Investigating Ferrofluids
Teacher Background information:
Ferrofluids are colloidal fluids of fine ferromagnetic nanoparticles suspended in a carrier
fluid (like water or oil). Ferrofluids have a variety of technological uses and applications
and are becoming increasingly more common in nanoscience research and industry.
The following document includes four investigations of ferrofluids and an STS synthesis
activity linking the nanoscience to technologies in society.
Connections to Alberta Programs of Study:
Science 9: Unit B - Investigate materials, and describe them in terms of their physical
and chemical properties. Distinguishing between pure substances, solutions and
mechanical mixtures. (Labs 1-4 and STS activity)
Physics 30: Unit 3 Concept 1 - Magnetic field theory is a model used to describe
magnetic behaviour. (Labs 1-4 and STS activity)
Science 30: Unit C Outcome 1 - Students will explain field theory and analyze its
applications in technologies. (Labs 1-4 and STS activity)
Chemistry 30: Unit B outcome 1 - Students will explain the nature of oxidation-reduction
reactions. (Lab / Activity 3 and STS activity)
Pedagogical Approach:
This lesson includes the following approaches to help build student understanding of
ferrofluids and can be used to approach a host of different concepts in the physical
sciences. Teachers will:
1) Make connections to student prior knowledge.
2) Help students make macroscopic descriptions from empirical observations.
3) Assist students to render microscopic or particle views of their empirical
observations.
4) Help students include symbolic representations to build visual imagery of a concept
and better visualize forces and fields that affect materials.
5) Build science literacy with students by identifying new terms and applying definitions
to the investigated situations.
6) Make connections with nanoscience in technologies and society.
Before labs / activities begin: Start with what students know and what they would like
to know. Have them begin the thinking by making drawings of magnetic fields, defining
terms they know as well looking up terms they have not heard. Have students make
reference to these preliminary thoughts, ideas, questions and drawings at the end of the
experiments to reflect on what they have learned.
Lab / Activity 1: This activity takes the longest and can be in progress as a kind of
demonstration as the students begin their thinking on the topic of ferrofluids. This
activity attempts to extract the ferromagnetic oxide coating off of the polymer cassette
tapes. Acetone is used to make that extraction as it denatures the binding of the coating
allowing it to become free. The tape can then be removed from the acetone and the iron
oxide dried. Once dried, vegetable or mineral oil can be added to the iron oxide and
tested for magnetic properties. This should produce particles ≥1 μm in size.
reference:
http://how2dostuff.blogspot.ca/2010/02/how-to-make-ferrofluid-cheap-fast-and.html
Lab / Activity 2: The purpose of this short activity is for students to construct a mental
image of a magnetic field (sphere of influence). The iron filings help give evidence of
that influence. It is intended that in this activity students will draw out their observations
on paper and make inferences from them about the nature of a field. Particle size of the
iron filings are less 1 mm.
Lab / Activity 3:
This activity explores the oxidation of iron II into iron III. It helps develop skills in using a
buret (needed for titrations) as well as comparing results of reactions (or non reactions)
of H2O and 3% H2O2 and iron (II) oxide. The size of the nanoparticles depends on how
fine of grade the iron (II) oxide is.
*Using a 10% solution of H2O2 is also effective and may decrease the reaction time but
it requires additional caution and preparation as the 10% solution is generally prepared
by dilution of higher concentrations of H2O2.
reference:
http://chemeducator.org/sbibs/s0010003/spapers/1030204tm.htm
The Chemical Educator, Vol. 10, No. 3, Published on Web 06/01/2005, 10.1333/s00897050908a, © 2005 The Chemical Educator
Lab / Activity 4: The idea for this lab is to use MICR toner which contains the
ferromagnetic particles and suspend them in a colloidal mixture using oil. The magnetic
properties can then be tested for by using a strong magnet. While the oil can weigh
down the suspension of particles, look for any peaking or spiking of the fluid. Students
will be able to manipulate the fluid using the magnet as well as manipulate its motion
when the fluid is placed in an alcohol water mixture. The nanoparticles size is estimated
to be larger than 30 nm as the MICR toner is coated with a copolymer that acts as a
surfactant. The strength of the magnet and the viscosity of the oil affect the degree of
“spiking” of the ferrofluid. Tests using light oils as a carrier fluid (like mineral oil) and
strong rare earth magnets appear to yield better “spiking” results.
