PERSPEX
Microtitration
Drop
chemistry
Cu2+ and CrO42- ions separate
Lead crystals
Diffusion of lead and iodide ions to form PbI2
Reduced Scale Science
With Bob Worley
Chemistry Adviser at CLEAPSS (UK)
Lead crystals
Hydrogen oxygen bang
The Hofmann Voltameter
Polymerization of methyl
methacylate
PERSPEX
Pros and Cons on the reduction of
copper oxide with hydrogen
Pros
Cons
• Time available for discussion of
this experiment and the concept
of oxidation and reduction
• Project onto a screen
• Very safe
•
•
•
•
•
Too small
Too fiddly
Not in the text book
Not normal chemistry equipment
Danger element of larger scale
activity adds to excitement
• Chemistry is nothing without a
Bunsen burner
First encounter!
The reduction of
copper oxide
with hydrogen
This stopped nearly every teacher in
the UK carrying out this demonstration
Education in Chemistry
This procedure has been known by
me since 1995.
Why is it only now you are hearing
about it?
http://mattson.creighton.edu/
Microscale_Gas_Chemistry.html
Bruce Mattson, Ph.D., Department
of Chemistry
Creighton University, Omaha
Nebraska, USA
Biology and Physics
New techniques in biology
include
• Microbiology
• Enzymes
• Gene
• Biotechnology
New techniques in physics
include
• LEDs
• Lasers
• Transistors leading to
silicon chips
• Microelectronics
Present day
Standard equipment
But what about chemistry
Modern Techniques
•
Analysis of ions is replaced by
spectrographic techniques
•
•
Problem
•
Equipment is hugely expensive
Have we moved beyond paper
chromatography ?
•
Thin layer and column chromatography is rare in
school chemistry is not common
Do we use support materials for
heterogeneous catalysis? What
about zeolites and ionic
exchange resins.
•
(I put MnO2 on sticky tape but no one else does
it). Many of the these catalysts are expensive.
•
Mentioned in A level syllabus but still uses
dichromates to oxidise alcohols
•
Do we really recognise that this term covers
much of what we teach now, eg soap, graphene
•
pH meters and datalogging equipment is
available but is it used?
•
Green chemistry?
•
Nanochemistry
•
pH (Modern? 1910!)
•Educational Psychology: working memory issues – smaller scale techniques
tend to be quicker – practical and theory aspect can be addressed in the
same lesson
•Research shows although students enjoy practical work on the whole it can
be regarded as a ‘switching off time’ and regarded not seen as “proper work”
because there is little writing.
•Some are frightened by practical work
•Problems with arithmetical manipulation holds back understanding
•Interpreting visible with the invisible is difficult!
•Problems of language
•Lack of awareness on the part of academics and industry of the need to
adapt their approaches for school practical work leading to school chemistry
appearing old fashioned
If a microchemical approach satisfies one or more of the following
points in a traditional setting, it should be seriously considered.
1. It allows a once dangerous experiment to be carried out more safely
2. It shortens practical time so that lessons are not so rushed.
3. It reduces overloading the working memory of students allowing them to see
the chemistry instead of the apparatus
4. It reduces the cost of equipment and consumable materials.
5. Users report a higher level of concentration amongst pupils
6. Mistakes are quickly rectified.
7. It reduces technician time in disposing and clearing up.
8. It reduces waste, a factor which is becoming more important in the UK.
9. It shows equivalent or better quantitative results (although comparison of
techniques is a useful exercise in error analysis).
10. It enables some stunning visible effects when filmed or projected onto a
whiteboard.
11. Students can take a record of the work using cameras in their phones. (This
could be done to provide examination Boards with a visable record)
Drop chemistry: reducing working
memory overload
Original used OHP
transparencies but
these are no longer
easily available in
the UK.
Instructions are
written on the
paper.
Polypropylene
envelope folders are
or you could print in
card and laminate
them.
The diffusing precipitate
Pros and Cons on diffusing
precipitates
Pros
Cons
• Time available for discussion of
this experiment and the concept
forming precipitates
• Explanation in terms of ions in
salts breaking apart on dissolving
by water and ions coming
together to form precipitates
• Project onto a screen
• Taker photographs
• Less mess and washing up
•
•
•
•
•
Too small
Too fiddly
Not in the text book
Not normal chemistry equipment
Danger element of larger scale
activity adds to excitement
• Where’s the test tube?
• Preparation is time-consuming
the first time it is done
The RSC initiative of 1999
The microscale kit on sale in the UK
There are many
enthusiastic users of
this equipment in
the UK but there
are also a lot of
traditionalists who
dismiss it without
trying it.
But many UK
teachers are
reluctant to test it
and look for new
applications
My favourite activity using the Comboplate
20 drops of A
18 drops of A and
2 drops of B
8 Drops of solution of
solution A and 12
drops of solution B.
12 Drops of solution
of solution A and 8
drops of solution B.
A is an acid solution (3.1 g of boric acid and 2.65 g of citric acid made up to 250 ml
of solution): B is an alkaline solution (9.0 g of disodium hydrogen phosphate-12water and 1 g of sodium hydroxide) (IRRITANT). The pH of the solutions is
measured with a calibrated Hanna pH ‘Checker’.
Colours of indicators
in Comboplates
Micro-electrolysis
0.5M potassium
bromide solution
0.2M potassium
iodide solution
The electrodes are
made of carbon fibre
from online kite selling
website.
0.5M copper(II)
chloride solution
Moist blue
litmus paper
Microelectrolysis of copper(II) chloride
Pros
Cons
• Takes less than 10 minutes
• Time available for discussion this
experiment and the concept
electrolysis
• Project onto a screen
• Concentration of chlorine is
below WEL
• Does not require fume cupboard
• Quickly try other salts
•
•
•
•
Too small
Too fiddly
Not in the text book
Not normal chemistry equipment
Silver crystals forming during micro electrolysis of
0.01M silver nitrate with paper clip electrodes.
