Pictures and videos

 

 Figure 1 - Anatomy of Chicken Wing Bone

(the ulna is used in this experiment)

 

Figure 2 - Tray of Labelled Bones 

 Figure 3 - Bottles with Submerged Bones

Ulna in 7-Up.  A visible hole is formed along the bone, with marrow oozing out.

              Another view of the same ulna.  Note several visible holes at the end of the bone.

Ulna in 100Plus.  Some tiny holes at the end of the bone. 

Ulna in Coke Classic. Bone turned dark brown.  Note the bubble at the end of the bone, meaning that a sizeable hole formed there.

Ulna in F&N Chrysanthemum.  No noticeable change except for colour.

 Ulna in Tap Water as a control. No visible change to the bone.  There are no holes noticeable on the ends of the bones.

F&N Chrysanthemum Tea showed effervescence when the cap was opened after 3 days.

Figure 2 - A Tray of Bones

Videos of the bone leaking marrow through a hole.

This is the bone in 7-Up which is the clearest of the acidic drinks.

SIP Report

Title
An Experimental study into the effects of acids in Soft Drinks on our bone mass.

Abstract
The aim of this experiment is to find out if drinking acidic soft drinks will indeed affect our bone,
and if the acidity level of the drink will affect the bones differently.

 Using the ulnas of chicken bones as a substitute, the bones are weighed before and after submerging in drinks of varying pH levels for 72 hours.  Water which is pH neutral is used as the control.

The acidity of the remaining drinks is also tested for changes in pH.

Hypothesis
The lower the pH of the drink, the greater it will affect our bones.

Materials
1. The ulnas of 5 mid-sized chicken wings with soft connective tissues removed at both ends (see Figure 1 - Anatomy of Chicken Wing Bones)

2. A bottle of 500ml of Coke

3. A bottle of 500ml of 100plus

4. A bottle of 500ml of 7UP

5. A bottle of 500ml of F&N Chrysanthemum Drink

6. A bottle 500ml of Tap Water, used as control

7. 5 beakers, to hold the drinks for testing of pH
8. Paper Towels, used to dry bones 
9. Permanent Marker
10. Aluminium foil
11. Baking tray

Apparatus

1. Chyo MP-3000 Electronic Balance Scale (weighs up to 1/100th of a gram) 

3. Universal Indicator
4. Fan-forced convection oven

Methods
A. Preparation

1. Cook the chicken wings thoroughly so that it will be easier to remove the bones. 

2. Remove the bones from the chicken wings.

3. Slice off the ligaments and tendon so that only the bones remain.

4. Use the paper towels to dry the bones throughly.  Place a sheet of aluminium foil on the baking tray and label with a permanent marker the various drinks.
5. Place each ulna above a label on the tray and place in the oven.  Turn it to 40 degree Celsius and set the convection mode to blow dry the bones for 2 hours to remove water content in the bones.   (see Figure 2 Tray of Labelled Bones).
6. Weigh each of the bones on a fine weighing scale. Record down the mass of each bone.

B. Submersion

1. Open a bottle of drink and pour out some into a beaker.  Measure its pH using the universal Indicator.  Record the pH.
2. Return the drink into the bottle and drop a bone into it. 

2. Screw the cap back on tightly.
3. Label the bottle with the mass of the bone with the permanent marker.

3. Repeat steps 1 and 2 with the rest of the drinks and bones. Each bottle should contain only one bone.
4. Leave the bottles untouched for 72 hours (See Figure 3 - Bottles with Submerged Bones)

C. Post-Submersion

1. Pour the drinks out into a beaker one at a time, and carefully remove the bones. 

2. Dry the bones of excess liquid with the paper towels.
3. Place each ulna on its label on the tray (See Figure 2) and place the tray in the oven. Turn it to 40 degree Celsius and set the convection mode to blow dry the bones for 2 hours to remove water content in the bones.
4. Measure the pH of each of the drinks.  Record.
5. Discard the drinks.

