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.5 Referencing

Key Point

An introduction to the practice of referencing.

In addition to finding and recording reliable information, you must be able to record yoursources in a way that will allow another person to find the same information.

Make sure that your answer includes a clear indication of where you have sourced yourdata. When you reference a website, ensure that you have included the entire URL(address).

It is good practice to type it into your web browser to check it works.


http://www.clonaid.com/news.php

http://www.cloninginformation.org/tag/americans-to-ban-cloning/

http://learn.genetics.utah.edu/content/cloning/whatiscloning/


Referencing: Exercise

5 min

Suppose you were researching the impact of the Haber Process on fertiliserdevelopment and used the following website:

• http://www.princeton.edu/~hos/mike/texts/readmach/zmaczynski.htm

This URL contains a symbol that is difficult to copy. Try to open the link below:

• http://www.princeton.edu/Xhos/mike/texts/readmach/zmaczynski.htm

In this case, you are redirected to the correct page. This will not be the case if you havemade a spelling or other mistake. For example, try and open the link below:

• http://www.princeton.edu/~hos/mike/texts/readmach/zmazynski.htm

One small typing error means that you cannot access the page.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.6 Practice research

Key Point

A chance to put your new researching skills into practice.

Choose one of the following focus questions to generate some web-based research foryourself:

A) What caused the hole in the ozone layer?

B) What are the benefits of vitamin C in the diet?

C) What are the effects of aluminium entering the water supply?

For the one(s) you have chosen ensure you do the following:

1. Present your information in a clean and coherent manner.

2. Find three relevant pieces of information about the topic.

3. Reference your sources.

4. If possible, allow another person to read your research and check your referencesand give you feedback on the research you have carried out.


http://www.princeton.edu/~hos/mike/texts/readmach/zmaczynski.htm

http://www.princeton.edu/Xhos/mike/texts/readmach/zmaczynski.htm

http://www.princeton.edu/~hos/mike/texts/readmach/zmazynski.htm


1.7 Summary

Summary

The following is a checklist for evaluating web pages, use it when you areanswering your focus question.

1. Author (source)

a) Can you find out the name of the author?

b) Is there information about the author provided?

c) Is it clear that an institution or university or organisation sponsored thewebsite (check the domain)?

2. Currency (date)

a) Is the date the website was put on the internet present?

b) Is an update or revision date present?

3. Level

a) Is the website intended for a general or a scientific audience?

b) Is the topic explored at a suitable level for Higher Chemistry?

4. Purpose

a) Is the purpose of the site stated (to persuade, inform, explain, sell)?

5. Bias

a) Is the information given and / or the views expressed biased?

6. Accuracy

a) Are the sources of the information listed in a bibliography?

ConclusionUsing the above information, is this an appropriate source for your research?Justify your opinion.

1.8 Resources

Texts

• Higher Chemistry for CfE, J Anderson, E Allan and J Harris, Hodder Gibson,ISBN 978-1444167528

Practical work

• Learners should have access to a computer with internet connection to put their



knowledge of web based research to the test.

1.9 End of topic test

End of Topic 1 test



. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q13: The first step in any research activity involves finding out about a particular topicby carrying out a

a) literature search.b) internet search.c) experiment.d) peer review.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q14: Which of the following should you check when assessing if a website is reliable?

a) Which country it is from?b) When was it last updated?c) Does it look nice?d) Are there any photos?

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q15: Which of the following is the least reliable domain?

a) .edub) .govc) .comd) .org

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q16: Websites with which of the following purposes of would be suitable to use in yourresearch?

a) To persuadeb) To informc) Blogsd) To sell

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Q17: What is the main purpose of including references in your research?

a) To fill up space in a word countb) To allow another person to find the same informationc) To give credit to other authorsd) All of the above

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


13

Topic 2

Planning an investigation

Contents


2.2 Planning an investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.3 Identifying the key stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.4 Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.4.1 Hazard symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.4.2 Risk assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.5 Practical techniques and apparatus . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.6 Planning ahead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

2.8 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28


You should already:









• be familiar with applying your knowledge of experimental techniques to unfamiliarsituations (National 5, Outcome 2.4).

14 TOPIC 2. PLANNING AN INVESTIGATION

Learning Objectives

Planning is an essential skill for life, learning and work. Effective planning enablespriorities to be dealt with in a controlled manner instead of simply reacting to thingsas they come along. During your Researching Chemistry investigation, planning aheadwill allow you to be better organised and will save you time, effort and resources. By theend of this topic, you should have the ability to:

• think of an investigation in terms of a number of key stages;

• identify the key stages in planning and carrying out a scientific investigation;

• select the appropriate practical technique(s) and apparatus for a particularprocedure;

• recognise that there are always significant safety risks when carrying out scientificprocedures that must be taken into account in the planning stages;

• appreciate the importance of planning before starting the experiment.


TOPIC 2. PLANNING AN INVESTIGATION 15



Q1: Which of the following would be the best piece of apparatus to use to heat aflammable liquid to 120◦C?

a) Any of theseb) Bunsen burnerc) Water bathd) Heating mantle

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Q2: Name a practical technique which involves reacting two solutions together toproduce a solid.


. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q3: Which of the following is the correct hazard symbol for an irritant?

a)

b)

c)

d)

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2.2 Planning an investigation

Key Point

An explanation of the importance of planning an investigation.

The ability to plan effectively will be crucial when undertaking your scientific investigationduring the Researching Chemistry unit. Indeed, in order to achieve Outcome 2 of thisunit you must show that you can ‘effectively plan and carry out investigative practicalwork relating to a topical issue in chemistry’.

Planning a scientific investigation can be a daunting prospect, however. Where shouldyou start? What are the planning priorities? Which technique should you use? Whatapparatus and chemicals will be required? How can you ensure the safety of yourselfand others during the practical aspects of the investigation?

This topic will help you to develop the skills of effectively planning a scientificinvestigation at Higher Chemistry level.

2.3 Identifying the key stages

Key Point

An introduction to planning ahead using an everyday situation.

What are the key stages involved in effectively planning and carrying out a scientificinvestigation? Let’s try to work them out by first identifying the key stages in a morefamiliar procedure - making a cup of tea!

Identifying the key stages: Exercise

Q4: You can probably make a cup of tea without really thinking about the stagesinvolved. However, imagine you need to write a list of instructions for someone whohas never made a cup of tea before.

Write down a list of the key stages involved in making a cup of tea. You have 1 minuteto complete this task!

Think about these questions:

• Have you all written the same steps?

• Have any important steps been missed?

• Are some steps not always required?

• What does this tell you about the importance of planning ahead?

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Note: There may be more than one way to sensibly carry out this procedure! Somestages may not always be required (for example, not everyone takes milk or sugar intheir tea).



There can be some flexibility in the order in which some of the stages are carried out(for example, some people may prefer to add the sugar after the milk, others before themilk).

The order of collection of equipment may be dependent on its location within the kitchen.

However, in general, planning ahead ensures that all the appropriate ingredients andequipment are available, that no key steps are missed out and that the procedure iscarried out smoothly and quickly.

An everyday procedure such as making a cup of tea can be summarised as a seriesof stages. The more complicated process of planning and carrying out a scientificinvestigation can also be broken down into a similar series of stages.

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Identifying the key stages: Question

The stages involved in making a cup of tea could be grouped into the broad categorieslisted below.

Q5:

Complete the table by matching the stages of teamaking to the equivalent stagesinvolved when planning and carrying out of a scientific investigation. Choose from:

• Collect apparatus

• Collect results

• Decide on topic for investigation

• Put away apparatus and dispose of chemicals safely

• Carry out the procedure

• Collect chemicals required

Making a cup of tea Scientific investigation

Decide to have a cup of tea

Source ingredients

Collect kitchen equipment

Make teaDrink teaTidy up

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2.4 Risk assessment

Key Point

An introduction to the idea of assessing risk for chemical reactions.

A crucially important part of the planning process for any everyday procedure involvesassessing how to safely carry out the procedures involved.

For example, when making a cup of tea it is important to take precautions to ensure thatwater and electricity are kept apart, and to avoid spilling boiling water on your skin.

2.4.1 Hazard symbols

Key Point

A chance to practice identifying hazard symbols.

Each chemical you plan to use in your investigation will have an associated risk. Thisrisk will be described on the hazard warning label on the chemical. The use of hazardsymbols is regulated by law, and the symbols used are internationally agreed.

Note: Some chemicals are too hazardous to be used in schools; therefore not all ofthese warning labels will be found in your chemistry laboratory!

Hazard symbols: Question

The table below contains a number of hazard warning labels. Match each one to thecorrect meaning.

Choose from:

Highlyflammable

Oxidising Harmful /irritant

Explosive Toxic

Harmful to theenvironment

CorrosiveGases underpressure

Respiratorysensitiser



Hazard symbol Meaning

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2.4.2 Risk assessment

Key Point

A practical application of assessing risk.

Once the hazards associated with a particular chemical have been identified, a riskassessment must be carried out.

The risk assessment allows appropriate precautions to be put in place to allow thechemical to be handled safely.

Note: It is appropriate to wear safety glasses at all times when handling chemicals.

Risk assessment: Question

For the following questions, match the laboratory situation to the required precaution(s).

Choose the precautions you would take to minimise risk in each of the followingsituations.

Q6: Lab situation: pouring a corrosive chemical.

a) Lab coat to protect clothingb) Carry out in a fume-cupboardc) Rubber gloves to protect handsd) Use the chemical on a small scale

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q7: Lab situation: weighing out a toxic chemical. Choose three from:

A) Lab coat to protect clothing

B) Carry out in a fume-cupboard

C) Rubber gloves to protect hands

D) Use the chemical on a small scale

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Q8: Lab situation: heating a reaction mixture involving a flammable reactant.


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Q9: Lab situation: a chemical reaction for which one of the products is a toxic gas.


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Q10: Lab situation: disposal of chemical waste which is harmful to the environment.Choose two from:

A) Lab coat to protect clothing

B) Carry out in a fume-cupboard

C) Rubber gloves to protect hands

D) Disposal in an appropriate waste container

E) Use the chemical on a small scale

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Note: The safety precautions required for each experiment and investigation will bedifferent. If you are in any doubt whatsoever about the safety procedures required foryour investigation, make sure you speak to your teacher before you start practical work!

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2.5 Practical techniques and apparatus

Key Point

A chance to practice identifying appropriate techniques for use.

A crucial stage in planning a scientific investigation is to identify the most appropriatepractical technique to allow you to safely carry out your experiment.