STS Activity: This activity is intended to assist students in making connections with the
nanoscience as it applies to various technologies used in society and new nanoscience
research. This activity has a list of various applications of ferrofluids. Divide the students
into working groups or pairs and have them search out how ferrorfluids are incorporated
or used in a specific technology. Have students report their findings to the class.
Reporting methods can vary in time and scope: think pair share groups or more formal
reports/presentations can be used.
Teacher Extension Experiment:
There are a few other methods to make ferrofluids teachers can investigate on their own
and add to their classroom activities. One such experiment uses magnetite (Fe3O4) 5%, oleic acid - 10% (oleic acid is the surfactant - joins magnetite to carrier fluid),
kerosene - 85% (carrier fluid).
Making the Fe3O4 Is done by combining ferric chloride (FeCl3) with ferrous chloride
(FeCl2), at a controlled rate and in a basic solution produces magnetite (Fe 3O4)
nanoparticles (~10nm).
2FeCl3+ FeCl2 + 8NH3+ 4H2O → Fe3O4 + 8NH4Cl
The oleic acid surfactant can then be added to the magnetite followed by the addition of
the kerosene carrier fluid.
http://www.popsci.com/diy/article/2009-09/making-ferrofluids-work-you
http://www.youtube.com/watch?v=LlQw9dfexBQ&feature=fvwp
Terms and Definitions for these investigations:
Ferrofluid
Nanoparticle
Colloid
Surfactant
Carrier fluid
Magnetic field
Magnetic force
Disposal of waste ferrofluid:
Whatever cannot be saved for recovery or recycling should be managed in an
appropriate and approved waste disposal facility. Processing, use or contamination of
this product may change the waste management options. State and local disposal
regulations may differ from federal disposal regulations. Dispose of container and
unused contents in accordance with federal, state and local requirements.
*High Schools with a laboratory technician should consult them for waste disposal
options.
Lesson and Lab activities compiled and organized by
Ben Oswald - Ross Sheppard High School, Edmonton, AB.
Science Teachers consulted for this set of labs and activities:
Tracy Onuczko - University of Alberta
Kerry-Ann Hyde - St. Joseph High School, Edmonton, AB.
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Ferrofluid Labs and Activities
Lab / Activity 1 (or teacher demonstration):
Purpose:
To extract ferromagnetic oxides and test them for magnetic properties
Hypothesis:
Design:
Ferromagnetic oxides can be removed from the surface of old cassette tapes. The substrate
can be collected and tested for magnetic properties.
Materials:
Acetone - 1 L
Beaker - 1 L
Hot plate
5-6 tape cassettes (check for brown coating on tape)
filter paper
funnel and ring stand
vegetable oil
glass vial or 50 mL beaker
Procedure:
1. Disassemble 5-6 tape cassettes
2. place cassette tape in large 1 L beaker
3. in a ventilated room and away from flames, add 500 mL of acetone
4. let it soak for several hours
5. place on a hot plate and heat for 1 hour if needed
6. after cooling, remove the plastic tape from the acetone
7. use filter paper to isolate the iron oxide from the acetone
8. let dry
9. in a small clean dry vial or 50 mL beaker add a small amount of vegetable oil to the dry iron
oxide particles (about 3 parts iron oxide to one part oil)
10. Use a strong rare earth magnet to test the ferrofluid for magnetic properties
11. Record your observations
Analysis:
Evaluation:
Lab / Activity 2:
Purpose: To map out the magnetic field (a.k.a lines of force) of a strong magnet
Design: Iron filings are suspended allowing field lines of a permanent magnet to be detected
and mapped.
Materials:
petri dish
clear corn syrup
iron fillings
electronic balance
glass stir rod
strong magnet (rare earth)
Procedure:
1. Cover the bottom of the Petri dish with corn syrup (approximately 20 mL - just enough to
cover the bottom)
2. Using an electronic balance, measure out 2 g of iron fillings
3. Using a glass stir rod, stir the filings into the corn syrup until evenly distributed in the petri
dish
4. Bring the magnet close to the bottom of the petri dish
5. Record your observations
Evidence:
Analysis:
Lab / Activity 3:
Problem: How does an oxidizing agent affect iron (II) oxide?
