Science Class 7 - Acids Bases-And-Salts Notes

Acids, Bases and Salts

Welcome to the chapter on Acids, Bases and Salts for Class 7. In this chapter, you will learn what acids, bases, and salts are, their properties, how they are used in daily life, and how to identify them. By the end of this chapter, you will be able to recognize common acids, bases, and salts and understand their importance!

Introduction

Acids, bases, and salts are important chemicals found all around us. They are present in the food we eat, the cleaning products we use, and even in our bodies!

What are Acids?

Acids are substances that taste sour and turn blue litmus paper red. They are found in many foods and drinks.

• Examples: Lemon juice (citric acid), vinegar (acetic acid), curd (lactic acid).
• Acids are used in making medicines, cleaning products, and food items.

What are Bases?

Bases are substances that taste bitter and feel slippery. They turn red litmus paper blue.

• Examples: Soap (sodium hydroxide), baking soda (sodium bicarbonate), lime water (calcium hydroxide).
• Bases are used in cleaning, making soaps, and medicines.

What are Salts?

Salts are formed when acids and bases react together. They are usually neutral and have many uses.

• Examples: Table salt (sodium chloride), washing soda (sodium carbonate), Epsom salt (magnesium sulfate).
• Salts are used in food, cleaning, and medicines.

Testing Acids and Bases

We use indicators to test whether a substance is an acid or a base.

• Litmus paper: Turns red in acids and blue in bases.
• Turmeric: Turns red in bases.
• China rose: Turns dark pink in acids and green in bases.

Uses in Daily Life

• Acids are used in making pickles, cleaning toilets, and medicines.
• Bases are used in soaps, detergents, and antacids.
• Salts are used in cooking, preserving food, and cleaning.

Fun Activity: Test with Litmus!

Take some lemon juice, soap water, and salt water. Dip litmus paper in each and note the color change. Which is acid, base, or salt?

Summary

• Acids taste sour and turn blue litmus red.
• Bases taste bitter and turn red litmus blue.
• Salts are formed by the reaction of acids and bases.
• Indicators help us test acids and bases.

Practice Questions

1. Name two acids found in food.
2. What color does red litmus turn in a base?
3. Give one use of salt in daily life.
4. What is an indicator?
5. How are salts formed?

Challenge Yourself

• List three things at home that are acids, bases, or salts.
• Try testing turmeric with soap water. What happens?

Did You Know?

• The acid in your stomach helps digest food!
• Antacids are bases that help reduce stomach acid.

Glossary

• Acid: A substance that tastes sour and turns blue litmus red.
• Base: A substance that tastes bitter and turns red litmus blue.
• Salt: A substance formed when an acid reacts with a base.
• Indicator: A substance that shows if something is an acid or base by changing color.

Answers to Practice Questions

1. Citric acid (lemon), acetic acid (vinegar).
2. Blue.
3. Cooking food.
4. A substance that changes color to show acid or base.
5. By reaction of acid and base.

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Explore acids, bases, and salts around you and try simple tests safely!