Milk, Soap, and Dye Unit - Sample Lesson
by Tim Sorey
Lesson Title: Milk Unit
Lesson Description
Lesson Description: This is a one day lesson that teaches students the properties of soap and
how it surrounds grease, fat, and oil.
Subject: Properties of Matter
Duration: 45 minute lesson
Grade Levels: K-8th
Standards:
NSES-S.K-4.A.2
STANDARD: Science As Inquiry -- As a result of activities in grades K-4,
all students should develop understanding about scientific inquiry
NSES-S.K-4.B.1
STANDARD: Physical Science -- As a result of the activities in grades K-4,
all students should develop an understanding of properties of objects and
materials
NSES-S.K-4.F.1
STANDARD: Science in Personal and Social Perspectives -- As a result of
activities in grades K-4, all students should develop understanding of
personal health
WA-GLE.SC.1.1
Component 1.1 Properties: Understand how properties are used to identify,
describe, and categorize substances, materials, and objects and how
characteristics are used to categorize living things.
Component 1.2 Structures: Understand how components, structures,
organizations, and interconnections describe systems.
WA-COMP-2007.CHEM.1.1.4.1
Physical and Chemical Properties of Matter
WA-COMP-2007.CHEM.1.2.6
Analyze why curiosity, honesty, cooperation, openness, and skepticism are
important to scientific explanations and investigations.
WA-COMP-2007.CHEM.2.1.1.6
Able to design investigations.
WA-GLE.SC.1.2
Standards Rationale:
Justification
In this lesson, students are asked to scientifically inquire about the action of soap as it reacts with
the milk fat (Standards - NSES-S-K-4.A.2 and WA-COM.K-4.1.2.2). It is also necessary that
they recognize how solving problems helps to gather data that arise. Ultimately, this experiment
is built to offer the students some resolution as to how the properties of oil and soap interact such
that they may better understand personal health and hygiene (Standards - WA-GLE.SC.1.1,
WA-GLE.SC.1.2, and NSES-S.K-4.F.1 ).
Vocabulary
Lesson vocabulary from OSPI website, found within STC Kit (Properties of Matter Part 2),
and defined using Brown, LeMay and Bursten – 10th Ed. of Chemistry: The Central Science.
liquid (5th) – pure matter that has a distinct volume but no specific shape
solution (5th) – a mixture of substances that has a uniform composition – homogeneous mixture
density (8th) – an intensive property that defines the ratio of an object’s mass to its volume – density
= mass/volume
mixture (8th) – a combination of two or more substances in which each substance retains its own
chemical identity
solubility (10th) – the amount of a substance that dissolves in a given quantity of solvent at a given
chelating agent (11th) – a polydentate ligand that is capable of occupying two or more sites in the
coordination sphere.
dipole moment (11th) – a measure of the separation and magnitude of the positive and negative
charges in polar molecules
extensive property(11th) – the property that depends on the amount of material considered
hydrocarbon (11th) –a molecule that contains only hydrogen and carbon atoms
hydrogen bond (11th) (pages 170-173 on Properties of Matter) – bonding that results from
intermolecular attractions between molecules containing hydrogen bonded to an electronegative
element. The most important examples involve OH, NH, and HF.
hydrophobic (11th) (water repelling) and hydrophilic (11th) (water attracting)
indicators (11th) (pH, protein, glucose, starch, etc.) – a substance added to a solution to indicate
whether a solute exists within a solvent mixture
intensive property(11th) – the property that is independent of the amount of material considered
immiscible (11th) – liquids that do not dissolve into one another to a significant extent
temperature to form a saturated solution.
miscible (11th) – liquids that mix in all proportions
non-polar molecules (11th) – a molecule that possesses no dipole moment
polar molecule (11th) - a molecule that possesses a nonzero dipole moment
solvent (11th) – the dissolving medium of a solution
solute (11th) – the substance dissolved into a solvent to form a solution
surfactant or surface-active agent (11th) - (detergent, foaming agent, emulsifiers, conditioning
agents solubilizers) – a molecule that usually has both hydrophobic and hydrophilic nature and acts
as a type of chemical stabilizer
Components
Objectives
The student objectives of this lesson include measurable quantities in both knowledge (What the
student should KNOW) and in skill (what the student should be able to DO, hands-on).
