Particulate Nature of Matter Class 8 Curiosity Worksheet

Q1. In solids, the movement of particles is:
a) Very fast b) Freely in all directions
c) Rotational d) Vibrational at fixed positions

Answer: (d) Vibrational at fixed positions
Explanation: In solids, particles are tightly packed and cannot move freely. They only vibrate around their fixed positions due to strong forces of attraction between them.

Q2. What happens to the interparticle spacing in a gas when pressure is applied?
a) Decreases b) Turns into a liquid
c) Increases d) Stays the same

Answer: (a) Decreases
Explanation: Applying pressure decreases interparticle spacing in gases by pushing particles closer together.

Q3. Why do sugar particles seem to disappear in water?
a) They become invisible due to dilution b) They chemically transform into another substance
c) They dissolve and occupy interparticle d) They become microscopic elements spaces

Answer: (c) They dissolve and occupy interparticle spaces
Explanation: Once dissolved, sugar particles spread into spaces between water particles, no longer visible.

Q4. How can particles in solids gain enough energy to become liquid?
a) Compressing the solid tightly b) Increasing thermal energy to overcome attraction
c) By applying cold water d) Shaking the particles vigorously

Answer: (b) Increasing thermal energy to overcome attraction
Explanation: Thermal energy helps particles overcome attractive forces to move into liquid state.

Q5. Which of the following is NOT a state of matter?
a) Vapour b) Liquid
c) Gas d) Solid

Answer: (a) Vapour
Explanation: The three main states of matter are solid, liquid, and gas. Vapour is not a separate state; it is the gaseous form of a substance (usually a liquid or solid) when it changes into gas.

Q6. Vibration happens between molecules of which state of matter:
a) Semi-solid b) Liquid
c) Gas d) Solid

Answer: (d) Solid
Explanation: In solids, particles are tightly packed and have fixed positions. They cannot move freely but only vibrate in place due to strong intermolecular forces. Therefore, vibration happens between molecules of solids.

Q7. How do gases differ from solids based on interparticle attractions?
a) Gases have very strong interparticle attractions compared to solids
b) Gases have negligible interparticle attractions compared to solids, allowing particles to move freely
c) Gases have equivalent interparticle attractions like solids
d) Gases have some interparticle attractions, slightly below that of solids

Answer: (b) Gases have negligible interparticle attractions compared to solids, allowing particles to move freely
Explanation: The negligible interparticle attractions in gases allow free movement, unlike solids where attractions are strong.

Q8. What happens when the interparticle distance increases?
a) The attraction between particles b) The attraction between particles increases decreases
c) The physical state changes d) New particles are formed automatically

Answer: (b) The attraction between particles decreases
Explanation: When the interparticle distance increases, the attraction between particles decreases drastically.

Q9. How does sugar behave when dissolved in water?
a) Changes its appearance but not its b) Remains visible but changes its state taste
c) Settles at the bottom of the glass d) Breaks into constituent particles

Answer: (d) Breaks into constituent particles
Explanation: Sugar breaks into its constituent particles when dissolved, becoming intermingled with water particles.

Q10. Which of these is NOT a form of matter?
a) Gas b) Energy
c) Liquid d) Solid

Answer: (b) Energy
Explanation: Matter exists in three main states: solid, liquid, and gas. These are physical forms of matter. Energy is not a form of matter because it does not have mass or occupy space.

Q11. What are the characteristics of liquids based on container shapes?
a) Liquids change shape to fit the container they are in but have a fixed volume
b) Liquids solidify immediately when poured into a container
c) Liquids neither have a fixed shape nor a fixed volume
d) Liquids maintain a fixed shape, regardless of the container

Answer: (a) Liquids change shape to fit the container they are in but have a fixed volume
Explanation: Liquids do not have a fixed shape but take the shape of their container while maintaining a fixed volume.

Q12. Which of these has the least interparticle space?
a) Air b) Wood
c) Steam d) Water

Answer: (b) Wood
Explanation: Wood is a solid, and in solids the particles are very closely packed with minimum space between them. Therefore, wood has the least interparticle space compared to liquids and gases.

