Science 7 Notes 21 Acids 1. Differentiate Bases between an acid and base Hydrogen ion Hydroxide ion 2. Describe the relationship pH between acids, bases, and pH Describe why + water has a Water molecules occasionally split apart and form a hydrogen ion (H ) and a netural pH. hydroxide ion (OH-) as shown below: + - H2O H + OH - OH In pure water, 1 out of 550 million water molecules will split in this way Because the number H+ ions equal the number of OH- ions, pure water has a neutral pH Describe the charateristice of Acids an acid. • Compounds that dissolve in water and will split into hydrogen ions (H+) and negative ions + - • HCl → H + Cl • They contain excess hydrogen ions (H+) • Taste sour • Turns litmus paper red • Examples: HCl, HNO , H SO 3 2 4 Describe the Bases charateristics of a base. • Compounds that dissolve in water and will split into positive ions (H+) and hydroxide ions (OH-) • In Water… NaOH → Na+ + OH- • Form excess hydroxide ions (OH-) • Tastes bitter • Turn litmus paper blue • Examples: NaOH, KOH, Mg(OH)2, Ca(OH)2 1 Science 7 Notes 21 pH (Potential of Hydrogen) What does the pH scale measure? + • A measurement scale to indicate the amount of H ions compared to Describe the - range of the pH OH ions in a solution scale. • The pH scale ranges from 0 to 14 – At a neutral pH (pH 7), + the concentration of H ions - equals the concentration of OH ions – At an acidic pH (pH less + than 7), there are more H ions - than OH ions - – At basic pH (pH greater than 7), there are more OH ions than What is the pH of + a neutral H ions substance? What is the pH of an acidic Neutralization substance? • If you react an acid with a base they will neutralize each other What happens when you mix an • Neutralization reactions produce a salt compound + water acid with a base? • HCl + NaOH → __________________ + ________________ Put the following substances in order of increasing acidity: coffee, bleach, orange juice, ammonia 2 .