Know: Students should be able to know:
 how to create a hypothesis.
 how to make predictions prior to their experimentation.
 how to make experimental observations.
 the basic parts of a soap molecule.
 the definitions of hydrophobic and hydrophilic.
Do: Students should be able to:
 perform experimentation that have pre-defined steps and procedures.
 design new experiments as an individual and in a group with newly defined steps and
procedures.
Materials and Equipment
Primary List:
 Skim, 2%, Whole milk
 food coloring - various colors
 Dish soap
 Petri dishes
 Pipe cleaners
 Styrofoam balls
 water
 vegetable oil
 olive oil
 cranberry juice
Extended List:
 Dry Soap, bar soap, shampoo, anti-bacterial soap
 Rubbing Alcohol, Karo syrup, soda pop
 sugar, salt, flower
Prior Knowledge
Prior to this experiment, students should know:
 soap helps to clean their hands and bodies
Prior to this experiment, students should be able to do:
 experiments that are pre-defined and that include following stepwise instructions.
Safety

Students should be reminded that placing any of the materials in their mouths or on their
neighbors is strictly prohibited. The teacher may consider having students wear their


painting shirts during this experiment so that none of these materials would cause
staining o f their school clothes.
They should also be warned that some materials, such as the soap, rubbing alcohol, and
food dye, can cause irritation of the skin or eyes. If they get any of the soap or rubbing
alcohol in their eyes or mouth, they should immediately get them flushed with water for
no less than 15 minutes.
When the experiment is complete, students should place their materials into a waste
container that is provided for them. Once thier pitri dish is emptied, they should be
encouraged to wash them out at the sink and place them on a paper towel for drying.
Engage
Have team of students, no more than two students, place a pitri dish in front of them. Have them
fill it 1/2 full with 2% milk. Next, have them place a drop of food dye in the middle of the pitri
dish. Once all of the students have done this, pass around a SINGLE BOTTLE of soap,
dropping a single drop of soap in the middle of the food dye.
Students should observe a 'REACTION', where the soap spreads from the middle to the outer
edges of the pitri dish.
Next, have a classroom discussion and make a list of observations on the chalkboard or
whiteboard. You may wish to have a couple students to come up and actually draw what they
observed.
Ask them a single question, "What do you think is CAUSING this observed reaction?" or "Can
you tell me what materials cause this reaction?"
Once you have a list of materials and have written them on the board, ask them to use these
materials to form a testable question. For example, "Does the different color of food dye cause
this reaction?" Time should be taken to explain that a testable question is referred to as a
'HYPOTHESIS'.
Once a HYPOTHESIS is formed, students should be encouraged to PREDICT what will
happen. For example, "The RED FOOD DYE will cause the REACTION to behave differently
than the GREEN FOOD DYE." Even though this may or may not be true, a prediction helps
students to 'STAKE A CLAIM' , getting them involved within a type of mental experimentation
before they actually DO the experiment.
The idea is to stimulate interest - DO NOT give the punchline away!
HAND OUT THE STUDENT WORK SHEETS AT THIS TIME! (Please see attachments!)
Explore
Once the students have made their initial observations, they should be encouraged to test the
'pre-made' hypothesis on the hand-out sheet.
Be sure that they read and understand this hypothesis, "Is milkfat an important factor in this
reaction?" You may need to explain that milk is made up of fat molecules and that SKIM MILK
contains less milk fat than 2% and whole milk. On their sheets, they should circle whether they
think Milk Fat DOES or DOES NOT effect theREACTION.
The only thing that they change, for this first experiment, is the % of milk fat. They should test
the Skim milk and the Whole Milk only.
The instructor should passively participate in observing the REACTIONS. The REACTION in
SKIM MILK should be faster than WHOLE MILK. It may not be obvious, but the REACTION
in SKIM MILK should be faster than the reaction in 2% MILK.