Q13. When the same volume of liquid is poured into containers of different shapes, which parameter changes?
a) Structure b) Volume
c) Shape d) Size

Answer: (c) Shape
Explanation: Liquids do not have a fixed shape but have a fixed volume. When the same liquid is poured into containers of different shapes, it takes the shape of each container. So, only the shape changes, not the volume.

Q14. Which force is responsible for holding the particles of matter together?
a) Electrostatic force b) Interparticle attractions
c) Gravitational force d) Magnetic force

Answer: (b) Interparticle attractions
Explanation: Interparticle attractions are the forces that hold particles of matter together.

Q15. Why gases and liquids are both classified as fluids.
a) Because they cannot be seen easily b) They occupy any container
c) Both have fixed shapes d) Both can flow and do not have a fixed shape

Answer: (d) Both can flow and do not have a fixed shape
Explanation: Both gases and liquids lack a fixed shape and can flow, classifying them as fluids.

Q16. The arrangement of particles in solids is:
a) Loose and irregular b) Random and moving freely
c) Widely spaced d) Tightly packed and fixed

Answer: (d) Tightly packed and fixed
Explanation: In solids, particles are very closely packed in a fixed and orderly arrangement. They cannot move freely and only vibrate in their fixed positions, which makes solids rigid.

Q17. Why does a solid state have low thermal energy compared to liquids?
a) It allows for easy evaporation b) Due to strong interparticle attractions and limited movement
c) Solid particles spread easily with heat d) Because particles are hot and expand

Answer: (b) Due to strong interparticle attractions and limited movement
Explanation: Low thermal energy limits particle movement, causing them to stay close together.

Q18. Which of the following is true about matter?
a) All of these b) It occupies space
c) It has mass d) It is made up of particles

Answer: (a) All of these
Explanation: Matter has mass and occupies space. It is also made up of tiny particles such as atoms and molecules.
Therefore, all the given statements are correct.

Q19. How does temperature affect the movement of particles in water?
a) The movement stops completely at b) Temperature has no effect room temperature
c) Particles move faster in hot water and d) It slows down in hot water slow in cold

Answer: (c) Particles move faster in hot water and slow in cold
Explanation: Higher temperature increases particle movement speed.

Q20. What are constituent particles?
a) Materials that are always visible b) Changes caused by physical forces
c) Chemical changes within matter d) Smallest units of a substance

Answer: (d) Smallest units of a substance
Explanation: Constituent particles are the basic units that make up a substance, such as chalk or sand.

Q21. Assertion (A): Particles in a solid vibrate but do not move from their positions.
Reason (R): The interparticle forces in solids are weak.
a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Answer: (c) A is true but R is false.
Explanation: In solids, forces are strong, restricting movement.

Q22. Assertion (A): Fragrance from an incense stick spreads throughout a room because air particles are stationary.
Reason (R): Air particles are constantly moving and help distribute the fragrance particles.
a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Answer: (d) A is false but R is true.
Explanation: The movement of air particles assists in spreading the fragrance.

Q23. Assertion (A): Sugar dissolves in water because its particles break up into constituent particles.
Reason (R): The constituent particles of sugar are small enough to occupy interparticle spaces in water.
a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: The explanation clarifies that sugar particles dissolve by occupying spaces.

Q24. Assertion (A): Gases occupy the entire space of their container.
Reason (R): The interparticle attractions in gases are negligible.
a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: Negligible interparticle attractions allow gas particles to move freely and fill available space.

Q25. Assertion (A): Interparticle spaces are present between particles of matter.
Reason (R): Matter is composed of tiny particles that fill the available spaces when mixed.
a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A.
c) A is true but R is false. d) A is false but R is true.

Answer: (a) Both A and R are true and R is the correct explanation of A.
Explanation: The passage explains the concept of interparticle spaces in terms of particle composition.

Q26. Why are solids considered to have minimal interparticle spacing?

Answer: Solids have minimal interparticle spacing because their particles are tightly packed due to strong forces of attraction between them.

