Master Class 7 Science Chap 5 Acids Bases And Salts Oxford

In Class 7 Science Chap 5 Acids Bases and Salts Oxford, students learn about the substances that make up many items we use in daily life – from the sourness of lemon juice to the bitterness of baking soda. This chapter introduces the basic concepts of acids, bases, and salts, along with their properties, uses, and the reactions between them.

The chapter also explains how to identify acids and bases using natural indicators like litmus, turmeric, and china rose. It covers important concepts such as neutralization reaction, and how this reaction is useful in treating acidity, insect bites, and more.

Whether you’re using the Oxford textbook, understanding this chapter is important for building a strong foundation in chemistry. The topics are explained with simple examples and activities to make learning engaging and practical.

Class 7 Science Chap 5 Acids Bases and Salts Oxford

C. Match the following.

Column A Column B

1. CH3COOH a. Silver nitrate

2. AgNO3 b. Calcium carbonate

3. NH₄NO₃ c. Acetic acid

4. Ca(OH)2 d. Ammonium nitrate

5. CaCO3 e. Calcium hydroxide

Ans:

Column A	Column B

1. CH₃COOH

c. Acetic acid

2. AgNO₃

a. Silver nitrate

3. NH₄NO₃

d. Ammonium nitrate

4. Ca(OH)₂

e. Calcium hydroxide

5. CaCO₃

b. Calcium carbonate

II. Very short answer type questions

Give one word for the following.

1. Bases that dissolve in water
Answer: Alkali

2. A substance that shows a change in colour when brought in contact with an acid or a base
Answer: Indicator

3. Universal indicator that is soaked into paper
Answer: Litmus

4. Substance formed when a strong acid reacts with a strong base
Answer: Salt

5. Salts with water of crystallization
Answer: Hydrated

III. Short answer type questions

1. State any two properties of acids and bases.

Answer:

Acids:
1. Acids have a sour taste.
2. They turn blue litmus paper red.
Bases:
1. Bases have a bitter taste and feel soapy to touch.
2. They turn red litmus paper blue.

2. Why acids or bases are sometimes added to soil?

Answer:
Acids or bases are added to soil to correct its pH level.

If the soil is too acidic, bases like quicklime or slaked lime are added.
If the soil is too basic, organic matter or acids may be added to make it neutral and suitable for plant growth.

3. What is a neutralization reaction? Give an example.

Answer:
A neutralization reaction is a chemical reaction in which an acid reacts with a base to form salt and water.
Example:
Hydrochloric acid (HCl) + Sodium hydroxide (NaOH) → Sodium chloride (NaCl) + Water (H₂O)

4. How can a hydrated salt be converted into an anhydrous salt? Give an example.

Answer:
A hydrated salt can be converted into an anhydrous salt by heating it, which removes the water of crystallization.
Example:
Copper sulphate (blue) → on heating → Copper sulphate (white) + Water

5. Complete the following table by filling the colour of the indicator in the given solutions:

Hydrochloric acid	Red litmus	Phenolphthalein	Methyl Orange
Sodium hydroxide solution	Red
Sodium chloride Solution

Ans:

Substance	Blue Litmus	Red Litmus	Phenolphthalein	Methyl Orange
Hydrochloric acid	Red	Red	Colourless	Red
Sodium hydroxide solution	Blue	Blue	Pink	Yellow
Sodium chloride solution	No change	No change	Colourless	Orange

IV. Long answer type questions

1. How are natural indicators prepared? Give examples of a flower, root, stem, and leaf that can be used as an indicator. What are the colour changes observed with red cabbage juice in acidic, neutral, and basic medium?
Ans: Natural indicators are prepared by extracting coloured substances from parts of plants like flowers, roots, stems, or leaves. These extracts change colour when mixed with acidic or basic solutions, helping to identify the nature of the substance.

Examples of natural indicators:

Flower: China rose – turns pink in acid and green in base
Root: Turmeric – yellow in acid and reddish-brown in base
Stem: Beetroot – shows colour change with pH
Leaf: Red cabbage – rich in anthocyanin, a natural pH indicator

Colour changes observed with red cabbage juice:

In acidic medium – Red or pink
In neutral medium – Purple
In basic medium – Green or yellowish-green

2. Explain the following:

a. Vinegar is used in packaged food items.

b. Slaked lime is added to factory waste.

c. Magnesium hydroxide is used as an antacid.

d. Strong acids and bases should be handled carefully.

Ans:

a. Vinegar is used in packaged food items.
Vinegar contains acetic acid, which acts as a preservative. It creates an acidic environment that prevents the growth of harmful bacteria and fungi in food, thereby increasing its shelf life. It also adds a sour taste to enhance flavour.

b. Slaked lime is added to factory waste.
Factory waste can be highly acidic. Slaked lime (calcium hydroxide), being a mild base, is added to neutralize the acidity before the waste is released into the environment. This prevents pollution and harm to aquatic life.

c. Magnesium hydroxide is used as an antacid.
Magnesium hydroxide is a weak base that helps neutralize excess acid in the stomach. It is used in medicines like milk of magnesia to relieve acidity, heartburn, and indigestion.

d. Strong acids and bases should be handled carefully.
Strong acids and bases are corrosive and can cause burns or injuries. They must be handled using safety equipment like gloves and goggles. Proper storage, dilution, and supervision are important while working with them in labs or industries.

3. What is water of crystallization? Explain with the help of an example.
Water of crystallization is the fixed number of water molecules that are chemically bound in the structure of a salt crystal. These water molecules are essential for maintaining the crystal’s colour and shape.

For example, copper sulphate (CuSO₄·5H₂O) is a blue-coloured salt. The five water molecules give it the blue colour. On heating, it loses its water of crystallization and turns white, forming anhydrous copper sulphate.

Reaction:
CuSO₄·5H₂O → (heat) → CuSO₄ (white) + 5H₂O

This shows that the water of crystallization plays an important role in the physical properties of certain salts.

Class-wise Solutions

Class 12:

Class 12 Physics – NCERT Solutions

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Class 11:

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Class 9:

Class 8:

Class 7:

Class 7 Science – Oxford Solutions

Class 6:

Class 6 Science – Oxford Solutions

Subject-wise Solutions

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Biology:

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Math:

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The topic of acids, bases, and salts is essential for understanding everyday chemical reactions around us. Class 7 Science Chap 5 Acids Bases and Salts Oxford explains these concepts with clarity through real-life examples and simple experiments. Whether it’s about the sour taste of lemon, the effect of litmus paper, or the neutralization of acid in the stomach, all these are well covered in Class 7 Science Chap 5 Acids Bases and Salts Oxford.

Students gain knowledge about natural indicators, neutralization reactions, and the importance of handling strong acids and bases with care. The examples and activities provided in Class 7 Science Chap 5 Acids Bases and Salts Oxford help make science more interactive and practical.

By thoroughly understanding Class 7 Science Chap 5 Acids Bases and Salts Oxford, students can relate scientific principles to their daily lives and develop a strong base in chemistry. Thus, it is highly recommended that every student revises Class 7 Science Chap 5 Acids Bases and Salts Oxford to strengthen their understanding and perform well in exams.