Once the students have completed this exercise, make sure that they carefully write their
observations down. Be sure to intervene at this time in order to discuss eachother's results in
class. The instructor may want to write some key words down on the blackboard/whiteboard.
Explain
Have 6 glasses ready to go. Two glasses of 1/2 full of water, two glasses of 1/2 filled with
vegetable oil, one glass of 1/2 full of cranberry juice, and one glass of Olive Oil.
Pour one glass of water into the oil and let the students observe the separation between water and
oil. Explain this phenomenon as oil being 'Hydrophobic' or 'WATER FEARING'. These layers
don't tend to mix and the scientific way of describing this is the term : 'IMMISCIBLE'.
Pour the other glass of water into the cranberry juice and let the students observe that there is NO
separation between water and cranberry juice. Explain this phenomenon as fruit juice being
'Hydrophilic' or 'WATER LOVING'. These layers DO mix and the scientific way of describing
this is the term: 'MISCIBLE'. Proof of the mixing can also be observed in comparing the
mixture to an original glass of cranberry juice, where the mixture looks diluted.
Finally, pour the glass of vegetable oil into the glass of Olive Oil. The students should observe
that these two liquids are MISCIBLE and that there is no separation between the two liquids.
You should explain to the students that some hydrophobic materials, such as oils, greases, and
fats, tend to mix with one-another.
Different types of Water Analyses include – Colorimetry, Turbidimetry, Nephalometry,
Fluorimetry, Conductance, pH (CO2) and temperature
See attached sheet of "TEACHER EXPLANATION OF SOAP" for further discussion of the
soap molecule.
See Student Hand-out of Teacher Explanation
Elaborate
If time permits, students should extend these concepts and skills toward investigation with other
materials. They may wish to try using the other materials, such as different types of soap,
colored food dyes, and liquids. They should test out at least 2 other hypotheses with the
materials given. You can say, " "Can you come up with at least two other hypotheses and test
them?" and "Don't forget to PREDICT before you experiment!"
Evaluate
You can assess both what the student KNOWS (knowledge) and what the student CAN DO
(skills) with regards to this milk unit. The attached worksheet and a rubric-based performance
assessment are used to assess student learning and alignment with the previous objectives.
Performance assessment rubrics are explicitly aligned with the state and federal science
education standards.
Performance:
Assessment Criteria
The primary assessment materials measure my students ability to achieve this lesson's student
objectives. Attached is a grading sheet that is used to help grade my students' performance. I
have also chosen to a grading rubric, seen below, in order to quantify may students' overall
achievement with this unit and its alignment with WA-COMP, NSES-S, and EALR
requirements.
See Student Hand-out of Teacher Explanation
Performance Assessment
Exceptional
(5 pts)
Knowledge Student is able to
provide a clear,
50%
concise, and accurate
description of all steps
in the milk unit
experimental
procedure and the
testing of other
hypotheses. Clearly
articulates how steps
are related and how to
apply process to
answering a scientific
question and testing a
prediction through
observations.
Skill 50% Student is able to
develop a novel
experiment testing
other variables that
Performance Assessment
Good Quality
In
(4 pts)
Development
(3 pts)
Student is mostly
able to provide a
clear, concise, and
accurate
description of all
steps in the milk
unit experiment
and the testing of
other hypotheses.
Articulates how to
apply process to
answering a
scientific question
and in testing a
prediction through
observations.
Student is
somewhat able to
provide a
description of
steps in the milk
unit experimental
procedure, but is
still working on
forming
hypotheses. Has
some trouble
explaining how to
apply process to
answering a
scientific
questions and in
testing a
prediction
through
observations.
Student is able to Student is able to
develop an original develop an
experiment testing experiment but
a single variable in combines
Needs
Rethinking
(2 pts)
Not Scorable
(1 pt)
Student has trouble
providing a
description of steps
in the milk unit
experiment and
forming other
testable hyptheses.
