GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY GIPHOTOSTOCK / SCIENCE PHOTO LIBRARY
Litmus changes its colour depending on the pH of the solution. Here after litmus paper strips were dipped in different solutions. The strip was left unchanged (left), changed to blue (centre), and changed to red (right) indicating neutral (water), alkaline (baking soda) and acidic (vinegar) solutions, respectively.
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