Transcript Document

Food and Nutrition
Acid Test
FOSS food and Nutrition, TESLA Science Notebooks
BIG IDEA:
Foods contain specific materials such as fats, proteins, sugars,
and acid that work together to create healthy or unhealthy
eating choices.
Engaging Scenario
The nutritionist for the Lewiston School District was happy to receive
your results on the sugar test. She has been so impressed with your
data that she would like you to conduct one more final investigation.
Certain foods contain acid and she would like us to test different fruits
to see if acids are present. There is one acid in particular, Ascorbic Acid,
which is an essential nutrient for humans.
To help us, she has sent a powder called baking soda and two liquids
called vinegar and indophenol that we can use in our tests.
The results of your investigation will help her determine which foods
should be added to the menu so students may receive a balanced diet
with essential nutrients.
What do we need to investigate?
What is the problem that needs to be solved?
Word Wall
Acid: a common, naturally occurring class
of chemicals. Acids are commonly added
to processed foods for taste and as a
preservative.
Nutrient: Important chemicals found in
food that helps keep an organism alive
and active.
Focus Question:
“What does the school nutritionist want us to do?”
-- Use the materials provided to test certain fruits for the presence of acid.
-- Help her determine which foods should be added to the menu
“Discuss with your group what we need to investigate and record it as the
FOCUS QUESTION. This is the problem we are going to investigate and
solve.”
How can we … use baking soda, vinegar, and
indophenol to determine if certain fruits contain acid?
Background Knowledge:
Scientists typically reference the acidity of a solution using what is called
a pH scale. The pH scale ranges from 0 to 14. It measures the acidity or
basicity of a solution. A pH of 7 means it is a neutral solution (in the
middle). Pure distilled water has a pH of 7. It is neither acidic nor basic.
A pH of less than 7 means the solution is acidic. A pH of more than 7
means the solution is basic (not acidic). The less pH, the more acidic the
solution is. The more pH, the more basic the solution is.
Acidic Solutions
0
1
2
3
Lemon Juice
Vinegar
4
Neutral
5
6
7
Pure
Water
Basic Solutions
8
9
Baking Soda
10 11 12 13 14
Ammonia
Background Knowledge:
Acidic Solutions
0
1
2
3
4
Neutral
5
6
Lemon Juice
Vinegar
7
Pure
Water
Basic Solutions
8
9
Baking Soda
10 11 12 13 14
Ammonia
“The district nutritionist sent use vinegar and baking soda to help with
our tests. How can we describe these two materials according to the pH
scale?
---Vinegar is an Acidic Solution
---Baking Soda is a Basic (non acidic) Solution
“Where have you seen these two materials before?”
“What were they used for?”
Prediction:
I would like you to record a prediction in your science notebook.
Discuss with your group what you think will happen when I add
5-ml of vinegar to a cup that contains 1-ml of baking soda.
EXAMPLE Prediction:
I think that if we _______________________________________
because ______________________________________________
Part One: Acid Indicator
Materials per Test/Group:
•
•
•
•
•
Syringe (Specially designed Syringe for vinegar tests)
Long handled 1-ml spoon
1-ml of baking soda
5-ml of vinegar
1 cup
1. Measure one level spoon of baking soda into an empty cup.
2. Demonstrate with students how to use the syringe to accurately
measure 5-ml of vinegar. When the flat part of the triangular notch is
even with the end of the syringe barrel, the syringe holds exactly 5-ml.
3. Squirt 5-ml of vinegar into the cup
Record Observations in the Science notebook using detailed
drawings with labels and explanations.
Observations:
“What changes did you see when I combined the two materials?”
The mixture starts to fizz or bubble
“Why do you think this happened?”
When we mixed the two materials together a chemical reaction occurred. The fizzing,
bubbling, change of smell, and foaming are all evidence of a chemical reaction. The acid
and baking soda reacted when mixed.
Chemical Reaction: a change that occurs as a result of
mixing two or more materials together. A reaction forms
new materials with different properties from the original.
Carbon Dioxide: a colorless, odorless gas. It is typically
produced by living organisms, and some chemical reactions.
Observations:
“How was this reaction different from the one we witnessed in
our sugar tests?”
In the sugar test the carbon dioxide was produced as a product of the yeast, a
living organism, turning a food source into energy. The yeast was metabolizing
its energy source.
In this reaction vinegar and baking soda are not living organisms so nothing is
being metabolized. Instead the carbon dioxide is a product of a chemical
reaction. The two ingredients are reacting to form a new material with different
properties.
“Was your initial prediction supported?”
