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Q1. Which state of matter has the largest intermolecular spaces?
Gases have the largest intermolecular spaces. The particles in gases are far apart from each other, with very weak forces of attraction. This is why gases are highly compressible and can expand to fill any container. The large spaces between particles allow them to move freely in all directions.
Q2. Boiling is called a bulk phenomenon because
Boiling is called a bulk phenomenon because the entire volume of the liquid changes into vapour, not just the surface. In boiling, particles throughout the liquid gain enough energy to overcome the forces of attraction and escape as gas. This is different from evaporation, which occurs only at the surface.
Q3. The melting point of ice is
The melting point of ice is 273.15 K (which is 0°C). At this temperature, ice changes from solid to liquid. This is a fixed temperature for pure ice at standard atmospheric pressure. 373 K is the boiling point of water, and 0 K is absolute zero.
Q4. On increasing temperature, kinetic energy of particles
On increasing temperature, the kinetic energy of particles increases. Temperature is a measure of the average kinetic energy of particles. Higher temperature means particles move faster, so their kinetic energy increases. This is why diffusion is faster at higher temperatures.
Q5. Water can exist in how many states of matter?
Water can exist in three states of matter: solid (ice), liquid (water), and gas (water vapour/steam). These are the three physical states that water can take under different temperature and pressure conditions.
Q6. Density is defined as
Density is defined as mass per unit volume. The formula is Density = Mass/Volume. It tells us how much mass is packed into a given volume. Weight per unit area is pressure, and volume per unit mass is specific volume.
Q7. Heating a solid mainly increases
Heating a solid mainly increases the kinetic energy of its particles. When a solid is heated, the particles gain energy and vibrate more vigorously. This increased kinetic energy can eventually lead to melting if enough heat is supplied.
Q8. Which factor helps gas fill the entire container?
Random motion of particles helps gas fill the entire container. Gas particles move randomly in all directions at high speed. They keep moving until they occupy all available space, which is why gases spread out to fill their container completely.
Q9. Gases fill the entire vessel because
Gases fill the entire vessel because their particles move freely in all directions. The particles are not held together by strong forces and move independently, spreading out to occupy all the space available in the container.
Q10. Which state of matter is most compressible?
Gas is the most compressible state of matter. Because gas particles have large spaces between them, applying pressure can bring them closer together, significantly reducing the volume. Solids and liquids are almost incompressible because their particles are already closely packed.
Q11. Particles in steam have more energy because they have absorbed
Particles in steam have more energy because they have absorbed latent heat of vaporisation. This is the heat energy required to change liquid water into vapour at its boiling point without changing the temperature. This energy is stored as potential energy in the particles, allowing them to overcome the forces of attraction.
Q12. Which substance has the lowest density?
Air has the lowest density among the options given. Air is a gas with particles far apart, while iron (solid), honey (liquid), and water (liquid) have much higher densities because their particles are more closely packed.
Q13. In the gaseous state, particles move
In the gaseous state, particles move randomly at high speed. They move in all directions, colliding with each other and the walls of the container. This random motion is what allows gases to expand and fill their containers.
Q14. Melting is the change of state from
Melting is the change of state from solid to liquid. This occurs when a solid is heated to its melting point, and the particles gain enough kinetic energy to overcome the forces holding them in fixed positions, allowing them to flow as a liquid.
Q15. Gas particles exert pressure because they
Gas particles exert pressure because they continuously hit the walls of the container. The force exerted by the particles colliding with the walls creates pressure. This is why gas pressure increases when particles move faster (higher temperature) or when more particles are present (higher density).
Q16. CNG is commonly used as
CNG (Compressed Natural Gas) is commonly used as vehicle fuel. It is a cleaner alternative to petrol and diesel. CNG is stored under high pressure in cylinders and is used in many vehicles, especially buses and cars. It is also used as cooking fuel but primarily known as vehicle fuel.
