* Acids are substances that donate protons (H+ ions) in water.

* They have a sour taste.

* They turn blue litmus paper red.

* They react with metals to produce hydrogen gas.

* They react with bases to produce salt and water.

Bases

* Bases are substances that accept protons (H+ ions) in water.

* They have a bitter taste.

* They turn red litmus paper blue.

* They feel slippery to the touch.

* They react with acids to produce salt and water.

The strength of an acid or base is determined by the extent to which it donates or accepts protons in water.

* Strong acids completely dissociate in water, releasing all of their protons.

* Weak acids only partially dissociate in water, releasing only a small fraction of their protons.

* Strong bases completely dissociate in water, accepting all of the protons that are available.

* Weak bases only partially dissociate in water, accepting only a small fraction of the protons that are available.

The pH scale is used to measure the acidity or basicity of a solution. The pH scale ranges from 0 to 14, with 7 being neutral. A solution with a pH below 7 is acidic, while a solution with a pH above 7 is basic.