Q27. What happens to gas particles when external pressure is applied?

Answer: Gas particles come closer together when external pressure is applied due to the reduction in interparticle spacing.

Q28. What is meant by erosion and how does it contribute to the formation of pebbles and sand?

Answer: Erosion involves rock breakdown, carried by rivers to form pebbles and sand when transported to plains.

Q29. Discuss the importance of interparticle attractions in gases.

Answer: In gases, negligible interparticle attractions allow for unrestricted movement, resulting in no fixed shape or volume.

Q30. Why do sand particles not dissolve in water?

Answer: Sand particles do not dissolve because their interparticle attraction is stronger than the force required to separate them into water's existing spaces.

Q31. What is the role of interparticle distance in determining states of matter?

Answer: Interparticle distance influences the strength of interparticle forces, determining whether a substance is solid, liquid, or gas.

Q32. Why do solids have a fixed shape and volume?

Answer: In solids, strong interparticle attractions tightly pack particles, restricting movement, thus maintaining a fixed shape and volume.

Q33. Explain why rivers transport eroded rock pieces to plains, forming sand and clay.

Answer: Rivers carry eroded rock fragments, depositing them in plains where further weathering transforms them into sand and clay.

Q34. What happens when incense sticks are burned in a room?

Answer: The fragrance from incense sticks spreads throughout the room.

Q35. What role do air particles play in spreading fragrance?

Answer: Air particles hit fragrance particles, promoting their spread throughout the room.

Q36. Apply the concept of particle movement to explain why gases fill their containers uniformly.

Answer: Gases consist of particles with high thermal energy, allowing them to move rapidly and freely. This rapid motion and frequent collisions enable gases to spread uniformly, occupying the entirety of the container, regardless of its shape or size.

Q37. Describe why grinding chalk is considered a physical change rather than a chemical change.

Answer: Grinding chalk is a physical change because it only alters the size and shape of the chalk particles, without changing its chemical composition. The substance remains chalk, only divided into smaller pieces, demonstrating a change in form but not in chemical identity.

Q38. Explain the result of grinding a chalk into a fine powder. Does it change its chemical composition?

Answer: When chalk is ground into a fine powder, its chemical composition does not change. The grinding is a physical change, where the chalk simply breaks down into smaller particles without altering its chemical properties. Each tiny grain remains composed of the same substance as the original piece of chalk.

Q39. What observable changes indicate the process of diffusion in liquids and gases?

Answer: Diffusion in liquids is observed when a solute like potassium permanganate evenly spreads in water. In gases, diffusion is detectable when a scent from an incense stick permeates a space, showcasing particle distribution due to constant motion.

Q40. Explain why potassium permanganate is used to demonstrate the movement of particles in a liquid.

Answer: Potassium permanganate is used because its visible pink color helps demonstrate how particles spread in a liquid by diffusion, illustrating the constant motion of water particles pulling and dispersing potassium permanganate particles throughout the liquid.

Q41. Describe a key difference in interparticle spacing in solids, liquids, and gases.

Answer: Solids have minimal interparticle spacing, making them rigid; liquids have moderate spacing, allowing particles to flow; gases have maximum spacing, making them highly compressible and free- moving.

Q42. Discuss why solids have a definite shape and volume.

Answer: Solids have a definite shape and volume because their particles are tightly packed with very little interparticle space and possess strong forces of attraction that hold them in fixed positions. The particles can only vibrate about their mean positions but cannot move freely, which prevents any change in shape or volume. This rigid arrangement explains why solids are generally incompressible and maintain a stable, definite structure under normal conditions.

Q43. A rubber band changes its shape when stretched. Can it be regarded as solid?

Answer: Rubber is a solid. It has elastic property due to which it undergoes change in shape when pressure is applied and regains its original shape when pressure is released.

Q44. Explain why gases fill their container completely.

Answer: Gases fill their container completely because their particles move freely in all directions, with negligible interparticle attractions, allowing them to occupy the entire space. In addition, gas particles have high kinetic energy, which makes them spread out continuously and uniformly. As a result, gases have no fixed shape or volume and always expand to take the shape and volume of the container.

