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Effect of Acids on teeth, bones and eggs

Effect of Acids on teeth, bones and eggs

Introduction: (Initial Observation)

Many foods that we each contain starch. Bread, cookies, potato and corn are just a few high starch foods. Our saliva contains chemicals that converts starch to sugar in just about 10 minutes. As soon as the sugar is ready bacteria start to work and convert sugar to acids.

Our teeth and sometimes jaw bones are exposed to the acid produced by bacteria. The question is “Can acid be harmful to our bones and teeth?”. In this project you will investigate the effect of acid on teeth, bones and eggs. The reason that we include eggs in our research is that egg-shells are very similar to bones and teeth in terms of hardness and chemical structure. Bones, egg-shells and teeth contain calcium carbonate, a chemical that makes them hard.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.  

Project advisor

Information Gathering:

Find out about bones and teeth. Read books, magazines or ask professionals who might know in order to learn about the effect of acids on material. Keep track of where you got your information from.

Information that you gather must include the following facts.

  • Vinegar that is a diluted acetic acid is made from sugar. Vinegar contains 5% acetic acid. Traditional vinegar was being made from grape juice because grape juice has lots of sugar.
  • Part of our teeth that is out of the gum is called crown. This part has a very strong layer that can resist against acids for a few months.
  • Foods containing calcium is needed for our body to provide strength to our bones and teeth. You must also know the foods that contain calcium.
  • Lime stone and sea shells also contain about 95% calcium carbonate.

What is pH?

Tooth Structure:

An individual tooth consists of an exposed crown and a root, buried in the gum and jaw. The crown is usually at least partly covered by an outer layer of an especially hard substance related to bone called enamel. Beneath the enamel (and sometimes exposed to the surface if the enamel is missing or worn away) is an intermediate layer of material called dentine, which is also similar to bone but is not nearly as hard as enamel. It surrounds an inner pulp cavity filled with pulp (a living, vascular and well innervated tissue).

Blood vessels and nerves reach the pulp cavity through a channel, the root canal, that penetrates the root. An additional layer of bony material, cementum, usually surrounds the root.

Bone Chemical Composition:

Bone is a dynamic, living tissue – not the hard, dry, lifeless frame seen in scary movies or desert scenes or even on a pirate flag. About 30% of bone is living tissue, cells, and blood vessels – the tissues that make your bones grow. The blood vessels go in and out of the bone carrying oxygen and nutrients, and taking away wastes. Bones contain marrow which produces red blood cells and white blood cells. Bones have nerves that can feel pressure and pain. Bones even help us hear! About 45% of bone is mineral (primarily calcium and phosphorus), giving bone its hardness and rigidity and storing these minerals for future use. Bone releases some of this mineral when other body parts, such as nerves, may need them. Bone also contains the proteins, collagen and elastin. Finally, about 25% of bone is made up of water. Source…

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this experiment is to see the effect of acetic acids (vinegar) on bones, teeth and other material containing Calcium Carbonate.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
The independent variable (also known as manipulated variable) is the time of reaction. This is the amount of time you place bone, tooth, egg, sea shell, etc. in an acid such as vinegar.

The dependent variable (also known as responding variable) is the loss of mass (weight loss).

Constants are the type and concentration of vinegar.

Controlled variables are the environmental factors that may affect your experiment results (temperature, light, wind). Do all the experiment trials at the same time and in the same place.

Other possible independent variables are: Change in the hardness or flexibility of the bone or The amount of carbon dioxide gas produced by the reaction.


Based on your gathered information, make an educated guess about the effect of acid on bone, egg shell, tooth and sea shell. Write one statement to describe what affects do you think acid will have on each test item. Identifying variables is necessary before you can make a hypothesis. Following are some examples.
About the effect of vinegar on bone, I think vinegar can partially dissolve bones and make it soft and flexible. My hypothesis is based on my gathered information about bones and the fact that bone contains live cells and blood vessels.

For the effect of vinegar on egg, I think …

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

In this experiment you test the effect of vinegar on egg. Vinegar is contains 5% acetic acid and 95% water.


