Key concepts

This fun and useful project turns mundane house chores into a magnificent learning experience. Make homemade nontoxic glass and surface cleaner that not only gets those windows streak-free shiny but also sneaks in a lesson about household chemicals and the pH scale. Enjoy!

The pH scale measures the concentration of hydrogen ions in an aqueous (water) solution. The "p" stands for percentage, or power. The "H," you might have guessed, stands for hydrogen. The power of hydrogen in a substance is determined on a sliding scale from one to 14. On this scale, 7 is the neutral number. So plain water would have a pH score of 7. The closer a water-based solution is to 14, the more alkaline, or "basic," it is, whereas the closer it is to 1, the more acidic. A substance's pH is an important measurement in chemistry, biology, oceanography, food science and even engineering! Today's project uses acids to make the perfect balance of cleaning agents.

•    One half cup of white vinegar
•    One half cup of water
•    One half cup of rubbing alcohol
•    One tablespoon of fresh lemon juice (which will take about one lemon)
•    Spray bottle
•    Mixing bowl
•    Spoon for mixing
•    Funnel (optional)

•    Be sure to use only measuring utensils and bowls that are not used for food preparation and eating.

•    Pour all the liquid ingredients together in a bowl. What kind of pH levels do you think all of the ingredients have?
•    Stir this solution for two full minutes. What does it smell like?
•    Pour the solution into your spray bottle (use a funnel if you have one to cut down on spillage).
•    Clean some glass! Just be careful to not get any of the solution in your eyes.
•    Extra: How well does your glass cleaner work? Test it against any store-bought cleaner you have at home. Does one work better than the other? How much does each cost?
•    Extra: Do a little research and see if you can find the pH of rubbing alcohol. You might be surprised at what you find! If you want to make even more of this solution and use this as your everyday glass and surface cleaner, just scale up the recipe proportionately.

Observations and results
Today's project uses a specific balance of acids to make a mild cleaning perfect for cleaning and shining everyday household surfaces. What type of solution is it? The lemon juice has a pH of about 2, and the vinegar has a pH balance of about 3. Why add the water? The neutral water makes the substance a little less acidic—around a 4 or 5 on the pH scale—so that it is gentler on surfaces, such as wood.

A common household material that is on the base side of the pH scale is baking soda (sodium bicarbonate—about pH 8), which you can learn more about in the "Carbonic Colors: Fizzy, Washable Sidewalk Paint" activity. Want to test other household solutions? Try the "Cabbage Chemistry—Finding Acids and Bases" activity for home-brewed answers.

More to Explore
"Homemade Non-Toxic Glass Cleaner: A Lesson in pH" from
"Acids and Bases are Everywhere" from Rader's
"What is pH" from the U.S. Environmental Protection Agency
"Invisible Ink Reveals Cool Chemistry"" from Scientific American

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