Q45. What are the observable behaviors of gases in terms of particle spacing?

Answer: Gases have wide interparticle spacing, which permits high flexibility and free expansion in all directions. When compressed, their particles are forced closer together, but they naturally move apart once the pressure is released due to negligible interparticle attractions. This large spacing allows gases to fill any available volume, adapt to the shape of the container, and be highly compressible. Additionally, the spacing makes gases less dense compared to solids and liquids, explaining why they can diffuse and mix rapidly.

Q46. Gases can be compressed, but solids cannot. Explain.

Answer: In gases, the interparticle spaces are very large, so when pressure is applied, these spaces can decrease significantly and the molecules of gas come much closer together. This makes gases highly compressible. In contrast, solids have particles that are very tightly packed with almost no interparticle space. Because of this compact arrangement, there is no scope for particles to move closer, and hence solids cannot be compressed under ordinary conditions.

Q47. Define interparticle spacing and explain its significance in solids.

Answer: Interparticle spacing refers to the distance between the particles within a substance. In solids, the particles are tightly packed, resulting in minimal interparticle spacing, which imparts rigidity, definite shape, and incompressibility. This close arrangement also gives solids a higher density compared to liquids and gases. The very small spacing limits particle movement to mere vibrations in fixed positions, which explains why solids maintain a definite structure and are generally hard to compress.

Q48. What is the role of interparticle spacing in determining the properties of gases?

Answer: Interparticle spacing plays a crucial role in defining the properties of gases. In gases, the particles are very far apart compared to solids and liquids, leaving large spaces between them. This wide spacing makes gases highly compressible, as pressure can push the particles closer together, reducing their overall volume. When the applied pressure is removed, the particles move apart again and the gas returns to its original volume. The large interparticle spacing also allows gas particles to move freely in all directions, enabling them to expand to fill the entire container, flow easily, and mix uniformly with other gases. This explains why gases have no fixed shape or volume and can spread rapidly.

Q49. How does the interparticle spacing influence the properties of liquids?

Answer: Interparticle spacing in liquids is relatively smaller than in gases but larger than in solids. This spacing grants liquids the property of fluidity, enabling them to adapt their shape according to the container but maintaining a definite volume. The intermolecular forces are stronger than in gases but weaker than in solids, providing some degree of compressibility, but they are less compressible than gases.

Q50. What is the role of interparticle spaces when sugar dissolves in water? Provide a detailed explanation.

Answer: Interparticle spaces are the tiny gaps present between the particles of a substance. When sugar is added to water, the sugar particles break apart and spread out into these interparticle spaces between the water molecules. This process leads to homogeneous mixing, where the sugar is evenly distributed throughout the water, making the solution uniformly sweet. The sugar is no longer visible because its particles are too small to be seen, yet they retain their properties. This demonstrates that the presence of interparticle spaces allows one substance to dissolve into another, highlighting an important characteristic of matter.

Q51. Read the following text carefully and answer the questions that follow: The spacing between particles determines the properties of solids, liquids, and gases. Solid particles are closely packed with very little space, making solids rigid and nearly incompressible. Liquid particles are less tightly packed, allowing them to flow and partially fill spaces. Gas particles have large spaces between them, making gases highly compressible and able to expand. Interparticle spacing explains why matter behaves differently in each state.
Questions:
a. Which state of matter has the largest interparticle spacing? (1)
b. Explain how interparticle spacing affects the compressibility of solids, liquids, and gases. (1)
c. Why does the volume of water decrease slightly when sugar dissolves in it? (2) OR Compare the interparticle spacing in solids, liquids, and gases and explain how it influences their shape and volume. (2)

Answer: a. Gas has the largest interparticle spacing among the states of matter. The particles in gases are far apart, which allows them to expand and be highly compressible.
b. Solids have very little interparticle space, so they are nearly incompressible. Liquids have more space, making them slightly compressible, while gases have large interparticle spaces, making them highly compressible and able to expand or contract easily under pressure.
c. When sugar dissolves in water, its constituent particles occupy the tiny spaces between water molecules. This efficient packing reduces the total volume of the solution slightly compared to the sum of the separate volumes of water and sugar. It demonstrates that liquids have interparticle spaces that allow other particles to fit in. OR In solids, particles are closely packed, giving a fixed shape and volume. In liquids, particles are less tightly packed, allowing them to flow and take the shape of their container while maintaining volume. In gases, particles are far apart, causing them to expand, occupy available space, and have neither fixed shape nor fixed volume.