% water of crystallisation in
hydrated copper(II) sulfate(VI)
Mass (g) of “crucible” =
X
Mass (g) of “crucible” plus copper sulfate(VI) crystals=
Y
Mass (g) of “crucible” plus anhydrous copper sulfate(VI) =
Z
% water of crystallisation in
hydrated copper(II) sulfate(VI)
(Y – Z) x 100
=
(Y – X)
% water of crystallisation in
hydrated copper(II) sulfate(VI)
Pros
Cons
• Takes less than 10 minutes
• Time available for discussion of
this experiment and the mole
concept
• Results are very close to accepted
value
• No overheating of salt and
further decomposition to give
toxic gases
• Quickly try other salts
•
•
•
•
•
Too small
Too fiddly
Not in the text book
Not normal chemistry equipment
Bunsen is not used
Microtitration
You do need a balance to 2
decimal places but Pocket
Balances can obtained very
cheaply from Amazon for
instance.
Mass (g) of “vial plus indicator” =
X
Mass (g) of “vial plus indicator + vinegar”
Y
Mass (g) of “vial plus indicator + vinegar” + 0.2M NaOH =
Z
Mass of ethanoic (acetic) acid in 100 cm3 vinegar is (Z - Y) x 4.8/ (Y - X)
Microscale titrating
Pros
Cons
• Introduces the procedure of
titrating without the clutter and
handling problems of equipment
• Time available for discussion of
this experiment and the mole
concept
• Results are very close to accepted
value
• Technique can be repeated
several times in 25 minutes
• The weight/volume issue
complicates the procedure
• Too small
• Too fiddly
• Not in the text book
• Not normal chemistry
equipment
Back to Biology: transpiration and enzymes
Back to Physics: Boyles laws
1.2
Volume (ml)
1
0.8
0.6
0.4
0.2
Mass applied (g)
0
0
200
400
600
800
Back to Physics: Charleslaws
1.2
1
y = 0.0054x + 0.7871
0.8
Volume of
0.6
air (ml)
0.4
0.2
0
0
10
20
30
40
50
Temperature (C)
At what temperature would the
straight line cross the
Temperature axis? This would be 0.7871/0.0054 or -146C
The CLEAPSS U-Tube channel
http://www.youtube.com/user/CLEAPSS
Microscale cracking
Microscale cracking
Pros
Cons
• Time available for discussion of
this experiment and the concept
of oxidation and reduction
• Project onto a screen
• Students can do it safely
• Very safe as no possibility of suck
back
•
•
•
•
Too small
Not in the text book
Not normal chemistry equipment
Danger element adds to
excitement
• Chemistry is nothing without a
Bunsen burner
Propene from propan-2-ol
And if butan-2-ol is used there are 3 possible alkenes!
Preparation of propene
Pros
Cons
• Much quicker that the preparation
of cyclohexene from cyclohexanol
• Time available for discussion of this
experiment and structure of alkenes
• Easily extended to the dehydration
of butan-2-ol to a number of
products.
• Students can do it safely
• Very little bromine water used
• Very safe as no possibility of suck
back
• Spectacular burning of alkenes to
give a smoky flame
•
•
•
•
Too small
Not in the text book
Not normal chemistry equipment
Danger element adds to
excitement
• Chemistry is nothing without a
Bunsen burner
Atmospheric chemistry – SO2
Atmospheric chemistry – NO
Atmospheric chemistry – SO2 + NO
Sprit burner versus the Bunsen burner
1. Can be used for more than just calorimetric experiments
2. The lower temperature of the spirit burner flame does not
bend soda glass and many reactions do not require
temperatures above 500 C.
3. The lower temperature of the spirit burner flame does not
decompose chemicals as quickly so there is more control.
4. There is no serious increase in carbon dioxide levels in the
room
1. The spirit burner is affected by draughts.
2. The lower temperature of the spirit burner cannot decompose
calcium carbonate
3. “It is not proper chemistry without a Bunsen burner!”
Hoffman voltameter
Pros
Cons
• Much less expensive
• Repairs are possible
• Time available for discussion of
this experiment and the concept
of oxidation and reduction
• Project onto a screen
• Very safe
•
•
•
•
Too small &fiddly
Not in the text book
Not normal chemistry equipment
Danger element adds to
excitement
Polymerisation of methyl
Methacrylate
Pros
Cons
• Each student can do it
• Quickfit refluxing takes time to
set up
• Can monitor progress looking at
viscosity
• Time available for discussion of
the concept of free radical
induced polymerisation of various
alkenes
• Very safe even though monomer
is highly flammable, skin and
respiratory irritant
• Can take the product home
•
•
•
•
•
Too small
Too fiddly
Not in the text book
Not normal chemistry equipment
Danger element of larger scale
activity adds to excitement
• Spent all this money of Quickfit,
should use it
• Chemistry is nothing without a
Bunsen burner
Too small, too fiddly?: but students
can
• Text using small keys on phones
• Play video games
• Apply make-up and eye liner while
moving in a car or on the train
• The main problem is the teacher, the author,
the examination boards!
International Microscale in Berlin 2013
Microscale on breakfast television in Kuwait
2011
Canadian Workshop at the
CHEM 13 Conference 2013
Uganda 2012
Training in Cyprus 2013
Ideas move to Oman
Bob.Worley@cleapss.org.uk
http://www.youtube.com/user/cleapss
@UncleBo80053383
Cu2+ and CrO42- ions separate
Lead crystals
PERSPEX
Diffusion of lead and iodide ions to form PbI2