How to Test Acids & Bases
Acids are substances with a pH less than seven. Substances with a pH greater than seven are called bases. Acids tend to be sour or tart, like lemon juice; bases, such as soap, usually feel slippery and taste bitter. You can guess whether a substance is an acid or base by examining its properties, but it's easier to test a substance's pH with litmus paper or pH paper. Litmus paper turns red or blue, indicating that a substance is acidic or alkaline; pH paper changes to a range of colors, indicating the approximate pH of a substance.
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Instructions
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Testing Acids and Bases with Litmus Paper
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Remove a drop of solution from the first substance with the dropper.
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Place the drop on a piece of red litmus paper. If the paper stays red, the substance is an acid. If it turns blue, the substance is a base.
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3
Remove another drop with the dropper and place it on blue litmus paper to check your previous conclusion. If it stays blue, it's a base; if it turns red, it is an acid.
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Record your observations and repeat with the rest of the substances. Use a separate dropper for each substance to prevent contamination.
Testing Acids and Bases with pH Paper
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5
Remove a drop of solution from the first substance with the dropper.
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Place the drop on a piece of pH paper. The paper will change colors.
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Compare the new color of the paper to the chart included with the pH paper to determine the approximate pH of the substance.
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Record your observations and repeat with the rest of the substances.
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Tips & Warnings
Never dip litmus paper or pH paper into substances, because this can cause contamination.
Neutralize acidic waste with baking soda before disposal. Neutralize alkaline waste with vinegar.
Do not touch or taste the substances.
References
- Photo Credit lemon image by Maria Brzostowska from Fotolia.com
