20 important questions along with their answers for the Class 9 Science chapter "Matter in Our Surroundings":
1. What is matter?
Answer: Matter is anything that has mass and occupies space. It is composed of particles and exists in different states such as solids, liquids, and gases.
2. Define the term 'matter in our surroundings'.
Answer: Matter in our surroundings refers to the physical substance that occupies space and possesses mass. It includes all objects and materials around us, whether natural or man-made.
3. What are the three states of matter? Give one example for each.
Answer: The three states of matter are:
- Solid (e.g., ice)
- Liquid (e.g., water)
- Gas (e.g., oxygen)
4. Explain the characteristics of particles of matter.
Answer: The characteristics of particles of matter include:
- They have space between them.
- They are in constant motion.
- They attract each other.
5. What is the difference between solids, liquids, and gases based on the arrangement of particles?
Answer:
- Solids: Particles are tightly packed in a fixed, orderly arrangement.
- Liquids: Particles are close together but not in a fixed arrangement, allowing them to flow.
- Gases: Particles are far apart and move freely.
6. How does the temperature affect the state of matter?
Answer: Temperature affects the kinetic energy of particles. Increasing temperature can change a solid to a liquid (melting) and a liquid to a gas (evaporation/boiling). Decreasing temperature can change a gas to a liquid (condensation) and a liquid to a solid (freezing).
7. Define melting point and boiling point.
Answer:
- Melting Point: The temperature at which a solid changes to a liquid.
- Boiling Point: The temperature at which a liquid changes to a gas.
8. What is sublimation? Give an example.
Answer: Sublimation is the process by which a solid changes directly into a gas without passing through the liquid state. Example: Dry ice (solid carbon dioxide) sublimates to form carbon dioxide gas.
9. Describe the process of condensation.
Answer: Condensation is the process by which a gas changes into a liquid when cooled. It occurs when gas particles lose energy and come closer together, forming a liquid.
10. What is evaporation? Mention any two factors that affect the rate of evaporation.
Answer: Evaporation is the process by which a liquid changes into a gas at temperatures below its boiling point. Factors affecting the rate of evaporation include:
- Temperature: Higher temperatures increase the rate of evaporation.
- Surface Area: Larger surface areas increase the rate of evaporation.
11. What is meant by the term 'latent heat'?
Answer: Latent heat is the amount of heat energy required to change the state of a substance without changing its temperature. It is used in processes like melting and boiling.
12. Differentiate between evaporation and boiling.
Answer:
- Evaporation: Occurs at any temperature below the boiling point, only at the surface of the liquid.
- Boiling: Occurs at a specific temperature (boiling point), throughout the liquid.
13. How does pressure influence the boiling point of a liquid?
Answer: Increased pressure raises the boiling point of a liquid because it requires more energy for the particles to escape into the gas phase. Decreased pressure lowers the boiling point.
14. What is the Kelvin scale of temperature? How is it related to the Celsius scale?
Answer: The Kelvin scale is an absolute temperature scale starting from absolute zero. The relation between Celsius and Kelvin scales is: K = °C + 273.
15. Explain the process of freezing with an example.
Answer: Freezing is the process by which a liquid changes into a solid when cooled. Example: Water freezes to form ice at 0°C (32°F).
16. What is the significance of the melting point in identifying a substance?
Answer: The melting point is a characteristic property of a substance and can be used to identify and determine its purity. Pure substances have a sharp melting point, while impurities lower and broaden the melting point range.
17. Why does ice float on water?
Answer: Ice floats on water because it is less dense than liquid water. The molecular structure of ice creates a lattice that occupies more space, making it less dense.
18. Define the term 'diffusion' and give an example.
Answer: Diffusion is the process by which particles of a substance move from an area of higher concentration to an area of lower concentration. Example: The fragrance of perfume spreading in a room.
19. What is the role of diffusion in the functioning of living organisms?
Answer: Diffusion plays a crucial role in the transport of substances in and out of cells, such as the exchange of oxygen and carbon dioxide in respiration and the absorption of nutrients in digestion.
20. Explain why gases are more compressible than solids and liquids.
Answer: Gases are more compressible because the particles are far apart and have more space to be compressed. In solids and liquids, the particles are closely packed, leaving little room for compression.
These questions and answers cover key concepts from the chapter "Matter in Our Surroundings" and can help students prepare effectively for their exams.
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