Matter in Our Surroundings Class 9 Extra Questions and Answers Free PDF Download
FAQs on CBSE Important Questions for Class 9 Science Matter in Our Surroundings - 2025-26
1. What are some frequently asked 1-mark and 2-mark questions from Chapter 1, Matter in Our Surroundings, for the 2025-26 CBSE exam?
Based on previous year trends, some expected short-answer questions for the CBSE Class 9 Science exam include:
- Defining key terms like diffusion, sublimation, and latent heat.
- Giving reasons for observations like why we can smell hot food from a distance.
- Converting temperatures between Celsius and Kelvin scales.
- Explaining why evaporation causes a cooling effect.
These questions test fundamental concepts and definitions from the chapter.
2. How are the five states of matter distinguished in the Class 9 syllabus? Briefly explain the two newly discovered states.
The five states of matter are Solid, Liquid, Gas, Plasma, and Bose-Einstein Condensate (BEC). The primary three are distinguished by the arrangement and energy of their particles. The other two states are:
- Plasma: This is the fourth state of matter, consisting of super-energetic and super-excited particles in the form of ionised gas. It has no definite shape or volume. Stars and fluorescent tubes contain plasma.
- Bose-Einstein Condensate (BEC): The fifth state is formed by cooling a gas of extremely low density to super-low temperatures. This causes the particles to lose their individual identity and behave as a single quantum entity.
3. For a 3-mark question, how would you demonstrate that the particles of matter have space between them using a simple experiment?
To demonstrate that particles of matter have spaces, we can perform the following activity:
- Take a 100 ml beaker and fill it half with water, marking the initial level.
- Add one or two spoons of salt or sugar to the water.
- Stir the solution with a glass rod until the salt or sugar dissolves completely.
- Observe the final water level.
The water level does not rise. This is a crucial observation because the particles of salt/sugar get into the intermolecular spaces between the particles of water. This is an important experiment to prove a key characteristic of matter.
4. Why does a desert cooler provide more effective cooling on a hot, dry day compared to a hot, humid day? Explain the scientific principle.
This is a classic higher-order thinking question. The cooling in a desert cooler is caused by the evaporation of water. The rate of evaporation depends on the amount of water vapour (humidity) present in the air.
- On a hot, dry day, the humidity is low. This allows water to evaporate at a much faster rate, absorbing a large amount of heat from the surroundings and thus providing significant cooling.
- On a hot, humid day, the air is already saturated with water vapour. This slows down the rate of evaporation, leading to less heat absorption and reduced cooling effectiveness.
5. What are the two conditions that can be applied to liquefy atmospheric gases? Explain the reasoning behind this important process.
Liquefying atmospheric gases is an important industrial application of the principles in this chapter. The two conditions required are:
- Increasing Pressure: Applying high pressure forces the gas particles to come closer together, reducing the intermolecular spaces between them.
- Decreasing Temperature: Lowering the temperature reduces the kinetic energy of the particles, causing them to slow down.
When both these conditions are applied together, the intermolecular forces of attraction become strong enough to overcome the kinetic energy of the particles, causing the gas to change into a liquid state.
6. Differentiate between boiling and evaporation, a frequently asked question in exams.
Boiling and evaporation both involve the conversion of a liquid to a gas, but they are different processes:
- Phenomenon: Evaporation is a surface phenomenon, occurring only at the surface of the liquid. Boiling is a bulk phenomenon, where bubbles form throughout the volume of the liquid.
- Temperature: Evaporation can occur at any temperature below the boiling point. Boiling occurs only at a specific temperature, known as the boiling point.
- Energy Source: Evaporation draws energy from the immediate surroundings, causing cooling. Boiling requires a direct external heat source.
7. When ice at 273 K (0°C) is heated, its temperature does not rise until all the ice has melted. What is this 'hidden' heat called and where does it go?
This is a critical concept for understanding phase changes. The 'hidden' heat is called the Latent Heat of Fusion. Even though heat is continuously supplied, the temperature of the ice-water mixture remains at 273 K because this energy is used to overcome the forces of attraction between the particles of ice. The heat energy is absorbed by the ice particles to change from a fixed, solid state to a mobile, liquid state, rather than increasing their kinetic energy, which would have raised the temperature.
8. Why are we able to sip hot tea faster from a saucer than from a cup? Explain with a concept from this chapter.
This observation is directly related to the factors affecting evaporation. The rate of evaporation increases with an increase in surface area.
- A saucer has a much larger surface area than a cup.
- This increased surface area exposes more of the hot tea to the air, causing it to evaporate faster.
- Since evaporation causes cooling, the tea in the saucer cools down much more quickly, making it easier to sip.
This is an important application-based question that tests a student's understanding of evaporation.
9. What is the expected marks weightage for the unit 'Matter - Its Nature and Behaviour' in the CBSE Class 9 Science exam for 2025-26?
As per the CBSE curriculum for the 2025-26 session, the unit 'Matter - Its Nature and Behaviour,' which includes Chapter 1 (Matter in Our Surroundings), holds significant weightage. This unit is allocated 27 marks out of the total 80 marks for the theory paper. Therefore, preparing the important questions from this chapter is crucial for scoring well.
10. Define the latent heat of vaporization. Why do steam burns feel more severe than burns from boiling water at the same temperature (373 K)?
The Latent Heat of Vaporization is the amount of heat energy required to change 1 kg of a liquid into its gaseous state at its boiling point without any change in temperature. For water, this value is very high. Steam burns are more severe because particles in steam (water vapour) at 373 K have absorbed extra energy in the form of the latent heat of vaporization. When steam condenses on the skin, it releases this massive amount of hidden heat before it even begins to cool down as water, causing a more severe burn than boiling water at the same temperature.











