1. Physical Science Chapter 23 ACIDS AND BASES

2.  Acid: A substance that produces hydrogen ions in a water solution.  The hydrogen ion then interacts with water molecules to form H 3 O + ions which are called hydronium ions ACIDS HCl + H 2 O  H 3 O + + Cl –

3.  Properties of acids:  Taste sour  Can cause painful burns  Are corrosive  May react strongly with certain metals  Turns litmus paper red PROPERTIES OF ACIDS Have a pH less than 7

4.  Base: Any substance that forms hydroxide ions, OH  (hydroxide ion), in a water solution  In addition, a base is any substance that accepts hydrogen ions (H +) from acids. BASES NH 3 + H 2 O  NH 4 + + OH -

5.  One way to think of bases is that they are opposites of acids  Properties of Bases:  Most are crystalline solids in pure form  Feel slippery  Have a bitter taste  Strong bases are corrosive and can cause burns  Turn litmus paper blue PROPERTIES OF BASES Have a pH greater than 7

6.  Indicator: Organic substance that changes color in an acid or base  Examples:  litmus - red/blue  phenolphthalein - colorless/pink  red cabbage juice - pink/green INDICATORS