Science Activity
Need Help With This
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Kitchen
Element
s
Model 1. All of the elements on the periodic table can be found in nature as pure substances. An element is made of atoms, therefore a sample of the element calcium would be made of many calcium atoms. A compound is also a pure substance. A compound is made of molecules, therefore a sample of the pure compound water would be made of many water (i.e.
H
2
O
) molecules.
Table 1.1. Examples of various types of matter at room temperature (70°F/21°
C
)
Item
Classification
Is it a Molecule?
Chemical Formula
Ca
lcium
No
Sodium
Element
No
Na
Iron
Element
No
Fe
Oxygen
Element
Yes
O2
Carbon dioxide
Compound
Yes
CO2
Water
Compound
Yes
H2O
Compound
Yes
C6H8O6
Sodium chloride (i.e. table salt)
Compound
Yes
NaCl
Sucrose
(i.e. table sugar)
Compound
Yes
C12H22O11
Monosodium glutamate (i.e. MSG)
Compound
Yes
NaC5H8O
4
N
Molecules are formed from the bonding of two or more atoms. Most matter on earth, including food, is a mixture of different types of molecules. A molecule is the smallest, neutral (that is, without charge) unit of a substance formed by bonding two or more atoms together. Molecules and compounds are often used interchangeably to describe a substance. The simplest way of thinking about it is that a compound must contain at least two different elements and a molecule is anything that has more than one atom.
|
Figure 1.1. The Periodic Table of the Elements lists all the known elements by increasing size (left to right and top to bottom) |
All living things (animals, plants microbes, and smaller life forms) are made of atoms and molecules. How those molecules are organized, interact and react are the building blocks for life. Molecules are often divided into two categories, organic (those molecules containing carbon atoms) and inorganic molecules (everything else).
|
Most food is a mixture of molecules. Consider the nutrition data for a medium orange in Figure 2. |
|
Food molecules are typically classified in three main categories: Fat , Carbohydrate , and Protein . Fat, Carbohydrate and Protein are large classes of molecules that contain many different specific examples. See Table 2. |
|
Cholesterol is a molecule; it has the molecular formula C27H46O. |
|
Vitamin A (C20H30O) and Vitamin C (C6H8O6) are both molecules. |
|
For Sodium, Calcium and Iron – see model 2. |
|
Figure 1.2. Nutrition Data for 1 medium orange |
1. Consider Table 1.1. How does the formula of an element differ from that of a compound? How can you distinguish elements from compounds based on their chemical formulas?
2. According to Table 1.1, oxygen exists as a molecule, but not a compound – why is this?
Table 1.2. Examples of food molecules from the major classes: fat, carbohydrate and protein.
|
Type |
Specific example |
Molecular formula |
|
| Fat |
Linolenic acid |
C18H30O2 |
|
|
Oleic Acid |
C18H34O2 |
||
| Carbohydrate |
Glucose (i.e. dextrose) |
C6H12O6 |
|
|
maltose |
|||
| Protein |
Alanine |
C3H7NO2 |
|
|
Glutamate4 |
C5H9NO4 |
3. Using the Periodic Table of the Elements in Figure 1.1, list the elements found the items of Table 1.2. How can you tell what elements are present?
Model 2. Sodium, Calcium and Iron appear on nutrition data labels for all foods
, and yet the pure elements sodium, calcium are indigestible by humans. In fact, the pure elements sodium and calcium are downright harmful! They will burn your skin and certainly your mouth if you try to consume them. The element iron is not harmful, but it is not very digestible. Sodium, calcium and iron are examples of metals. How then can most benefit from these metals in our food?