Has considerable
trouble explaining
how to apply
process to
answering a
scientific question
and recognizing if
the prediction is
true or false form
observations.
Student is unable
to provide any
kind of
description of the
scientific method
or hypothesis in
the milk unit
experiment. Is
unable to apply
method to
answering a
scientific question
and cannot
recognize if
prediction is true
or false from
observations.
Student is able to
develop an
experiment but
uses more than one
Student does not
develop an
experiment...only
plays with the
the class has not yet
considered.
Experiment is
controlled by changes
to single variables
within the milk
experiment.
Explanation for
results is clear,
concise, succinct and
accurate. Can
efficiently and
effectively work as a
team member who codesigns new
experiments.
the milk
experiment.
Experiment is
controlled.
Explanation for
results is clear,
concise, succinct
and accurate. Can
make contributions
in team work to
design
experimentation.
variables or does
not control the
experiment to
single cause and
effect
relationships.
Explanation for
results is
adequate. Can
perform
positively with a
partner to
accoplish major
tasks.
variable without
recognizing it.
Explanation for
results is only
partial, at best. Has
difficulty in
working as a team
member in
performing
experiments.
variables or
generally observes
them. Explanation
for results is
missing.
Teamwork tends
to be more of a
distraction than
benefit during
experimentation.
Supplemental Info.:
Teacher Background Info
Sodium oleate is a soap made from olive oil. A protonated carboxylic ending would
produce Oleic Acid.
Experience from practicing lesson:
This lesson seems to work best when done with partners and teams working face to face.
Students should be encouraged to not only write observations, but also to DRAW before and
after pictures. This helps the students to recognize that non-scientific words and pictures are
VALID forms of observations. Some pitfalls to this lesson include lack of understanding the size
of a molecule in regards to oil, grease and fatty molecules. It may be important to offer a size
examples, along with information manipulatives to express what level this soap is working.
A college-level explanation of the Soap Molecule.
A soap molecule is formed from a process known as saponification. It is usually a process that
includes rendering of lard into large hydrocarbon or "Fatty" chains. When heated to a boil, lye is
added (NaOH), and molecules called 'FATTY SALTS" or "FATTY ACIDS" are formed. Upon
drying, the soap molecule contains a carboxyllic ending, as shown in the molecular diagram
below. The hydrocarbon chain is made up of hydrogen and carbon bonds and is referred to as
the 'HYDROPHOBIC TAIL'. The Carboxillic ending, C-OO-Na, is soluble in water and is
considered the 'HYDROPHILIC HEAD'.
See: http://chemistry.about.com/library/glossary/bldef825.htm and
http://www.drgreene.com/21_1760.html
Three content areas that could be integrated into this lesson include social studies, art, and
health.
In regards to social studies and health, the westward movement and settling of the west
depended a great deal on making soap. Lye (NaOH) was one of the important staples within a
wagon train. When a carcass, pig or beef, was cooked, its' lard was rendered and soap was
made. Soap helped to keep health and hygeine within a wagon train, reducing illnesses and
bacterial spread diseases, such as typhoid and influenza. (WA.R.5-7.1.2.1 and NSES-S.K-4.F.1)
Students should develop their skills in regards to art. Students could be asked to draw micelles,
grease, and soap molecules during this lesson. They could also be asked to create them with pipe
cleaners and Styrofoam balls. (WA.ART.1.2)
Resources:
Resources
Saponification http://www.kcpc.usyd.edu.au/discovery/9.5.5-short/9.5.5_saponification.html
This is a website that shows a molecular representation of a fatty acid and the process of making
soap, called "saponification".
Science: Teachers Guide To Science http://tlc.ai.org/scienclp.htm
Teacher Resource Science Lesson Plans referenced with Indiana state standards. Covers many
topics from caterpillars and bubbles to physics and nuclear energy. Grades K-12 Rating**
Chapter 13.6, pages 558-562 of Brown and Lemay’s “Chemistry: The Central Science”, Tenth
Edition. This entry describes colloids and how micelles are produced from soap molecules of
sodium stearate.