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Educational Resources – Science Experiments
For most of the science experiments below, you will need a pH indicator, such as wide-range litmus or pH paper, a garden soil pH testing kit, or a pH indicator that you can make yourself in Experiment 3. These pH indicators contain a chemical that changes color when it comes in contact with acids or bases. For example, litmus and pH paper turn red in strong acids and blue in strong bases. Because only a few pH indicators measure pH over a wide range of pH values, you will need to find out the pH range of the indicator you use. Typically, the color chart provided with each pH indicator kit will show the pH range of that indicator. Color pH indicators provide only an approximate measure of the pH, or the strength of the acid or base. They are not as accurate as the expensive instruments scientists use to measure pH, but they are adequate for the experiments below.
It is recommended that teachers and student review the section on preparation below before beginning any of the science experiment. In addition, all experiments should be conducted under the supervision of an adult.
Preparation
- General Tips
- How to Measure with pH Paper
- How to Measure Liquids with a Garden Soil pH Test Kit
- Safety in the Laboratory
- How to Record Observations
Experiments
- Experiment 1—Measuring pH
- Experiment 2—Determining pH of Common Substances
- Experiment 3—Making a Natural pH Indicator
- Experiment 4—Measuring the pH of Natural Water
- Experiment 5—Measuring Soil pH
- Experiment 6—Soil Buffering
- Experiment 7—Observing the Influence of Acid Rain on Plant Growth
- Experiment 8—Observing Buffers in Lakes, Ponds, and Streams
- Experiment 9—Looking at Acid Effects on Metals
General Tips
- Except for wide-range pH test paper, all the materials called for in these experiments, including distilled water and borax, can be obtained at grocery stores or from local lawn and garden stores or nurseries.
- Wide-range pH test paper is inexpensive, but not easily obtained. A school science laboratory will probably have it or can order it, or you may order it through a biological supply company. Litmus pH paper is usually included in chemical sets sold at toy stores for children over 8 years old.
- For the names of supply companies, you can consult the yellow pages of your telephone directory under a heading such as “Laboratory Equipment and Supplies.” If your local directory does not have such a heading, ask your teacher for suggestions or try the yellow pages from a larger city. Telephone directories are available at many libraries.
- Inexpensive garden soil pH testing kits are available at most lawn and garden stores or nurseries. These testing kits usually contain a pH indicator solution that covers a range of at least pH 4 to 10, which is wide enough for most of the following experiments.
- You may substitute baking soda for household ammonia in the experiments. If you do, be sure to stir well because baking soda does not dissolve easily in water unless heated. The pH of undissolved baking soda will not be the same as dissolved baking soda.
- You may substitute fresh-squeezed lemon juice for white vinegar. Lemon juice is slightly more acidic than the vinegar sold in grocery stores. White vinegar is preferred over cider vinegar or lemon juice because it is colorless and relatively free of impurities.
- Use clean, dry containers and utensils.
How to Measure With pH Paper
When measuring pH with pH paper, dip the end of a strip of pH paper into each mixture you want to test. After about two seconds, remove the paper, and immediately compare the color at the wet end of the paper with the color chart provided with that pH indicator. Write down the pH value and color. Always use a clean, unused strip of pH paper for each mixture that you test.
How to Measure Liquids with a Garden Soil pH Test Kit
Soil pH test kits are designed to measure the pH of soil, but they may also be used to measure the pH of liquids, such as water and water mixtures. Most of these kits contain a test solution (liquid pH indicator), color chart, and clear plastic test container, such as a test tube.
To measure pH, pour 1/4 teaspoon of the mixture you want to test into the test container, and add 1/4 teaspoon of the test solution provided in the kit. Cover the container and shake once or twice to mix, or stir if necessary. Compare with the color chart provided with the kit and write down the result.
Safety in the Laboratory
A science or chemistry laboratory can and should be a safe place to perform experiments. Accidents can be prevented if you think about what you are doing at all times, use good judgment, observe safety rules, and follow directions. Each experiment will include comments to alert you to probable hazards, including how to protect yourself and others against injury.
- Eye protection (goggles or safety glasses) must be worn when working on experiments. Make a habit of putting them on before the experiment begins and keeping them on until all clean-up is finished.
- Do not eat, drink, or smoke while in the laboratory.
- Do not taste any chemical.
- Long-sleeved shirts and leather-topped shoes must be worn at all times.
- Long hair must be tied back, so it will not fall into chemicals or flames.
- Do not work alone; work with an adult.
- Never perform any unauthorized experiment.
- All glassware must be washed and cleaned. Wipe all counter surfaces and hands with soap and water.
- All experiments that produce or use chemicals that release poisonous, harmful, or objectionable fumes or vapors must be done in a well-ventilated area.
- Never point the open end of a test tube at yourself or another person.
- If you want to smell a substance, do not hold it directly to your nose. Instead, hold the container a few centimeters away and use your hand to fan vapors toward you.
- When diluting acids, always add the acid to the water; never water to acid. Add the acid slowly.
- Flush with large quantities of water when disposing of liquid chemicals or solutions in the sink.
- If you spill any acid or base material on you, wash the exposed area with large amounts of cold water. If skin becomes irritated, see a physician.
How to Record Observations
Writing your observations on these experiments will help you to keep better track of the progress of the experiment. Written data are not forgotten. Record keeping can be very simple and still be helpful. These hints can help you organize and record your thoughts.
- Use a bound notebook so that pages are not lost.
- Write complete sentences for all written entries.
- Use drawings as needed.
- Date each entry (even drawings).
- Use the title of the experiment as your first entry.
- When your observation entries have been completed, write your answers to the questions that follow each experiment.
- Write your own thoughts about the experiment as the conclusion.