Having identified the most appropriate technique for a particular scientific investigation,apparatus must then be selected to allow that technique to be carried out effectively andsafely.

Practical techniques and apparatus: Common lab techniques

Match up the laboratory technique in with its most appropriate use.

Q11: Separating a solid from a liquid

a) Heating using a water bathb) Distillationc) Filtrationd) Use of a balancee) Heating using a Bunsen burnerf) Use of a gas syringe to collect a gasg) Titrationh) Collecting a gas over wateri) Heating using a heating mantle

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Q12: Collecting a water-soluble gas


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Q13: Heating an aqueous solution rapidly to 60◦C


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Q14: Heating a flammable liquid to 120◦C


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Q15: Maintaining an enzymatic reaction at 37◦C


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Q16: Weighing out chemicals


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Q17: Collecting a gas which is insoluble in water


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Q18: Determining the concentration of a solution


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Q19: Separating a mixture of liquids


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Practical techniques and apparatus: Question

The tables below contain apparatus diagrams. Match each one to the correctdescription. Choose from:

Measuring cylinder Boiling tube FunnelPipette and safety filler Conical flask BuretteDropper pipette Thermometer Evaporating dish

Volumetric flask Test tube Delivery tube



Apparatus

Name

Apparatus

Name

Apparatus

Name

Apparatus

Name

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



2.6 Planning ahead

Key Point

A chance to put your new planning skills into practice.

Planning ahead is essential for safe and effective practical experimentation in chemistry.For example, some of the stages required to successfully carry out an experimentalprocedure may be implied, rather than explicitly written in the text.

Consider the following procedure for testing solubility:

The solubility in water of ammonium sulfate, potassium nitrate, sodium nitrate, calciumphosphate and ammonium phosphate was tested by adding a spatula of eachcompound to 10 cm3 of water. The results for each compound were recorded as solubleor insoluble.

This procedure could be broken down into simpler stages to assist with planning. Forexample:

1. Place five test-tubes in a test-tube rack.

2. Pour 10 cm3 of water from a measuring cylinder into each test-tube.

3. Add a spatulaful of ammonium sulfate to one of the test-tubes.

4. Gently agitate the test-tube to identify whether or not the ammonium sulfatedissolves.

5. Record whether the ammonium sulfate is soluble or insoluble.

6. Repeat steps 3 to 5 for each of the remaining compounds.

Planning ahead: Questions

Q20: Which of the stages in the list of instructions above was not specifically mentionedin the original experimental procedure?

a) Place five test-tubes in a test-tube rack.b) Pour 10 cm3 of water from a measuring cylinder into each test-tube.c) Add a spatulaful of ammonium sulfate to one of the test-tubes.d) Gently agitate the test-tube to identify whether or not the ammonium sulfate

dissolves.e) Record whether the ammonium sulfate is soluble or insoluble.f) Repeat steps 3 to 5 for each of the remaining compounds.

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Q21: What types of issues could arise during practical work if proper planning has notbeen carried out in advance?

a) Running out of chemicals in the middle of the experiment.b) Not having the required apparatus to hand at the appropriate time.c) Working unsafely because inappropriate apparatus has been selected.d) Running out of time to complete practical work.e) All of the above

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2.7 Summary

Summary

The checklist below will help you to successfully plan and carry out the practicalaspects of your Researching Chemistry investigation.

Checklist√

Choose a topic (Your teacher maygive you one)

Identify the most appropriatetechnique(s) you might use

Plan the stages of the experiment

Assess risks and plan to safelyovercome these risks*Identify and collect the requiredchemicalsIdentify and collect the requiredapparatus

Carry out the experimentalprocedure to produce and collectresultsClean up

*Safety considerations must be revisited throughout all planning and practicalstages.Good luck with planning and carrying out your Researching Chemistryinvestigation!



2.8 Resources

Texts


Practical work

• Pupils could have access to chemicals with a variety of hazard symbols on themso they can become familiar with them.

• Pupils could have access to apparatus so they can become familiar with them.


End of topic 2 test

Q22: What does the following hazard symbol represent?

a) Harmful / Irritantb) Respiratory Sensitizerc) Toxicd) Corrosive

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Q26: What piece of apparatus does the following diagram represent?

a) Conical flaskb) Measuring cylinderc) Buretted) Volumetric flask

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31

Topic 3

Carrying out an investigation

Contents


3.2 Carrying out an investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.3 Identifying the key stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.4 Practical techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4.1 Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4.2 Distillation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4.3 Use of a balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.4.4 Titration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.4.5 Methods for the collection of a gas . . . . . . . . . . . . . . . . . . . . . 38

3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.6 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.7 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40


You should already:









• be familiar with applying your knowledge of experimental techniques to unfamiliarsituations (National 5, Outcome 2.4);

32 TOPIC 3. CARRYING OUT AN INVESTIGATION

• have the ability to:

– select the appropriate practical technique(s) and apparatus for a particularprocedure;

– recognise that there are always significant safety risks when carrying outscientific procedures that must be taken into account in the planning stage.

Learning Objectives

Before starting any experiment you should have devoted some time to planning.Breaking an experiment down into key stages involves looking at areas such asapparatus required, chemicals required, procedures to be carried out and risks. Effectiveplanning will help you to save time in the long term and will ensure you are fully preparedbefore you start your investigation.In addition, your investigation may require you to order chemicals or apparatus notnormally found in the lab so it is helpful to identify these so they can be requestedbefore you wish to start.These steps should ensure that when you come to carry out your investigation, it willrun more smoothly. By the end of this topic, you should have the ability to:





TOPIC 3. CARRYING OUT AN INVESTIGATION 33



Q1: Which of the following would be the best piece of apparatus to use to quickly heatwater and bring it to the boil?

a) Any of theseb) Bunsen burnerc) Water bathd) Heating mantle

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Q2: Name a practical technique which involves reacting a vitamin C tablet with iodinein order to determine the mass of vitamin C present?


. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q3: Which of the following is the correct hazard symbol for a respiratory sensitiser?

a)

b)

c)

d)

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3.2 Carrying out an investigation

Key Point

An explanation of areas to be considered before carrying out an investigation.

This topic will help you to develop the skills of effectively carrying out a scientificinvestigation at Higher Chemistry level.

It will focus on identifying key stages in a reaction and identifying practical techniques.

3.3 Identifying the key stages

Key Point

An introduction to breaking an experiment down into its key stages.

What are the key stages involved in effectively carrying out your investigation?

It is good practice to work these out before you start your investigation in order to savetime later.

You may find that some stage must be carried out before others as they require productsfrom one experiment are reactants in another. Or, you may find that some techniquesmay take so long that you need to set them up as soon as you arrive in the lab.

Identifying the key stages: Exercise

Consider the following procedure for separating salt from rock salt.

Five spatulafuls of rock salt and 50 cm3 of water were added to a beaker andstirred for approximately 5 minutes. The mixture was subsequently filtered, andthe filtrate transferred to an evaporating basin. The filtrate was then evaporatedalmost to dryness using a Bunsen burner. The heat was removed and the saltcrystals were left to dry overnight at room temperature.

Q4: Break the procedure down into a logical and detailed series of stages. In orderto do this, you will have to plan ahead. Note these down on a piece of paper and thencompare them with the model answer.

Consider which apparatus and chemicals you will need to collect, and at what point inthe procedure it would be most appropriate to collect and assemble them.

Note: There may be more than one way to sensibly carry out this procedure! Therecan be some flexibility in the order of the stages. However, in general, planning aheadensures that all the appropriate chemicals and apparatus are available, that no key stepsare missed out and that the procedure is carried out smoothly and quickly.

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3.4 Practical techniques

Key Point

An overview of practical techniques from the course that students should befamiliar with.

Throughout the Higher course, you will have become familiar with a variety of techniquesand have developed the skills to carry these out safely in the lab.

For your investigation, you are expected to be familiar with the following techniques:

1. Filtration

2. Distillation

3. Use of a balance

4. Titration

5. Methods for the collection of a gas

3.4.1 Filtration

Filtration is used to separate an insoluble solid from a solid / liquid mixture.

Filter funnel Beaker

Filter paper

Conical flask

The liquid goes through the small holes in the filter paper but the solid does not andstays on the filter paper.

The substance(s) left in the filter paper at the end is called the residue.

The substance(s) which pass through the filter paper into the conical flask are known asthe filtrate.



Evaporation

Filtration is often followed by evaporation.

Evaporation is a technique for separating a solvent from a solution. The solution is eitherleft to evaporate in an evaporating dish or it can be heated so the process happensfaster.

Gauze

Bunsen burner

Evaporating dish

Tripod stand

Safety mat

The disadvantage of this method is that the solvent is lost to the air. Therefore it shouldnot be used if your solvent is harmful or flammable.

3.4.2 Distillation

Distillation is a practical technique used for separating miscible liquids with differentboiling points. The liquid with the lowest boiling point will distil first.

Heat Source

Thermometer

Condenser

Distillate



The liquid which evaporates, is condensed and is collected in the conical flask is knownas the distillate.

A thermometer tells you the exact temperature of the gas being distilled but it is goodpractice to check that your thermometer is of the correct range before you begin. Forexample, a thermometer with range 0◦C to 100◦C would not be used if the boiling pointsof your substances are over 100◦C!

Safe methods for heating

You should also carefully consider your heating method. Bunsen burners can reach hightemperatures quickly but can be hard to control the heating and should never be used ifflammable liquids are being distilled. Heating mantles are slow to heat but can be usedsafely to heat all liquids and allow much greater control of the temperature. Water bathsare safe to use but are very slow to heat, cannot heat anything above 100◦C (the boilingpoint of water) and have poor temperature control.

We have come across it before as a method for evaporating water (bp 100◦C) from asolution of alcohol and ethanol (bp 79◦C) in order to increase the alcohol content ofspirits.

3.4.3 Use of a balance

There are many different methods for using a balance to measure a mass accurately.One is shown below.

Steps to using a balance:

1. Turn on the balance.

2. When the balance reads 0.00 g place the container on the balance.

3. "Tare" the balance (may be marked as T).

4. When the balance reads 0.00 g again it is ready to be used for that container.

5. Place substance into container (not on balance).

6. Place the container onto the balance.

7. Record the reading with correct units for mass (g/mg).

2 4 6 8

64.00

63.80

63.60

63.40

63.20

63.00

62.8063.74 g

Time (minutes)

Mass of beaker andcontents (g)



3.4.4 Titration

Titrations are practical techniques used to determine an exact quantity or concentrationof a reactant.

Burette

Stopcock

Acid of unknownconcentration

Base of knownconcentration

In previous topics, we have looked at a variety of titrations including acid/base titrationsand redox titrations.

