1059 Main Avenue, Clifton, NJ 07011

The most valuable resources for teachers and students

(973) 777 - 3113


1059 Main Avenue

Clifton, NJ 07011

07:30 - 19:00

Monday to Friday

123 456 789


Goldsmith Hall

New York, NY 90210

07:30 - 19:00

Monday to Friday

Compare the PH levels in mouths of various animals and humans at different times in the day

Compare the PH levels in mouths of various animals and humans at different times in the day

Introduction: (Initial Observation)

Every time that I see a decayed tooth, I am wondering why teeth decay. I know that acids are corrosive and can dissolve metals and carbonates. I have also seen what a simple weak acid such as vinegar can do to egg and bone. But why should we have acid in our mouth. What is the cause of acid? Is it the food that acidifies in our mouth or it is the acid from our stomach that comes up to our mouth? Is presence of acid in our mouth an indication of certain conditions or activities in our body? Do we have more acids in our mouth when we are hungry or after a meal? Can the pH of our mouth be an indication of our health condition?

Testing and comparing the pH of our mouth at different times of the day is a good project that can help me to determine if there is a relation between the mouth pH and our eating hours.


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

Following is a sample project plan.

Project plan/outline:

Following is what I am planning to do for my project.

  1. Visit a local library and find books related to food, mouth, dental health and biology. In these books, I will look for any topic related to pH. I am trying to identify any known condition that may affect the pH of food, mouth and stomach.
  2. Gather information about methods and instruments of measuring pH and the cost of each method.
  3. Find out if I can safely measure the pH of mouth in animals. I will ask adults and a veterinarian.
  4. Decide who are going to be tested and at what times.
  5. Perform the tests (experiments) and recording the results in a data table.
  6. Compile the data and drawing a conclusion.

Information Gathering:

Find out about acids and pH. Read books, magazines or ask professionals who might know in order to learn about mouth pH. Keep track of where you got your information from. Following are some information available online at http://stopcancer.com/phtest2.htm .

Testing the saliva pH 2 hours after a meal reflects

the cellular pH, and the state of health a person is in.

The pH of a healthy person will be around 7.43.

The pH of a healthy person will be around 7.43. 


HEALTH TESTpH paper, range 4.5 to 7.5

pH 4.5








Follow These Three Simple Steps:

  1. Wait for two hours after having anything in your mouth (the purpose is to test the saliva produced by the body, about 7 quarts each day, and not just the saliva and food in your mouth.)
  2. Swallow the saliva in your mouth, and then suck new saliva from below your tongue (there are two saliva glands below the tongue). Repeat 2 more times.
  3. Apply saliva to a piece of the pH paper provided, wait 20 seconds, and compare the resulting color to the pH color chart above.


Check Your Results:

  1. If your pH is 7.5, your body fluids are in the healthy range, meaning that, for the moment at least, you are not mineral deficient.
  2. If your pH is between 6.0 and 6.5, you are becoming acidic and therefore developing one or more of the 150 degenerative diseases.
  3. If your pH is below 6.0, then you are highly acidic, very mineral deficient, and have contracted at least one degenerative disease.Now That You Know the State of Your Health…
    Find Out How To “Bulletproof” Your Body From Disease.


These test strips allow you to determine the pH of the mouth in a simple and quick test. Why test pH? The pH of our bodies is an important factor in our overall health. All living creatures survive in a particular pH environment. When this environment is not correct, their growth and survival is threatened. The formation of plaque on the teeth can be associated in some cases with the pH of the mouth. The pH Test Strips can help to identify patients who are susceptible to caries due to plaque buildup caused by improper pH.


Do you know why sugar rots your teeth? The truth is that it is not actually the sugar that rots your teeth. It is the plaque and sugar combination that does the dirty deed. Plaque is a collection of bacteria that adheres to your teeth and gets its energy by breaking down the sugars you eat. During sugar breakdown, many products are formed, one of which is lactic acid which decreases the pH in your mouth. In an acidic environment, the hard enamel that protects your teeth dissolves, which leaves your teeth vulnerable to decay and cavities. The saliva (average pH 6.8) in your mouth counteracts this decrease in pH by using buffers such as bicarbonate ion (HCO) and the COOH and NH groups of proteins. However, the time it takes for the saliva to neutralize the acid depends on the amount of sugar that has been ingested. Therefore, the more sugar that is available, the more the bacteria multiply, the lower the pH in your mouth becomes, and the longer your teeth are susceptible to decay. Since the pH of the mouth is so important for the health of our teeth and also is an indication of what’s going on in our mouth. That is why in this project we will investigate the pH of the mouth in animals and humans at different times of the day.

