Sam Redstone
January 30, 2014
Title:You Are What You Eat
Appropriate Level:Students Grades 3-8
Abstract: Students will gain familiarity with the three macromolecules most crucial to nutrition: carbohydrates, lipids and proteins. They will perform various qualitative chemical tests on food to determine the presence of these macromolecules. Students will collect skin, fingernail and/or hair samples from themselves to demonstrate that we truly are made of what they eat. Finally, they will participate in various physical activities to demonstrate that different activities require different amounts of energy.
Time Required:60 Minutes
Objectives: Students will learn the relationship between the food that they eat and the energy that it provides, in addition to the difference in energy it takes to complete various physical activities. Additionally, students will learn that we truly are what we eat. This will be done by collecting hair samplesandperforming tests that demonstrate the presence of protein.
Chemical Concepts:Macromolecules: Large molecules consisting of smaller sub-units. The three relevant to nutrition are carbohydrates, lipids and proteins.
Carbohydrates: Compounds used to provide short-term energy. Also referred to as sugars, carbohydrates provide 4 Calories of energy per gram.
Lipids: Compounds used to provide insulation and act as a concentrated source of energy. Characterized by being insoluble in water, lipids provide 9 Calories of energy per gram.
Proteins: Compounds used to catalyze metabolic reactions. Also used to build and provide structure to tissues, proteins provide 4 Calories of energy per gram.
Energy: Commonly found in the forms of light, heat and electricity, energy is needed to do work on an object. All life requires energy to carry out its function.
Materials
• Stopwatch
• White Bread
• Egg Whites
• Saltine Cracker
• Marshmallow
• Energy Drink
• Mortar and Pestle (Optional)
• Beakers
• Water
• Pipettes
• Matches
• Copper(II) Sulfate and Sodium Hydroxide Crystals
• Spot Plates
• Weigh Boats
• 2 Hydrometers
Preparation Work
To be completed by the instructor prior to the start of the experiment.
1. Set up work stations with weigh boats, spot plates, pipettes and water. If time allows, students can grind the food products themselves. If this is the case, each group should also have a mortar and pestle.
2. Prepare the food sources: (a) mix 2-3 egg whites with 10-15 mL water; (b) Crush the potato chips and store in an air-tight container.
3. Prepare a 0.1% CuSO4 solution by adding 0.1 g of the copper (II) sulfate and diluting to 100 mL.
Demonstrations
1. Explain that the energy we need to live all comes from the food we eat, and that energy can be found in many forms, including light and heat. For this demonstration, the instructor will burn two food products to visualize that different food products contain different amounts of energy. The two objects to be burned will be a saltinecracker and a marshmallow.
2. Add several drops of iodine to the white bread and allow the class to observe any changes. Then test the egg white for protein by adding 1 mL of 6 M NaOH to the white followed by ~1 mL of the 0.1% CuSO4 solution.
3. Use the hydrometers to demonstrate that soda, or an energy drink, contains more sugar than water. To use the hydrometer, fill each one up to the 100 mL mark with either water or soda. Then place the buoy into the liquid and spin it. When it comes to a stop, it will float in the beverages at different levels depending on their sugar content. The buoy will float higher in beverages with higher sugar content.
4. Ask a student volunteer to provide several strands of hair, then perform the test for proteins on it. Note that it will take longer for the purple color to appear with hair than it will with the eggs. It may be helpful to wait until the end of the lesson to show the students the positive test for proteins. Furthermore, it may be helpful to cut the hair up into smaller pieces to increase its surface area, which will maximize the surface area that the CuSO4 and NaOH have to react with.
Detecting a Pulse
If time allows, show students how to find a pulse on their necks. Have them record their resting heart rate by allowing them to count the number of pulses in 15 seconds. To find their heart rates in beats per minute (bpm), have them multiply the number that they counted by four. Next, have them perform jumping jacks for 30 seconds, and then have them count their pulses again, the same way as described above. The children should notice that their heart rates increase after performing exercise. You should explain to the students that different physical activities require different amounts of energy to perform and that this is why their heart rates differ during different activities. Encourage them to measure their heart rates at home before and after various activities, such as a soccer game, first thing in the morning, after eating or after watching an exciting athletic competition.