3.4.5 Methods for the collection of a gas

There are two main methods for collecting a gas. The one that you use will depend onwhether your gas is soluble or insoluble.

Insoluble gases only

Reactionproducing gas

Water

Collected gasTest tube

Insoluble gases can be collected over water. An upturned measuring cylinder or a gas



jar is filled with water and inverted in a water bath. A delivery tube is placed underneathand the gas bubbles through.

Soluble and insoluble gases

Reactionproducing gas

Gas syringe Plunger

A gas syringe is the most accurate way of collecting a gas. The scale is marked on itand can simply be read off. However, there is a limit to the volume of gas that can becollected this way (normally only 100 cm3).

3.5 Summary

Summary

You should now have the ability to:




You should be able to describe each of the following practical techniques and beaware of when to use them:

1. Filtration

2. Distillation

3. Use of a balance

4. Titration




3.6 Resources

Texts


Practical work

• Pupils could have access to chemicals with a variety of hazard symbols on themso they can become familiar with them.

• Pupils could have access to apparatus for the practical techniques so they canbecome familiar with them.

• Pupils should already have covered the practical techniques as part of the Highercourse.


End of topic 3 test

Use the following image to help you identify elements of titration equipment.

Q5: Which part of the diagram indicates the burette?

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Q6: Which part of the diagram indicates the pipette?

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Q7: Which part of the diagram indicates the indicator?

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Q8: Which part of the diagram indicates the volumetric flask?

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Q9: Match up each practical technique in the table below to its most appropriate use.Choose from:

1. Collecting a water-soluble gas 2. Heating an aqueous solution rapidly to60◦C

3. Separating a mixture of miscible liquids 4. Weighing out chemicals

5. Collecting a gas which is insoluble inwater

6. Determining the concentration of asolution

7. Separating a solvent from a solution8. Separate an insoluble solid from a solid/ liquid mixture

9. Heating a flammable liquid to 120◦C

Technique UseFiltrationEvaporation

DistillationUse of balanceHeating using a Bunsen burner

Use of a gas syringe to collect a gas

TitrationCollecting a gas over water

Heating using a heating mantle

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43

Topic 4

Processing & analysing results

Contents


4.2 Representing experimental data using a scatter graph . . . . . . . . . . . . . . 46

4.2.1 Guidelines for plotting a scatter graph . . . . . . . . . . . . . . . . . . . 46

4.2.2 Drawing the line - the best fit . . . . . . . . . . . . . . . . . . . . . . . . 46

4.3 Replicate measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.4 Calculating the mean value for experimental data . . . . . . . . . . . . . . . . . 49

4.5 Identification and elimination of 'rogue' points . . . . . . . . . . . . . . . . . . . 49

4.6 Qualitative appreciation of the relative accuracy of volume apparatus . . . . . . 51

4.7 Qualitative understanding of uncertainty associated with a measurement . . . . 52

4.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.9 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54


You should already:










44 TOPIC 4. PROCESSING & ANALYSING RESULTS



– recognise that there are always significant safety risks when carrying outscientific procedures that must be taken into account in the planning stage.

Learning Objectives

The ability to process data correctly and make decisions about the quality of the datais an essential skill for a practising chemist. Outcome 3 of the Researching Chemistryunit of Higher Chemistry states that the student has the ability to present and analyseinformation in an appropriate format, draw valid conclusions and make a valid evaluationof procedures. The aim of this topic is to help you to obtain a qualitative understandingof the approaches used to estimate the reliability of data obtained from experiments.By the end of this topic, you should have the ability to:

• represent experimental data using a scatter graph;

• sketch lines and/or curves of best fit;

• carry out calculations of averages (means) for experimental data;

• identify and eliminate ‘rogue’ points from results;

• qualitatively appreciate the relative accuracy of apparatus used to measure thevolume of liquids;

• qualitatively appreciate the reproducibility of repeated measurements fromvariability of data values;

• qualitatively understand the uncertainty associated with a measurement.


TOPIC 4. PROCESSING & ANALYSING RESULTS 45



Q1: Which of the following would be the best piece of apparatus to use to accuratelymeasure out a volume of alkali of unknown concentration to be titrated against an acid?

a) Dropperb) Pipettec) Measuring cylinderd) Conical flask

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Q2: Name the practical technique which involves increasing the concentration ofethanol in an alcoholic drink.


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Q3: Which of the following is the correct hazard symbol for a respiratory sensitiser?

a)

b)

c)

d)

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4.2 Representing experimental data using a scatter graph

Scatter graphs are similar to line graphs in that they use horizontal and vertical axes toplot data points. However, they have a very specific purpose. Scatter plots show howmuch one variable is affected by another. The relationship between two variables iscalled their correlation.

When you carry out an experiment, you normally change one variable and measureanother. For example, you might investigate the effect of changing temperature on rateof reaction - changing the temperature and measuring the time taken for the reaction.

Best-fit lines can also be called trend lines or linear regressions. Plotting data asa scatter graph suggests that you are investigating the relationship between the twovariables.

4.2.1 Guidelines for plotting a scatter graph

1. Draw axes at right angles to each other:

• The horizontal is the x-axis - the independent variable (the one that youchange) is plotted here.

• The vertical is the y-axis - the dependent variable (the one you measure) isplotted here.

2. Label the axes with the variables and their units. The variable that you change willgo on the x-axis and the variable that you measure will go on the y-axis.

3. Put the correct scale on each axis. The correct scale is decided from the rangeof points you have to plot but must always be uniform. So if you have a range ofpoints, 0.5, 1.3, 1.9, 3.4, 4.8, then the scale will be from 0-5, evenly spread.

4. Plot the points.

4.2.2 Drawing the line - the best fit

Key Point

A short summary of scatter graphs and lines of best fit.

When you have plotted the points, you have to join them up with some sort of line. Theusual graph shapes are a straight line or a smooth curve.

If the graph is a straight line, use a ruler to draw it. Ideally, the line would go throughall the points, but this rarely happens and so you draw the line which goes as near aspossible to as many points as possible. This is called the line of best fit.

Do not draw a line from one dot to the next. This will give a ‘join the dots’ look to thegraph and can prevent you from seeing the trend to the graph.



An example of a graph where a line has been drawn by ‘joining the dots’ is shown below.

It would be difficult to draw a conclusion about the trend of this graph the way it has beendrawn. However, when a line of best fit is drawn, a trend can be seen, as shown here:

When drawing a straight line of best fit, try to draw the line through the middle of thepoints. You might not hit any of the points directly but you should aim to have the samenumber of points above and below your line.

If the graph is not a line but a curve, then the line joining the points has to be drawnfreehand, but it should still be drawn as a smooth curve which fits as many points aswell as possible.



Drawing the line - the best fit: Question

Q4:

On graph paper, plot the following data as a scatter plot and draw the line of best fit.

Concentration of KI (mol l-1) Rate of reaction (s-1)

0.01 0.0130.02 0.0210.05 0.0440.10 0.1220.20 0.212

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4.3 Replicate measurements

Key Point

An introduction to replicate results.

Replicate experiments should always be performed. The number of replicateexperiments carried out will depend on the particular experiment, but a minimum ofthree times is recommended.

The purpose of replicate measurements is to assess the variability and prevent amistake affecting the conclusion of an experiment. The closer together the values fromrepeated experiments are, the better the reproducibility. Generally, an experiment canbe considered to be reliable if the results are reproducible.

Replicate measurements: Question

Q5:

Sample results from a titration using two different indicators are given below. Whichindicator provides the most reproducible results?

Indicator A Indicator B9.8 9.910.1 9.89.5 9.99.8 10.010.0 9.89.6 9.89.3 10.0

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4.4 Calculating the mean value for experimental data

The mean is the sum of the measured values divided by the number of measurements.

When rounding, it is best to express the mean with one more digit than was present inthe original data.

For example the mean can be calculated from the set of results below:

0.114, 0.165, 0.210, 0.186, 0.139

Step 1 : Calculate the sum of all the values

• (0.114 + 0.165 + 0.210 + 0.186 + 0.139) = 0.814

Step 2: Divide this by the total number of results added together to calculate the mean:

• (0.814 / 5) = 0.1628

Calculating the mean value: Questions

Q6: Calculate the mean of 0.123, 0.109, 0.128, 0.116, 0.119.

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Q7: Calculate the mean of 10.2, 11.8, 11.0, 10.8, 11.3.

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4.5 Identification and elimination of 'rogue' points

Key Point

An introduction to identifying and eliminating rogue points.

Errors will always be present in any measurement you make. Sometimes it is easy toidentify when you have made a mistake.

For example, when you weigh a solid sample and transfer it to a flask to prepare asolution, you might spill some solid and so you know that the mass of solid transferredto the flask does not match the mass you recorded from the reading on the balance.

In most cases, you will have no obvious errors but still obtain a data point that does notseem to match the trend in the rest of your data. As you have already seen in drawinga best-fit line or curve, you do not ‘join the dots’ in drawing a graph, you draw the lineto pass through most of the points. In this case, points far away from the line can beconsidered to be ‘rogue’ points, but they do not affect the line that you have drawn.

It is more difficult to identify rogue points when you have repeated the same experimenta number of times and are calculating the average. You cannot ignore a point justbecause it does not ‘look’ right, but there are occasions when you can reject a point.

Example

A student is using titration to determine the vitamin C content of a carton of orange juice.



The student performs 10 replicate measurements using 10 ml of orange juice each time.

The mass of vitamin C, in milligrams, found in each 10 ml sample is as follows:

• 1.95, 2.12, 1.89, 2.04, 2.68, 1.99, 2.09, 2.01, 1.92, 2.11

From this data, 2.68 mg ‘looks’ like a rogue point because it seems much higher thanthe rest of the numbers obtained. In this case, we can check if it can be eliminatedbecause the carton will have a vitamin C content that we can use for comparison. Thestated content of vitamin C on the carton is 2 mg per 10 ml.

Q8:

Calculate the average of all 10 data points.

• 1.95, 2.12, 1.89, 2.04, 2.68, 1.99, 2.09, 2.01, 1.92, 2.11

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Q9:

Calculate the average of 9 data points, eliminating 2.68.

• 1.95, 2.12, 1.89, 2.04, 1.99, 2.09, 2.01, 1.92, 2.11

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By comparing these two means to the 2 mg stated content on the carton, we can seethat, in this case, it is valid to reject the rogue value of 2.68 mg.

Identification and elimination of 'rogue' points: Questions

A student is using titration to determine the vitamin C content of a carton of lemon juice.The student performs 10 replicate measurements using 10 ml of lemon juice each time.

