Particulate Nature of Matter

Easy (15)

1. What are the basic building blocks that make up a substance called?
   • Molecules
   • Atoms
   • Constituent particles (correct)
   • Compounds

   Why: Constituent particles are the basic units that make up a larger piece of a substance.

2. When sugar dissolves in water, what happens to the sugar particles?
   • They settle at the bottom
   • They disappear completely
   • They break down into atoms and combine with water
   • They occupy the spaces between water particles (correct)

   Why: Sugar particles fit into the empty spaces between water particles, which is why the water level doesn't significantly rise.

3. What determines the physical state of a substance?
   • Its color
   • Its weight
   • The strength of interparticle attractions (correct)
   • Its taste

   Why: The strength of interparticle attractions dictates whether a substance is solid, liquid, or gas.

4. Which state of matter has a definite volume but no fixed shape?
   • Solid
   • Liquid (correct)
   • Gas
   • Plasma

   Why: Liquids take the shape of their container but maintain a constant volume.

5. In which state of matter are particles tightly packed and held in fixed positions?
   • Liquid
   • Gas
   • Solid (correct)
   • Plasma

   Why: Solids have tightly packed particles with strong interparticle forces, giving them a fixed shape.

6. What is the term for the forces that hold constituent particles of matter together?
   • Gravitational forces
   • Magnetic forces
   • Interparticle attractions (correct)
   • Frictional forces

   Why: Interparticle attractions are the attractive forces between the particles of matter.

7. Which of the following is a characteristic of gases?
   • Fixed shape and fixed volume
   • Fixed volume but no fixed shape
   • No fixed shape and no fixed volume (correct)
   • Fixed shape but no fixed volume

   Why: Gases expand to fill their container, thus having neither a fixed shape nor a fixed volume.

8. What happens to the interparticle forces when the distance between particles increases slightly?
   • They increase drastically
   • They remain unchanged
   • They decrease drastically (correct)
   • They become stronger

   Why: Interparticle forces weaken significantly with even a small increase in distance between particles.

9. True or False: All matter is composed of extremely large particles.

   Why: Matter is composed of extremely small particles, not large ones.

10. True or False: Liquids have a fixed shape.

    Why: Liquids take the shape of their container, meaning they do not have a fixed shape.

11. True or False: Solids can flow like liquids and gases.

    Why: Solids do not flow; only liquids and gases are classified as fluids because they can flow.

12. The process of breaking down chalk into smaller particles continues until tiny units called __________ particles are obtained.

    Why: The basic units of matter are called constituent particles.

13. Substances like liquids and gases that flow and do not retain a fixed shape are called __________.

    Why: Fluids are substances that can flow and do not have a fixed shape.

14. Identify the state of matter shown in Fig. 7.12 (a).
    • Liquid
    • Gas
    • Solid (correct)
    • Plasma

    Why: The tightly packed, ordered arrangement of particles indicates a solid state.

15. Which diagram represents the arrangement of particles in a gas?
    • Fig. 7.12 (a)
    • Fig. 7.12 (b)
    • Fig. 7.12 (c) (correct)
    • None of the above

    Why: Fig. 7.12 (c) shows widely spaced, randomly moving particles, which is typical of a gas.

Medium (15)

1. Why does the fragrance of an incense stick spread quickly across a room?
   • Due to strong interparticle attractions in the smoke particles
   • Because smoke particles are very heavy and fall quickly
   • Due to the free and rapid movement of gas particles (correct)
   • Because the incense stick generates a strong air current

   Why: Gas particles move freely and rapidly, allowing the fragrance to diffuse throughout the room.

2. A solid object is heated, and its particles start vibrating more vigorously. What is the next stage in this process?
   • The particles become stationary
   • The solid directly turns into a gas
   • The interparticle forces weaken, and the solid melts into a liquid (correct)
   • The particles become more tightly packed

   Why: Increased vibration weakens interparticle forces, leading to melting into a liquid.

3. Why can you easily move your hand through the air, but not through a solid block of wood?
   • Air particles are heavier than wood particles
   • Wood has no interparticle spaces, while air has large spaces (correct)
   • Air has strong interparticle attractions, while wood has weak ones
   • Your hand is designed to move only through gases

   Why: The large interparticle spaces and weak forces in air allow easy movement, unlike the tightly packed particles in wood.

4. Which of the following statements correctly describes the interparticle spacing in the three states of matter?
   • Solid > Liquid > Gas
   • Liquid > Solid > Gas
   • Gas > Liquid > Solid (correct)
   • Solid = Liquid = Gas

   Why: Gases have the largest interparticle spacing, followed by liquids, and then solids.