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 problem is that excessive acid contents in human and animal mouth can cause damages to our teeth. Knowing about the pH of our mouth at different hours can help us to know the cause of the acid and do whatever is necessary to keep the pH of our mouth neutral.

The purpose of this project is to compare the pH levels in mouth of various animals and human in different times of the day. Since pH of the mouth is important and can be a factor in our health condition, we hope that we can find a pattern for the pH of the mouth and use the results of our experiment to achieve a higher level of health.

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.

Many different variables may affect the pH of the mouth. Some of these variables are:

  1. The type of the last food
  2. Time passed from the last food
  3. Bacteria in the mouth

In order to find any relation between the pH of the mouth and factors that may affect it, you may simply record the pH of the mouth in different hours of the day. For this experiment, this is how you may define variables:

Independent variable (manipulated variable) is the time of the day.

Dependent variable (responding variable) is the pH of the mouth.

Controlled variable is the time of eating (feeding) and the type of food, mouth washing and brushing.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

My hypothesis is that the pH of the mouth will be high in hours that we are hungry. That is the time that we also have bad breath. This can also be true for animals.

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.”

In order to test the pH of the mouth we can use pH indicator paper. Since the highest pH (basic) in mouth is 7.5 and the lowest pH (acidic) is 4.5, we need to get a pH indicator that measures this range. If we use the pH indicators that are designed for a widest range of pH such as 1 to 14, their color change in the mouth pH will not be noticeable enough to get an accurate result. In other words the produced colors will be very close to each other.

We can also use inexpensive pH meters such as soil pH meters, but we should be very careful to avoid cross contamination. In other words after each test we need to rinse the pH meter probes in alcohol or similar anti-bacterial cleaner.

Who are your guinea pigs?

You can test the pH on yourself and your pet (if you have one). It is good if do the test in a weekend so you can continue it all day long, from the moment that you wake up until the time that you go to the bead.

I suggest you to repeat the test in two or three different days. so you can compare the results.

Your first test can be at 7 a.m. and your lat test can be 10 p.m. before you go to the bead. Color the box for the tests that are done after breakfast, lunch or dinner. In this way you will be able to compare the pH of your mouth before and after each food. Try not to eat in between.

Write the results for human in a table like this

7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10

Write the results for animal in a table like this:

7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10

Calculate the average pH for each hour and enter them in the results tables.

After your results are all in the table, try to use them and make a graph.

For best results you may repeat this experiment on a few different people. Specially if you know someone who has indications of teeth and mouth bacteria or someone who has digestion problem. If you are testing any one but yourself and your pet, wear latex gloves (available at pharmacies) an try to avoid touching the wet pH paper. Also dispose your used pH papers immediately.

Draw a Graph:

Draw a line graph to show how does the average pH of human mouth changes in different hours of the day. Use the X axis for hours of the day and use the Y axis for pH. You may make to separate line graphs or you may combine two graphs on one.

Some helpful hints:

1. Only touch one end of the paper and dip the other end into the sample of urine or saliva. Avoid touching the paper to anything else to avoid contamination. Do not touch the pH paper to your tongue or mouth. Some individuals may have an allergic reaction to the chemicals in the paper.

2. Compare the wet paper to the pH color guide immediately after dipping into the sample. This should take 3-5 seconds.

3. Saliva testing – Use a clean spoon to test your saliva. Don’t just spit out any fluid in your mouth. Don’t try to get a sample by clearing your throat and mouth. Instead, close your mouth and briefly and gently suck on your tongue for 1-2 second to produce a watery fluid. Gently spit your saliva into the spoon and dip the clean, untouched pH strip into it. After dipping, immediately compare the color of the paper to the color guide and note your pH.

Materials and Equipment:

Material that you need is only a pH indicator paper. pH paper comes in packs of about 100 strips for 100 tests. Purchase a roll of pH paper calibrated from 4.5 to 8.0 or 5 to 7.5.

Note the color guide on the front of the plastic dispenser. You will use this to determine your pH each time you test.

You can cut them in half or other smaller pieces in order to use them for more experiments.

Results of Experiment (Observation):

  1. Do you see any pattern in the your experiment results?
  2. In what hours the pH of your mouth is the highest?
  3. In what hours the pH of your mouth is the lowest?
  4. Do you see any relation between the pH and your food time?
  5. Do you see any difference in mouth pH between human and animals?

Think about more similar questions and try to find the answer in your test results table or graph.


Calculate the average pH for each hour and enter them in the results tables.

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 find some books about food, mouth, dental health, biology. Look for any topic related to pH.

List the books that you find as your references. You can also name internet based references such as: