Introduction: (Initial Observation)
For thousands of years people have known that vinegar, lemon juice and many other foods taste sour. However, it was not until a few hundred years ago that it was discovered why these things taste sour – because they are all acids. The term acid, in fact, comes from the Latin term acere, which means sour. For some people acids and bases are known with their violent reactions and varieties of hazards for human and the environment. In this project we will study acids and bases around the house.
Information Gathering:
Find out about acids and bases. Read books, magazines or ask professionals who might know in order to learn about acids and bases, their applications, their risks and hazards. Keep track of where you got your information from.
If you like Internet sources, following are some links:
Water molecules (H2O or HOH) can brake down to smaller pieces of H+ and (OH)-. In water or water solutions, H+ is the acidic factor and OH- is the basic factor. Since the number of H+ and OH- in pure water are the same they neutralize each other and pure water is neither an acid nor a base. We call it neutral. When other substances dissolve in water, they may also brake down to smaller pieces or ions. If one of such ions is H+, then the concentration of H+ in water will increase and water will become acidic. If one of such ions is OH-, then the concentration of OH- in the solution increases and the solution becomes basic.
In other words acids are substances with lots of H+ (or Hydrogen ions).
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. This is a sample:
The aim of this project is to identify different acids and bases around us.
I will test vinegar, lemon juice, water, soap, liquid detergent, baking soda, ammonia, a soft drink (sprite) and a Liquid plumber or any other material use to open clogged drain.
You may also attempt to perform some chemical reactions between acids and bases that you can find in order to make their salts.
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. This is a sample:
You will test different material that you can find at home for their acidity or alkalinity properties. So:
Independent variable (also known as manipulated variable) is the type of substance I test. Possible values are: vinegar, lemon juice, water, soap, liquid detergent, baking soda, ammonia, sprite, and Liquid plumber.
Dependent variable (also known as responding variable) is the acidity of the substance. Possible values are: Acid, Neutral, Base.
By using these terms we are saying that various materials may have various pH.
Hypothesis:
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.
This is a sample hypothesis: (updated)
Among the materials I will test (Lemon Juice, Vinegar, and liquid detergent), vinegar and lemon juice are acidic but liquid detergent is basic. My hypothesis is based on my gathered information about the sour taste of acids and bitter taste of bases.
Experiment Design:
In this project we will design an experiment that helps us to identify acids and bases. We will then test different material that can be found at home to see if we can find any acid or base at home. Finally we will perform chemical reactions involving acids and bases.
Experiment 1:
In order to identify acids and bases, you can use pH indicator paper. To test the pH of liquids simply insert the pH paper in to a small sample of the liquid, remove it and read the result while it is still moist. To test solids, first dissolve them in water and then insert the pH paper in that solution. Each pH paper will come with it’s own color chart that helps you to read the pH associated with a certain color combination. This is a sample color chart for pH indicator strips.
Some of the material that you can test are:
- Water
- Milk
- Lemon juice (Citric acid)
- Vinegar (Acetic acid)
- Yogurt
- Wood ash
- Battery Acid (Sulfuric acid)
- Muriatic acid (Hydrochloric acid)
- Vitamin C (Ascorbic Acid)
- Aspirin (acetylsalicylic acid)
- Soaps and other detergents (not an acid or base, but very basic pH)
- Liquid plumber or any other material use to open clogged drains.
- Baking soda (Sodium bicarbonate)
- Ammonia (strong base)
Record the results of your tests in a table in the order of their pH. Lower pH indicates acids and higher pH indicates Bases.
Sulfuric Acid is a strong acid. It can burn your skin without any fire. It can also make holes on your shirt (not immediately, you will discover them later). Perform your experiments near running water so you can wash your hands or face immediately in case of a spill.
Drain openers are usually caustic soda (Sodium Hydroxide) or Potash (Potassium Hydroxide). These are strong bases and are extremely dangerous for your eyes. When I use them I wear goggles, close my eyes and turn my face away from them.
Both acids and bases can hurt your skin. Symptoms usually appear in a day and will last about a month. To avoid any trouble, wear rubber gloves.
Experiment 2:
React any of the acids with any base from your list to make a salt. Each salt will have it’s own chemical properties and industrial applications. For example ammonium chloride is used in batteries, soldering flux, electroplating.
| If your acid is | and your base is | Your salt will be |
| Acetic acid (Vinegar) | Ammonia | Ammonium acetate |
| Acetic Acid | Sodium Hydroxide | Sodium Acetate |
| Citric Acid (Lemon Juice) | Sodium Hydroxide | Sodium Citrate |
| Hydrochloric acid | Ammonia | Ammonium chloride |
| Hydrochloric acid | Sodium Hydroxide | Sodium Chloride (table salt) |
You can experiment many other combinations as well:
Procedure:
- Start adding the base to the acid (or acid to the base) gradually and stir your compound. Check the pH frequently. Continue until the pH of your compound is about 7. Leave your mixture in a flat and wide plastic tray or container until it dries. Collect and save the crystals. (When a liquid is spread in a wider surface, it will evaporate and dry faster.)
- What you will have at home are usually diluted version of acids or bases. For example vinegar has only about 5% acetic acid. If you were going to use pure chemicals, you most likely had to add some water too. For example pure citric acid (available as a food additive) is solid crystals. Also sodium hydroxide is white solid flakes or granules. You can not simply react two solids. In such cases you will first make a saturated solution of each substance and then start the chemical reaction.
Materials and Equipment:
List of material can be extracted from the experiment section.
Results of Experiment (Observation):
For the experiment 1, test all all the material that you have access to and write the results in a table ordered by pH from lowest to highest.
Calculations:
If you do any calculations, also write them in your report.
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.
Conclusion:
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.
References:
List of References