The following results are obtained (cm3):

1.45, 1.62, 1.39, 1.54, 2.18, 1.49, 1.59, 1.51, 1.42, 1.61

Q10: Calculate the average of all 10 data points.

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Q11: The label on the lemon juice states that there is 1.5 mg present, reject the roguevalue and calculate the new average.

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4.6 Qualitative appreciation of the relative accuracy ofvolume apparatus

Key Point

An introduction to calculating uncertainties in volume apparatus.

The volume of liquids can be measured using several pieces of common laboratoryequipment. Beakers, measuring cylinders, burettes, pipettes and volumetric flasks areused to measure volume with differing degrees of accuracy.

Accuracy means closeness to the true value. On the pieces of apparatus that are usedto measure volume, you will see a number with a plus or minus (±) then another number.This is a measure of the accuracy of the apparatus for measuring the specified volume.The ± value is called the uncertainty of the measurement.

A pipette is a more accurate piece of equipment for measuring volume than a measuringcylinder. All pieces of equipment will have a stated uncertainty. The uncertainty valuescan be used to compare the relative accuracies of the different pieces of equipmentused to measure volume.

A piece of laboratory glassware may specify that it contains a certain volume when it isfilled to a certain mark. For example, a measuring cylinder may specify a volume of 100± 5 cm3 when filled to the top mark. This means that when you fill the cylinder to the100 cm3 mark, as carefully as you can, the actual volume will be between 95 and 105cm3.

Examples of the tolerances of common laboratory equipment for measuring volume aregiven below. Note that these values are examples only; the actual values will varydepending on the glassware available.

ApparatusVolume measured±uncertainty (cm3)

10 ml pipette25 ml pipette

100 ml volumetric flask250 ml volumetric flask

10 ml measuring cylinder100 ml measuring cylinder

50 ml burette50 ml beaker100 ml beaker

10 ±0.0425 ±0.06100 ±0.2250 ±0.310 ±0.2

100 ±0.150 ±0.10

40 ±280 ±4

Most accurate

Least accurate

There will always be an error associated with volume measurement. Even if you areextremely careful, use a volumetric flask and fill the flask exactly to the line, the stateduncertainty on the flask tells you that it will not contain exactly the volume printed on theflask.



4.7 Qualitative understanding of uncertainty associatedwith a measurement

Key Point

An introduction to calculating uncertainties in measuring apparatus.

When considering volume measurements, we saw that there will always be errorattached to the measurement regardless of how careful you are. The same rule appliesto all measurements. All measurements have an uncertainty built into them.

The uncertainty of a measurement can be taken as half the value that they estimate.For example, if a thermometer is marked to 0.1◦C and the temperature is recorded to0.01◦C, then the hundredths of a degree are being estimated and so the error can beup to half of this value.

Qualitative understanding of uncertainty associated with a measurement:Question

Q12: Consider the different types of measuring equipment in the laboratory. Picture theequipment used for measuring length, mass and temperature.

Using the information above, match the uncertainty value to the apparatus. Fill in theblanks to show the equivalent categories involved when planning and carrying out of ascientific investigation. Choose from:

• 0.05 g

• 0.0005 g

• 0.05◦C

• 0.05 cm

Apparatus Uncertainty

Thermometer with 0.1◦C divisions1 decimal place balance

3 decimal place balance

Ruler with 0.1 cm divisions

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There is always an uncertainty associated with a measurement. The level of uncertaintyvaries depending on the complexity of the equipment.

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4.8 Summary

Summary

You should feel confident in:

• representing experimental data using a scatter graph;

• sketching lines and/or curves of best fit;

• calculating averages (means) for experimental data;

• identifying and eliminating of ‘rogue’ points from results;

• describing the relative accuracy of apparatus used to measure the volumeof liquids;

• describing how the reproducibility of repeated measurements fromvariability of data values;

• describing the uncertainty associated with a measurement.

Make sure that you do not add your own errors when making measurements bybeing as careful as you can when reading scales, transferring solids and liquidsand copying down numbers.

4.9 Resources

Texts


Practical work

• Pupils could have access to apparatus to check their uncertainties.




End of topic 4 test

Q13: A student carried out an experiment to investigate how the conductivity of anionic solution (mA) varies with concentration (mol l-1). Which of the following shouldbe discarded as a “rogue” point?

a) Ab) Bc) Cd) D

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Q14: Sodium hydroxide solution (0.1 mol l-1) was reacted with vinegar in a titrationexperiment. The experiment was repeated several times and the following resultsobtained:

1 2 3 4Initial burette(cm3) 0.0 20.0 10.0 0.0

Final burette(cm3) 24.1 43.5 33.6 23.8

Volume ofvinegar (cm3) 24.1 23.5 23.6 23.8

Which of the following shows the correct volume for the average titre?

a) 23.75 cm3

b) 23.63 cm3

c) 23.55 cm3

d) 23.80 cm3

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Q15: A student weighs out a sample of a chemical on a digital balance that read to±0.01 g. The measured mass was 3.75 g. What is the true mass of the sample?

a) 3.74 gb) 3.76 gc) 3.75 gd) 3.74 g - 3.76 g

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Q16: A student carries out a redox titration of vitamin C with iodine. The experimentwas repeated several times and the following results obtained:


Final burette(cm3) 18.0 37.4 27.3 17.4


The correct value for the titre was calculated to be 18.3cm3. Which of the followingstatements best describes the student’s results?

a) Accurate and reproducibleb) Inaccurate and reproduciblec) Accurate and not reproducibled) Inaccurate and not reproducible

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57

Topic 5

Evaluating & drawing conclusions

Contents

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

5.2 Evaluating procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

5.3 Evaluating results and drawing conclusions . . . . . . . . . . . . . . . . . . . . 64

5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

5.5 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

5.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69


You should already:

• have carried out a variety of practical experiments throughout the course. (Higher);










– recognise that there are always significant safety risks when carrying outscientific procedures that must be taken into account in the planning stage;

• have confidence in:

58 TOPIC 5. EVALUATING & DRAWING CONCLUSIONS

– representing experimental data using a scatter graph;

– sketching lines and/or curves of best fit;

– calculating averages (means) for experimental data;

– identifying and eliminating of ‘rogue’ points from results;

– describing the relative accuracy of apparatus used to measure the volume ofliquids;

– describing how the reproducibility of repeated measurements from variabilityof data values;

– describing the uncertainty associated with a measurement.

Learning Objectives

By the end of this topic, you should have the ability to:

• evaluate an experimental procedure - assess its effectiveness, plan for futuremodifications and to judge whether an alternative method might be more suitable;

• evaluate experimental results - spot trends and patterns in the data, to makepredictions in similar situations in the future and to assess and explain therelevance of the results obtained.


TOPIC 5. EVALUATING & DRAWING CONCLUSIONS 59

5.1 Introduction

The aim of this topic is to develop the skills of evaluating and drawing conclusions withinthe context of an investigation in chemistry.

We are constantly evaluating situations in our everyday lives and drawing conclusionsbased on the available evidence to help decide the best way forward. Most of the timewe do this without even thinking about it.

For example, imagine baking a cake. We might evaluate how the finished cake looks.If it is too pale, then it probably should have been left in the oven for a bit longer. Ifit is burnt around the edges, however, then a cooler oven should have been used orperhaps the cake should have been removed from the heat sooner. We will probablyalso evaluate how the cake tastes. If it is not moist enough, then perhaps some extraliquid ingredients should have been added or maybe less flour should have been used.If the cake is very heavy, it is likely that the ingredients should have been stirred forlonger to introduce more air to the mixture.

The skill of evaluating experimental procedures and data and then drawing relevant,evidence-based conclusions is crucial for carrying out effective investigative research inchemistry.

The Researching Chemistry unit of the Higher Chemistry will give you the opportunity todemonstrate these skills whilst writing your report.

Top Tip

Evaluate experimental data and procedures as you go along. Don’t wait until youare writing up your report - it may be too late to fix any problems at that stage.Your conclusion(s) should relate back clearly to the aim(s) of the investigation.Make sure you are very clear about what you are setting out to do from the start - itwill make life much easier when you are producing your scientific communication.Make sure your conclusion is both accurate (gives the correct result) andreproducible (could be achieved again if the experiment was repeated).



5.2 Evaluating procedures

Evaluating procedures: Questions

Q1: A burette is used to measure volume during a redox titration.

Which of the diagrams correctly shows where the meniscus reading should be taken?

a) Ab) Bc) C

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Q2: Here are the results of a redox titration.

Titration Volume (cm3)

Rough 25.01 24.52 25.53 24.6

Which two results in the table should be discarded before calculating the average titre?

A) Rough

B) Titration 1

C) Titration 2

D) Titration 3

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Q3: What is the average titre for the experiment?


Rough 25.01 24.52 25.53 24.6

A) 24.55 cm3

B) 24.87 cm3

C) 24.90 cm3

D) 25.10 cm3

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Q4: Select the piece of apparatus that would be most suitable for carrying out each ofthe tasks in an investigation.

Choose from:

• 100 cm3 beaker

• 50 cm3 burette

• Graduated plastic dropper

• 50 cm3 pipette

Task Apparatus

Accurately measuring exactly 50 cm3 ofhydrochloric acid (0.5 mol l-1) into avolumetric flask for a titration experimentinvolving a neutralisation reaction.

Measuring about 100 cm3 of water, to beused as a hot water bath during anesterification reaction.

Adding about 1 cm3 of starch indicatorsolution to the volumetric flask being usedin a redox titration involving iodine.

Accurately measuring the volume ofpotassium permanganate solution (0.20mol l-1) required to react with 25.0 cm3 ofoxalic acid (0.40 mol l-1).

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Q5: Many different heating methods are available in a chemistry laboratory. Match upthe most appropriate heating method to each task in the table below.

Choose from:

• Water bath

• Bunsen burner

• Heating mantle

Task Heating method

Distillation of ethanol at 78◦CMaintaining an enzymatic reaction atabout 40◦CHeating water quickly to about 60◦C

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Q6: Why would it be inappropriate to use a Bunsen burner to warm a chemical reactionbetween an alcohol and a carboxylic acid?

a) It would heat the reaction too quickly.b) The reactants are flammable.c) The products are flammable.d) Both the reactants and the products are flammable.

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Q7: What are two advantages of heating a reaction mixture with a Bunsen burnercompared to heating it with a heating mantle?

A) It is safer.

B) It is quicker.

C) It can heat to a higher temperature.

D) You have better control over the temperature.