Design: iron (II) oxide is mixed separately with water and then with hydrogen peroxide. The
results are then tested for ferromagnetic properties using a strong magnet.
Hypothesis/Prediction:
Materials:
fine black iron (II) oxide
electronic balance
2- 150 mL erlenmeyer flasks
1- buret
3% hydrogen peroxide
distilled water
Procedure:
1. Using 2 clean 150 mL erlenmeyer flasks measure out and add 0.200 g of black iron oxide
(FeO) into each flask.
2. Label each flask 1 and 2
3. Using a clean buret deliver 10 mL of distilled water to one of the flasks
4. Prepare the buret to deliver 3% hydrogen peroxide
6. Deliver 10 mL of hydrogen peroxide to the iron oxide in the second beaker slowly (drop by
drop if possible) while swirling
7. Allow both flasks to sit for 30 minutes
8. Using the rare earth magnet test the substance in each flask by bringing the magnet close to
the bottom of each flask
9. Record your observations
10. hold the magnet at the bottom to draw as much ferrofluid as possible and decant the
peroxide out of the flask.
Evidence:
Analysis:
Evaluation:
Lab / Activity 4:
Purpose: to create a colloidal mixture of ferrofluid (~ 10 nm nanoparticles) and observe its
effects in a magnetic field.
Design: Using MICR toner mixed with oil, ferrofluids can reveal the magnetic field of a strong
rare earth magnet.
Materials:
1 - 50 mL beaker
1 - 100mL beaker
1 - 150 mL beaker
MICR toner
a light oil like mineral oil (can also use vegetable oil)
graduated cylinder
stir rod
petri dish
ferromagnetic bolt or screw (~1/4 inch or more in width)
eyedropper
rare earth magnet
glass vial
distilled water
isopropyl alcohol
Procedure: (Check this . . .add oil to petri dish first then add toner to it, stir??)
1. In a small 50 mL beaker, add 40 mL of MICR Laser jet toner
2. Using a graduated cylinder stir in (approximately) 25 ml of mineral oil using a stir rod
3. Stir until you get an even consistency (more oil can be added if necessary).
4. Put into a 100mL beaker or 150 mL Erlenmeyer flask (a capped vial may also be used).
5. tip the beaker or flask on its side (without spilling the fluid) and bring the rare-earth magnet to
the bottom of the flask.
6. Note the shape of the ferrofluid and its influence by the magnetic field.
7. record your observations
8. Place some ferrofluid in a petri dish
9. Place the petri dish on top of the rare earth magnet
10. Note the shape of the ferrofluid. Can a diagram of the magnetic field be drawn? Record your
observations.
11. Place an iron screw (standing on end) so that it is magnetised by the magnet.
12. Using an eyedropper place ferrofluid at the bottom of the petri dish onto the screw
13. Note the shape of the ferrofluid
14. Pour a small amount of ferrofluid into a clean 150 mL beaker filled with water
15. Use the rare earth magnet to observe the behavior of the fluid. Record your observations.
16. Using a clean glass vial, fill it 75% with isopropyl alcohol, add a small amount of ferrofluid
(~2 mL) and then add the additional 25% distilled water to fill the vial.
17. Tightly cap the vial and use the magnet to influence the ferrofluid. Record your observations.
18. Clean up fluid with soap and warm water
Observations:
Analysis / Questions:
Do you think the mixture is a solid or a liquid?
Can liquids be magnetic?
What observations did you make when you placed the magnet under the ferrofluid?
What are the spikes (if any are noted)?
Are the spikes permanent?
Is the magnetic effect of a ferrofluid a physical or chemical change? Explain.
Where are forces experienced?
What are the causes of the forces or interactions?
Evaluation or concluding statements:
Classroom STS connection activity (Synthesis):
The following is an abbreviated list of where ferrorfluids are used in science technology and
society. Use the instructions provided by your teacher (as well as the internet) to investigate one
of the following. Be prepared to share what you learn according to your teacher’s instructions.
algae removal for biofuels, ferrofluid pumps, water purifying systems, electronic devices (high
end speaker systems or DVD players), low friction engineering, magnetic drug targeting, MRI
enhancement, health research (treating ulcers or cancer research), NASA applications,
deformable mirrors, other uses not listed . . .