Acids & BasesAcids & BasesAcids & BasesAcids & Bases

Hammer & RundellHammer & Rundell

Review: How Do We Set Up an Experiment?

(used as a standard of comparison) Control

Dependent Variable (depends on the independent variable – effect)

Independent Variable(manipulated or controlled by the experimenter – cause)

Constants (things that remain the same for all test groups)

Graphing the ResultsDependent (y) – Each

finger in the group depends on the others.

Independent (x) – Thumb stands

alone relying on no one but himself.

Acids and Bases are common

• Acids– Citrus fruits– Vitamin c– Vinegar– Household cleaners

– Stomach acid– Soft Drinks

• Bases– Antacids– Household cleaners

– Soap

Acids and BasesClassifying based on

properties

• Acids– Sour– Corrosive

• Bases– Bitter– Slippery

Another way to look at acids

• Acids donate hydrogen ions when dissolved in water

• Bases donate hydroxide ions when dissolved in water.

•HCl H+ + Cl- (acid)

•NaOH Na+ + OH- (base)

Practice• Identify as acid or base based on their ionization

• Ca(OH)2 Ca2+ + OH-

• HBr H+ + Br-

Acids Ionize in Water:

• HBr H+ + Br-

• The hydrogen will bond with a water molecule to produce hydronium.

H30+

Strength of Acids & Bases

• The strength of acids & bases is determined by how many hydrogen or hydroxide ions have been produced.

• Lots of hydrogen ions = strong acid

• Lots of hydroxide ions = strong base

Measuring Strength of Acids & Bases

• We measure the strength of acids and bases using the pH scale.

• Acids range from 0 to 7

• Bases range from 7 to 14

• 7 is Neutral

pH and Indicators• Indictors are chemicals used to determine the pH of a substance.

Acids and Bases neutralize each other• HCl + NaOH H2O + NaCl

Acid base neutral

+

• Acids and bases combine to form water and a salt.

Our Environment• We have all heard of acid rain. It forms when pollutants such as sulfur oxides combine with water to form sulfuric acid.

• Sulfur oxides + water acid rain

Question 1

• Where on the pH scale are the acids?

pH Scale

0 7 14

Question 2• The directions on a can of oven cleaner say that you must use gloves. The cleaner is slippery and turns litmus paper blue. It is probably a _____.

• A. Acid• B. Base• C. Salt• D. isotope

Question 3

• A beaker contains 100 mL of a solution with a pH = 3. One hundred mL of a second unknown solution is added to the first solution and stirred. The pH of the mixture is now 2.5. The second solution

• A. has a high concentration of hydroxide ions

• B. is neutral• C. is a strong acid• D. is a salt

Question 4

• Which of the following is a base?

• A. a substance with a pH = 6• B. A solution with more hydrogen ions than hydroxide ions

• C. Ba(OH)2

• D. NaBr

Question 5• Acid rain is the result of water combining in the atmosphere with sulfur oxides to form sulfuric acid. Which of the following might occur in a region that has acid rain?

• A. Lakes have a lower pH than normal

• B. Plants die• C. Rocks weather• D. All of the above