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Q8: A student wants to collect and measure the volume of carbon dioxide gas beinggiven off in her experiment. She decides to collect the gas over water, using an upturnedmeasuring cylinder.

Why is she likely to be unsuccessful in obtaining an accurate measurement using thismethod?

a) Carbon dioxide is soluble in water so some will dissolve in the water.b) Carbon dioxide will escape out of the measuring cylinder.c) You must use a gas jar to collect gas, not a measuring cylinder.d) Not enough carbon dioxide gas will be given off to displace the water.

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Q9: Name a gas that could be successfully collected and measured over water.

a) Carbon dioxideb) Sulphur dioxidec) Nitrogen monoxided) Hydrogen

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Q10: Suggest a more appropriate method that she could use to collect and measurethe volume of carbon dioxide gas.

a) Pipetteb) Burettec) Gas jard) Gas syringe

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Q11: A student is carrying out a distillation to separate ethanol and water. Theinstructions say that the distillation should be carried out using a heating mantle setat about 80◦C, but the student wants to speed the reaction up by increasing thetemperature to the maximum setting of 150◦C. Use your skills of evaluation to explainwhy this suggestion would be unsuccessful.

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5.3 Evaluating results and drawing conclusions

Key Point

A series of questions designed to help you evaluate your results and drawconclusions from them.

This activity will take you through a series of questions, all designed to help you evaluateyour results and enable you to draw conclusions from them.

Evaluating results and drawing conclusions: Questions

Q12: What general trend can be observed in the graph below?

a) As we cross Period 2, the first ionisation energy increases.b) As we cross Period 2, the first ionisation energy decreases.c) As we cross Group 2, the first ionisation energy increases.d) As we cross Group 2, the first ionisation energy decreases.

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Q13: Why is a line graph not the correct way to present the information in the graph?

a) The information to be graphed is types and numbers, not two sets of numbers.b) The scale does not fit.c) It does not give a smooth line.d) The graph is too small.

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Q14: Suggest a more appropriate presentation method for the information in the graph.

a) Bar graphb) Pie chartc) Diagramd) Scatter graph

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Q15: Identify the problem with the graph below.

a) The line of best fit should be a curve.b) The scale is incorrect.c) The x and y axis are the wrong way around.d) The reaction time should be in seconds.

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Q16: What trend is shown in the graph below?

a) As temperature increases, rate of reaction increases.b) As temperature increases, rate of reaction decreases.c) As rate of reaction increases, temperature increases.d) As rate of reaction decreases, temperature increases.

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Q17: Why would this reaction in the previous question be unlikely to be successful if itwas carried out at room temperature?

a) The colour change would be too slow to accurately stop the timer.b) The reaction will not occur at room temperature.c) The colour change would be too quick to accurately stop the timer.d) The reaction will not occur below 10◦C.

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Q18: Describe the relationship between the variables in the graph below.

a) As concentration increases, absorbance increases.b) As concentration increases, absorbance decreases.c) As absorbance decreases, concentration increases.d) As absorbance increases, concentration decreases.

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Q19: From the graph in the previous question, estimate the absorbance value for asolution with concentration 2.5 mg cm-3.

a) 0.25b) 0.75c) 1.00d) 2.50

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Q20: What are the two problems with the graph below and how could they be corrected?(3 marks)

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5.4 Summary

Summary


• evaluate an experimental procedure:

– assess its effectiveness;

– plan for future modifications;

– judge whether an alternative method might be more suitable.

• evaluate experimental results:

– spot trends and patterns in the data;

– make predictions in similar situations in the future;

– assess and explain the relevance of the results obtained.



5.5 Resources

Texts


Practical work

• Pupils could carry out some of the reactions demonstrated by the graphs in thistopic and record their own results.


There is no end of topic test for this topic as the topic itself is a series of questions.


71

Topic 6

Scientific communication

Contents

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.2 The passive voice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.3 Chemical grammar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

6.4 Formal language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

6.5 Formats of scientific communication . . . . . . . . . . . . . . . . . . . . . . . . 76

6.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

6.7 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

6.8 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80


You should already:










– recognise that there are always significant safety risks when carrying outscientific procedures that must be taken into account in the planning stage;

• have confidence in:

72 TOPIC 6. SCIENTIFIC COMMUNICATION

– representing experimental data using a scatter graph;

– sketching lines and/or curves of best fit;

– calculating averages (means) for experimental data;

– identifying and eliminating of ‘rogue’ points from results;

– describing the relative accuracy of apparatus used to measure the volume ofliquids;

– describing how the reproducibility of repeated measurements from variabilityof data values;

– describing the uncertainty associated with a measurement.

Learning Objectives

By the end of this topic, you should be able to:

• write up a report on your investigation using the skills of scientific communication.


TOPIC 6. SCIENTIFIC COMMUNICATION 73

6.1 Introduction

As part of the Researching Chemistry unit you will be asked to prepare a scientificcommunication about your investigation. The aim of this topic is to help you to developthe skills required in doing this.

It is very important that scientists effectively communicate their work and results. There’sno point in having a great scientific discovery and not telling anyone about it!

The scientific communication can take any of the formats in which the results of scientificresearch are commonly reported, including:

• PowerPoint presentation;

• conference poster;

• video presentation/podcast;

• web page;

• scientific paper;

• traditional lab report, etc.

However, regardless of the format chosen, your scientific communication must containthe following essential features:

• A clear statement of the aim of your work;

• An analysis of your results;

• A valid evaluation of the procedures and results;

• A valid conclusion based on the evidence in your results.

It can also be helpful (although not essential to pass the unit) to set the scene byincluding a summary of the background chemistry as part of an introduction (youwill have looked up information on this as part of your focus question), and a briefexplanation of the procedure(s) used. These additional sections would usually appearbetween the aim and the results.

6.2 The passive voice

Key Point

An introduction to writing in the past tense and passive voice.

Good scientific writing includes all the normal conventions of good writing practice.However, there are some additional ‘golden rules’ that should be observed in scientificwriting.

• Write in the past tense and passive voice.



For example, ‘Sodium chloride was added to the solution.’ is correct whereas ‘Addsodium chloride to the solution.’ or ‘I added the sodium chloride to the solution.’ are bothincorrect.

The passive voice: Questions

5 min

Try putting the following sentences into the past tense and passive voice.

Q1: I poured 5 ml of concentrated sulphuric acid into the flask.

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Q2: Record the volume of sodium hydroxide solution required to neutralise 25 ml acid.

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Q3: We then heated the reaction mixture gently using a water bath at 37◦C.

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6.3 Chemical grammar

Key Point

An introduction to the use of capital letters in scientific communication.

The name of an element or compound should not have a capital letter, except at thestart of a sentence.

Chemical symbols should be written exactly as they appear in the periodic table Forexample, use ‘Au’ and not ‘au’.

The name of a technique should not have a capital letter, except at the start of asentence. For example: ‘The distillation was set up to’ or ‘An acid-base titration wascarried out’.

Appropriate use of abbreviations. The expression should be written in full the firsttime it is used in the text, immediately followed by the abbreviation in brackets. Theabbreviation should be used from then onwards, eg International Union for Pure andApplied Chemistry (IUPAC) should thereafter be referred to as IUPAC.

Use the correct scientific spellings for chemical words For example IUPAC and the RoyalSociety of Chemistry (RSC) both adopted the spellings ‘sulfur’ and ‘sulfuric acid’ (insteadof ‘sulphur’ and ‘sulphuric acid’) in the early 1990s.



Chemical grammar: Question

Choose the correct version of the duplicated word.

Q4:

1. 5.1 g of powdered Lead / lead was added to hydrochloric acid / Hydrochloric Acid.

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Q5:

1. Tin/ tin has the symbol Sn.

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Q6:

1. The chemical symbol for iron is fe / Fe.

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Q7:

1. The technique used to separate miscible liquids with different boiling points is calleddistillation / Distillation.

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Q8:

1. 20 cm3 of sulphuric acid / sulfuric acid was measured out using a pipette.

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6.4 Formal language

Key Point

An introduction to the use of formal language in scientific communication.

A list of rules you should remember when writing up your report:

• Always use formal language in your investigation report.

• Colloquial (slang) language is never appropriate in scientific writing!

• Scientific writing should be both concise and precise.

• Scientific writing should contain sufficient accurate, detailed information to allowthe experiment to be repeated but without using redundant words or information.

• Be consistent with units and names.

• Do not change between different units or names, e.g. use either ml or cm3. Do notuse both in the same report.



Formal language: Questions

Think of an appropriate formal phrase to replace the colloquial phrase.

Q9: A spatula of carbon was chucked into the beaker.

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Q10: Loads of tiny bubbles were given off.

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Q11: The solid looked kind of like a silver mirror.

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Q12: The rest of the stuff needed for the reaction was added to the conical flask.

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6.5 Formats of scientific communication

Key Point

An introduction to the use of different formats for scientific communication.

Scientists can use a number of different methods to communicate about their work. Themost appropriate method will depend on the target audience and in how much detailthe information needs to be shared. Commonly used scientific communication formatsinclude:

1. Traditional lab report

• a formal account of an experiment

• contains enough detail to be used to repeat the experiment

• can be used to evaluate the procedure and results of an experiment

• written using the notes recorded in a lab book

2. Scientific report

• summarises the contents of many lab reports

• reviews some of the scientific literature in the topic

• makes recommendations based on both the research results and theliterature

• related lab reports, diagrams and raw data may be attached as appendices

3. Scientific paper

• a scientific report which is submitted to be an article in a scientific journal

• peer-reviewed by a respected scientist to evaluate the experiments, theresults and the writing



• the more high-quality scientific papers a scientist produces, the morerespected the scientist!

4. Scientific poster

• a large poster used to communicate research results at scientific conferences

• a highly visual method of presentation

• summarises key points briefly on a single page

5. PowerPoint presentation

• used to share results at meetings and conferences

• visual, interactive form of communication

• slides contain minimal information

• information on slides is expanded upon orally

6. Video presentation

• modern form of scientific communication

• visual and engaging

• means of interaction with wide audiences over the internet

7. Podcasts

• short soundbites of information on websites

• modern form of scientific communication

• means of interacting with wide audiences over the internet

8. Blogs

• short, regular ‘diary’-like posts on a website

• allow scientists to ‘drip-feed’ information to a wide audience

• another modern form of scientific communication

Formats of scientific communication: Exercise

In the past, scientists would almost always have produced a written report tocommunicate their research findings. Nowadays, they can choose to communicate inany one of a diverse range of communication media.

Examine and compare the four different resources listed below.

