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Introduction
Introduction
Some acids are stronger than others and produce the highest concentrations of hydrogen ions, H+. Weaker acids produce lower concentrations of hydrogen ions, H+. Likewise, some bases are stronger than others and produce the highest concentrations of hydroxide ions, OH- , whilst weak bases produce lower concentrations of hydroxide ions, OH-.
The pH Scale
The pH Scale
The pH scale is used to measure how acidic or basic a substance is. pH stands for potential hydrogen.
Acids have a pH of less than 7.
Bases have a pH of greater than 7.
Neutral substances have a pH of 7.
The pH of a substance can be measured using a pH meter or by using universal indicator paper or solution.
Another representation of the ions present at different pH level1.pdf
Acid-Base Indicators
Acid-Base Indicators
At NCEA Level 1 there are a couple of indicators you need to know about:
Universal Indicator
Litmus Indicator
Universal Indicator
Universal Indicator
We have already covered Universal Indicator (UI) in the sections above, but here is a little more about it. UI is an indicator that is made up of several compounds that show gradual colour changes over a wide range of pH values to show or indicate how acidic or basic a substance is. UI comes in a solution or in paper form. The colours that form relate to specific pH values on the pH scale.
Litmus
Litmus
Litmus indicator can also come in two forms: a solution and as blue or red litmus paper.
Litmus solution is purple in neutral substances, red in acidic substances, and blue in basic substances.
Litmus paper comes in two forms: red litmus paper and blue litmus paper. Red litmus paper stays red in acidic and neutral substances, and turns blue in basic substances. Blue litmus paper stays blue in basic and neutral substances, and turns red in acidic substances.
The diagram below shows a summary of the colours that different indicators turn.
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