6. Measure the mass of the bones after 2 hours using the same fine weighing scale.  Record.

5. Pour a sufficient amount of the drink into a beaker.  Test the pH with the universal indicator.  Record.

Data

Graphical Representation
A.  Mass of Bone before and after the submersion in the drinks, and the percentage change:

B. Change in pH of the drinks before and after the submersion of the bone:

 

Data Analysis

1.  The mass of the bones increased slightly for the ones submerged in alkaline drinks (Tap Water and F&N Chrysanthemum).  This could be due to greater moisture in the bones after the 72 hour submersion.  However, the mass of the bones decreased for the bones that were submerged in acidic drinks (100Plus, 7-Up and Coke Classic).

The decrease in mass of the bones in the acidic drinks is likely caused by the breaking down of calcium compounds (mainly calcium phospate, also known as hydroxyapatite, or HA) in the bones by citric acid (100Plus, 7-Up) or phosphoric acid (Coke) in the drinks. However, it cannot be determined that the decrease is solely due on the decomposition of calcium compound as there are other compounds present in both the bones and the drinks. (Point 1, Bibliography).

2.   It appears that the higher the acidity of the drink, the greater the decrease in mass of the bones after the experiment.  However this is not true of Coke Classic.  One possible reason is that the acidic substance in Coke Classic is phosphoric acid while in 100Plus and 7-Up, it is citric acid.

The use of more acidic drinks and with only one type of acid in this experiment would help me determine if the decrease in bone mass is directly related to the acidity of the drinks.

3.  100Plus, 7-Up and Coke Classic became more alkaline at the end of the experiment, whereas Tap Water and F&N Chrysanthemum became slightly more acidic. This is because the acids in the drinks reacted with the calcium compounds in the bones.   The concentration of OH- ions as compared to H+ ions increased for the acidic drinks thus increasing its alkalinity.

As for Tap Water and F&N Chrysanthemum, I have researched on the possible cause.  It is likely due to the demineralisation of calcium phosphate Ca₁₀ (PO₄)₆(OH)₂ (the main compound in animal bones) in water.  The OH ^–  of water is removed by H+ in water to form HPO ^2-

--> .  This will further be acidified to H2PO4^–. The  calcium in not affected but the remaining drink becomes more acidic. (Point 2, Bibiliograhpy).

4.  The higher the acidity of the drink, the greater the increase in pH of the drinks after the experiment, as there was a greater amount of chemical breakdown of calcium by the acids present in the drink.

Conclusion
My conclusion is that the acid in soft drinks (pH) does affect bones.  There is bone mass loss.  As our bone is mainly made of calcium compounds, there is calcium loss.  Also, it appears that the lower the pH of the drink (ie the more acidity the drink is), the more it affects the bone in terms of bone mass loss.

In the video I have included of the bone in 7-Up at the end of the experiment, a visible hole has formed along the length of the bone with blood in the bone oozing out.  The acids present in the acidic drinks appear to be breaking down the calcium in the bones. 

Calcium is the substance that makes the bones strong. Bones that don't have enough calcium can become hollow and fracture or break easily, a condition known as osteoporosis.

Bibliography
1. University of Cambridge DoItPoMS Teaching and Learning Packages at http://www.doitpoms.ac.uk/tlplib/bones/structure.php
2.   The Effect of Beverages on the Release of Calcium from the Enamel Surface by A.R. Fahilah, Z.H.A. Rahim, Annal Dentistry University Malaya 2008 at http://ejum.fsktm.um.edu.my/article/639.pdf)

Acknowlegments
1. My father Mr Choo Joon Yong for helping me transport the dried bone samples before and after submission to his engineering lab in his office, in order for me to have an accurate measurement of the mass of the bones, up to 1/100th of a gram.
2. My teacher Mr Chris Chong for his guidance and for allowing me access to the school chemistry
lab to use the universal indicator and beakers.