  • 1 egg (hard boiled is less messy if you accidentally break it, but you can use a raw one)
  • 1 cup vinegar
  • clear jar or glass

The egg experiment is simple. Just put an ordinary, uncooked egg into a bowl of vinegar for a couple of days.

The shell will start fizzing as the calcium carbonate that is in the shell is dissolved away by the acid in the vinegar. After a couple of days, you can gently wipe away any left over bits of shell, leaving a squishy, see-through egg!



  • Pour 1 cup of vinegar into jar
  • Add the egg
  • Record what you see (bubbles rising from the egg)
  • Leave the egg in the vinegar for one day.
  • Remove the egg and feel it.
  • Record your observations (the egg shell will be soft)

Eggs contain something called “calcium carbonate”. This is what makes them hard.

Vinegar is an acid known as acetic acid.

When calcium carbonate (the egg shell) and acetic acid (the vinegar) combine, a chemical reaction takes place and carbon dioxide (a gas) is released. This is what the bubbles are made of.

The chemical reaction keeps happening until all of the calcium carbonate in the egg shell is used up — it takes about a day.

When you take the egg out of the vinegar it’s soft because all of the calcium carbonate is transformed to other material by the action of the acid.


Leave the same egg sitting out on the table for another day.

Now feel it again.

It’s hard!

The calcium left in the egg shell get some carbon dioxide from the air and make a new layer of calcium carbonate.

Experiment Extension: (For more advanced students)

Introduction: Previous procedure showed that vinegar is reacting with eggshell and as a result of this reaction, eggshell is dissolved and a gas is being released. Now you need to know the rate of reaction and present it in the form of a table and a graph. You may also try this experiment with seashell or cooked chicken bone.


  1. Break six eggs and save the eggshell pieces (separately) for your experiment.
  2. Use a paper towel to clean and dry each eggshell or its pieces.
  3. Number the eggshells from 1 to 6, make sure you do not mix the pieces of one eggshells with each other.
  4. Weight each eggshell and record the initial weights.
  5. Prepare five different cups half filled with vinegar. Number the cups from 1 to five.
  6. Prepare a cup half filled with water. Number this cup as 6. This will be the control.
  7. Drop broken pieces of each eggshell in one cup. For example eggshell number 1 will be in cup number 1, eggshell number 2 will be in cup number 2,…
  8. After one hour, remove the eggshell in cup number 1, let it dry and weight it.
  9. After another hour remove the eggshell in cup number 2, let it dry and weight it.
  10. Continue this process and every one hour remove a new eggshell. At the end also remove the eggshell from cup number 6 that has no vinegar.

Record your results in a table like this:

Eggshell Number Initial Dry weight Hours in vinegar Remaining weight Percent of weight lost
1 0.33
2 0.45
3 0.55
4 0.70
6 (Control) None

* Percents of weight loss in this table are not real. They are unreal samples that later we will use them to show a sample graph.

The last column (percent of weight loss) must be calculated. To calculate the rate of weight loss, first subtract the weight of each eggshell from its initial weight to determine the weight loss. Then divide the weight loss by the initial weight to get the rate of weight loss.

This is a sample graph using the four unreal values displayed in the results table.

Your real results table will have five bars (one bar for each egg).


Question: All my eggshells dissolved in the first 30 minutes, what should I do?

Answer: Repeat your experiment, but this time reduce the exposure time or dilute your vinegar to slow down the reaction.

Experiment 2:

What makes our bones hard? is it calcium carbonate? — the same thing that made the egg shells hard.

This experiment simulates an acid attack on bones (bones are rich with calcium, just like your teeth).


2 clean chicken bones (ask your parents to save them for you the next time you have chicken for dinner)

1 container

1 bottle of white vinegar (5% acetic acid)


  1. Ask an adult to cut as much meat off the chicken leg bone as possible.
  2. Examine the flexibility of the bone by trying to bend it with your fingers.
  3. Place the cleaned bone in the jar.
  4. Cover the bone with vinegar.
  5. Secure the lid on the jar.
  6. After 24 hours, remove the bone from the jar and examine the flexibility.
  7. Replace the bone in the vinegar.
  8. Examine the bone for flexibility each day for 7 days.


