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Revision Notes

Class 7

Science

Chapter 6 Physical And Chemical Changes

Physical and Chemical Changes Class 7 Science Chapter 5 CBSE Notes - 2025-26

Q: 2. How can I quickly tell if a change is physical or chemical?

The easiest way is to ask if a new substance is formed. If no new substance is created and the change is usually reversible (like melting ice into water), it's a physical change. If a completely new substance appears, often with signs like a colour change, gas release, or heat, it's a chemical change (like burning paper to ash).

Q: 7. What is the simple chemical reaction for rusting that I should remember from these notes?

A simple way to remember the reaction for rusting is: Iron (Fe) + Oxygen (O₂) + Water (H₂O) → Rust (Iron Oxide, Fe₂O₃). This summary helps you recall that both oxygen and moisture are essential for rust to form.

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Science Notes for Chapter 5 Physical and Chemical Changes Class 7 - FREE PDF Download

Physical and Chemical Changes Chapter 5 Notes PDF is available here for free download of the CBSE Class 7 students. This PDF comprises notes which will help the CBSE Class 7 students to prepare and revise the chapter on Physical and Chemical Changes for their Science exams thoroughly.

Students preparing for their Class 7 science examination are encouraged to refer to the NCERT Class 7 Science Chapter 5 Notes that are designed by our subject experts at Vedantu. The Class 7 Science Chapter 5 Notes PDF is available for download from our official website and Vedantu mobile app allowing students to learn in a convenient environment. Download NCERT Solutions PDF and opt to refer to the questions and answers to score good marks. You can also download NCERT Solutions for Class 7 Maths to revise the complete syllabus and score more marks in your examinations.

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Students can also download additional study materials provided by Vedantu for Class 7 Science Chapter 5 Physical and Chemical Changes.

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Access Class 7 Science Chapter 5 - Physical and Chemical Changes

Physical and chemical changes are the two sorts of changes that might occur.

Physical alterations refer to changes in a substance's physical qualities. These alterations do not result in the formation of any new compounds. These modifications might be reversible. Crushing a can, lighting an electric bulb, ripping paper, and mixing sand and water are just a few examples.
Chemical alterations occur when the substance's composition and chemical characteristics are altered. New chemicals are created as a result of chemical reactions. This is a permanent and irrevocable transformation. For instance, a candle is lit, the curd is formed from milk, and fruits ripen.

Chemical Reactions in the Real World:

Iron Rusting: Iron rusting is the transformation of iron into iron oxide. When iron comes into touch with water and oxygen, something happens. The process is a sort of corrosion that happens frequently in nature.

Prevention of Rusting:

i. By Painting

ii. By Oiling and greasing

iii. By Chromium plating

iv. By Galvanizing

v. By Alloying

Cooking of Food: Cooking breaks down complex carbs, lipids, and protein molecules into smaller molecules.

It's thought to be a breakdown process. Food that has been prepared is easier to digest than food that has not been cooked.

Decay of Organic Substances: Enzymes are produced by microorganisms such as fungi and bacteria, which break down complex chemical materials into simpler components. It's also referred to as a breakdown process.

Crystallization can be used to obtain pure compounds from their solutions.

Benefits of Physical and Chemical Changes Chapter 5 (Class 7) Science Revision Notes

Check out the benefits of Chapter 5 Class 7 Science Revision Notes below.

Class 7 Science Chapter 5 revision notes will function as a great reference tool for the students to strengthen their understanding and revision of the important concepts of the chapter.
Students will become more confident about solving even the complex questions of the chapter during the exam.
Exam stress and anxiety will therefore be greatly reduced.
The revision notes will enable students to revise their chapters quickly and efficiently without compromising on the quality of preparation.
The revision notes are prepared in a concise manner, thus the students can revise from these notes a day before the exam when time is limited and the chapters to study are vast.
The revision notes are in a convenient pdf form, this will help the students to study these revision notes from anywhere and at any time.

Topics Covered in Physical and Chemical Changes Chapter 5 (Class 7) Science

Following are the topics represented in the tabular form which are covered in Class 7 Chapter 5 Science.

Section Name	Topic Name
5	Physical and Chemical Changes
5.1	Physical Changes
5.2	Chemical Changes
5.3	Rusting of Iron
5.4	Crystallisation

Physical and Chemical Chapter 5 Class 7 Science - Key Takeaways of the Chapter

Physical Changes: During a physical change, substances go through changes only in its physical properties like size, colour, state, and shape. Most importantly, no new substance is generated in these changes. To understand the topic, it is essential to perform a few activities and see how physical changes take place around us. Generally, all the physical changes are momentary changes that can easily be reversed to create the original substance. If there is little energy as heat, it is either absorbed or evolved. For example, water can change its state from solid to liquid and liquid to gas.

Crystallisation: As seawater has salts dissolved in it, the sea becomes salty. Salt can be acquired from seawater by a procedure called evaporation. The salt acquired in this way is not pure, and its crystals are tiny. The shape of the crystals can’t be seen clearly. However, giant crystals of pure substances can be acquired from their solutions by the process of crystallisation.

The method of cooling a hot concentrated solution of a substance to acquire crystals is known as crystallisation. It is a primary example of a physical change.