Q52. Read the following text carefully and answer the questions that follow: Matter is composed of extremely small particles called constituent particles, which are the basic units of any substance. Large pieces, like chalk or rocks, are made up of numerous such particles. Even when sugar dissolves in water, it breaks into its constituent particles, which occupy spaces between water molecules. These particles are so tiny that they cannot be seen through an ordinary microscope, yet they form the building blocks of all matter.
Questions:
a. What are the basic units that make up a substance called? (1)
b. Explain why grains of sand or sugar are not considered the smallest units of matter. (1)
c. How does the dissolution of sugar in water demonstrate the existence of constituent particles? (2) OR Why is it important to understand that matter is made of tiny particles when studying physical changes? (2)

Answer: a. The basic units that make up a substance are called constituent particles. These tiny particles form the fundamental building blocks of all matter and retain the properties of the substance they compose.
b. Grains of sand or sugar can be broken down further into extremely small constituent particles. These particles cannot be divided further and form the true basic units of the substance, making grains themselves not the smallest unit.
c. When sugar dissolves in water, the sugar particles separate into extremely small constituent particles that mix uniformly with water molecules. These particles occupy spaces between water molecules, cannot be seen, and retain the sugar’s properties. This shows that matter is composed of basic, indivisible particles. OR Understanding that matter consists of tiny constituent particles helps explain physical changes like grinding chalk or dissolving sugar. These changes alter the arrangement or size of particles without forming a new substance, allowing us to distinguish between physical and chemical changes and understand matter’s fundamental structure.

Q53. Read the following text carefully and answer the questions that follow: Matter is made of extremely small particles called constituent particles. Large objects like rocks, sand grains, and sugar consist of countless tiny particles. These particles retain the properties of the substance and cannot be broken down further by physical means. When sugar dissolves in water, its particles spread out and occupy spaces between water molecules. Interparticle spaces explain why substances mix and why matter has volume but is composed of discrete particles.
Questions:
a. What are the smallest units of a substance that retain its properties called? (1)
b. Explain why sugar can dissolve in water but sand cannot, based on constituent particles and interparticle spaces. (1)
c. How do constituent particles support the idea that matter is composed of extremely small units? (2) OR Describe the role of interparticle spaces in the mixing of substances and in determining their physical state. (2)

Answer: i. The smallest units of a substance that retain its properties are called constituent particles. They form the fundamental building blocks of matter and preserve the characteristics of the substance they belong to.
ii. Sugar particles are small enough to fit into the spaces between water molecules, forming a solution. Sand particles are too large and do not mix with water, so they settle at the bottom instead of dissolving.
iii. Observations from grinding chalk or dissolving sugar show that matter can be broken into very small units called constituent particles. Each particle retains the substance’s properties and cannot be divided further physically. This supports the concept that all matter is composed of countless tiny, indivisible building blocks. OR Interparticle spaces allow particles of one substance to occupy gaps between particles of another, as seen when sugar dissolves in water. The size of these spaces also influences physical states: solids have minimal spaces, liquids have moderate spaces, and gases have large spaces, explaining compressibility, flow, and the ability of substances to mix.

