Introduction to Acids and Bases (Theory-Based)

Open Ended

Do Now Question

What is a neutral substance? Can you give an example?

​Review responses on Quizizz.

Cold Call: Select 2-3 students to share their answers

3 minutes

Introduction to Acids and Bases

Objective:

• We Will: Explore the properties of acids and bases and understand how the pH scale helps classify substances.

• I Will: Compare and contrast acids and bases and explain their differences.

TEK Review:

• TEK 8.6D: Compare and contrast the properties of acids and bases, including pH relative to water.

1 minutes

Vocabulary Activity - Guided Notes

• Fill in the blanks for the following terms:

  • Acid: A substance that increases the concentration of hydrogen ions (H⁺) when dissolved in water.

  • Base: A substance that increases the concentration of hydroxide ions (OH⁻) when dissolved in water.

  • pH Scale: A measure of how acidic or basic a solution is.

  • Neutral: A substance with a pH of 7, neither acidic nor basic.

4 minutes

Introduction to Acids

• Acids increase the concentration of hydrogen ions (H⁺) when dissolved in water.

• They have a sour taste and can corrode metals.

• Common examples: Lemon juice, vinegar, and hydrochloric acid (HCl).

4 minutes

Multiple Choice

Which of the following is a common characteristic of an acid

• Bitter taste

• Slippery Feel

• Sour tast

• Does not react with metals

1 minutes

​Which of the following is a common characteristic of an acid?

Explanation: Acids are known for their sour taste, which is one of their distinguishing characteristics. For example, common acids like lemon juice and vinegar have a sour taste because they contain citric acid and acetic acid, respectively. Acids release hydrogen ions (H⁺) in solution, and these ions contribute to their sour flavor.

The other choices (bitter taste, slippery feel) describe characteristics of bases, not acids.

Introduction to Bases

• Bases increase the concentration of hydroxide ions (OH⁻) when dissolved in water.

• They have a bitter taste and feel slippery.

• Common examples: Baking soda, soap, and sodium hydroxide (NaOH).

3 minutes

Multiple Choice

Which of the following is a property of a base?

• Sour taste

• Turns red litmus paper blue

• Reacts with metals

• turns blue litmus paper red

1 minutes

Which of the following is a property of a base?

Explanation: A base has several distinguishing properties, and one of the most notable is that it turns red litmus paper blue. Litmus paper is used as a simple indicator to test whether a substance is acidic or basic. When a base is present, it changes the color of red litmus paper to blue.

The other options:

• Sour taste refers to acids, not bases.

• Reacts with metals is typically a property of acids rather than bases.

• Turns blue litmus paper red is what happens

  when an acid is present, not a base

The pH Scale

• The pH scale measures how acidic or basic a solution is.

• It ranges from 0 to 14:

  • Acids: pH less than 7.

  • Neutral: pH 7 (e.g., pure water).

  • Bases: pH greater than 7.

• The lower the pH, the more acidic the substance.

3 minutes

Multiple Choice

What is the pH range for a base?

• 0 - 6

• 7

• Greater than 7

• 0-14

1 minutes

What is the pH range for a base?

Explanation: The pH scale measures how acidic or basic a substance is. The scale ranges from 0 to 14:

• A pH less than 7 indicates an acidic substance.

• A pH of 7 is considered neutral (e.g., pure water).

• A pH greater than 7 indicates a basic or alkaline substance.

Bases typically have a pH between 7 and 14, with stronger bases closer to 14. For example, substances like baking soda or soap have a pH greater than 7, making them basic.

Neutral Substances

• Substances with a pH of 7 are neutral, meaning they are neither acidic nor basic.

• Example: Pure water.

3 minutes

Multiple Choice

Which of the following substances is neutral?

• Lemon juice

• Soap

• Baking soda

• Pure water

1 minutes

Which of the following substances is neutral?

A neutral substance has a pH of 7, meaning it is neither acidic nor basic. Pure water is the most common example of a neutral substance because it has an equal concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻), which results in a balanced pH of 7.

The other options (lemon juice, soap, baking soda) are either acidic or basic:

• Lemon juice is acidic, with a pH less than 7.

• Soap and baking soda are basic, with a

• pH greater than 7.

1 minutes

Turn & Talk Discussion

• Discussion Question:

  • How do acids and bases differ in terms of their chemical properties?

• Cold Call: Be prepared to share your thoughts after discussing in pairs.

How do acids and bases differ in terms of their chemical properties?
Acids and bases have distinct chemical properties based on the ions they release in water and how they interact with other substances.

​Acids	​Base
​ Acids have a sour taste (e.g., lemon juice or vinegar). They turn blue litmus paper red. Acids react with metals to produce hydrogen gas. They neutralize bases to form water and a salt.	​B Bases have a bitter taste and a slippery feel (e.g., soap or baking soda). They turn red litmus paper blue. Bases can react with oils and fats to create soap (saponification). They neutralize acids to form water and a salt.

Thus, the primary difference lies in the type of ions released (H⁺ for acids, OH⁻ for bases) and their behavior in reactions with substances like metals, litmus paper, and neutralization processes.

Open Ended

Exit Ticket:

What pH range would you expect from an acid? From a base?