  1. Check out the bones after they’ve soaked in the vinegar overnight. Are they softer or harder?
  2. How does the flexibility of the bone changes every day?
  3. Did your bone sample feel rubbery at the end of the test period?
  4. Be sure to throw the bones away in the garbage after you’re finished.


Need a data table?

I don’t recommend this experiment if need to have measurable results and a data table for your project; however, if you have to select this experiment and must have a data table, following are what you need to know:

  1. You must plan to repeat your experiment a few times. All with the same acidic solution (vinegar) or with different solutions (vinegar, lemon juice, soda, …)
  2. You must use identical and same size bones for your experiment trials.
  3. You must devise a method to measure the changes in the hardness or softness of the bone after remaining in the solution for a fixed amount of time.

How to measure?

You may measure the amount a bone bends as a result of a certain force. Such tests needs a device that you may make at home. For example you may place each bone between two tables (like a bridge) and then hang a 2 lbs weight in the middle of the bone and measure how much it bends. That will make your data. Your data table may look like this:

Bones could bend by a 2 Lbs weight after being in the solution for 24 hours

Sample 1 Sample 2 Sample 3 Average
Vinegar  7mm 8mm 6mm
Lemon Juice
Soft Drink
Water (Control)

12 identical bone samples are used. 3 bones for each solution.

The values in this table are the bending amounts of bones in millimeters or inches. For example 8mm means that the center of the bone was pulled down 8 millimeters by the weight.

Experiment 3: The Power of Fluoride

We are told that fluoride protects our teeth. We want to test the effect of fluoride to see how does it work. This experiment simulates the protection power of Fluoride for your teeth.


1 bottle of Fluoride rinse solution (available from your dentist, local dental supply company and some pharmacies)

2 eggs

1 bottle of white vinegar

3 containers


Pour four inches of Fluoride rinse solution into one of the containers and then place an egg in the solution. Let it sit for five minutes. Remove the egg. Pour four inches of vinegar into each of the remaining two containers. Put the egg that has been treated with the Fluoride into one container of vinegar and the untreated egg in the other container of vinegar.

What will happen?

One egg will start to bubble as the vinegar (an acid) starts to attack the minerals in the egg shell. Which egg do you think will start to bubble?

Experiment 4:

Since teeth are stronger than bone and egg shells, we expect a slower acid reaction. In this experiment we will test the effect of vinegar on real teeth.


  • 1 container
  • 1 bottle of white vinegar
  • a few teeth from human, or animals.
  • High precision scale



  1. Weight the teeth and record the total weight of the teeth while they are fully clean and dry.
  2. Place the teeth in a container.
  3. Add white vinegar to the container enough to submerge the teeth.
  4. Make daily observations and record your observations for seven days.
  5. After 7 days remove the teeth, wash and dry them.
  6. Weight the final weight of the teeth.


  1. Did you see any bubbles coming from the teeth?
  2. Did the color of vinegar change?
  3. Did the teeth have a weight loss?
  4. Did you observe any physical change on the teeth? (Physical changes are change in color, size, shape)

Have fun with bones:

Take some thin chicken bones and drop them in vinegar for a day. Take them out and they’ll be soft just like the egg shells were.

Now you can tie them in a knot, just like a piece of string.

Leave them sitting out on the table and they’ll get hard again!

Take them to school for sharing time and see if your classmates can figure out how you did it.

Materials and Equipment:

List of material can be extracted from the experiment section. Additional safety equipment such as goggles and rubber gloves are recommended.

Were can I get teeth?

It is easier to use shells for this projects. Shells are sold in Dollar stores and craft stores. If you really want to get teeth, get animal teeth from a local butcher. In some places you can even buy a complete lamb head.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


No calculation is required for this investigation, however for the experiment 4 you may want to calculate the percent of weight loss of teeth.

To do that subtract the weight of teeth after experiment from the initial weight to calculate the amount of weight loss. You can then divide this number by the initial weight of teeth to calculate the rate of weight loss.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


Visit your local library and review the material about teeth and bone.

Parts of a tooth

Tooth structure