Q54. Read the following text carefully and answer the questions that follow: The physical state of matter-solid, liquid, or gas-is determined by the strength of interparticle attractions. Solids have tightly packed particles with strong forces, giving them fixed shape and volume. Liquids have weaker attractions, allowing particles to move freely while retaining volume but no fixed shape. Gases have negligible interparticle forces, so particles move freely, occupying all available space. Temperature changes can alter particle motion, causing melting, boiling, or evaporation.
Questions:
a. Why do gases not have a fixed shape or volume? (1)
b. How do interparticle forces determine the state of matter? (1)
c. Compare the particle arrangement and movement in solids, liquids, and gases. (2) OR Explain how temperature affects the change of states of matter. (2)

Answer: a. Gases do not have a fixed shape or volume because their particles move freely with negligible attraction. The weak or negligible interparticle forces allow the particles to spread out and occupy all available space.
b. The strength of interparticle forces determines whether matter is solid, liquid, or gas. Strong forces keep particles fixed in solids, moderate forces allow movement in liquids, and negligible forces let particles in gases move freely in all directions.
c. In solids, particles are closely packed and vibrate in place, giving a definite shape and volume. In liquids, particles are close but can move past each other, so liquids have definite volume but no fixed shape. In gases, particles move freely and spread out to occupy the entire space, so gases have neither fixed shape nor fixed volume. OR Temperature increases particle motion. In solids, heating makes particles vibrate vigorously, weakening interparticle forces and causing melting. In liquids, further heating allows particles to escape as vapour at the boiling point. Evaporation occurs at all temperatures, though slower, demonstrating that particle motion and energy directly influence the transition between solid, liquid, and gaseous states.

Q55. Read the following text carefully and answer the questions that follow: Particles in matter are in constant motion, and their movement depends on thermal energy. In solids, particles vibrate in place due to low thermal energy and strong interparticle forces. In liquids, particles move around within limited space as energy increases. In gases, particles have high energy and move freely in all directions, overcoming attractive forces. Thermal energy governs particle motion, spreading substances in liquids and gases, and influencing changes between states.
Questions:
a. Why do particles in gases move more freely than in solids? (1)
b. How does thermal energy affect particle motion in different states of matter? (1)
c. Compare particle movement and interparticle forces in solids, liquids, and gases. (2) OR
d. Explain how particle motion is responsible for spreading substances in liquids and gases. (2)

Answer: a. Particles in gases move more freely than in solids because they have high thermal energy and negligible attraction. This allows gas particles to overcome interparticle forces and move in all directions.
b. Thermal energy determines particle motion. In solids, low energy limits movement to vibrations. In liquids, increased energy allows particles to move within limited space. In gases, high energy enables free movement in all directions, overcoming interparticle attraction.
c. In solids, particles vibrate in fixed positions due to strong interparticle forces. In liquids, particles move around freely but stay close, as forces are weaker. In gases, particles have negligible attraction and move freely in all directions. The thermal energy of particles governs their speed and ability to overcome these forces in each state. OR Particle motion allows substances to spread. In liquids, moving particles collide with solute particles, distributing them uniformly, as seen in diffusion. In gases, constantly moving particles collide and disperse substances throughout the container. Higher thermal energy increases the speed of particle movement, causing faster mixing or spreading in both liquids and gases.

Q56. State whether the given statement is True or False:
(a) In solids, particles vibrate but remain in their fixed position.
(b) Solids have closely packed particles with very little space between them.
(c) Liquids have a definite volume but no fixed shape.
(d) Solid particles are completely free to move past each other.
(e) Grinding chalk changes it into a new substance.

Answer: State whether the given statement is True or False:
(a) (a) True
Explanation: In solids, particles are tightly packed due to strong forces of attraction. They cannot move freely but only vibrate around their fixed positions.
(b) (a) True
Explanation: The passage describes solids as having closely packed particles with little space between them.
(c) (a) True
Explanation: Liquids fill the shape of the container they are in but maintain a consistent volume.
(d) (b) False
Explanation: In solids, particles are held in fixed positions and cannot move past each other.
(e) (b) False
Explanation: Grinding doesn't change the identity of the chalk.

Q57. What role does temperature play in changing the state of a substance from solid to liquid?