Q17. Boiling point of water at atmospheric pressure is
The boiling point of water at atmospheric pressure is 373 K (which is 100°C). At this temperature, water changes from liquid to gas (steam). 273 K is the melting point of ice, 300 K is approximately room temperature, and 400 K is much higher.
Q18. Water vapour represents water in the
Water vapour represents water in the gaseous state. When water evaporates or boils, it becomes water vapour (steam). This is the gaseous form of water, where particles are far apart and move freely.
Q19. LPG used for cooking is an example of
LPG (Liquefied Petroleum Gas) used for cooking is an example of a compressed gas. It is stored in cylinders under pressure, which keeps it in liquid form inside the cylinder. When released, it becomes a gas that can be burned for cooking. It is not a liquid fuel or solid fuel.
Q20. Latent heat of fusion is the heat required to
Latent heat of fusion is the heat required to change 1 kg of a solid into liquid at its melting point without any change in temperature. It is the energy needed to overcome the forces of attraction holding the particles in fixed positions in the solid state.
Q21. Change of state occurs due to change in
Change of state occurs due to change in temperature or pressure. Increasing temperature provides particles with more kinetic energy, allowing them to overcome forces of attraction. Changing pressure can also cause state changes, such as when gases are compressed into liquids.
Q22. Which property best explains diffusion in gases?
High kinetic energy of particles best explains diffusion in gases. Gas particles move at high speeds in random directions, which allows them to spread and mix rapidly. This is why diffusion is fastest in gases compared to liquids and solids.
Q23. During melting, temperature remains constant because
During melting, temperature remains constant because the heat energy supplied is used to change the state of the substance rather than increasing its temperature. This heat, called latent heat of fusion, is used to overcome the forces of attraction between particles and break the solid structure.
Q24. The smell of cooked food reaches us quickly because
The smell of cooked food reaches us quickly because gases diffuse rapidly. The aroma particles mix with air and spread quickly due to the high kinetic energy of gas particles. This rapid diffusion allows us to smell food from a distance.
Q25. Oxygen supplied to hospitals is stored as
Oxygen supplied to hospitals is stored as compressed gas in high-pressure cylinders. It is compressed to fit more gas into a smaller volume. It is not stored as liquid oxygen (which is used in some other applications) or as solid oxygen.
Q26. Latent heat of vaporisation is the heat required to
Latent heat of vaporisation is the heat required to change 1 kg of a liquid into gas at its boiling point without any change in temperature. This energy is used to overcome the forces of attraction between particles, allowing them to escape as gas.
Q27. Ice floats on water because
Ice floats on water because ice has lower density than water. When water freezes, its molecules arrange in a crystalline structure that takes up more space, making ice less dense. This lower density causes ice to float on liquid water.
Q28. Boiling point is the temperature at which
Boiling point is the temperature at which a liquid changes into gas. At this temperature, the vapour pressure of the liquid equals the atmospheric pressure. Bubbles form throughout the liquid, and the entire mass changes to gas.
Q29. Boiling occurs when particles
Boiling occurs when particles gain enough energy to overcome the forces of attraction and escape as vapour. This happens throughout the liquid, not just at the surface. The particles have sufficient kinetic energy to break free from the liquid state.
Q30. The state with maximum kinetic energy of particles is
The state with maximum kinetic energy of particles is gas. Gas particles move most freely and at the highest speeds. They have the most kinetic energy because they are far apart and have overcome the forces of attraction almost completely.
Q31. Fusion refers to
Fusion refers to the change of state from solid to liquid. It is the process of melting. The term “fusion” means melting, and the latent heat of fusion is the heat required for this change of state.
Q32. Change of state does not change
Change of state does not change the chemical nature of the substance. The substance remains chemically the same—it is still the same compound or element. For example, ice, water, and steam are all chemically H₂O. Only the physical state and particle arrangement change.
Q33. Random motion of particles is maximum in
Random motion of particles is maximum in gases. Gas particles move freely in all directions at high speeds. Their motion is completely random, which is why gases spread quickly and fill their containers. In solids, motion is limited to vibration only.
