Universal pH test paper is a qualitative pH test strip that gives you approximate pH values of a solution. Typically, with Universal pH test strips, you don’t get an exact pH value. Or at least, it’s not as accurate as a quantitative pH test strip that might measure in 1.0 or 0.5 pH increments. Universal pH paper is often used to determine if a solution is very acidic, mildly acidic, neutral, mildly alkaline, or very alkaline.

Universal pH test paper is great for teaching students about pH, acids and bases. It’s a quick, accurate measurement of where a solution falls on the pH scale. Today, we’ve got a quick, easy experiment to do just that. It’s very similar to the experiments you might perform using litmus paper. We’re just going to use some common household items and Universal pH paper, so let’s get started!

Materials

  • Sodium hydroxide (NaOH)
  • Hydrochloric acid (HCl)
  • Vinegar
  • Sodium bicarbonate (baking soda)
  • Lemon Juice
  • Window Cleaner
  • Drano
  • Detergent
  • Distilled Water
  • Universal pH Test Papers (8)
  • Plastic cups, small beakers, or test tubes

Instructions

  1. Make a chart of all the items you are going to be testing. We’re going to use this chart to record the pH results of the Universal pH test paper. Mark letters A-H next to each solution name, for example, NaOH (A), HCl (B), so on and so forth.
  2. On your chart, make two sections for each solution: one for your hypothesis, and one for the actual results.
  3. Now, make your hypothesis. Where do you think each solution will fall on the pH scale?
  4. Prepare 9 clean cups or beakers. These will be used for each solution.
  5. You don’t need much solution in each cup, just enough to dip about half the test strip into the solution. Depending on the size of your cup or beaker, fill each about halfway with a solution. You will need to dilute some solutions with distilled water, such as the baking soda. Distilled water has a neutral pH and will not affect the outcome.
  6. Make sure to mark each cup or beaker with the letter associated with each solution. For example, if you marked NaOH with (A) on your chart, mark the cup containing this solution with the letter A. This is to avoid any confusion of what each liquid is and ensure accurate results in your experiment.
  7. You will use one piece of Universal pH test paper per solution. The paper cannot be reused. Thus, if you have 8 solutions, you will need 8 strips of paper.
  8. Dip a strip into the first solution, NaOH, and remove. Immediately compare it to the color chart. You should see that it is a strong alkaline solution. Record these results in your chart.
  9. Continue following step 5 for each solution. Be sure to record all results in your chart.
  10. Compare your results to your hypothesis. How accurate were your guesses?

Results

universal pH paper, universal pH paper color chart, pH test strips

Here are the results you should have found:

  • Sodium hydroxide (NaOH) is strongly alkaline with a pH of about 13. It will result in a dark green color change of the Universal pH paper.
  • Hydrochloric acid is very strongly acidic. It has a pH of about 2, so it will turn the Universal pH paper bright red.
  • Vinegar is also fairly strongly acidic, with a pH of about 2.4. It will turn the Universal paper bright red, although maybe not quite as bright red as the hydrochloric acid.
  • Sodium bicarbonate (baking soda) is mildly alkaline with a pH of about 8.4. It will fall in between the light green and dark green colors on the Universal color chart.
  • Lemon juice has a pH of about 2 and is fairly strongly acidic. The color change on the Universal pH paper should be very similar to that of the vinegar.
  • Window cleaner contains ammonia and is weakly to mildly alkaline. It may vary slightly by brand, but you should see a yellow to light green color change.
  • Drano is a very strong base. You should get a dark green color change on the pH paper.
  • Detergent is mildly alkaline, resulting in a light green color change. Again, this may vary slightly by brand.
  • Lastly, distilled water has a neutral pH of 7, resulting in a yellow-green color change.

That’s it for today’s science experiment! We hope you enjoyed experimenting with our Universal pH papers and learning about acids and bases!