pH Level Analysis of Household Substances: Lab Report

Abstract

This experiment aimed to determine the pH levels of common household substances, categorizing them into acids, bases, or neutral solutions. The substances were selected from various product categories, including cleaning, personal care, and food items. Through the use of red litmus, blue litmus, and pH indicator paper, the pH values of these substances were identified. The results provided insights into the acidic or basic nature of everyday household products.

Introduction and Background

The pH scale is a valuable tool for characterizing the acidity or basicity of liquid solutions.

It ranges from 0 to 14, with lower values indicating acidity, higher values indicating basicity, and 7 representing neutrality. Household products can fall into different pH categories, making it important to understand their pH levels for safety and usability.

The concept of pH was introduced by Danish chemist Søren Sørensen in 1909 as a measure of hydrogen ion concentration in a solution. Acids are substances that release hydrogen ions (H+) when dissolved in water, resulting in a low pH.

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Bases, on the other hand, release hydroxide ions (OH-) when dissolved, leading to a high pH. Neutral solutions have an equal concentration of H+ and OH- ions, resulting in a pH of 7.

Common household acids include citrus juices, vinegar, and some cleaning products. Strong acids can be corrosive and harmful to skin, while weak acids are less hazardous. Bases, such as soaps and detergents, are used for cleaning and are typically slippery. Understanding the pH of household products is crucial for safety and effective use.

The pH scale is used to determine the acidity or basicity level of liquid solutions. Solutions with a pH level of 1-6 are acidic, with 1 being the most acidic and 6 being the least acidic. A pH level of 7 indicates a neutral solution, meaning it is neither acidic nor basic. Solutions with a pH level of 8-14 are basic, with 8 being the least basic and 14 being the most basic. Many common household items can fall into these categories as well, ranging from acidic to basic, or even neutral.

Hypothesis:

Food items are likely to be weak acids because they are not slippery, can be consumed, and often have a sour taste. Cleaning products are expected to be strong bases because they exhibit a fundamental property of bases – slipperiness. Personal care products are anticipated to be neutral solutions since they are not corrosive like acids and bases that can harm the skin.

Materials:

• 12-well dish
• Paper indicators:
  • Red litmus
  • Blue litmus
  • pH paper
• Different common household substances:
  • Shampoo
  • Lemon juice
  • Green tea
  • Sprite
  • Detergent
  • Milk
  • Windex

Procedure:

1. Obtain a small sample of each substance to be tested and place it in one well of the 12-well dish.
2. Assess the effect of each sample on red litmus and blue litmus to determine if the substance is acidic, basic, or neutral. (Ensure you have a substance from EACH product category)
3. Test each sample with universal pH indicator paper. Match the color of the pH paper with the provided chart to determine the approximate pH value of the substance. Record the pH value and classify the substance as:
   • Strong base (pH= 11-14)
   • Weak base (pH= 8-10)
   • Approximately neutral (pH= 7)
   • Weak acid (pH= 4-6)
   • Strong acid (pH= 0-3)

Observations

Results

In this lab, household products were categorized into three classes: cleaning, personal care, and food products. The only personal care product tested was shampoo, which exhibited acidic properties, scoring a pH level of 4. It remained red with red litmus, turned pink with blue litmus, and stayed orange with pH paper.

Among food products, lemon juice was the first to be tested and proved to be a very strong acid with a pH level of 1. It remained red with red litmus, turned red with blue litmus, and became bright red with pH paper. Green tea was found to be neutral, maintaining a pH level of 7. It stayed red with red litmus, remained blue with blue litmus, and stayed orange with pH paper. Sprite, another food product, was a weak acid with a pH level of 4. It remained red with red litmus, turned pink with blue litmus, and stayed orange with pH paper. Lastly, milk was neutral with a pH level of 7. When tested with red litmus, it turned light purple, remained blue with blue litmus, and turned yellow with pH paper.

Within the cleaning product category, detergent was a base with a pH level of 10. It turned red litmus blue, maintained blue litmus, and turned pH paper yellow. Windex, another cleaning product, was a weak base with a pH level of 9. It turned red litmus blue, kept blue litmus blue, and turned pH paper light green.

Discussion

1. Food products varied in their pH levels, with some being acidic and others neutral. Sour foods like lemon juice were identified as acids, while neutral foods like milk and green tea maintained a neutral pH.
2. Household products, regardless of category, tended to be weak acids or bases. This is because high acidity or strong alkalinity can be harmful to the skin, and these products are designed for everyday use.
3. Possible errors in the experiment include contamination between substances when placed in the 12-well dish, accidental contact between substances, insufficient time to observe color changes in indicator papers, and contamination of fingers with other acidic, basic, or neutral solutions. To ensure greater accuracy, the experiment could be repeated with greater care.

Conclusion

When red litmus paper was tested on substances from the food category, they mostly remained red, except for milk, which turned light purple. Blue litmus paper yielded varying results; lemon juice turned red (as it is an acid), green tea and milk remained blue (as they are neutral), and Sprite turned pink (as it is a weak acid). When tested with pH paper, lemon juice turned bright red (a strong acid), green tea and Sprite stayed orange, and milk turned yellow (a base).

Among the tested personal care products, shampoo exhibited acidic properties with all three indicators, confirming it as a weak acid.

Cleaning products generally showed consistent results. Both detergent and Windex turned red litmus blue, maintained blue litmus as blue, and exhibited alkaline properties when tested with pH paper, with detergent being a stronger base than Windex.