All questions of Matter for Grade 9 Exam

Understanding States of Matter
Matter exists in different states, primarily solid, liquid, gas, and plasma. Each state has unique characteristics based on the arrangement and movement of its particles.
Characteristics of Gases
- Particle Movement: In gases, particles move freely and rapidly. They do not have a fixed position, allowing them to spread out in any direction.
- Spacing: There is maximum space between gas particles compared to solids and liquids. This spacing allows gases to expand and fill the entire volume of their container.
Comparison with Other States
- Solids: In solids, particles are tightly packed and vibrate in fixed positions. This results in a definite shape and volume.
- Liquids: In liquids, particles are close together but can slide past one another. Liquids have a definite volume but take the shape of their container.
- Plasma: Plasma consists of ionized gases with free-moving charged particles. While particles in plasma can also move freely, they are significantly affected by electric and magnetic fields.
Conclusion
The correct answer is option C: Gas because gases have particles that move freely with a maximum distance between them, allowing for the properties of expansion and compressibility. This unique arrangement makes gases distinct from solids and liquids, which have more structured particle arrangements.

Gas

Understanding the Smell of Food
The rapid detection of food aromas can be attributed to the properties of gases and how they interact with our sensory systems.
High Speed of Gas Particles
- Gases consist of particles that are in constant motion.
- These particles travel at high speeds, allowing them to disperse quickly in the air.
- When food is cooked or heated, volatile compounds are released.
- These compounds are tiny particles that move rapidly, reaching our noses almost instantaneously.
Diffusion of Odors
- The process by which these particles spread out is known as diffusion.
- In the case of gases, diffusion occurs quickly due to the high energy levels of the particles.
- As the food particles collide with air molecules, they disperse throughout the surrounding environment.
Human Sensory Response
- Our olfactory receptors, located in the nasal cavity, are highly sensitive to these odor particles.
- When these particles reach our noses, they bind to the receptors, sending signals to our brain that interpret the smell.
- This system is extremely efficient, enabling us to detect food odors within seconds.
Conclusion
In summary, the reason we can smell food almost instantly is primarily due to the high speed of particles in gases. The rapid motion and diffusion of these tiny particles allow their scent to reach us quickly, stimulating our sense of smell and enhancing our experience of food.

Understanding Latent Heat of Fusion
The latent heat of fusion is a crucial concept in thermodynamics, particularly in understanding phase changes of matter. Here’s a detailed explanation of why option 'B' is correct.
Definition of Latent Heat of Fusion
- The latent heat of fusion refers specifically to the amount of heat energy required to convert a solid into a liquid at its melting point, without changing its temperature.
Phase Change Process
- When a solid absorbs heat, it eventually reaches a temperature where it starts to melt.
- At this melting point, the temperature remains constant as the solid transforms into a liquid.
- The energy added during this process does not increase the temperature but is instead used to break the bonds holding the solid structure together.
Comparison with Other Options
- Option A: Heat Energy for Liquid to Gas
This describes the latent heat of vaporization, which is different from fusion.
- Option C: Heat Energy to Increase Temperature of Solid
This refers to sensible heat, which is not related to phase changes.
- Option D: Heat Energy for Gas to Liquid
This describes the latent heat of condensation, which again is not the same as fusion.
Importance of Latent Heat of Fusion
- Understanding latent heat of fusion is essential in various applications, such as melting ice into water or in refrigeration processes.
- It helps in determining energy requirements in industrial processes and understanding climate phenomena.
In conclusion, the latent heat of fusion is fundamentally about the transition from solid to liquid, making option 'B' the correct answer.

Understanding States of Matter
The states of matter—solid, liquid, and gas—are distinguished by the arrangement and behavior of their particles. Among these, solids are unique in their structural integrity and particle arrangement.
Characteristics of Solids
- Tightly Packed Particles: In solids, particles are closely packed together. This close proximity allows them to exert strong intermolecular forces on each other, which keeps them in fixed positions.
- Fixed Shape and Volume: The arrangement of particles in solids results in a definite shape and volume. Unlike liquids and gases, which can change shape and volume, solids maintain their form unless subjected to external forces.
- Vibration in Place: While particles in solids are not free to move about, they can vibrate in their fixed positions. This vibration contributes to the solid’s thermal properties and resistance to deformation.
Comparison with Other States
- Liquids: In liquids, particles are still close together but can slide past one another, allowing liquids to flow and take the shape of their container while retaining a fixed volume.
- Gases: In gases, particles are far apart and move freely. This arrangement allows gases to expand to fill any container, resulting in neither a fixed shape nor a fixed volume.
Conclusion
In summary, the key feature that defines solids is the tight packing of particles in fixed positions, making option 'A' the correct answer. This characteristic is fundamental to understanding the distinct properties of solids compared to liquids and gases.

Understanding Shape Change Under Force
When evaluating which materials can change their shape under force, it's essential to consider their physical properties and behavior when subjected to stress.
Characteristics of Materials

• Rubber Band:
  - Rubber bands are elastic materials, meaning they can stretch and return to their original shape when the force is removed.
  - This elasticity allows them to deform significantly under tension.
• Piece of Wood:
  - Wood is a rigid material.
  - While it can bend slightly under a significant force, it typically breaks or splinters rather than returning to its original shape.
• Metal Rod:
  - Metal rods are generally strong but also rigid.
  - They can bend under enough force, but like wood, they are likely to remain in that deformed state or fracture if the force exceeds their yield strength.
• Stone:
  - Stone is an extremely rigid material.
  - It does not change shape easily under force and will typically break or shatter instead.