Expected Results and Explanation
Simple Sugar Testing
A hydrometer is used to compare the density or various liquids, where the higher the buoy floats in solution, the denser the liquid is. The buoy will float higher in the energy drink because other molecules in it, namely sugars, increase its density.
Starch Testing
Starch is a coiled polysaccharide. Iodine fits into these coils and when it forms a complex with starch, a deep purple or black color will appear.
Lipid Testing
Fats are insoluble in water. Students should observe a thin film of fat appear on the surface of the water after they rub their fingers on crushed potato chips and dip them into a cup of water. It may be easier to see the film of lipids if the water is held against a dark background.
Protein Testing
The NaOH will first break down the proteins that will then undergo a chemical reaction and turn a purple color when introduced to CuSO4.
Accommodations for Different Age Levels
• Younger students should not handle any of the chemicals used for the qualitative tests (i.e. 6 M HaOH, 0.1% CuSO4, Iodine) themselves, nor should they handle the matches. Instructors should perform these demonstrations and allow the students to make observations. Older students (Grades 7-8) may be able to handle these chemicals and matches; however, they should be under the supervision of an adult at all times.
• The math involved in Activity 3 can be difficult for students in grades 3-4. Instructors, if you feel that your group of students is not yet ready for this multiplication, feel free to skip that activity.
Sources Used:
Hassell, C.A., Marshall, P., Hill, J.W. Chemical Investigations for Changing Times, 8th ed.; Prentice Hall: Upper Saddle River, NJ; p. 139-142.
Calories burned in 30 minutes for people of three different weights. Harvard Medical School. (Accessed January 21, 2014).
Lee, Lyoe (2010) Who Stole the Playstation? Colby College CH 151 website.
You Are What You Eat
Background
Your baseball-playing friend wants your help again, this time with nutrition. He understands that there are three different major nutrients: carbohydrates (sugars), proteins and fats, but he does not understand the differences between the three of them or what foods to find them in. Furthermore, he knows that the food he eats is what provides him with energy, but he is having trouble visualizing it. Your job will be to complete tests to determine which foods the nutrients can be found in, in addition to monitoring your heart rate before and after different physical tasks. Finally, you will participate in a math activity that will help you and your friend make the connection between the amounts of proteins, fats and sugars in a serving of chocolate milk and the number of Calories it contains.
Procedure:
Activity 1: Tests for Nutrients
Based on the demonstrations you saw, draw a line connecting the food item with the nutrient it contains the most of.
FoodNutrients
BreadSugars
Potato ChipProteins
Energy DrinkFats
Egg WhiteStarch
Activity 2: Detecting a Pulse
1. Find your pulse by tracing your middle and pointer fingers from the back of your ear down your jaw line.
2. Find your resting heart rate by counting the number of times you feel your heart beat over a 15 second time interval. Then multiply that number by four to obtain a value for your heart rate in beats per minute (bpm).
3. Perform jumping jacks for 30 seconds then repeat step 2. Take a 3-minute break to allow your heart rate to return to resting. Then walk around the classroom for 30 seconds and repeat step 2 again. Which activity raises your heart rate more? Which requires more energy?
Number of heartbeats counted in 15 seconds: ______
Resting heart rate in beats per minute: ______bpm
Number of heartbeats in 15 seconds after performing jumping jacks: ______
That number multiplied by 4: ______bpm
Humber of heartbeats in 15 seconds after walking: ______
That number multiplied by 4: ______bpm
Table 1: Calories burned by a 125 pound person over 30 minutes of various activities.
Activity / Calories BurnedSleeping / 19
Watching TV / 23
Lifting Weights / 90
Yoga / 120
Walking / 120
Hiking / 180
Jumping Rope / 300
Activity 3: Calorie Calculation:
An 8 oz. serving of chocolate milk contains 12 grams of fat, 25 grams of carbohydrates and 2 grams of protein. How many Calories does it contain? Use the chart below to help you with your math.
To calculate Calories from fat:
12 grams of fat X9 Calories per gram=______Calories
To calculate Calories from carbohydrates:
25 grams of carbs X4 Calories per gram=______Calories
To calculate Calories from protein:
2 grams of protein X 4 Calories per gram=______Calories
To get the final answer, add your answers to the three previous parts of the problem.
There are ______Calories in one serving of chocolate milk. Based on the numbers in Table 1, which activity, or combined activities, would you need to participate in to burn the Calories consumed in the chocolate milk?
1