Table 1.3. Sodium, calcium and iron in food.
|
Pure Element |
As found in food |
Food sources |
|
Sodium (Na) |
sodium chloride (i.e. table salt, NaCl), monosodium glutamate (i.e. MSG, NaC5H8O4N ), sodium bicarbonate (baking soda, NaHCO3), sodium benzoate ( NaC7H5O2 ) |
Milk, celery, bacon and condiments like Worcestershire sauce. |
|
Calcium (Ca) |
calcium citrate ( Ca3C12H10O14 ) calcium lactate ( CaC6H10O6 ) |
Calcium supplements, cheese |
|
Iron (Fe) |
Heme (FeC34H32O4N4)
ferrous FeSO4 ) ferrous fumarate ( FeC4H4O2 ) |
Meat, fortified infant cereal |
4. Compare the column Pure Element versus the column As found in food from Table 1.3. What can you conclude about the sodium, calcium and iron represented in the As found in food column.
Model 3. Sodium, calcium, iron and other metals found in food are most often consumed as part of ionic compounds. Ionic compounds are comprised of two halves: a cation (pronounced CAT-EYE-UN) and an anion (pronounced AN-EYE-UN). The cation carries positive charge, while the anion carries negative charge – together the charges balance each other and the overall compound is net neutral. Finally, an ion is different from an element. For example, the element sodium has a neutral charge, but the sodium ion does not.
Table 1.4. Examples of ionic compounds found in food.
|
Ionic Compound |
Cation |
Anion |
||||
| sodium chloride |
NaCl |
Na+ |
Cl- |
|||
| monosodium glutamate | NaC5H8O4N |
[C5H8O4N]-1 |
||||
|
sodium bicarbonate |
NaHCO3 |
[HCO3]-1 |
||||
| sodium benzoate | NaC7H5O2 |
[C7H5O2]-1 |
||||
| calcium citrate | Ca3C12H10O14 |
3x Ca+2 |
2x [C6H5O7]-3 |
|||
| calcium lactate | CaC6H10O6 | Ca+2 |
[C6H10O6]-2 |
|||
|
ferrous sulfate |
FeSO4 |
Fe+2 |
[SO4]-2 |
|||
| ferrous fumarate | FeC4H4O2 |
[C4H4O2]-2 |
In an ionic compound – for example, sodium chloride – the cation is always carrying a positive charge (Na+) and the anion is always carrying a negative charge (Cl-), but sometimes the ionic compound will be represented with cation and anion listed one after the other (e.g. NaCl) – without the charges explicitly shown. In the NaCl example, the combination of one positive charge and one negative charge creates the overall neutral compound (NaCl). While the charges on the sodium cation and chloride anion might not always be shown – they are always present. You should learn to recognize the pattern of naming that identifies an ionic compound like sodium chloride.
In addition, all but one of the anions in Table 1.4 is made of many atoms – and these ions are said to be polyatomic
. In these cases, the charge is associated with one or more discreet atoms. For example, the anion fumarate is drawn in Figure 1.3.
O
C
C
C
C
O
O
O
H
H
C
4
H
2
O
4
2-
thelinesconnectingtheatomsarecalledbonds,
Thenatureofbondswillbeaddressedin
Activity3
thetwonegativechargesinthe
anionfumaratearelocatedon
twodifferentoxygenatoms
Figure 1.3. The anion fumarate.
5. From Table 1.4, what can you tell about the pattern of naming ionic compounds? What comes first, what comes second?
6. Explain how calcium citrate in Table 1.4 is a net neutral ionic compound. Remember, the negative and positive charges must balance out in the final compound.
7. Using Figure 1.3 and Table 1.4, propose a molecular formula for calcium fumarate. Give a rationale for your answer.
8. While sodium chloride is what we know a “table salt”, all the other compounds in Table 1.4 are also examples of “salts”. What must be the basic requirements for a salt?
Putting it all together:
9. Find the molecular formula for the following compounds. Determine the types of atoms present in each substance using the Periodic Table. For each substance determine whether it is an element or a compound.
a. Fructose
b. Sodium citrate
c. Aspartame
10. Are any of the compounds in the preceding problem an ionic compound? How can you tell? List the cation and anion.
Key Concept
Molecules are formed from the bonding of two or more atoms.
Most matter on earth, including food, is a mixture of different types of molecules.
