Understanding pH and Indicators

Mr. Young explains the pH scale, emphasizing its absence in reference tables and the need to memorize it. He describes acids, bases, and neutral solutions, using examples to illustrate their pH values. The video introduces Table M, which lists indicators that change color at different pH levels. Mr. Young provides practical exercises to identify whether substances are acidic, basic, or neutral. He also discusses pH strips, which offer precise pH readings, and concludes with a summary of the key points.

What does the pH scale measure?

• The concentration of oxygen ions

• The power of hydrogen ions

• The density of a liquid

• The temperature of a solution

Which of the following pH values indicates a neutral solution?

• 3.4

• 7.0

• 8.2

• 6.9

If a substance has a pH of 8.2, what is it classified as?

• Acid

• Base

• Salt

• Neutral

What is the role of indicators in pH measurement?

• To measure temperature

• To increase acidity

• To change color based on pH

• To dissolve in water

Which indicator turns blue at a pH of 7.0?

• Methyl orange

• Brom thymol blue

• Brom cresol green

• Phenolphthalein

At what pH does methyl orange turn yellow?

• Above 4.4

• Below 3.1

• At 7.0

• Above 9.0

Which indicator is colorless at a pH below 7?

• Litmus

• Phenolphthalein

• Brom thymol blue

• Methyl orange

What is the purpose of pH strips?

• To measure temperature

• To provide exact pH values

• To change the color of a solution

• To neutralize acids

Which of the following is true about pH paper?

• It is not used in laboratories

• It provides a unique color for each pH value

• It uses a single indicator

• It can only measure pH above 7

What should you do if you have a pH number that is exact and in the middle range on Table M?

• Assume it is neutral

• Consider it as changing color

• Classify it as a base

• Ignore the value