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Chapter 1| Matter in our surrounding| Class 9 Science NCERT Video Lecture

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FAQs on Chapter 1- Matter in our surrounding- Class 9 Science NCERT Video Lecture

1. What is matter and why is it important?
Ans. Matter refers to anything that occupies space and has mass. It can exist in various forms such as solid, liquid, and gas. Matter is important because it forms the basis of everything around us, including living organisms. It plays a crucial role in the functioning of the natural world and is essential for chemical reactions, energy transfer, and the existence of life itself.
2. What are the different states of matter?
Ans. The three states of matter are solid, liquid, and gas. - Solids have a definite shape and volume. The particles in solids are closely packed and have strong intermolecular forces. - Liquids have a definite volume but take the shape of the container. The particles in liquids are loosely packed and have weaker intermolecular forces compared to solids. - Gases have neither a definite shape nor volume. The particles in gases are widely spaced and have very weak intermolecular forces.
3. What are the characteristics of solids, liquids, and gases?
Ans. - Solids: Solids have a fixed shape and volume. They are not compressible and have a high density. The particles in solids vibrate about fixed positions and have a strong intermolecular force. - Liquids: Liquids have a definite volume but take the shape of the container. They are not compressible and have a lower density compared to solids. The particles in liquids are free to move, but they are still close together and have weaker intermolecular forces. - Gases: Gases have neither a definite shape nor volume. They are highly compressible and have a low density. The particles in gases are far apart and move randomly with high speed. They have very weak intermolecular forces.
4. What is the difference between physical and chemical changes in matter?
Ans. Physical changes in matter are changes that do not alter the chemical composition of a substance. These changes can be reversible, such as changes in state (solid to liquid to gas) or irreversible, such as breaking a glass. In physical changes, the substance retains its chemical identity. Chemical changes, on the other hand, result in the formation of new substances with different chemical properties. These changes are usually irreversible. Examples of chemical changes include burning of wood, rusting of iron, and digestion of food. In chemical changes, the substance undergoes a chemical reaction and its chemical composition is altered.
5. What is the significance of the particle theory of matter?
Ans. The particle theory of matter helps us understand the behavior and properties of matter. According to this theory, all matter is composed of tiny particles called atoms or molecules. It explains how these particles are in constant motion, have space between them, and interact with each other. The particle theory of matter helps in explaining phenomena like diffusion, evaporation, and condensation. It also helps us understand the different states of matter and how they can change from one state to another. Additionally, this theory forms the basis of many scientific principles and laws, making it essential in our understanding of the physical world.
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