� The nutrition data for 1 medium Florida orange was supplied by the United States Department of Agriculture Agricultural Research Service, National Nutrient Database for Standard Reference Release 27. The data is in the public domain.
� An omega-3 fatty acid found in green leaves and some seed oils.
� The primary fatty acid found in olive oil
� Alanine and glutamate are components of protein
� � HYPERLINK “http://www.nutrition.gov” ��www.nutrition.gov�
� MedlinePlus. Sodium in your diet.
� The word ferrous is derived from the latin word ferrum, which means iron
� Poly = many, atomic = atoms, as in elements.
Copyright © 2016 Wiley, Inc.
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1
Laboratory Exercise – Ice Cream
Making Ice Cream
Introduction:
When it comes to food preparation, humans have developed many techniques to alter the
temperature of foods and beverages to optimize the eating and drinking experience. This
sometimes comes in simply heating or cooling foods directly and other times comes in using
temperature changes to alter the properties of the food or
beverage. When doing so, we frequently take advantage
of the physical properties of particles in solution,
colligative properties, to facilitate temperature changes.
If you live in a cold weather climate your daily life is
enhanced by an understanding of colligative properties.
During icy road conditions, highway crews treat the roads
with salts (NaCl or CaCl2) or brine solutions made of these
salt to reduce ice build-up. Adding NaCl brine to highways
helps to melt the existing ice and prevents the formation
of new ice. In a similar fashion, to keep the engine coolant
in vehicles from freezing during severe cold, people use
antifreeze. Most common antifreeze solutions contain
ethylene glycol which when mixed with water lowers the
freezing point. Having an understanding of the colligative
properties of solutions enhances our lives in many
practical ways, and also in less practical and more enjoyable ways, like making ice cream.
2
Laboratory Exercise – Ice Cream
Solutions are homogenous mixtures of two or more substances. The solvent is the major
component of the solution and the majority of the physical properties of the solution are due to
the solvent. The minor component or components of a solution are called solutes. Some of the
physical properties of a solution are independent of the type of solute present and are only
dependent upon the concentration of dissolved particles. These properties are referred to
colligative properties. Colligative properties include boiling point elevation and freezing point
depression. Properties that we take advantage of in preparation of foods such as homemade
ice cream.
In this exercise we will take advantage of one of the colligative properties of solutions, freezing
point depression, to make homemade ice cream. Then we will evaluate another property of ice
cream, taste, to evaluate how changes to the ingredients used to make ice cream impact flavor.
Background:
Colligative Properties
As you have learned several times, pure water freezes at 0 °C (32 °F) and boils at 100 °C (212
°F). We also know that these values can be altered by the addition of different solutes to the
water. Using two examples from the introduction, we know that NaCl brines can be prepared
to decrease the freezing point of water. A 23.3% solution of NaCl freezes at -51°C or -60°F,
dramatically colder than the freezing point of pure water. The use of antifreeze in vehicles
provides a similar impact. A 50/50 (v/v) mixture of antifreeze and water has a freezing point of
-34°C or -29°F. Using a 70/30 mixture of antifreeze to water extends the freezing point to -84°C
or -119°F.
How does understanding colligative properties help us with making ice cream? When you make
ice cream whether in an old-fashioned, hand-cranked, ice cream maker or in a sealable plastic
bag the temperature of the cream mixture needs to be maintained at temperatures below 0°C
(32°F). Since ice water only reaches a minimum temperature of 0°C, we take advantage of
colligative properties to reduce the temperature of the ice bath around the ice cream maker to
accelerate the freezing.
Ice Cream Making and Tasting
As we have learned throughout this course, the perception of taste and flavor is a personal
characteristic. Your preferences for spicy or salty food is a personal characteristic similar to
your choice of chocolate, vanilla, or cookies and cream ice cream. The challenge with doing a
taste test is endeavoring to place on objective measurement on a very subjective topic. To help
3
Laboratory Exercise – Ice Cream
in this process, we will need to define a series of terms that will be used to address flavor, body,
and texture characteristics of ice cream. In this experiment we will taste test a series of vanilla
ice cream products that vary both in price and the nature of the ingredients.
