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Key Idea 1
Acids and Bases: What are they?
Concept Question: What are acids and bases?

Think back to chemistry courses you have taken in the past. How have you learned to identify acids and bases?

Perhaps you have learned that acids tend to have a tart taste, while bases are bitter and feel slippery. However, as you also know, these tests cannot be used to identify acids and bases in a laboratory; tasting and touching unknown chemicals is never a good idea.

 Graduated cylinders

You have also likely identified acids and bases using litmus paper, which changes color when it reacts with acids and bases. But what are the actual chemical reactions that define acids and bases? How do chemists understand acids and bases at the molecular level?