Part One: Acid Indicator
“Lets try the reaction again, but this time we are going to use a
different bottle and set-up”
Materials per Test/Group:
•
•
•
•
•
•
1.
2.
3.
Syringe (Specially designed Syringe for vinegar tests)
Long handled 1-ml spoon
1-ml of baking soda
5-ml of vinegar
1 Reaction bottle
1 Rubber stopper
Measure one level spoon of baking soda into the reaction bottle. Insert the rubber
stopper tightly into the bottle with a twisting motion.
Draw 5 ml of vinegar into the syringe. Push and hold the tip of the syringe into the
hole in the rubber stopper.
Squirt the vinegar into the bottle. Don’t pull the syringe out of the stopper, and don’t
hold the plunger down.
Record Observations in your Science notebook using detailed drawings
with labels and explanations.
Observations:
“What happened when we squirted vinegar into the reaction
bottle?”
The syringe plunger went up or rose.
“Why did this happen?”
Gas produced from the chemical reaction of vinegar and baking soda filled the
syringe causing the plunger to rise. The previous test created gas, but we
couldn’t see it. The gas just mixed into the air. The gas that is produced is
carbon dioxide, the same gas that was produced in our sugar tests when the
yeast metabolized sugar. In that investigation carbon dioxide was produced as a
product of respiration from a living organism. In this investigation carbon
dioxide is being produced as a product of a chemical reaction. Neither the
baking soda nor vinegar are living organisms.
Prediction:
“Lets try the reaction again, but this time we are going to use
5-ml of water instead of 5-ml of vinegar. What do you think will
happen?”
EXAMPLE Prediction:
I think that if we _______________________________________
because ______________________________________________
Baking Soda and Water
Materials per Test/Group:
•
•
•
•
•
•
1.
2.
3.
Syringe (Specially designed Syringe for vinegar tests)
Long handled 1-ml spoon
1-ml of baking soda
5-ml of water
1 Reaction bottle
1 Rubber stopper
Measure one level spoon of baking soda into the reaction bottle. Insert the rubber
stopper tightly into the bottle with a twisting motion.
Draw 5 ml of water into the syringe. Push and hold the tip of the syringe into the hole
in the rubber stopper.
Squirt the water into the bottle. Don’t pull the syringe out of the stopper, and don’t
hold the plunger down.
Record Observations in your Science notebook using detailed drawings
with labels and explanations.
Observations:
“What happened when we squirted the water into the reaction
bottle?”
Nothing, the water soaked into the baking soda, but a gas producing reaction
does not occur.
“Was your initial prediction supported?”
“Why did this happen?”
Mixing water and baking soda does not produce a chemical reaction. The water
did not react with the baking soda. We know this because the solution did not
fizz, bubble, smell, or produce gas. The result of mixing these two substances
does not produce a new substance.
Observations:
“Why does the baking soda react with the vinegar, but does not
react with the water?
Acidic Solutions
0
1
2
3
Lemon Juice
Vinegar
4
Neutral
5
6
7
Pure
Water
Basic Solutions
8
9
Baking Soda
10 11 12 13 14
Ammonia
Baking soda can be used as an indicator of acidic solutions. When the baking
soda is mixed with vinegar a reaction occurred because vinegar is an acidic
solution. When the baking soda was mixed with water, no reaction occurred
because water is a neutral solution neither acidic nor basic.
Prediction/Quick Write:
Why do you think the district nutritionist sent us baking soda, if she
wants us to determine if acids are present in fruit juice? Justify
your prediction with a because statement.
I think that the district nutritionist sent us baking soda to
determine if acids are present in fruit juice because…
Part Two: Acid in Fruit
We now know that baking soda can be used as an indicator to determine if acid
is present in a solution. We know this because when we mixed baking soda
with vinegar, an acidic solution, a chemical reaction occurred producing carbon
dioxide. When we mixed baking soda with water, a neutral solution, no
reaction occurred.
I sent your results to the food nutritionist and she was very happy to see that
you identified baking soda as an indicator of acid in foods. She sent us some
more materials; a 50/50 solution of water and vinegar, and squeezed juice from
limes, grapefruits, oranges, and lemons. She is hoping that you could help her
determine if certain fruits contain acid. She would also like to know if there is
a way to determine if certain fruits contain more acid than others.
What do we need to investigate?
What is the problem that needs to be solved?
Focus Question:
“What does the school nutritionist want us to do?”
-- Use the materials provided to test certain fruits for the presence of acid.
-- Help her determine if certain fruits contain more acid than others.
How can we … use baking soda to determine if certain
fruits contain acid?
