7. Acids, Bases and Salts (Part 1) (1/3) (Cambridge IGCSE Chemistry 0620 for 2023, 2024 & 2025)

Summary

This video covers the fundamentals of acids, bases, and salts from the IGCSE Chemistry syllabus. It explains the properties and behaviors of acids and bases, including their reactions with metals, bases, and carbonates, as well as the concept of neutralization. The script also introduces key indicators for determining pH, and clarifies the difference between bases and alkalis. Additionally, it explores the proton donor-acceptor theory and compares strong and weak acids. Finally, the video highlights the use of the universal indicator to measure pH and acidity/alkalinity, providing a thorough foundation for understanding these essential concepts in chemistry.

Takeaways

• 😀 Acids are substances that release hydrogen ions (H+) when dissolved in water, making the solution acidic with a pH less than 7.
• 😀 Bases release hydroxide ions (OH-) in water, making the solution basic with a pH greater than 7.
• 😀 A neutralization reaction occurs when an acid reacts with a base to form a salt and water.
• 😀 Common indicators like litmus, thymol blue, and methyl orange are used to determine if a solution is acidic or basic based on color changes.
• 😀 Acids react with metals to produce a salt and hydrogen gas (e.g., hydrochloric acid and zinc).
• 😀 Acids react with carbonates to produce a salt, water, and carbon dioxide (e.g., nitric acid and calcium carbonate).
• 😀 Strong acids completely dissociate in water, while weak acids only partially dissociate.
• 😀 Alkalies are bases that dissolve in water and release hydroxide ions (OH-), making the solution alkaline.
• 😀 Acids are proton donors (H+), while bases are proton acceptors in reactions (e.g., HCl donating a proton to NH3).
• 😀 The pH of a solution can be measured using universal indicators, which change color to show the acidity or alkalinity of the solution, with red indicating acid and blue/purple indicating alkali.
• 😀 Neutralization reactions between acids and alkalis result in the formation of water and salt, neutralizing their respective properties.

Q & A

What is the definition of an acid?

An acid is a substance that releases hydrogen ions (H⁺) when dissolved in water, resulting in a solution with a pH less than 7.

How do acids and bases differ in terms of their pH?

Acids have a pH less than 7, while bases have a pH greater than 7. A pH of 7 is considered neutral.

What happens during the dissociation of nitric acid in water?

When nitric acid (HNO₃) dissociates in water, it releases hydrogen ions (H⁺) and nitrate ions (NO₃⁻), making the solution acidic.

What are the products when an acid reacts with a metal?

When an acid reacts with a metal, it produces a salt and hydrogen gas.

Give an example of an acid reacting with a metal.

An example is hydrochloric acid (HCl) reacting with zinc (Zn) to produce zinc chloride (ZnCl₂) and hydrogen gas (H₂).

What is the outcome of a neutralization reaction between an acid and a base?

A neutralization reaction between an acid and a base results in the formation of a salt and water.

What are indicators, and how do they work?

Indicators are substances that change color to show whether a solution is acidic or alkaline. They respond to pH changes by shifting colors.

What color does litmus paper turn when it is exposed to an acid?

Litmus paper turns red when exposed to an acid.

How does a strong acid differ from a weak acid in terms of dissociation?

A strong acid completely dissociates into ions in water, while a weak acid only partially dissociates.

What is the role of the universal indicator in determining pH?

The universal indicator changes color to indicate the pH of a solution: red for acidic (pH < 7), green for neutral (pH = 7), and blue or purple for alkaline (pH > 7).