Flavor Characteristics
• Flavoring or Sweetness: Is the flavor or sweetness lacking or too strong. We will evaluate
both flavor and sweetness. For the vanilla ice cream we will be tasting we will ask is the
vanilla too weak, too strong, exactly what you like. We will also ask whether the ice cream
is too sweet, not sweet enough or exactly what you like.
• Syrup Flavor: The syrup flavor is a measure of the presence of corn syrup sweetener
present in the ice cream. Liquid corn syrup is the common reference point for this
characteristic. Most people prefer their ice cream to be sweet without being syrupy.
• Whey Flavor and Texture: Whey is the common form of non-fat milk solids (NMS) added to
ice cream that contribute to both flavor and texture. High levels of whey protein or the use
of low quality whey protein lead to a flavor described as earthy, grassy or alfalfa-like in the
ice cream that most people do not like.
• Bloom / Bouquet: These terms are used (often interchangeably) to describe the emergence
of flavors as odorants are volatilized as the ice cream melts in your mouth and enter rear of
the nasal cavity (retronasal). The bloom of ice cream is describe using terms such as
insufficient, delicate, light, full, rich, overpowering.
Process of Science:
You will be evaluating the various properties of ice cream and how they relate to the ingredient
list. To get ready to write the introduction to your report next week, you should answer the
following question (note: this handout will not be collected, this is merely to help you in the
preparation of your report).
1. A key question being investigated in each of the exercises below.
2. A hypothesis or proposed answer to the question asked.
3. A prediction for the outcome of the experiment based upon your hypotheses you
developed. The prediction should written as an if/then statement and be specific to the
measurements being made.
4. An explanation of your reasoning for each of your hypotheses and predictions.
4
Laboratory Exercise – Ice Cream
Procedures:
Exercise 1: Making Vanilla Ice Cream
In this exercise we will be making vanilla ice cream. The recipe makes about 1 cup of ice
cream.
A. Ingredient Preparation
1. Obtain a 1 quart zip seal plastic freezer bag.
2. To this bag add:
a. ½ cup whole milk
b. ½ cup heavy whipping cream
c. ¼ cup table sugar (sucrose)
d. ¼ teaspoon vanilla or vanilla flavoring
3. Seal the bag.
4. Mix the contents gently by squeezing and rocking the bag.
5. Place this bag in the freezer or on ice while preparing for part C.
B. Ice Bath Preparation
1. Obtain a 1 gallon zip seal plastic freezer bag.
2. To this bag add:
a. 3 cups crushed ice.
b. ½ cup cold water.
c. ¾ cup table salt (NaCl)
3. Seal the bag.
4. Mix the contents gently by squeezing and rocking the bag.
C. Ice Cream Making
1. Open the 1 gallon zip seal plastic freezer bag.
2. Carefully place the 1 quart zip seal plastic freezer bag with the ice cream
ingredients into the 1 gallon bag.
3. Seal the 1 gallon bag.
4. Gently rock the 1 gallon bag from side to side gently squeezing the contents
occasionally. (You may want to wear a pair of winter gloves since the bag will get
quite cold.)
5. Continue to rock and squeeze the bag for 10 to 20 minutes until the contents of the
quart bag harden to form ice cream.
6. Remove the quart back from the gallon bag and dry the outside of the quart bag.
7. Taste your ice cream!
5
Laboratory Exercise – Ice Cream
Exercise 2: Ice Cream Taste Test
In this exercise you will be taste testing different brands and qualities of ice creams.
A. Preparation
1. By Thursday at 11:59pm, in the discussion forum you should decide as a group who
is responsible for obtaining and rating which ice cream brands.
B. Tasting
1. Take a small amount of each the store-bought ice cream and rate it on a scale of 1
(poor) to 5 (exceptional) for each of the following:
a. Sweetness
Self-explanatory and very much a personal preference
b. Flavor
Self-explanatory and very much a personal preference
c. Syrup
Syrupiness is associated with the addition of corn syrup as a sweetener.
d. Bloom
Describes the emergence of the flavor as the ice cream melts in your mouth.
