Transcript Milk Unit

CWU – Chemistry and Sci-Ed – Tim Sorey, PhD.
INITIAL OBSERVATIONS – (Work in teams of 2 or 3 people.)
(Wear Goggles, please.)
Procedure
1) Fill petri dish ½ full of 2% milk.
2) Place a single drop of food
Coloring (red) in the middle of the
2% milk.
3) Within 15 seconds, place a drop
of soap in the center of the food
coloring.
1)
Observations
2)
3)
??????
Question: Does milkfat play a role in the speed of the observed chemical reaction?
Prediction: Increasing milkfat will cause the observed chemical reaction to speed up.
Repeat the previous procedure with Skim Milk, Whole Milk, and Half-and-Half Milk.
What did your team find out?
What do your collective data suggest?
Do you all agree with one another?
Let’s do this together on the overhead projector!
WHAT ABOUT A SCIENTIFIC HYPOTHESES?
The so-called hypothetico-deductive method of science is a term that some have
misconceived as a scientific educated GUESS followed by confirming or denying its
validity through quantitative data, only.
NOT THE CASE! Probably the most important part of this ‘old school’ dogma is the
EDUCATED guess. “EDUCATED” presumes that prior knowledge or experience has
preceded the guess. Also, either qualitative and/or quantitative data are adequate for
analysis of the “guess”.
An acceptable “FORMULA” for an HYPOTHESIS:
1) Know what you are trying to study with no less than ONE previous experiment or
activity with the provided materials.
2) Know what you are manipulating (x), what you believe is responding (y), and
follow this with a reasonable scientific explanation of WHY this may be the case.
Hypothesis = (If a manipulated variable is ‘tweaked’ then a responding variable (y) will react)
+ (because of a plausible scientific explanation)
“If__(x)_____then__(y)____because__(scientific explanation)__.”
Identified Variables:
Milkfat = Manipulated Variable
(Independent Variable)
(x)
Speed of Reaction = Responding Variable
(Dependent Variable)
(y)
Hypothesis: If milkfat increases then the speed of the
initial reaction will increase because soap is used to
“cut through” fats and greases.
Hypotheses are difficult to construct and they take quite a
lot of practice.
For K-8th Grade, students should be able to inquire by
asking scientifically testable questions and formulating
scientific questions.
Scientific Question: A scientifically testable question.
Scientific Prediction: Stating an educated inference and
taking a stand on how you believe the idea or question will
turn out after collecting data. (Staking a claim.)
What about YOUR OWN inquiries?
1)
2)
3)
4)
5)
6)
7)
8)
Change a single variable
Ask a different testable question
Create a Hypothesis
Make a prediction
Run a few experiments to test your question
Discuss your results
Did you answer your questions….(CONCLUSION!)
Did you have OTHER questions?
RESEARCH = Search + Search + Search for the best
possible answer to your question
Explanation of Soap interacting with WATER and OIL!
Go to OVERHEAD and enjoy the DEMONSTRATION and
HAND-OUTS!
Bubbles….what’s up with that?
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5 stage model:
 Safety
▪ Create a physically safe learning environment
 Engage
▪ Create interest/curiosity, raise questions
▪ HOW? – INITIAL MILK EXPERIMENT
 Explore
▪ Student explore with intermittent teacher facilitation
▪ HOW? – Teacher-Based Inquiry using %milkfat as a focus QUESTION
 Explain
▪ Students/Teacher discuss concepts and experiences
▪ HOW ? – DEMO that displays miscibility and like dissolves like
 Extend
▪ Apply developed concepts/skills toward a new experiemnt
▪ HOW? – Student-Based Inquiries using other materials.
 Evaluate
▪ Ongoing process, teacher- and student-based
▪ HOW? – Journaling, Worksheets, Questioning, Discussing….etc.
Saturated Fats/Oils/Greases - HydroCarbons
H
H
H
C
H
H
C
H
H
C
H
C
H
H
C
H
C
C
H
H
H
H
H
Unsaturated Fats/Oils/Greases - Hydrocarbons
H
H
H
H
C
C
H
H
H
C
C
H
H
C
H
C
H
H
C
H
H
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Sugars – WHAT ARE THEY?
 Sugar - a water soluble mixture of “sugars” C6H12 O6
▪ Fructose (monosaccharide)
▪ Glucose (monosaccharide)
▪ Sucrose (disaccharide)
▪ Page 58 of manual – sugar sources
 Cornstarch? – Alarge molecule with repeating structural units…
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Corn Starch is a large molecule of repeating structural
units or POLYMER.