Chemical Changes: The Class 7 Science CH 5 Notes include chemical changes, which are also widely referred to as chemical reactions. A chemical change happens when two substances react chemically to generate a new substance with totally different chemical properties. All these new substances that we utilize in multiple fields of our life are generated due to chemical changes or chemical reactions.

Let’s take a look at an example of chemical changes. A change with which almost everyone is familiar is the rusting of iron. All the iron or steel items kept in the open space or area get rusted slowly. It develops a coating of a brownish substance known as rust, and the procedure is known as rusting. Usually, we see iron gates of farms and parks, iron benches kept in gardens, and almost all the iron items kept in the open space rusted with time. Other things, like agricultural tools, kitchen tools, etc., also get rusted. Rust is not iron; it is a different substance but gets deposited on iron.

Rusting of Iron: When an iron item is left exposed to a moist environment, it chemically reacts with oxygen and water in the air to generate a red-brown flaky substance known as rust. The following equation can represent the procedure of rusting:

Iron (Fe) + Oxygen (O₂) (From air) + Water (H₂O) → Rust (Iron oxide, Fe₂O₃)

Rusting happens due to the presence of both water and oxygen. The more humid the environment, the quicker the rusting happens. The rust slowly eats away or corrodes the iron, resulting in considerable loss. As iron is utilized in building ships, cars, bridges, truck bodies, and various other items, the temporary loss because of the rusting is massive.

Importances of CBSE Class 7 Science Chapter 5 Physical and Chemical Changes Revision Notes

The importance of CBSE Class 7 Science Chapter 5 - "Physical and Chemical Changes Revision Notes" cannot be overstated. These notes play a crucial role in students' academic journey by providing a succinct yet comprehensive recap of the chapter's key concepts. They serve as an invaluable revision tool, helping students consolidate their understanding of physical and chemical changes in matter. Furthermore, these notes are instrumental in exam preparation, allowing students to focus on essential topics and concepts. They promote efficient study habits, time management, and self-assessment, ultimately enhancing the learning process. Overall, these revision notes are an indispensable resource that empowers students to excel in their science studies while fostering a deeper appreciation for the intriguing world of chemistry.

Conclusion

CBSE Class 7 Science Chapter 5 - "Physical and Chemical Changes Revision Notes" are a valuable resource for students embarking on a journey through the intriguing world of chemistry. These notes offer a concise and comprehensive overview of the chapter, elucidating the distinctions between physical and chemical changes. They serve as a vital tool for revision, aiding students in consolidating their understanding of chemical transformations and their practical implications. Moreover, these revision notes foster critical thinking and problem-solving skills, preparing students to excel in examinations and develop a lasting appreciation for the fascinating realm of science.

FAQs on Physical and Chemical Changes Class 7 Science Chapter 5 CBSE Notes - 2025-26

1. What are the main topics I should cover for a quick revision of Chapter 5, Physical and Chemical Changes?

For a quick and effective revision, you should focus on these key concepts:

The definitions and core differences between physical and chemical changes.
Everyday examples of both types of changes.
The process of rusting, including the conditions required for it.
Methods to prevent rusting, like painting and galvanisation.
The concept and process of crystallisation.

2. How can I quickly tell if a change is physical or chemical?

The easiest way is to ask if a new substance is formed. If no new substance is created and the change is usually reversible (like melting ice into water), it's a physical change. If a completely new substance appears, often with signs like a colour change, gas release, or heat, it's a chemical change (like burning paper to ash).

3. What are the key signs that show a chemical change has happened?

When revising, look for these four main indicators of a chemical change:

Production of heat or light (e.g., burning a magnesium ribbon).
Formation of a gas (e.g., adding vinegar to baking soda).
A noticeable change in colour (e.g., an apple slice turning brown).
Formation of a solid precipitate.

4. Why is rusting of iron considered a chemical change and not a physical one?

Rusting is a chemical change because the iron reacts with oxygen and water in the air to form a completely new substance called iron oxide, which we know as rust. The original iron is transformed, and this process is not easily reversible, which is a key characteristic of chemical changes.

5. How does crystallisation work as a method of purification?

Crystallisation is a great example of a physical change used for purification. It involves dissolving a substance in a liquid and then allowing it to cool or evaporate slowly. This process separates a pure solid from a solution in the form of its crystals. For example, large, pure crystals of copper sulphate can be obtained from an impure solution this way.

6. Are all physical changes reversible? Can you explain with an example from the chapter?

While most physical changes are reversible, not all are. For example, melting ice is reversible because you can freeze the water back into ice. However, breaking a glass or tearing a piece of paper is a physical change that is irreversible because you cannot easily put the pieces back together to form the original object.

7. What is the simple chemical reaction for rusting that I should remember from these notes?

A simple way to remember the reaction for rusting is: Iron (Fe) + Oxygen (O₂) + Water (H₂O) → Rust (Iron Oxide, Fe₂O₃). This summary helps you recall that both oxygen and moisture are essential for rust to form.

8. What is galvanisation and how does it relate to the concepts in this chapter?

Galvanisation is a practical application of understanding chemical changes. It is the process of applying a protective layer of zinc onto iron or steel to prevent rusting. This works because zinc is more reactive and corrodes first, sacrificing itself to protect the iron underneath. It's a key method for preventing the unwanted chemical change of rusting.