NCERT Solutions and Key Concepts for Class 9 Science Chapter 1 (Pages 1-3)
Understanding the Basics of Matter 🧐
This section covers the solutions to the in-text questions on page 3 of Chapter 1, “Matter in Our Surroundings”. We’ll then dive into the key concepts, interesting questions, and essential points from the first three pages of the chapter to build a strong foundation.
NCERT In-text Questions & Answers (Page 3)
1. [cite_start]Which of the following are matter? [cite: 129]
[cite_start]Chair, air, love, smell, hate, almonds, thought, cold, lemon water, smell of perfume. [cite: 130]
To identify matter, we check if something has mass and occupies space. [cite: 7, 8]
Items that ARE Matter:
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[cite_start]
- Chair, Air, Almonds, Lemon water: All these items have mass and take up space, so they are matter. [cite: 6]
Items that are NOT Matter:
- Love, Hate, Thought: These are feelings, emotions, or ideas. They do not have mass or volume.
- Cold: This is a sensation related to the absence of heat; it is not matter.
- Smell, Smell of perfume: The sensation of smell is not matter. However, this sensation is caused by tiny gaseous particles that travel from the source (like perfume) to our nose. These tiny particles *are* matter, but the sensation itself is not.
2. [cite_start]Give reasons: The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close. [cite: 131, 132, 133]
This happens because particles of matter are in constant motion and this motion increases with temperature. [cite: 96, 97]
[cite_start]The particles of aroma from hot food have high kinetic energy. [cite: 97] [cite_start]They move very fast, mix with air, and travel (diffuse) quickly over long distances. [cite: 100, 101] Particles from cold food have low kinetic energy, move slowly, and do not travel far. This is why you must be close to smell it.
3. A diver is able to cut through water in a swimming pool. [cite_start]Which property of matter does this observation show? [cite: 133, 134]
This shows two key properties of matter:
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[cite_start]
- Particles of matter have spaces between them. [cite: 74, 77] The diver can move into these empty spaces. [cite_start]
- Particles of matter attract each other, but this force can be overcome. [cite: 102, 126] [cite_start]In liquids like water, the force of attraction between particles is strong enough to keep them together but weak enough for a diver to break through them. [cite: 127]
4. [cite_start]What are the characteristics of the particles of matter? [cite: 135]
The particles of matter have three main characteristics: [cite: 73]
- [cite_start]They have space between them (intermolecular space). [cite: 74] [cite_start]This is proven by how substances like salt can dissolve in water without raising its level. [cite: 35]
- [cite_start]They are continuously moving. [cite: 52, 96] [cite_start]This constant motion gives them kinetic energy and is responsible for processes like diffusion. [cite: 96, 100]
- [cite_start]They attract each other (intermolecular force). [cite: 102] [cite_start]This force keeps the particles together, and its strength varies in solids, liquids, and gases. [cite: 127]
Key Concepts from Chapter 1 (Pages 1-3) 🧪
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[cite_start]
- Definition of Matter: Everything in the universe is made of material called “matter”. [cite: 5] [cite_start]It is anything that occupies space and has mass. [cite: 7] [cite_start]
- Particulate Nature of Matter: Matter is not continuous but is made up of very small particles. [cite: 17, 19] [cite_start]
- Particles are Unimaginably Small: Experiments show that just a few crystals of potassium permanganate contain millions of tiny particles that can color a large volume of water. [cite: 68, 69] [cite_start]These particles are small beyond our imagination. [cite: 72] [cite_start]
- Kinetic Energy and Temperature: Particles are always moving because they possess kinetic energy. [cite: 96] [cite_start]As temperature rises, particles move faster, and their kinetic energy increases. [cite: 97] [cite_start]
- Diffusion: The intermixing of particles of different types of matter on their own is called diffusion. [cite: 100] [cite_start]Heating makes diffusion faster. [cite: 101]
Mind-Boggling Questions 🤔
- If particles are always moving, why does a solid table look perfectly still? [cite_start]
- When salt dissolves in water without raising the water level, where do the salt particles actually go? [cite: 26, 27, 28] [cite_start]
- How can just one or two tiny crystals of a substance colour thousands of litres of water? [cite: 68]
Points to Remember ✅
The entire behavior of matter is explained by three simple rules about its particles:
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[cite_start]
- There are spaces between them. [cite: 77] [cite_start]
- They are always moving. [cite: 96] [cite_start]
- They attract each other. [cite: 102]
Further Reading
To dive deeper into the properties of matter, you can refer to the official NCERT Class 9 Science textbook available on their website: https://ncert.nic.in/.