Note: It is not necessary to understand all of the chemistry content in the resourcesto undertake this activity. These resources can be evaluated with your current level ofchemistry knowledge.

1. A video clip from the TV programme ‘Brainiac’, in which scientists investigate thereaction of thermite with liquid nitrogen.

• http://youtu.be/MWncO6C1-XU


http://youtu.be/MWncO6C1-XU


2. A scientific paper from an on-line chemistry journal which looks at the effect ofantioxidants on heavy smokers.

• http://www.journal.chemistrycentral.com/content/3/1/13

3. An article from Highlights in Chemical Science on recent advances in the PeriodicTable.

• http://www.rsc.org/Publishing/ChemScience/Volume/2010/11/Extended�elements.asp

4. A conference poster entitled ‘Making Esters’.

• Download poster (.jpg)

Once you have looked over these resources, answer the following questions:

Q13: Which one was most eye-catching?

A) The video clip

B) The scientific paper

C) The journal article

D) The conference poster

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Q14: Which one looks like it will be the easiest to read and understand?

A) The video clip




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Q15: Which one looks most credible and reliable?

A) The video clip




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Q16: Which one was most interesting?

A) The video clip




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http://www.journal.chemistrycentral.com/content/3/1/13

http://www.rsc.org/Publishing/ChemScience/Volume/2010/11/Extended_elements.asp

http://demo.scholar.hw.ac.uk/vle/asset/Downloads/JOOSTY/Study%20Guides/A09504F2-BA70-043E-619F-FAA79D9F1457/hg-cche4-6-2poster.jpg


Q17: Which one gave the most information?

A) The video clip




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Q18: For which of the following did you need to understand everything in the resourceto gain a general understanding of the experiment?

A) The video clip




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6.6 Summary

Summary


• evaluate an experimental procedure;

• assess its effectiveness;

• plan for future modifications;

• judge whether an alternative method might be more suitable;







6.7 Resources

Texts


It would be helpful for students to have access to a variety of chemical posters, journals,web pages and scientific reports for reference.

Practical work

• Pupils could carry out some of the reactions demonstrated by the graphs in thistopic and record their own results.


End of topic 6 test

Q19: Look at the following sentences taken from a third year student’s lab report:

“Pour 10 cm3 acidified Sodium Dichromate into a boiling tube. To this was added, someEthanol and then the mixture was shaken gently. The mixture was then cooled by placingthe boiling in a small beaker of cold water. Once the reaction had calmed down a bit,the mixture is gently warmed lending to formation of Ethanoic Acid.”

Rewrite the student’s lab report to bring it up to the standard required for a real scientificreport. Check the golden rules of scientific writing to help you!

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Q20: Change the list of instructions below into scientific report format by converting tothe past tense (as the experiment was carried out in the past by the time of writing) andpassive voice, and joining the sentences up into a paragraph.

1. Using a measuring cylinder add 20 cm3 of dilute sulfuric acid to a beaker.

2. Add a spatulaful of magnesium or magnesium carbonate to the acid and stir thereaction mixture with a glass rod.

3. If all the solid reacts add another spatulaful of magnesium or magnesium carbonateand stir the mixture.

4. Continue adding the magnesium or magnesium carbonate until no more bubblesof gas are produced and some of the solid remains unreacted.

5. Place the filter funnel in the neck of the conical flask. Fold the filter paper and insertit in the funnel.

6. Carefully pour the reaction mixture into the filter paper.

7. When the filtration is complete, transfer the salt solution from the conical flask intothe evaporating basin.

8. Place the evaporating basin on the tripod and carefully heat the salt solution untilabout half the water has boiled off.

9. Let the basin cool before transferring it to a safe place. Leave it until your nextlesson to allow the solution to crystallise slowly.

10. Transfer the crystals onto a piece of filter paper to dry.

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Q21: The format chosen for a scientific communication will depend largely on the targetaudience.

Choose the most appropriate form of scientific communication for each of the situationsin the table below. Choose from:

Lab report Scientific poster Blog Scientific paper

Video (onwebsite)

Scientific reportPowerPointpresentation

Situation Type of communication

You are a scientist working in the qualityassurance lab of a pharmaceuticalcompany. You are undertaking anexperiment to analyse the purity of aspirintablets and need to record the details soyou don’t forget what you did.

You are a university professor who hasjust completed some highly significant,ground-breaking research that needs tobe communicated to other experts in thescientific community.

You are a scientific journalist working for apopular science magazine and want toprovide your wide readership with short,regular news updates on the latest hotscientific topics.

You are a scientist who is giving a one-offschools lecture entitled ‘Fun Explosions inChemistry’. You think that students whoare not able to be in the live audiencewould also benefit from seeing theseexciting experiments.

You are a young researcher who needsan eye-catching visual method ofcommunicating a summary of your resultsat an international conference.You are a young researcher who needsan eye-catching visual method ofcommunicating a summary of your resultsat an international conference.You are a product development scientistworking for a large consumer goodscompany. You have been asked to presentthe results of your recent research work tothe company director. You know he willwant to ask lots of questions.

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83

Topic 7

End of unit test

Contents

7.1 End of unit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

7.2 Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

84 TOPIC 7. END OF UNIT TEST

You should now be familiar with the following content.

Key Point

Web based researchThe following is a checklist for evaluating web pages; you should be familiar withthis and have used it to help you answer your focus question.Author (source)

• Can you find out the name of the author?

• Is there information about the author provided?

• Is it clear that an institution or university or organisation sponsored thewebsite (check the domain)?

Currency (date)

• Is the date the website was put on the internet present?

• Is an update or revision date present?

Level

• Is the website intended for a general or a scientific audience?

• Is the topic explored at a suitable level for Higher Chemistry?

Purpose

• Is the purpose of the site stated (to persuade, inform, explain, sell)?

Bias

• Is the information given and / or the views expressed biased?

Accuracy

• Are the sources of the information listed in a bibliography?

Conclusion

• Using the above information, is this an appropriate source for yourresearch? Justify your opinion.


TOPIC 7. END OF UNIT TEST 85

Key Point

Planning an investigationThe checklist below will help you to successfully plan and carry out the practicalaspects of your Researching Chemistry investigation.

Checklist√

Choose a topic (Your teacher may giveyou one)

Identify the most appropriatetechnique(s) you might use

Plan the stages of the experiment

Assess risks and plan to safelyovercome these risks*Identify and collect the requiredchemicalsIdentify and collect the requiredapparatus

Carry out the experimental procedureto produce and collect results

Clean up

*Safety considerations must be revisited throughout all planning and practicalstages.

Key Point

Carrying out an investigationYou should now have the ability to:




You should be able to describe each of the following practical techniques and beaware of when to use them:

1. Filtration

2. Distillation

3. Use of a balance

4. Titration




Key Point

Processing and analysing resultsYou should feel confident in:

• representing experimental data using a scatter graph;

• sketching lines and/or curves of best fit;

• calculating averages (means) for experimental data;

• identifying and eliminating of ‘rogue’ points from results;

• describing the relative accuracy of apparatus used to measure the volumeof liquids;

• describing how the reproducibility of repeated measurements fromvariability of data values;

• describing the uncertainty associated with a measurement.

Make sure that you do not add your own errors when making measurements bybeing as careful as you can when reading scales, transferring solids and liquidsand copying down numbers.

Key Point

Evaluating and drawing conclusionsYou should now have the ability to:

• evaluate an experimental procedure:

– assess its effectiveness;

– plan for future modifications;

– judge whether an alternative method might be more suitable.







Key Point

Scientific communicationYou should now have the ability to:

• evaluate an experimental procedure;

• assess its effectiveness;

• plan for future modifications;

• judge whether an alternative method might be more suitable.





7.1 End of unit test

End of unit 4 test



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Q2: The first step in any research activity involves finding out about a particular topicby carrying out:

a) a literature search.b) an internet search.c) an experiment.d) a peer review.

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Q3: Which of the following should you check when assessing if a website is reliable?

a) Which country it is from?b) When was it last updated?c) Does it look nice?d) Are there any photos?

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Q4: Which of the following is the least reliable domain?

a) .edub) .govc) .comd) .org

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Q5: Websites with which of the following purposes of would be suitable to use in yourresearch?

a) To persuadeb) To informc) Blogsd) To sell

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Q6: What is the main purpose of including references in your research?

a) To fill up space in a word countb) To allow another person to find the same informationc) To give credit to other authorsd) All of the above

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Q15: Match up each practical technique in the table below to its most appropriate use.Choose from:

Collecting a water-soluble gas Heating an aqueous solution rapidly to60◦C

Separating a mixture of miscible liquids Weighing out chemicals

Collecting a gas which is insoluble inwater

Determining the concentration of asolution

Separating a solvent from a solutionSeparate an insoluble solid from a solid /liquid mixture

Heating a flammable liquid to 120◦C

Technique UseFiltrationEvaporation

DistillationUse of balanceHeating using a Bunsen burner

Use of a gas syringe to collect a gas

TitrationCollecting a gas over water

Heating using a heating mantle

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Q16: A student carried out an experiment to investigate how the conductivity of anionic solution (mA) varies with concentration (mol l-1). Which of the following shouldbe discarded as a “rogue” point?

a) Ab) Bc) Cd) D

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Q17: Sodium hydroxide solution (0.1 mol l-1) was reacted with vinegar in a titrationexperiment. The experiment was repeated several times and the following results wereobtained:


Final burette(cm3) 24.1 43.5 33.6 23.8


Which of the following shows the correct volume for the average titre?

a) 23.75 cm3

b) 23.63 cm3

c) 23.55 cm3

d) 23.80 cm3

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Q18: A student weighs out a sample of a chemical on a digital balance that read to±0.01 g. The measured mass was 3.75 g. What is the true mass of the sample?

a) 3.74 gb) 3.76 gc) 3.75 gd) 3.74 g - 3.76 g

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Q19: A student carries out a redox titration of vitamin C with iodine. The experimentwas repeated several times and the following results obtained:


Final burette(cm3) 18.0 37.4 27.3 17.4


The correct value for the titre was calculated to be 18.3 cm3. Which of the followingstatements best describes the student’s results?

a) Accurate and reproducibleb) Inaccurate and reproduciblec) Accurate and not reproducibled) Inaccurate and not reproducible

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Q20: A burette is used to measure volume during a redox titration.

Which of the diagrams correctly shows where the meniscus reading should be taken?

a) Ab) Bc) C

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Q21: Here are the results of a redox titration.


Rough 25.01 24.52 25.53 24.6

Which two results in the table should be discarded before calculating the average titre?