Q34. Gases are highly compressible as compared to
Gases are highly compressible as compared to solids and liquids. Gas particles are far apart with large spaces between them, so they can be pushed closer together easily. Solids and liquids are almost incompressible because their particles are already closely packed.
Q35. Particles in water at 0°C have
Particles in water at 0°C have more energy than ice at the same temperature. The heat absorbed during melting (latent heat of fusion) is stored in the water particles, giving them greater energy than ice particles, even though they are at the same temperature.
Q36. The temperature at which a solid melts is called
The temperature at which a solid melts is called its melting point. At this temperature, the solid changes to liquid. For pure substances, the melting point is a fixed temperature that is characteristic of the substance.
Q37. We can move our hand easily in air because
We can move our hand easily in air because air particles have weak attraction. The forces between air particles are very weak, so they offer very little resistance to movement. This is why air is easy to move through, unlike solids or liquids.
Q38. Diffusion in gases is fastest due to
Diffusion in gases is fastest due to the high speed of particles and large spaces between them. Gas particles move rapidly and can easily travel through the gaps between other particles, allowing them to mix quickly.
Q39. Change of state involves change in
Change of state involves change in particle energy and arrangement. The particles gain or lose energy, which changes their arrangement from closely packed (solid) to loosely arranged (liquid) to far apart (gas). The chemical composition remains unchanged.
Q40. Melting point of a solid indicates
The melting point of a solid indicates the strength of the force of attraction between its particles. A higher melting point means stronger attractive forces, requiring more heat energy to break the solid structure and melt it.
Q41. Which statement is correct?
The correct statement is that solid particles vibrate in place. In solids, particles are held in fixed positions by strong forces of attraction, but they continuously vibrate about their positions. Liquid particles have motion, gas particles have weak attraction, and gas particles do not have fixed positions.
Q42. Pressure of a gas is due to force exerted
Pressure of a gas is due to the force exerted per unit area on the walls of the container. When gas particles collide with the walls, they exert a force. The pressure is this force divided by the area of the container walls. Temperature affects pressure, but it is the collisions that directly create it.
Q43. Increase in temperature mainly affects
An increase in temperature mainly affects the speed of particles. Temperature increases the kinetic energy of particles, causing them to move faster. This affects the rate of diffusion, pressure, and state changes, but the mass and shape of particles themselves do not change.
Q44. A wooden table is classified as a solid because it has
A wooden table is classified as a solid because it has a fixed shape and fixed volume. The particles in a solid are closely packed and held in fixed positions, giving the table a definite shape and volume. It does not flow like liquids or gases.
Q45. Increase in kinetic energy causes particles to
An increase in kinetic energy causes particles to vibrate faster. As particles gain kinetic energy, their motion increases. In solids, they vibrate more vigorously; in liquids and gases, they move faster and more freely. This increased motion can lead to changes of state.
Q46. Which conclusion is supported by the text?
The text supports the conclusion that temperature affects kinetic energy. When temperature increases, the kinetic energy of particles increases, leading to faster motion and changes in state. This is a fundamental concept in the study of matter.
Q47. Heat energy helps particles overcome
Heat energy helps particles overcome the forces of attraction between them. When particles absorb heat, their kinetic energy increases, allowing them to break free from the attractive forces that hold them together. This is how melting and boiling occur.
Q48. Latent heat is absorbed without change in
Latent heat is absorbed without a change in temperature. During melting or boiling, the heat energy is used to change the state of the substance, not to increase its temperature. The temperature remains constant during the phase change until the change is complete.
Q49. The hidden heat absorbed during change of state is called
The hidden heat absorbed during change of state is called latent heat. “Latent” means hidden because this heat does not cause a temperature rise. It is the energy required to change the state of a substance without changing its temperature. It is stored as potential energy in the particles.
Q50. Large volumes of gas can be transported easily because gases are
Large volumes of gas can be transported easily because gases are highly compressible. By applying pressure, gases can be compressed into a much smaller volume. This allows large quantities of gas to be stored in cylinders and transported efficiently.