If you look closely, you can see a pattern…what is
repeating?
HINT:
C6H11O5 - (C6H11O5)x - C6H11O6
Where x is a VERY LARGE number!
***Corn Starch is a POLYsaccharide***
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What properties of starch (given its chemical structure) allow it to be used as an indicator?
Davender Khera, Yale University
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When starch is mixed with iodine in water, an intensely colored starch/iodine complex is
formed. Many of the details of the reaction are still unknown. But it seems that the iodine
(in the form of I5- ions) gets stuck in the coils of beta amylose molecules (beta amylose is a
soluble starch). The starch forces the iodine atoms into a linear arrangement in the central
groove of the amylose coil. There is some transfer of charge between the starch and the
iodine. That changes the way electrons are confined, and so, changes spacing of the
energy levels. The iodine/starch complex has energy level spacings that are just so for
absorbing visible light- giving the complex its intense blue color. The complex is very
useful for indicating redox titrations that involve iodine because the color change is very
sharp. It can also be used as a general redox indicator: when there is excess oxidizing
agent, the complex is blue; when there is excess reducing agent, the I5- breaks up into
iodine and iodide and the color disappears.
Author: Fred Senese [email protected]
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Reduction/oxidation Reaction or REDOX RXN – Electrons are exchanged and chemical
bonds are rearranged (both broken and formed)
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Oxidation is LOSS of electrons
Reduction is GAIN of electrons
OIL RIG
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Coomassie Blue is an organic molecule that is used to
stain proteins. Remember that “LIKE DISSOLVES LIKE”.
The original Coomassie dye was developed as a wool dye
and named to commemorate the 1896 British
occupation of Coommassie (now Kumasi) in Ghana.
Proteins, also known as polypeptides, can bond to one
another in acid-base pair combinations called “PEPTIDE
BONDS”. These AMINO ACIDS are the basic building
blocks of life.
Scientists have found many different amino acids in
protein, but 22 of them are very important to human
health.
Of those 22 amino acids, your body can make 13
You can figure out how much protein you need if you
know how much you weigh. Each day, kids need to eat
about 0.5 grams of protein for every pound (0.5
kilograms) they weigh. That's a gram for every 2 pounds
(1 kilogram) you weigh. Your protein needs will grow as
you get bigger, but then they will level off when you
reach adult size. Adults, for instance, need about 60
grams per day.
http://kidshealth.org/kid/stay_healthy/food/protein.html
Coomassie Blue
Protein Pairs
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Usually due to one or more REDOX reactions that change
colors due to the presence of a particular compound.
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These strips are specific to glucose. You will not get a
reaction with soft drinks or regular sugar since these are
mainly fructose or sucrose. However, one simple
demonstration anyone can do is to chew a saltine (salty
cracker) and spit out a bit after a few seconds & test it. Then
try it again but chew longer so that the salty taste
disappears and begins to taste slightly sweet. The strips are
sensitive enough to detect this.
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The glucose test strips are intended for demonstrating
osmosis across a membrane similar to the way the small
intestine works. One can show that starch does not cross
the barrier but glucose does. The color test chart indicates
concentration levels in mg/dL but you can convert this to
mmol/L by multiplying by 0.055. eg. 100mg/dL is equal to
5.5mmol/L.
OTHER TESTING REAGENTS for SUGARS!
 Benedict's reagent is used as a test for the presence of
all monosaccharides. These include glucose, galactose,
mannose, lactose, and maltose. Even more generally,
Benedict's test will detect the presence of aldehydes
(except aromatic ones), and alpha-hydroxy-ketyones.
Benedict's reagent contains blue copper(II) ions (Cu2+)
which are reduced to red copper(I) (Cu+).
•pH is the measure of acidity or H+ and OH- ions in water (H2O)
•At 25oC water has a pH scale from a range of 0.0 to 14.0
•pH>7 is basic
•pH < 7 is acidic
•pH = 7 is neutral
http://www.erowid.org/archive/rhodium/chemistry/equipment/pictures/ph-cabbage.jpg
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Classic Reaction…what’s going on?
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Baking soda (HCO3-) and acid(H+) decompose
to create two new compounds, carbon
dioxide gas(CO2) and water(H2O).
HCO3- (aq)+ H+(aq) CO2(g) + H2O(l)
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Timothy L. Sorey, PhD.
Central Washington University
Department of Chemistry
Department of Science Education
 [email protected]
 1-509-963-814