A) Rough

B) Titration 1

C) Titration 2

D) Titration 3

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Q22: What is the average titre for the experiment?


Rough 25.01 24.52 25.53 24.6

A) 24.55 cm3

B) 24.90 cm3

C) 24.87 cm3

D) 25.10 cm3

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Q23: Select the piece of apparatus that would be most suitable for carrying out each ofthe tasks in an investigation.

Choose from:

• 100 cm3 beaker

• 50 cm3 burette

• Graduated plastic dropper

• 50 cm3 pipette

Task Apparatus




Accurately measuring the volume ofpotassium permanganate solution (0.20mol l-1) required to react with 25.0cm3 ofoxalic acid (0.40 mol l-1).

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Q24: Many different heating methods are available in a chemistry laboratory. Match upthe most appropriate heating method to each task in the table below.

Choose from:

• Water bath

• Bunsen burner

• Heating mantle

Task Heating method

Distillation of ethanol at 78◦CMaintaining an enzymatic reaction atabout 40◦CHeating water quickly to about 60◦C

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Q25: Why would it be inappropriate to use a Bunsen burner to warm a chemical reactionbetween an alcohol and a carboxylic acid?

a) It would heat the reaction too quickly.b) The reactants are flammable.c) The products are flammable.d) Both the reactants and the products are flammable.

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Q26: What are two advantages of heating a reaction mixture with a Bunsen burnercompared to heating it with a heating mantle?

A) It is safer.

B) It is quicker.

C) It can heat to a higher temperature.

D) You have better control over the temperature.

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Q27: A student wants to collect and measure the volume of carbon dioxide gas beinggiven off in her experiment. She decides to collect the gas over water, using an upturnedmeasuring cylinder.

Why is she likely to be unsuccessful in obtaining an accurate measurement using thismethod?

a) Carbon dioxide is soluble in water so some will dissolve in the water.b) Carbon dioxide will escape out of the measuring cylinder.c) You must use a gas jar to collect gas, not a measuring cylinder.d) Not enough carbon dioxide gas will be given off to displace the water.

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Q28: Name a gas that could be successfully collected and measured over water.

a) Carbon dioxideb) Sulphur dioxidec) Nitrogen monoxided) Hydrogen

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Q29: Select a more appropriate method that she could use to collect and measure thevolume of carbon dioxide gas.

a) Pipetteb) Burettec) Gas jard) Gas syringe

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Q30: What general trend can be observed in the graph below?

a) As we cross Period 2, the first ionisation energy increases.b) As we cross Period 2, the first ionisation energy decreases.c) As we cross Group 2, the first ionisation energy increases.d) As we cross Group 2, the first ionisation energy decreases.

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Q31: Why is a line graph not the correct way to present the information in the graph inquestion 1?

a) The information to be graphed is types and numbers.b) The scale does not fit.c) It does not give a smooth line.d) The graph is too small.

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Q32: Select a more appropriate presentation method for the information in the graph inquestion 1.

a) Bar graphb) Pie chartc) Diagramd) Scatter graph

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Q33: Identify the problem with the graph below.

a) The line of best fit should be a curve.b) The scale is incorrect.c) The x and y axis are the wrong way around.d) The reaction time should be in seconds.

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Q34: What trend is shown in the graph below?



a) As temperature increases, rate of reaction increases.b) As temperature increases, rate of reaction decreases.c) As rate of reaction increases, temperature increases.d) As rate of reaction decreases, temperature increases.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q35: Why would this reaction be unlikely to be successful if it was carried out at roomtemperature?

a) The colour change would be too slow to accurately stop the timer.b) The reaction will not occur at room temperature.c) The colour change would be too quick to accurately stop the timer.d) The reaction will not occur below 10◦C.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q36: Describe the relationship between the variables in the graph below.

a) As concentration increases, absorbance increases.b) As concentration increases, absorbance decreases.c) As absorbance decreases, concentration increases.d) As absorbance increases, concentration decreases.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Q37: From the graph in the previous question, estimate the absorbance value for asolution with concentration 2.5 mg cm-3.

a) 0.25b) 0.75c) 1.00d) 2.50

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Q38: Choose the correct version of the duplicated word.

1. 5.1 g of powdered Lead/ lead was added to hydrochloric acid/ Hydrochloric Acid.

2. Tin/ tin has the symbol Sn.

3. The chemical symbol for iron is fe / Fe.

4. The technique used to separate miscible liquids with different boiling points is calleddistillation / Distillation.

5. 20 cm3 of sulphuric acid / sulfuric acid was measured out using a pipette.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



Q39: The format chosen for a scientific communication will depend largely on the targetaudience.

Choose the most appropriate form of scientific communication for each of the situationsin the table below. Choose from:

Video (on website) Scientific report Scientific poster Blog

PowerPointpresentation

Scientific paper Lab report






You are a young researcher who needsan eye-catching visual method ofcommunicating a summary of your resultsat an international conference.You are a young researcher who needsan eye-catching visual method ofcommunicating a summary of your resultsat an international conference.You are a product development scientistworking for a large consumer goodscompany. You have been asked to presentthe results of your recent research work tothe company director. You know he willwant to ask lots of questions.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



7.2 Resources

Texts



ANSWERS: TOPIC 1 103

Answers to questions and activities

1 Web-based research

Test your prior knowledge (page 3)

Q1: d) All of the above

Q2: d) Distillation

Q3: c) Aim, Method Results, Conclusion

Reliability: Questions (page 6)

Q4:

• The epa site is much more reliable than the Wikipedia site.

• This is because anybody can add anything to Wikipedia at any time without provingthat it is correct.

• The epa site is a .gov site and so will have been fact checked to ensure allinformation there is correct.

• Both sites have been updated in the last six months.

Q5:

• The epa site is much more accurate than the Wikipedia site.

• This is because anybody can add anything to Wikipedia at any time without provingthat it is correct.

• The epa site is a .gov site and so will have been fact checked to ensure allinformation there is correct.

Q6:

• In general, both sites are accurate but upon closer inspection some of theinformation on the Wikipedia site is not correct.

Assessing level: Questions (page 7)

Q7: http://www.science.uwaterloo.ca/~cchieh/cact/applychem/heterocat.html

Q8: http://www.chemguide.co.uk/physical/basicrates/catalyst.html

Assessing bias: Questions (page 7)

Q9: Two of the sites have bias: http://www.clonaid.com/news.php andhttp://www.cloninginformation.org/tag/americans-to-ban-cloning/.

Q10: The following site is the most accurate: http://learn.genetics.utah.edu/content/cloning/whatiscloning/(It has a .edu domain)


http://www.science.uwaterloo.ca/~cchieh/cact/applychem/heterocat.html

http://www.chemguide.co.uk/physical/basicrates/catalyst.html

http://www.clonaid.com/news.php

http://www.cloninginformation.org/tag/americans-to-ban-cloning/


104 ANSWERS: TOPIC 1

Q11: http://learn.genetics.utah.edu/content/cloning/whatiscloning/ It has a .edu domainand has been recently updated.

End of Topic 1 test (page 11)


Q13: a) literature search.

Q14: b) When was it last updated?

Q15: c) .com

Q16: b) To inform

Q17: b) To allow another person to find the same information




2 Planning an investigation


Q1: d) Heating mantle

Q2: a) Precipitation

Q3: b)

Identifying the key stages: Exercise (page 16)

Q4:

Model answer:

1. Decide to have a cup of tea

2. Turn on tap

3. Put water in kettle

4. Turn off tap

5. Switch on kettle to boil water

6. Get out the cup

7. Get out the teaspoon

8. Put teaspoon in cup

9. Get out the teabag

10. Put teabag in cup

11. Get out the sugar

12. Add sugar

13. Add boiling water to cup

14. Leave for 2 minutes

15. Get out the milk

16. Add milk

17. Stir with teaspoon

18. Remove teabag with teaspoon

19. Put teabag in bin

20. Drink tea

21. Wash dishes

22. Tidy up



Identifying the key stages: Question (page 17)

Q5:

Making a cup of tea Scientific investigation

Decide to have a cup of tea Decide on topic for investigation

Source ingredients Collect chemicals required

Collect kitchen equipment Collect apparatus

Make tea Carry out the procedure

Drink tea Collect results

Tidy upPut away apparatus and dispose ofchemicals safely

Risk assessment: Question (page 20)

Q6: c) Rubber gloves to protect hands

Q7: B, C, and D

Q8: b) Carry out in a fume-cupboard

Q9: b) Carry out in a fume-cupboard

Q10: D and E

Practical techniques and apparatus: Common lab techniques (page 21)

Q11: c) Filtration

Q12: f) Use of a gas syringe to collect a gas

Q13: e) Heating using a Bunsen burner

Q14: i) Heating using a heating mantle

Q15: a) Heating using a water bath

Q16: d) Use of a balance

Q17: h) Collecting a gas over water

Q18: g) Titration

Q19: b) Distillation

Planning ahead: Questions (page 26)

Q20: a) Place five test-tubes in a test-tube rack.

Q21: e) All of the above



End of topic 2 test (page 28)

Q22: d) Corrosive

Q23: c) Toxic

Q24: a) Harmful / Irritant

Q25: b) Respiratory Sensitizer

Q26: b) Measuring cylinder

Q27: a) Conical flask

Q28: d) Volumetric flask

Q29: c) Burette



3 Carrying out an investigation


Q1: b) Bunsen burner

Q2: b) Titration

Q3: d)

Identifying the key stages: Exercise (page 34)

Q4:

Model answer

1. Measure out five spatulafuls of rock salt into a 100 cm3 beaker. Measure out 50cm3 of water using a measuring cylinder.

2. Add the water to the beaker of rock salt.

3. Stir the mixture for 5 minutes using a glass stirring rod.

4. Fold a filter paper into a cone and put it in a filter funnel. Put the filter funnel into aconical flask.

5. Filter the salt solution through the filter funnel.

6. Pour the filtrate (liquid) from the conical flask into an evaporating basin.

7. Set up a tripod on a heatproof mat and put the evaporating basin onto the tripod.

8. Light a Bunsen burner and place it under the tripod to heat the salt solution in theevaporating basin. Heat the solution until most of the water has gone.

