Introduction to Acids and Bases

What are they and how do we as scientists measure them?

pH Scale

1. The pH scale ranges from 0 to 14.

2. A solution with a pH of 7 is neutral.

3. Pure water has a pH of 7.

pH is a measure of how acidic or basic a solution

is.

Acids Bases

• Turns red litmus paper blue.

• Acidic solutions have pH values below 7

• Basic solutions have pH values above 7.

• Turns blue litmus paper red

Guess and CheckIn your notes, predict whether the objects below are acids or bases. What color will each turn the

litmus paper? Explain your reasoning.

1. Baking Soda and Water

2. Orange Juice

3. Vinegar

Three Ways to Measure pH

1. Liquid indicator

2. pH paper

3. pH meter

Pay Attention as I demonstrate how to use each of the three. You will need to know how to use each of these methods in the lab activity, which will count

as a grade.

Lab Activity• You will be assigned a group. You will be demonstrating

your knowledge on how to use the three pH measuring techniques.

• In your notes, begin by measuring the pH of water for each of the three techniques.

• Then measure the four other substances at your station.

• Create a data table to record your results. Remember to include three separate areas to record the data for each technique. o This will be collected and graded. If you fail to follow class expectations, you

will return to your seat and receive a zero!

Example Data TableSubstance Liquid

IndicatorpH Paper pH Meter Observations Acid or Base

Water          

Lemon Juice          

Bleach          

Dishwasher Detergent

         

Soda          

Stop and JotIn your lab notes, write 3-5 sentences to the following question. Be sure to explain your

answer clearly and support your answer with information learned from today’s lesson.

What method of measurement was the most accurate and which was the least?