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Q1. Which state of matter has neither definite shape nor definite volume?
Gases have neither a definite shape nor a definite volume. They completely fill any container they are placed in, taking both the shape and volume of the container. This is because gas particles are far apart, have very weak forces of attraction, and move freely in all directions.
Q2. Which change of state requires absorption of heat?
Melting (solid to liquid) requires absorption of heat. Heat energy is needed to overcome the forces of attraction between particles in the solid state, allowing them to move more freely as a liquid. This absorbed heat is called latent heat of fusion. Condensation, freezing, and deposition release heat.
Q3. Which substance commonly shows sublimation?
Camphor commonly shows sublimation. When camphor is kept open, it changes directly from solid to gas without becoming liquid. Other substances that sublime include naphthalene and dry ice. Sugar, salt, and sand do not sublime; they melt or dissolve instead.
Q4. Which statement is scientifically correct?
The scientifically correct statement is that liquids can flow. Liquids have the property of fluidity because their particles can slide past one another. Solids have minimum kinetic energy, plasma is ionised gas (not cold), and gases have no fixed volume.
Q5. Plasma in stars exists due to
Plasma in stars exists due to very high temperature. Stars are extremely hot, and at such high temperatures, atoms lose their electrons, creating ionised gas (plasma). This state of matter is the most common in the universe and is what makes stars shine.
Q6. Which state of matter is used to explain neon sign glow?
The glow in neon signs is explained by plasma. When an electric current passes through the neon gas in the tube, the gas becomes ionised, forming plasma. The ionised particles emit light as they return to their normal state, creating the characteristic glow.
Q7. Which state of matter has minimum kinetic energy of particles?
Solids have the minimum kinetic energy of particles. In solids, particles are held in fixed positions by strong forces of attraction and can only vibrate about their positions. They do not have enough energy to move freely like particles in liquids or gases.
Q8. Why is ice wrapped in sawdust?
Ice is wrapped in sawdust to reduce heat transfer. Sawdust is a poor conductor of heat, so it acts as an insulator. It prevents the outside heat from reaching the ice quickly, which slows down the melting process and keeps the ice cold for longer.
Q9. Which device works on plasma principle?
A fluorescent tube works on the plasma principle. Inside the tube, gas is ionised by electric current, creating plasma. This plasma emits ultraviolet light, which then causes the phosphor coating on the tube to glow. Batteries, fans, and torch bulbs do not use plasma.
Q10. Why do we feel cooler after swimming?
We feel cooler after swimming because water evaporates from the skin. As the water evaporates, it absorbs latent heat of vaporisation from our body. This removal of heat cools the skin, making us feel cooler. This is the same principle behind sweating.
Q11. Which of the following is an example of matter that cannot be seen but can be felt?
Air is an example of matter that cannot be seen but can be felt. We cannot see air, but we can feel it when it moves (wind) and when we breathe. Heat and light are forms of energy, not matter. Sound is also energy, not matter.
Q12. Evaporation increases when wind speed increases because
Evaporation increases when wind speed increases because the wind carries away the water vapour formed near the surface. This reduces the humidity around the liquid, allowing more water to evaporate. Wind does not decrease temperature, surface area, or increase pressure directly.
Q13. Which property helps us conclude that air is matter?
The property that helps us conclude that air is matter is that it has mass and occupies space. A simple experiment, like weighing a balloon when empty and when inflated, shows that air has mass. This is the defining property of matter.
Q14. Which factor increases boiling point of a liquid?
Higher pressure increases the boiling point of a liquid. When pressure is increased, it becomes harder for particles to escape as gas, so more heat is required for boiling. This is why pressure cookers cook food faster—the higher pressure raises the boiling point of water.
Q15. Which change of state releases heat?
Condensation releases heat. When a gas changes to a liquid, the particles lose energy and release latent heat. This is why condensation warms the surroundings. Evaporation, boiling, and sublimation all absorb heat.
Q16. Which state of matter is most compressible?
Gases are the most compressible state of matter. Because gas particles have large spaces between them, they can be pushed closer together easily by applying pressure. Solids, liquids, and ice are almost incompressible because their particles are already closely packed.
Q17. Dry ice is solid form of
Dry ice is the solid form of carbon dioxide. It is called dry ice because it does not melt into a liquid; it sublimes directly from solid to gas at atmospheric pressure. It is used for cooling purposes and for creating special effects.