9. Turn off the gas and let the salt dry at room temperature.


Q5: A

Q6: E

Q7: D

Q8: C

Q9:



Technique Use

FiltrationSeparate an insoluble solid from a solid /liquid mixture

Evaporation Separating a solvent from a solution

Distillation Separating a mixture of miscible liquids

Use of balance Weighing out chemicals

Heating using a Bunsen burner Heating an aqueous solution rapidly to60◦C

Use of a gas syringe to collect a gas Collecting a water-soluble gas

TitrationDetermining the concentration of asolution

Collecting a gas over water Collecting a gas which is insoluble inwater

Heating using a heating mantle Heating a flammable liquid to 120◦C



4 Processing & analysing results


Q1: b) Pipette

Q2: d) Distillation

Q3: d)

Drawing the line - the best fit: Question (page 48)

Q4: Answer: The equation of the line is given as y = 1.0795x + 0.0004. Calculate thegradient of your graph and compare it to this value of 1.079.

Replicate measurements: Question (page 48)

Q5: Answer: Indicator B as the values are closer together.

Calculating the mean value: Questions (page 49)

Q6: 0.119

Q7: 11.0

Answers from page 50.

Q8: (1.95 + 2.12 + 1.89 + 2.04 + 2.68 + 1.99 + 2.09 + 2.01 + 1.92 + 2.11) / 10 = 20.8 /10 = 2.08 mg

Q9: (1.95 + 2.12 + 1.89 + 2.04 + 1.99 + 2.09 + 2.01 + 1.92 + 2.11) / 10 = 18.12 / 10 =2.01 mg

Identification and elimination of 'rogue' points: Questions (page 50)

Q10: (1.45, 1.62, 1.39, 1.54, 2.18, 1.49, 1.59, 1.51, 1.42, 1.61) / 10 = 15.8 / 10 = 1.580cm3

Q11: Eliminate the rogue value - 2.18 (1.45, 1.62, 1.39, 1.54, 1.49, 1.59, 1.51, 1.42,1.61) / 10 = 13.62 / 9 = 1.513 cm3



Qualitative understanding of uncertainty associated with a measurement:Question (page 52)

Q12:

Apparatus Uncertainty

Thermometer with 0.1◦C divisions 0.05◦C1 decimal place balance 0.05 g

3 decimal place balance 0.0005 g

Ruler with 0.1 cm divisions 0.05 cm


Q13: b) B

Q14: c) 23.55 cm3

Q15: d) 3.74 g - 3.76 g

Q16: b) Inaccurate and reproducible



5 Evaluating & drawing conclusions

Evaluating procedures: Questions (page 60)

Q1: a) A

Q2: A and C

Answer Explanation:The rough (25.0 cm3) and Titration 2 (25.5 cm3) should be discarded. These values arenot concurrent as they are more than 0.2 cm3 or away from the other readings.

Q3: A

Answer Explanation:The rough (25.0 cm3) and Titration 2 (25.5 cm3) should be discarded. The average titreis the mean of Titration 1 and Titration 3. Working: (24.5 + 24.6) /2 = 24.55 cm3

Q4:

Task Apparatus


50 cm3 pipette


100 cm3 beaker


Graduated plastic dropper


50 cm3 burette

Answer Explanation

Line 1:An accurate measurement of exactly 50 cm3 is required. A pipette will achievethis more quickly than a burette.

Line 2: The volume required does not need to be measured accurately.

Line 3: As the indicator is not taking part in the reaction, a volume of roughly 1 cm3 willbe adequate. A dropper pipette is cheap and quick to use.

Line 4: An accurate volume measurement is required. As the accurate volume beingmeasured is not fixed, a burette is the most appropriate piece of apparatus to be used.

Q5:



Task Heating method

Distillation of ethanol at 78◦C Heating mantle

Maintaining an enzymatic reaction atabout 40◦C Water bath

Heating water quickly to about 60◦C Bunsen burner

Q6: d) Both the reactants and the products are flammable.

Q7: B and C

Q8: a) Carbon dioxide is soluble in water so some will dissolve in the water.

Q9: d) Hydrogen

Q10: d) Gas syringe

Q11:

• Distillation separates liquids according to their different boiling points. (1 mark)

• At 80◦C ethanol boils and turns into a gas, whilst water remains below its boilingpoint (100◦C) and therefore remains as a liquid. (1 mark)

• At 150◦C, both ethanol and water would turn to gases and therefore separation bydistillation would be unsuccessful. (1 mark)

Evaluating results and drawing conclusions: Questions (page 64)

Q12: a) As we cross Period 2, the first ionisation energy increases.

Q13: a) The information to be graphed is types and numbers, not two sets of numbers.

Q14: a) Bar graph

Q15: a) The line of best fit should be a curve.

Q16: a) As temperature increases, rate of reaction increases.

Q17: a) The colour change would be too slow to accurately stop the timer.

Q18: a) As concentration increases, absorbance increases.

Q19: b) 0.75

Q20: Problem 1The independent variable should be plotted on the x-axis, and the dependent variableon the y-axis. In this graph, time is the independent variable and should be on the x-axis.The volume of hydrogen is dependent on the time and therefore should be on the y-axis.

Problem 2

The graph is of the “join the dots” type. The line should be a curve of best fit.



6 Scientific communication

The passive voice: Questions (page 74)

Q1: 5 ml concentrated sulphuric acid was poured into the flask.

Q2: The volume of sodium hydroxide solution required to neutralise 25 ml acid wasrecorded.

Q3: The reaction mixture was heated gently using a water bath at 37◦C.

Chemical grammar: Question (page 75)

Q4:

1. lead / hydrochloric acid

Q5:

1. Tin

Q6:

1. Fe

Q7:

1. distillation

Q8:

1. sulfuric acid

Formal language: Questions (page 76)

Q9: A spatula of carbon was added to/placed in the beaker.

Q10: A large number of tiny bubbles were given off. Vigorous effervescence wasobserved.

Q11: The solid formed on the side of the test tube resembled/had the appearance of asilver mirror.

Q12: The remainder of the reactants/chemicals was added to the conical flask.

Formats of scientific communication: Exercise (page 77)

Q13: Any answer is correct.


Q15: B, C and D are correct.




Q17: B and C are correct.



Q19: 10 cm3 acidified sodium dichromate was poured into a boiling tube. 2 cm3 ethanolwas added and the mixture was gently shaken. The mixture was then cooled by placingthe boiling tube in a beaker of cold water. Once the reaction had subsided the mixturewas gently warmed, leading to the formation of ethanoic acid.

Q20: Please note that this is not the only correct answer. There will be many othervariations that would all be acceptable. This is only provided as a specimen answer.

20 cm3 of diluted sulfuric acid was added to a beaker. To this was added a spatulafulof magnesium and the reaction was stirred with a glass rod. Addition of magnesiumcontinued a spatulaful at a time until no more bubbles of gas were produced andsome magnesium remained unreacted. The mixture was filtered. The filtrate was thentransferred to an evaporating dish and heated on a tripod with a Bunsen burner untilhalf of the water had evaporated. The heat was removed and the evaporating basinleft to cool overnight, allowing the solution to crystallise slowly. The crystals were thentransferred onto filter paper to examine with a hand lens and a drawing of one of thesecrystals was made.

Q21:





Lab report


Scientific paper


Blog


Video (on website)

You are a young researcher who needsan eye-catching visual method ofcommunicating a summary of your resultsat an international conference.

Scientific poster


Scientific report

You are a product development scientistworking for a large consumer goodscompany. You have been asked to presentthe results of your recent research work tothe company director. You know he willwant to ask lots of questions.

PowerPoint presentation



7 End of unit test

End of unit 4 test (page 87)


Q2: a) a literature search.

Q3: b) When was it last updated?

Q4: c) .com

Q5: b) To inform

Q6: b) To allow another person to find the same information

Q7: d) Corrosive

Q8: c) Toxic

Q9: a) Harmful / Irritant

Q10: b) Respiratory Sensitizer

Q11: b) Measuring cylinder

Q12: a) Conical flask

Q13: d) Volumetric flask

Q14: c) Burette

Q15:

Technique Use

FiltrationSeparate an insoluble solid from a solid /liquid mixture

Evaporation Separating a solvent from a solution

Distillation Separating a mixture of miscible liquids

Use of balance Weighing out chemicals

Heating using a Bunsen burner Heating an aqueous solution rapidly to60◦C

Use of a gas syringe to collect a gas Collecting a water-soluble gas

TitrationDetermining the concentration of asolution

Collecting a gas over water Collecting a gas which is insoluble inwater

Heating using a heating mantle Heating a flammable liquid to 120◦C

Q16: b) B

Q17: c) 23.55 cm3



Q18: d) 3.74 g - 3.76 g

Q19: b) Inaccurate and reproducible

Q20: a) A

Q21: A and C

Answer Explanation:The rough (25.0 cm3) and titration 2 (25.5 cm3) should be discarded. These values arenot concurrent as they are more than 0.2 cm3 or away from the other readings.

Q22: A

Answer Explanation:The rough (25.0 cm3) and titration 2 (25.5 cm3) should be discarded. The average titreis the mean of titration 1 and titration 3. Working: (24.5 + 24.6) /2 = 24.55 cm3

Q23:

Task Apparatus


50 cm3 pipette


100 cm3 beaker


Graduated plastic dropper


50 cm3 burette

Answer Explanation

Line 1: An accurate measurement of exactly 50 cm3 is required. A pipette will achievethis more quickly than a burette.

Line 2: The volume required does not need to be measured accurately.

Line 3: As the indicator is not taking part in the reaction, a volume of roughly 1 cm3 willbe adequate. A dropper pipette is cheap and quick to use.

Line 4: An accurate volume measurement is required. As the accurate volume beingmeasured is not fixed, a burette is the most appropriate piece of apparatus to be used.

Q24:



Task Heating method

Distillation of ethanol at 78◦C Heating mantle

Maintaining an enzymatic reaction atabout 40◦C Water bath

Heating water quickly to about 60◦C Bunsen burner

Q25: d) Both the reactants and the products are flammable.

Q26: B and C

Q27: a) Carbon dioxide is soluble in water so some will dissolve in the water.

Q28: d) Hydrogen

Q29: d) Gas syringe

Q30: a) As we cross Period 2, the first ionisation energy increases.

Q31: a) The information to be graphed is types and numbers.

Q32: a) Bar graph

Q33: a) The line of best fit should be a curve.

Q34: a) As temperature increases, rate of reaction increases.

Q35: a) The colour change would be too slow to accurately stop the timer.

Q36: a) As concentration increases, absorbance increases.

Q37: b) 0.75

Q38:

1. lead / hydrochloric acid

2. Tin

3. Fe

4. distillation

5. sulfuric acid

Q39:





Lab report


Scientific paper


Blog


Video (on website)


Scientific poster


Scientific report

You are a product development scientistworking for a large consumer goodscompany. You have been asked to presentthe results of your recent research work tothe company director. You know he willwant to ask lots of questions.

PowerPoint presentation


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