1. Acids, Bases, Salts and pH Physical Science

2. Acids Acids are chemicals in which the positive ion is a hydrogen atom. n for example; HCl or H 2 SO 4 n When mixed with water they produce a free hydrogen ion that combines with a water molecule to produce a hydronium ion (H 3 O) H +1 + H 2 O  H 3 O +1 n An acid is a substance that releases hydrogen ions when it breaks apart in water.

3. Physical Properties of Acids 1. Taste sour 2. React with metals to produce hydrogen 2HCl + 2Na  2NaCl + H 2 3. Conduct electricity.

4. Bases n Bases are substances in which the negative ion is an ion called hydroxide (OH) -1. n For example; NaOH, or KOH – used to make soap, household cleaners, fertilizers, and explosives.

5. Physical Properties of Bases 1. Taste bitter 2. Feel slippery 3. Conduct electricity 4. Sometimes Caustic. That is they eat away at certain substances and they are irritating or damaging to skin.

6. Salts n A salt is a compound formed from the positive metal ions of a base and a negative nonmetal ion of an acid. n For example NaCl, K 2 SO 4 n Are the product of a reaction between an acid and a base, along with water.

7. Physical Properties of Salts n They form crystals when in solid form n They usually have a higher hardness because of their ionic bonding. n An acid plus a base yields a salt and water. HCl + NaOH  NaCl + HOH or HCl + NaOH  NaCl + H 2 O

8. Neutralization n A reaction between an acid and base. n The products of a neutralization reaction are a salt and water.

9. The pH Scale n The pH scale gives a measure of the concentration of positive hydrogen ions in a solution. – a way of describing the acidic or basic strength of a solution. – the acidity of a solution can be expressed by using the pH scale

10. The pH Scale n the scale ranges from 0 to 14 n acids range from 0 to 7, with 0 being the strongest acid n bases range from 7 to 14, with 14 being the strongest base. n pure water, which is neither acid nor base, has a pH level of 7 or is neutral

11. Indicators n Indicators are substances that visibly show a change in the nature of a chemical system. n Universal indicator- an acid/base indicator that shows, by color, the pH of a substance. ACIDICNEUTRALBASIC 789106543