Q18. Which condition will slow down evaporation the most?
High humidity will slow down evaporation the most. When the air is already saturated with water vapour, there is less room for additional vapour, so evaporation slows down significantly. High temperature, high wind speed, and large surface area all increase evaporation.
Q19. Which factor helps maximum evaporation from wet clothes?
Wind helps maximum evaporation from wet clothes. Wind carries away the water vapour from the surface of the clothes, reducing humidity and allowing more water to evaporate. High humidity slows evaporation, shade reduces temperature, and cold air also slows evaporation.
Q20. Bose–Einstein Condensate is formed at
Bose-Einstein Condensate (BEC) is formed at extremely low temperatures, close to absolute zero (0 K). At such temperatures, atoms slow down and merge into a single quantum entity. This state of matter was predicted by Bose and Einstein and was experimentally created in 1995.
Q21. Plasma is best described as
Plasma is best described as ionised gas. It is a state of matter in which a gas has been heated to such high temperatures that its atoms lose electrons, becoming ions. Plasma contains free electrons and positive ions, making it electrically conductive.
Q22. Which everyday observation proves gases have very low density?
The observation that gas cylinders are light when empty proves that gases have very low density. The cylinder is much heavier when filled with compressed gas, showing that the gas has mass but very low density. This is why gases are light compared to liquids and solids.
Q23. Which of the following is NOT a factor affecting change of state?
Colour is NOT a factor affecting change of state. Temperature, pressure, and inter-particle distance all affect the state of matter. Colour is a physical property that does not determine whether a substance is solid, liquid, or gas.
Q24. Why does ice float on water?
Ice floats on water because it has lower density than liquid water. When water freezes, its molecules arrange in a crystalline structure that takes up more space, reducing its density. This lower density causes ice to float on water, which is why lakes and rivers freeze from the top down.
Q25. Increase in temperature mainly affects which property of particles?
An increase in temperature mainly affects the kinetic energy of particles. Temperature is a measure of the average kinetic energy of particles. As temperature increases, particles gain kinetic energy and move faster. This leads to changes in state and other physical properties.
Q26. Increase in pressure generally causes particles to
An increase in pressure generally causes particles to come closer. When pressure is applied, the volume decreases, and particles are pushed closer together. This reduces the spaces between particles and can lead to liquefaction of gases.
Q27. Which conclusion best summarises matter behaviour?
The conclusion that best summarises matter behaviour is that particle motion and attraction decide the states of matter. The state of a substance depends on the balance between the kinetic energy (motion) of particles and the forces of attraction between them. Temperature and pressure affect this balance.
Q28. Which liquid evaporates fastest at room temperature?
Alcohol evaporates fastest at room temperature among the given options. Alcohol has a low boiling point and weak intermolecular forces, allowing its particles to escape easily as vapour. Water evaporates slower, mercury has very low evaporation, and kerosene evaporates slower than alcohol.
Q29. Which state of matter shows maximum randomness of particles?
Gases show the maximum randomness of particles. Gas particles move randomly in all directions at high speeds with no fixed positions or order. In solids, particles are arranged in an orderly pattern, and in liquids, they are less ordered than solids but more than gases.
Q30. Which factor does NOT directly affect particle motion?
Colour does NOT directly affect particle motion. Particle motion is affected by temperature (higher temperature means faster motion), state (particles in gases move faster than in solids), and pressure (pressure can affect the distance between particles). Colour is a separate property.
Q31. Which state of matter has particles vibrating about fixed positions?
Solids have particles vibrating about fixed positions. In solids, particles are held in a fixed lattice structure by strong forces of attraction. They cannot move freely but continuously vibrate about their positions. This gives solids their definite shape.
Q32. Which property allows liquids to be poured?
The property that allows liquids to be poured is fluidity. Fluidity is the ability to flow. Liquid particles can slide past one another, which allows liquids to flow and take the shape of their container. Gases also have fluidity, but liquids are not as compressible.
Q33. Which of the following pairs shows both mass and volume?
Air and water both show mass and volume. They are matter and therefore have mass and occupy space. Heat, sound, light, shadow, thought, and ideas are not matter—they do not have mass or volume.
Q34. Which process skips the liquid state completely?
Sublimation skips the liquid state completely. In sublimation, a solid changes directly into a gas (or a gas changes directly into a solid) without becoming a liquid. Camphor, dry ice, and naphthalene are examples of substances that sublime.