Answer: Temperature plays a crucial role in transitioning a substance from a solid to a liquid. As temperature increases, the particles in a solid absorb thermal energy, causing them to vibrate more vigorously. When this energy surpasses the strength of the interparticle attractions that keep the particles in fixed positions, the solid starts to lose its rigidity. This point, known as the melting point, leads to a phase change as the particles have gained enough energy to break free from their fixed positions, allowing them to move more freely in a fluid manner, resulting in a liquid state.

Q58. What is the process that causes rocks to break down into pebbles, stones, and sand?

Answer: Rocks break down into pebbles, stones, and sand through the process of erosion. Erosion involves the gradual degradation and wearing away of rocks, caused by natural agents such as wind, rain, flowing rivers, ice, and even temperature changes. As rivers flow over rocks, they continuously hit, rub, and grind them, carrying away smaller fragments. Over long periods, these fragments are eroded into pebbles, stones, sand, or even finer particles like clay. This process is slow but continuous, shaping landscapes and contributing to the formation of beaches, riverbanks, and fertile plains where these smaller materials get deposited.

Q59. Provide examples of substances with low and high melting points and their significance in daily life.

Answer: Examples of substances with low melting points include ice and urea, with melting points of 0°C and 133°C respectively. Ice melts readily at room temperature, making it useful for cooling and refrigeration. Urea, dissolving easily even in lower temperatures, is commonly used in fertilizers and chemistry labs. Comparatively, substances like iron have high melting points around 1538°C, granting them significant utility in construction and manufacturing due to their strength and durability under high temperatures. These melting point distinctions are vital for practical applications in diverse fields, showcasing how material properties influence functionality and usage.

Q60. Discuss the role of erosion in the formation of sand from larger rocks.

Answer: Erosion plays a fundamental role in the transformation of larger rocks into sand. It involves the breakdown and dispersal of rocks through natural processes like wind, water flow, and temperature variations. As rivers flow over rocks, they contribute significantly to erosion, gradually wearing down surfaces and carrying away smaller pieces. Over time, these fragments, often pebbles or stones, become further reduced in size to form grains of sand. This transformation highlights the dynamic interplay between environmental forces and geological materials, illustrating the ongoing natural cycle that shapes landscapes and contributes to sediment formation.

Q61. Explain the interconversion of three states in terms of force of attraction and kinetic energy of the molecules.

Answer: Matter exists in three main states-solid, liquid, and gas. These states can change into one another by varying temperature and pressure. These changes are based on two key properties of particles: Intermolecular Force of Attraction and Kinetic Energy
i. Solids: In solids, the particles are tightly packed due to strong forces of attraction. The kinetic energy is very low, so particles only vibrate at fixed positions.
ii. Liquids: When a solid is heated, its particles gain energy and vibrate more vigorously. At a certain temperature (melting point), the force of attraction is weakened, and the solid becomes a liquid. Particles in liquids have more kinetic energy and can slide past each other.
iii. Gases: Further heating of the liquid increases kinetic energy so much that the particles overcome almost all the attraction and move freely. The liquid changes into gas (boiling point). Gases have the weakest forces of attraction and the highest kinetic energy.
Hence, increasing temperature or decreasing pressure leads to a change of state by altering the kinetic
energy and intermolecular attraction among particles. Changes in temperature or pressure can cause these states to convert into one another: Sublimation: Solid to gas without becoming liquid. Deposition: Gas to solid without becoming liquid. Boiling: Liquid to gas throughout the liquid. Evaporation: Liquid to gas from the surface.

Q62. Fill in the blanks:
(a) Forces of attraction in liquids are ________ than in solid.
(b) Matter is made up of small ________.
(c) The smell of perfume gradually spreads across a room due to ________.
(d) The particles in a solid are packed very ________.
(e) ________ effects how fast molecules moves. (f) Evaporation causes ________. (g) As the temperature of a system increases, the pressure of the gases ________. (h) Solid, liquid and gas are called the three ________ of matter.
(i) ________ take the shape of container but have fixed volume. (j) Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its ________.

Answer: Fill in the blanks:
(a) Weaker
(b) Particles
(c) diffusion
(d) Closely
(e) Temperature (f) cooling (g) increases (h) states
(i) Liquid (j) Melting point