Acids and Bases
Acids donate H⁺; bases accept H⁺ or donate OH⁻.
About this topic
Acids release hydrogen ions (H+) in water and taste sour; bases release hydroxide ions (OH−) and feel slippery. The Brønsted-Lowry definition is broader: an acid is a proton donor and a base is a proton acceptor. Conjugate pairs differ by one H+, as in HCl/Cl− or NH4+/NH3.
Acids turn blue litmus red and react with metals to give hydrogen and with carbonates to give carbon dioxide. Bases turn red litmus blue and neutralise acids. In water, a proton transfers to a water molecule to form hydronium, H3O+. Substances that can act as both acid and base, such as water, are amphoteric. Lewis theory goes further, defining acids as electron-pair acceptors.
Examples: lemon juice and vinegar contain citric and acetic acids; baking soda, soap and ammonia cleaners are bases. Your stomach contains hydrochloric acid for digestion, while antacids contain bases. Acids and bases are used in fertilisers, batteries, soap making and food preservation.
Misconceptions: all acids are dangerous and all bases are safe. Vinegar is safe to eat but concentrated sodium hydroxide is highly corrosive. Never taste chemicals to test them. Also, strength is different from concentration; a dilute solution of a strong acid may be less hazardous than a concentrated weak one.
Key ideas
- Arrhenius and Brønsted–Lowry definitions
- Sour vs bitter
- Indicators change colour
Quick check
Use cases: where Acids and Bases helps
- Homework: review the key idea behind Acids and Bases before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Acids and Bases without notes.
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Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Acids and Bases?
Acids donate H⁺; bases accept H⁺ or donate OH⁻.
What will I learn in Acids and Bases?
Arrhenius and Brønsted–Lowry definitions. Sour vs bitter. Indicators change colour.
Is Acids and Bases part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Acids and Bases lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Acids and Bases?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
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