Conclusion
Among the options provided, only the rubber band can change its shape under force and return to its original form once the force is removed. This characteristic is due to its elastic nature, which allows for significant deformation without permanent change. In contrast, the other materials mentioned have rigid structures that resist deformation and do not revert to their original shapes once the force is applied.

State of Matter: Gases
The state of matter in which particles move randomly at high speed is indeed gas. Let's explore this in detail.
Characteristics of Gases
- Random Motion: In gases, particles are in constant motion, moving freely in all directions. This random movement is a key characteristic that distinguishes gases from solids and liquids.
- High Speed: The particles in a gas have high kinetic energy, which means they move at high speeds. This is due to the large amounts of space between them, allowing for greater freedom of movement.
Comparison with Other States of Matter
- Solids: In solids, particles are closely packed and vibrate in fixed positions. This limited movement results in a definite shape and volume.
- Liquids: In liquids, particles are still close together but can slide past one another. This allows liquids to take the shape of their container while maintaining a fixed volume.
Behavior Under Different Conditions
- Compressibility: Gases can be compressed easily because of the significant space between particles. This is unlike solids and liquids, which resist compression due to their tightly packed particles.
- Expansion: Gases expand to fill their containers, regardless of the shape or size, due to the rapid movement of particles.
Conclusion
In summary, the defining feature of gases is the random and high-speed motion of their particles. This behavior leads to unique properties such as compressibility and expansion, setting gases apart from solids and liquids. Understanding these fundamental differences is crucial in the study of matter and its various states.

Understanding the Three States of Matter
Matter is anything that has mass and occupies space. The three classical states of matter are:
Solid
- Solids have a definite shape and volume.
- The particles in solids are closely packed together, creating a rigid structure.
- They vibrate in place but do not move freely, which gives solids their fixed form.
Liquid
- Liquids have a definite volume but take the shape of their container.
- The particles are less tightly packed than in solids, allowing them to slide past each other.
- This fluidity enables liquids to flow and take the shape of their surroundings.
Gas
- Gases have neither a definite shape nor a fixed volume.
- The particles are far apart and move freely, resulting in gases expanding to fill any available space.
- This characteristic makes gases compressible and easily adjustable to changes in temperature and pressure.
Why Option B is Correct
- Option 'b' (Solid, Liquid, Gas) correctly identifies the three fundamental states of matter.
- While other options may include terms like "Plasma" and "Energy," they do not represent the three primary states of matter.
- Plasma, for example, is a state of matter formed at extremely high temperatures, but it is not one of the classical states typically taught at the basic level.
Conclusion
Understanding these three states is crucial for grasping the behavior of matter in different physical conditions. Each state has unique properties that determine how substances interact in our world.

Understanding Diffusion in Water
Diffusion is the process by which particles move from an area of higher concentration to an area of lower concentration. In the context of water, it's important to note which types of substances can diffuse.
1. Solids
- Most solids do not diffuse in water because their particles are tightly packed and do not have the ability to move freely.
- Some solids can dissolve in water (e.g., sugar, salt), but this is not the same as diffusion, as they must first break apart into smaller particles.
2. Liquids
- Liquids can diffuse in water. For example, when you add food coloring to water, the color spreads throughout the liquid.
- This occurs because the molecules in liquids can move past one another, allowing them to mix and spread out.
3. Gases
- Gases can also diffuse in water. When a gas like carbon dioxide is dissolved in water, it disperses throughout the liquid.
- Gases have much larger spaces between their particles, allowing them to move freely and mix with water molecules.
4. Conclusion
- Therefore, the correct answer is option 'D': Liquids and gases can diffuse in water.
- Solids generally do not diffuse in water, while liquids and gases exhibit the ability to spread and mix due to their molecular structures.
Understanding these principles of diffusion helps illustrate how different states of matter interact with water and each other.

Substance Overview
Water is the substance that can exist in all three states of matter: solid, liquid, and gas. Let's explore how this occurs.
1. Solid State (Ice)
- Water freezes at 0°C (32°F) to form ice.
- In this state, water molecules are tightly packed in a crystalline structure, making ice less dense than liquid water.
- Ice can be found in nature in glaciers, snowflakes, and icebergs.
2. Liquid State (Water)
- Water is most commonly found in its liquid form at temperatures between 0°C and 100°C (32°F to 212°F).
- This state is vital for life, serving as a solvent and medium for various biological processes.
- Oceans, rivers, and lakes are examples of liquid water.
3. Gas State (Water Vapor)
- Water evaporates at temperatures above 0°C, turning into water vapor or steam.
- This gaseous state is present in the atmosphere and plays a critical role in weather patterns and the water cycle.
- Water vapor can be invisible, contributing to humidity levels in the air.
Conclusion
Water's unique ability to transition between solid, liquid, and gas is due to its molecular structure and the hydrogen bonds that hold its molecules together. This versatility makes water essential for life and a key substance in various natural phenomena. Other substances like oxygen and nitrogen primarily exist in gaseous states under normal conditions, while sand is a solid. Thus, water is indeed the correct answer as it can be found in all three states of matter.