“We already know that baking soda is an indicator for acid,
how we can solve the new problem presented to us by the
district nutritionist.”
I think that if we…
because ....
Acid in Fruit -Designing a Fair Test
What are you going to change
What are you going to keep the same
The 5-ml solutions tested
50/50 vinegar and water
Orange juice
Lemon juice
Grapefruit juice
Lime juice
Testing Method:
1-ml of baking soda
5-ml of solution tested
Clean reaction bottle
Rubber stopper
Syringe
Which fruit juices do you think will react with the baking soda? Will some
react more than others? Justify your prediction with a because statement.
I think that…
because…
Acid in Fruit Test
We will follow the same procedure we used in the vinegar and water test
except this time we will test and record the results from other 5-ml
solutions. The variable we are testing in this investigation is different
solutions.
After you complete each test I
would like you to record your
results using this chart. Identify
how much the plunger in the
syringe has rose for each solution
tested.
“What causes the plunger to rise?”
Making Meaning of our
Results
“Was your initial prediction supported?”
“What happened when you squirted the different solutions into the reaction
bottle containing baking soda?”
“Which solutions tested reacted with the baking soda? What does this reaction
tell us?”
“The nutritionist was also hoping that we could identify if certain solutions
contain more acid than others. Does your data provide us with information that
could help us identify if some fruit juices contain more acid than others?”
“Many of you have eaten these fruits before or drank their juice. What did they
taste like? Do you think there could be a relationship between a fruits taste and
acid concentration?”
Concentration: the amount of material dissolved in a
liquid. The more material dissolved in the liquid, the
more concentrated the solution.
Making Meaning of our
Results
Develop a claim that identifies a relationship between the amount of
acid found in fruit juices and the amount of carbon dioxide produced
when a fruit juice is mixed with baking soda.
I claim that…
I claim this because…
I claim that fruit juices with higher concentrations of acid produce more carbon dioxide
when mixed with baking soda than fruit juices with lower concentrations of acid. I claim
this because…
Develop a claim that identifies the relationship that exists between
sour tastes of fruit and acid concentration?
I claim that…
I claim this because…
I claim that fruits with sour taste have a higher concentration of acid. I claim this
because the fruits tested that produced the most carbon dioxide are also the sourest
tasting.
Part Three: Vitamin-C Search
From our investigations so far we know that citrus fruits contain acid and some citrus
fruits contain a higher concentration of acid than others, but our tests did not tell us
what kind of acid was in the fruits. The nutritionist told us earlier that there are
different types of acid and one acid in particular, Ascorbic Acid, is an essential
nutrient for humans. Ascorbic acid is commonly called, vitamin C. Humans cannot
make vitamin C in their bodies, so they must get this nutrient by eating foods or
supplements that contain vitamin C.
We are going to use the indophenol liquid the nutritionist sent us to test some more
foods because indophenol is an indicator for vitamin C. She is hoping that you could
help her determine if certain fruit juices contain vitamin C. She would also like to
know if there is a way to determine if certain fruit juices contain higher
concentrations of vitamin C than others. The results of your investigation may help
determine which fruit juices would be healthy and beneficial additions to the school
lunch program.
What do we need to investigate?
What is the problem that needs to be solved?
Word Wall
Indophenol: Can be used as an
indicator of vitamin C in foods
Ascorbic Acid: Vitamin C, an
essential acid in human nutrition
Focus Question:
“What does the school nutritionist want us to do?”
-- Determine if certain fruit juices contain vitamin C.
-- Determine if certain fruit juices contain higher concentrations of vitamin C.
How can we … determine if certain fruit juices contain
vitamin C and if some fruit juices contain higher
concentrations of vitamin C than others.
Background Knowledge:
If you were to drink this 175-ml cup of vitamin-C solution your body
would receive the appropriate amount of vitamin-C it needs to stay
healthy for one day.
In nutrition this is called RDA the recommended daily allowance. The
solution in the jar was created by mixing 700-ml of water with a 250-mg
vitamin-C tablet. We mixed and diluted the vitamin C concentration
from the tablet with 700-ml of water because one of these tablets
provides more than 4 times the recommended daily allowance.
700-ml of the solution divided by 4 is 175-ml or one daily serving
Vitamin-C Test:
When we test fruit juices for the presence of vitamin-C we are going to
compare them to our recommended vitamin-C solution.
1. Squirt exactly 10-ml of the blue indophenol indicator from the
dispensing bottles into a reaction bottle. (Fill to the 10-ml
line)
2. Use a dropper to put drops of the material you are testing
(Vitamin-C solution from your 175-ml cup) into the reaction
bottle. Add one drop at a time. Gently swirl the bottle after
each drop.