Q35. Which gas is used as vehicle fuel due to easy compression?
CNG (Compressed Natural Gas) is used as vehicle fuel due to easy compression. Gases are highly compressible, so large quantities of natural gas can be stored in small volumes under high pressure. This makes it practical for use in vehicles. Helium, neon, and oxygen are not commonly used as vehicle fuels.
Q36. Which state of matter has particles with maximum freedom of movement?
Gases have particles with maximum freedom of movement. Gas particles are not held together by strong forces and move freely in all directions. They have no fixed positions and can spread out to fill any container. Solids have the least freedom, and liquids have moderate freedom.
Q37. Why are pressure cookers able to cook food faster?
Pressure cookers are able to cook food faster because higher pressure raises the boiling point of water. In a pressure cooker, steam is trapped, increasing the pressure. This raises the boiling point above 100°C, allowing food to cook at a higher temperature and faster.
Q38. Which substance generally has the highest density?
Solids generally have the highest density among the states of matter. In solids, particles are closely packed, so they have more mass in a given volume. Gases have the lowest density because their particles are far apart. Liquids are in between.
Q39. Why do gases diffuse faster than liquids?
Gases diffuse faster than liquids because gases have higher kinetic energy. Gas particles move at high speeds and have large spaces between them, allowing them to spread and mix quickly. Liquid particles have lower kinetic energy and are closer together, so diffusion is slower.
Q40. Which of the following changes involves energy absorption without temperature rise?
Melting ice involves energy absorption without a temperature rise. The energy absorbed (latent heat of fusion) is used to change the state from solid to liquid, not to increase temperature. Cooling steam and freezing water release heat, and heating water raises temperature.
Q41. Which state of matter flows but is not easily compressible?
Liquids flow but are not easily compressible. Liquid particles can slide past one another, so liquids can flow and take the shape of their container. However, the particles are still close together, making liquids almost incompressible. Gases are easily compressible.
Q42. Which state of matter has definite volume but variable shape?
Liquids have a definite volume but variable shape. A given amount of liquid will always have the same volume, but it will take the shape of whatever container it is placed in. Gases have variable volume, and solids have fixed shape and volume.
Q43. Which property makes gases spread throughout a room?
The property that makes gases spread throughout a room is diffusion. Gas particles move randomly and spread out to fill all available space. This diffusion is due to the high kinetic energy and weak forces of attraction between gas particles.
Q44. Why does temperature remain constant during melting?
Temperature remains constant during melting because the heat energy supplied is used to break the forces of attraction between particles, not to increase temperature. This absorbed heat is called latent heat of fusion. It is stored as potential energy in the particles.
Q45. Which principle helps refrigerators cool?
The principle that helps refrigerators cool is evaporation absorbs heat. In a refrigerator, a liquid refrigerant evaporates, absorbing heat from inside the fridge and cooling it. The refrigerant then condenses outside, releasing the heat. This is the same principle as sweating.
Q46. Which process occurs when steam changes into water droplets?
Condensation occurs when steam changes into water droplets. Steam is water vapour (gas), and when it comes into contact with a cooler surface, it loses energy and changes into liquid water. This is how clouds form and how dew forms on cold surfaces.
Q47. Which gas is commonly stored in compressed form for household use?
LPG (Liquefied Petroleum Gas) is commonly stored in compressed form for household use. It is stored in cylinders under pressure, which keeps it in liquid form. When released, it becomes a gas that can be burned for cooking. LPG is used in homes for cooking and heating.
Q48. Which everyday process is an example of evaporation?
Drying of clothes is an everyday example of evaporation. When wet clothes are hung out, the water from the clothes evaporates into the air, leaving the clothes dry. Ice melting is melting, fog and dew formation are condensation.
Q49. Which state transition needs latent heat of vaporisation?
The state transition from liquid to gas (boiling or vaporisation) needs latent heat of vaporisation. This is the heat energy required to change a liquid into gas at its boiling point without changing the temperature. Gas to liquid releases heat, solid to gas is sublimation, and solid to liquid needs latent heat of fusion.
Q50. Why are solids almost incompressible?
Solids are almost incompressible because of strong attraction between particles and very little space between them. The particles are already closely packed, so applying pressure cannot significantly reduce the volume. This is why solids have a fixed shape and volume.