What Is pH?
pH stands for “potential of hydrogen,” and it measures how acidic or basic a liquid is on a scale of 0 to 14. In chemistry, pH is a logarithmic scale where each whole number change represents a tenfold change in acidity or alkalinity. A pH of 7 is neutral (like pure water), while values below 7 indicate acidity, and values above 7 indicate alkalinity.
The pH scale is essential in various fields like biology, environmental science, and household applications, as it helps to identify whether a substance is safe, corrosive, or suitable for certain tasks. For instance, acidic solutions can clean metal surfaces by dissolving rust, while alkaline solutions can neutralize oils and fats.
pH of Common Household Items
Household products vary widely in their pH levels. Here’s a quick overview of the pH values of some items you might find around your house:
- Battery Acid: 0-1 (extremely acidic) – Used in car batteries; highly corrosive and dangerous to handle without proper safety precautions.
- Vinegar & Lemon Juice: 2 (very acidic) – Used for cooking and cleaning.
- Orange Juice: 3-4 (acidic) – Contains natural citric acid, making it tangy and slightly acidic.
- Coffee: 5 (mildly acidic) – Consumed daily but slightly acidic.
- Milk: 6.5-6.9 (close to neutral) – Lactic acid is produced when bacteria in milk consume the milk sugar. As milk spoils, the pH decreases due to this lactic acid production. The pH of fresh milk is typically between 6.5 and 6.9, which is slightly below neutral.
- Pure Water: 7 (neutral) – Considered neutral with no acidity or basicity.
- Baking Soda Solution: 9 (slightly alkaline) – Used in cleaning and neutralizing odors.
- Hand Soap: 9-10 (alkaline) – Soapy substances are generally more alkaline, aiding in breaking down grease.
- Ammonia Cleaner: 11 (alkaline) – Strong cleaner but must be handled carefully due to its high pH.
- Bleach: 11-13 (highly alkaline) – Used for disinfecting and cleaning but can be corrosive. Must be handled carefully due to its high pH.
Understanding these pH levels can help you make informed choices about product usage, particularly for cleaning and safety.
Using Test Strips to Measure pH
Testing pH is fairly simple, especially with pH test strips, which are widely available. These strips have color-changing indicators that respond to the acidity or alkalinity of a solution. Bartovation actually offers over 20 different quantitative pH test strips. Here’s a step-by-step guide for testing pH with strips:
- Prepare the Sample: For liquids like vinegar or orange juice, you can simply dip the strip directly into the liquid. For solids, dissolve a small amount in water first. Make sure to always test a discrete sample (liquid that you dispose of and do not drink).
- Dip the Strip: Submerge the pH test strip in the solution following the timing on the instructions, then remove it.
- Wait for the Reaction: After a few moments, the strip will change color based on the pH level of the sample.
- Compare with the Chart: Each quantitative test strip comes with a color chart that correlates the color of the strip to a specific pH value. Match the strip to the chart to determine the pH.
Note: For best results, avoid touching the test strip to anything else before testing, as this can affect the reading. Please also note for highly pigmented solutions such as red wine and coffee the pigments may cover up the color reaction of the test pads.
Advantages of Test Strips Over Other Methods
pH test strips offer several advantages over other testing methods, including pH meters and liquid indicator solutions:
- Convenience and Portability: Test strips are easy to carry, making them ideal for on-the-go testing. They don’t require calibration, batteries, or special maintenance.
- Easy to Use: Test strips are simple to use, requiring no special skills or equipment. Just dip, read, and compare – perfect for quick checks.
- Affordability: Test strips are generally more affordable than high quality pH meters, making them a cost-effective solution for occasional testing needs.
- Reduced Contamination Risk: pH meters can sometimes be contaminated if not cleaned properly between uses, potentially affecting readings. Strips are disposable, so each test is as clean as the last.
Qualitative vs. Quantitative pH Testing: Understanding the Key Differences and When to Use Each
- Qualitative pH Test: This type of test gives a general indication of whether a substance is acidic, neutral, or basic but does not provide a specific pH value. Qualitative pH tests often use simple color changes, like with pH paper or universal indicator solutions, to show approximate ranges of pH. These tests are easy, quick, and inexpensive, but they are less precise and are generally best for quick or visual checks.
- Quantitative pH Test: Quantitative pH tests provide an exact pH measurement, often displayed as a number, and are more precise than qualitative methods. Quantitative tests are essential in applications where precise pH control is required, such as in laboratories, food production, or water treatment.
In short, qualitative tests indicate general pH ranges through visual cues, while quantitative tests measure exact pH values, providing greater accuracy for detailed pH analysis.
While pH test strips may lack the high precision of digital pH meters (which can read to decimal places), they are more than adequate for household and hobbyist applications. Additionally they do not give you a false sense of accuracy that you would get from an uncalibrated pH meter. Whether you’re checking the acidity of homemade kombucha or assessing cleaning supplies, pH test strips are a versatile, user-friendly option.