3. Count the number of drops needed to make the blue indicator
colorless. Place the reaction bottle on white paper for
contrast.
(There should be no hint of color)
4. Record the number of drops needed.
5. Dump the materials from the reaction bottle into a 1-liter
waste container, and rinse the reaction bottle thoroughly
before testing the next juice.
Observations/Prediction
What is happening? Why did the blue indophenol indicator
change color when we added drops from the Vitamin-C solution?
The blue indophenol indicator is reacting with the vitamin-C present in the drops
of vitamin-C solution we added. The reaction causes the indophenol to change
from blue to clear.
Develop a prediction with your group -- how can we use an indophenol
test to determine if certain fruits juices contain vitamin C and if some fruit
juices contain higher concentrations of vitamin C than others?
I think that we …
because....
Vitamin-C in Fruit
Designing a Fair Test
What are you going to change
What are you going to keep the same
The solutions tested
Vitamin-C Solution
Fruit Juices Collected
Testing Method:
10-ml of blue indophenol indicator
Testing dropper
Swirl after each drop
Fruit juices that contain a higher concentration of vitamin-C will take fewer drops to
change the color of the indophenol indicator. Fruit juices that contain lower
concentrations of vitamin-C will take more drops to change the color of the indophenol
indicator. Which fruit solutions do you think will contain the highest and lowest
concentrations of vitamin-C? Justify your prediction with a because statement.
I think that…
because…
Making Observations and
Collecting Accurate Data:
Source of Vitamin-C
Vitamin-C Solution (RDA Concentration)
Other fruit juices collected
Drops needed to Clear 10-ml of
Indophenol Indicator
Math Extension:
Calculating RDA % of
Vitamin – C in fruit drinks
Since we know that 175ml of our standard vitamin-C solution provides
100% of our RDA, can we calculate (or estimate) the percentage of RDA in
one serving of the fruit drinks we tested?
Hint: If the vitamin-C solution took 20 drops to neutralize 10ml of indophenol
indicator and a sample of fruit juice takes 10 drops to neutralize 10ml of
indophenol indicator, what is the % of RDA in the fruit juice tested?
20 drops is 100% RDA
200%
10 drops is ___________RDA
Less drops means there is a higher concentration of vitamin-C in the
solution. If the solution requires half the amount of drops to change the
indicator, there is twice as much vitamin-C in the solution.
Making Meaning of our
Results
“What is Vitamin-C?”
Ascorbic Acid, an essential nutrient humans must consume
“What indictor is used to detect vitamin-C?”
Indophenol
“What is the evidence that vitamin C is present?”
When enough juice containing vitamin-c is added to the
indophenol solution, the solution changes from blue to clear
“Which solutions tested reacted with the indophenol indicator?
What does this reaction tell us?”
The solution/juice added contains some concentration of
vitamin-C.
Making Meaning of our
Results
“The nutritionist was hoping that we could identify if certain juices
contain more vitamin-C than others. Does your data provide us with
information that could help us identify which fruit juices contained the
most vitamin-C, which contained the least?”
Juices that contain higher concentrations of vitamin-c will turn the indicator colorless with
just a few drops; a juice with a small amount of vitamin-C will require many more drops.
“How do you know?”
Our control was a solution that contained the recommended daily allowance of vitamin-C.
Juices that required less drops to turn the indicator colorless contain a higher than RDA
concentration of vitamin-C; juices that required more drops contain a lower than RDA
concentration of vitamin-C.
What recommendations would you provide the district nutritionist for
offering juices that provide good sources of vitamin-C?
Making Meaning
The Acid Tests
How can baking soda be used to indicate the presence of acid in
foods?
What relationship exists between acid concentration in fruit juice
and the amount of carbon dioxide produced when fruit juice and
baking soda are mixed?
What relationship exists between sour tastes of fruit and acid
concentration?
How can we determine which fruit drinks have the highest
concentration of Vitamin C?
Claims and Evidence:
Based on what you have learned from your investigation of acids,
you need to record some claims and evidence statements in your
science notebook… Your evidence must be based on your data!
I claim that…
I know this because…
Possible Example:
I claim that baking soda can be used as an indicator for the presence of
acid in foods. I know this because…
I claim that fruit juices with higher concentrations of acid produce more
carbon dioxide when mixed with baking soda. I know this because…
REFLECTION AND CONCLUSION
November
11/8
• What did you learn…?
• What really surprised you…?
• What new questions do you have…?
• What would you like to know more about…?
2011