pH Scale - Science 7000 Nutrition Laboratory

Oct 12, 2026

pH Scale content explains how acids and bases are identified using the 0–14 pH range, linking lower values to stronger acids, higher values to stronger bases, and noting neutrality at pH 7. It describes hydrogen ions and hydroxide ions, how the stomach maintains an acidic environment, and how pH indicators such as litmus and natural cabbage-juice indicators reveal color changes. It also outlines an activity for testing liquids, recording indicator color and classification, and introduces electrolytes and nonelectrolytes and their role in body fluid and pH balance.

LanguageEnglish

CategoryPaper Templates

FormatPDF

Pages6

Reading Time2 min

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pH Scale

Acids, Bases, and the 0–14 pH Range

Ions in Water Solutions

Measuring pH with Indicators

Lab Activity: Part A

Electrical Properties: Part B (Electrolytes vs Nonelectrolytes)

Kingsborough Community College City University of New York The Science of Nutrition Laboratory Science 7000 pH Scale Humans come in contact with acids and bases all the time-when cooking, cleaning, and eating. Baking soda is base used in household cleaners. Vinegar is a weak form of acetic acid used in salad dressing. Citrus fruits contain citric acid. Sodas are loaded with carbonic acid which is made when carbon dioxide combines with the water in your body. If you combine vinegar with baking soda a chemical reaction occurs with lots of fizzing and foaming that result from the interaction between the acid (vinegar) and the base (baking soda) . There are also acids in the human body. Hydrochloric acid is in your stomach and is used to digest food. The stomach acid has to be kept away from therest of the body because it is very harsh and can cause serious damage. The lining of the stomach is especially built to survive an acidic environment. The pH scale is used to classify substances as acids and bases. The scale goes from 0 to 14. Things that are acids have a pH number that is less than 7. The lower the number, the stronger the acid. Bases have pH values higher than 7. The higher the number, the stronger the base. An example of a strong base is drain cleaner or oven cleaner. Both strong acids and strong bases can be very harmful to your skin and tissues. Distilled water has a pH of 7, which is neutral. Water is made of 2 hydrogen atoms and 1 oxygen atom. When water breaks apart, it can form hydrogen ions (H+) or hydroxide ions (OH-) . Solutions are classified as acids or bases depending upon what kinds of ions they release. Acid solutions have lots of hydrogen ions present and basic solutions have lots of hydroxide ions present. For example, stomach acid has a pH of 2 or 3, which means that it is very acidic and has lots of hydrogen ions. The pH outside of your stomach is much closer to neutral. Most of the cells in living things cannot live in the presence of a strong acid. That is why it is important that the stomach acid stays in the stomach. The cells in the stomach lining replace themselves continually because it is a rough environment in which to live. One of the easiest ways to measure the pH of a substance is to use a pH indicator. Litmus is a paper coated with an indicator that turn red in an acid and blue in a base. Other pH indicators have a whole range of colors-one for every number on the pH scale. There are also pH indicators that can be found in nature. The juice produced by boiling red cabbage is useful for determining pH. A very acidic solution will turn red cabbage juice red. Neutral solutions appear purple and basic solutions turn a greenish-yellow when cabbage juice is added. Environmental and chemical engineers who focus on water quality, water treatment and water remediation need to measure, monitor and sometimes even adjust the pH of water. For example, in the water treatment process, important chemical reactions are affected by the pH of the water. Through today's activity, we will learn more about the pH of different liquids. Part A Goal This activity is designed for students to identify the pH level of compounds. By testing substances, they will understand how the pH determines why a compound reacts with other substances and for what purpose. Students will understand the property of acid and base; and how to test the pH of a liquid. Students may engage in a water quality field study and testing the pH of water in a local area. Procedure 1. Label a cup with each of the liquids to be tested. 2. Fill cup approximately ½ full with corresponding liquid. 3. Record the test result of each substance. Write name of the liquid next to the number which corresponds to the tested result. 4. Dispose of acids and bases in separate containers or at separate sinks. Table 1. | Substance | Indicator color | pH | Classification | | --- | --- | --- | --- | | 1. | | | | | 2. | | | | |

FAQs

How is the pH scale used to classify acids and bases?

Substances with pH less than 7 are acids and stronger acids have lower pH values. Substances with pH greater than 7 are bases and stronger bases have higher pH values. Distilled water is neutral at pH 7.

What do hydrogen ions and hydroxide ions indicate in a solution?

Acid solutions contain many hydrogen ions (H+), while basic solutions contain many hydroxide ions (OH-). Solutions are classified based on which ions they release.

How can pH be measured using indicators?

Litmus paper changes color in acids and bases, turning red in acids and blue in bases. Other indicators provide a range of colors for different pH numbers, and red cabbage juice changes red for very acidic solutions, purple for neutral, and greenish-yellow for basic solutions.

Oct 12, 2026

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