Typically described as delicate, full, rich, or powerful. Include both a description
and a score.
e. Body
The substance or structure of the ice cream. Typically described as weak,
gummy, fluffy or chewy. Include both a description and a score.
f. Texture
Refers to the relative smoothness of the ice cream. Can be describes as coarse,
thin, or greasy. Include both a description and a score.
2. Record the results of the taste test in Data Table 1.
3. Repeat for your homemade ice cream.
6
Laboratory Exercise – Ice Cream
Results (to be posted in the Discussion forum by Sunday night):
Data Table 1. Ice Cream Taste Comparison. Rank your homemade and store-bought ice creams
1 to 5 for each category. Average the total scores for each ice cream.
Ice Cream Brand
Characteristic
1.
Homemade
2.
Sweetness
Flavor
Syrup
Bloom
Body
Texture
Average
Results and Conclusions (to be completed after all data is collected from your peers):
Use the following questions to help you to write your Results and Conclusions sections of your
laboratory report. Again, this handout will not be collected and scored, but use these questions
to guide you.
Exercise 2: Ice Cream Taste Test
1. Recreate Data Table 1, now with at least 4 store-bought brands represented from
yourself and your peers (along with your homemade ice cream):
Ice Cream Brand
Characteristic
1.
Homemade
2. 3. 4. 5.
Sweetness
Flavor
Syrup
Bloom
Body
Texture
Average
7
Laboratory Exercise – Ice Cream
2. Rank the ice cream brands you and your peers tasted highest to lowest based on
average score. If several of your classmates used the same ice cream brand, you may
either select the data from one peer, or average all of the scores (more accurate). Which
ice cream brand scored the highest on the taste test? Which was the lowest?
3. Was there a correlation between the cost of the ice cream and the taste rankings? Was
the correlation what you expected?
4. Compare the ingredients list for each of the ice creams tasted. Do the ingredients give
you an indication why certain ice creams rated higher or lower in the scale?
Process of Science Questions and Conclusions:
Earlier you created a key questions, hypotheses, predictions, and explanations for this
prediction for each of the experiments in this laboratory exercise.
Based upon your data and the questions you have answered related to this exercise you should
be able to complete the process of science questions and conclusions.
Answer the following questions.
1. Did your data support or falsify your hypothesis?
2. How did you come to this conclusion?
3. Did these results change your thinking about this topic? How?
4. What changes would you make to your hypothesis based on this new data?
5. What changes would you make to the experiments to better clarify your results?
By Thursday:
We are going to perform that lab and collect data that we will share with our peers. Please read through the
attached document
before getting started this week.
Pick an ice cream brand at the store that you want to buy in vanilla flavor (so that it can be directly compared to your peers’ choices and your homemade ice cream). The subject line in this post should include the brand of ice cream that you purchased to help your peers find the information that they need quickly while writing their reports next week.
Likely you are selecting a particular brand because you like it. Tell your classmates why you like that particular brand. Is it the richness of the flavor? The texture? If you see that many of your classmates are picking the same brand, it may be helpful to select something different to add some variety. Feel free to go for the store brand if you like it better than a national brand!
By Sunday:
Run the lab. Feel free to get your family involved too! This means making your own homemade ice cream per the lab instructions. Also, tasting the store-bought ice cream and comparing it to your own ice cream.
Use the table in the attached lab handout to rate the various characteristics of the two ice creams (homemade and store bought). Feel free to take videos or pictures if it helps you to share this information with everyone. Have fun with this!
Post your data table as a response to your initial post (no need to respond to peers directly, unless you want to!). In the text of this post, you MUST include the ingredients of the store-bought ice cream and the price that you paid per unit (pint, ounce, etc.). You should also be clear about why you gave the ratings that you gave. Maybe you have an aversion to corn syrup? Maybe you like an airier ice cream? These explanations will help your peers to understand your ratings and make it easier to directly compare to their own ratings.