5. Match the state of matter with its characteristic property.

   Why: Each state of matter has distinct properties regarding shape, volume, and flow.

6. Match the substance with its typical melting point (approximate values).

   Why: Melting points are specific temperatures at which solids transition to liquids.

7. Match the property with the state of matter it best describes.

   Why: The strength of forces and particle mobility define the characteristics of each state of matter.

8. Match the activity with the concept it demonstrates.

   Why: Each activity provides evidence for a specific property of matter or its particles.

9. The minimum temperature at which a solid melts to become a liquid at atmospheric pressure is called its __________ point.

   Why: Melting point is the specific temperature for solid-to-liquid transition.

10. The process where particles of one substance spread into the spaces between particles of another substance is called __________.

    Why: Diffusion is the intermixing of particles due to their random motion.

11. When a solid is heated, its particles start to __________ more vigorously.

    Why: Heating increases the kinetic energy of solid particles, causing them to vibrate faster.

12. Arrange the following states of matter in increasing order of interparticle spacing: Liquid, Solid, Gas.

    Why: Solids have the least spacing, liquids have moderate, and gases have the most.

13. Arrange the following events in the correct sequence for dissolving sugar in water: 1. Sugar particles separate. 2. Water level remains almost the same. 3. Sugar is added to water. 4. Sugar particles occupy spaces between water particles.

    Why: The process involves adding sugar, its particles separating, occupying water's spaces, and thus not significantly changing the volume.

14. Identify the arrangement of particles in a liquid state.
    • Fig. 7.12 (a)
    • Fig. 7.12 (b) (correct)
    • Fig. 7.12 (c)
    • None of the above

    Why: Fig. 7.12 (b) shows particles that are close but disordered, characteristic of a liquid.

15. The diagram shows water in containers of different shapes. What property of water is being demonstrated?
    • Water has a fixed shape.
    • Water has a fixed volume.
    • Water takes the shape of its container. (correct)
    • Water is incompressible.

    Why: The water changing its shape to fit each container demonstrates that liquids have no fixed shape.

Hard (10)

1. Assertion (A): Solids have a definite shape and volume. Reason (R): The constituent particles in solids are tightly packed and held by strong interparticle attractions.

   Why: Strong interparticle forces and tight packing in solids directly cause their definite shape and volume.

2. Assertion (A): Gases are highly compressible. Reason (R): Gases have large interparticle spaces and negligible interparticle attractions.

   Why: The vast empty spaces between gas particles allow them to be easily compressed.

3. Assertion (A): When ice melts, its temperature remains at 0 °C until all the ice has turned into water. Reason (R): The heat supplied during melting is used to overcome the interparticle attractions, not to increase kinetic energy.

   Why: During melting, energy breaks bonds, keeping temperature constant until the phase change is complete.

4. A student performs Activity 7.7, adding two teaspoons of sugar to half a glass of water. After stirring, the water level (C) is marked. If the student then adds another two teaspoons of sand to the same glass and stirs, what would likely happen to the water level, and why?
   • The water level would decrease because sand is denser than sugar.
   • The water level would remain the same because sand particles also fit into water spaces.
   • The water level would increase significantly because sand does not dissolve and its particles are larger. (correct)
   • The water would turn cloudy but the level would not change, as sand is insoluble.

   Why: Sand does not dissolve, so its particles add to the volume, increasing the water level.

5. Consider a situation where a gas jar containing smoke is inverted over an empty gas jar (as in Activity 7.5). If the experiment is conducted at a very low temperature, how would the spreading of smoke be affected, and why?
   • The smoke would spread faster due to increased density at low temperature.
   • The smoke would spread slower because particle movement decreases at lower temperatures. (correct)
   • The smoke would not spread at all, as gases become solids at very low temperatures.
   • The smoke would spread at the same rate, as temperature does not affect gas particle movement.

   Why: Lower temperatures reduce particle kinetic energy, slowing down their movement and thus the rate of diffusion.

6. Imagine you have three identical balloons, each filled with the same mass of a different substance: one with air (gas), one with water (liquid), and one with fine sand (solid). If you try to compress each balloon, which one would be the most difficult to compress and why?
   • The balloon with air, because gas particles are widely spaced.
   • The balloon with water, because liquid particles are free to move.
   • The balloon with sand, because solid particles are tightly packed with minimal empty space. (correct)
   • All three would be equally difficult to compress because they have the same mass.

   Why: Solids are least compressible due to tightly packed particles and minimal interparticle space.

7. The image shows the magnified schematic pictures of interparticle spacing in the three states of matter. Which diagram best represents a substance at its boiling point, where it is transitioning from liquid to gas?
   • Fig. 7.12 (a)
   • Fig. 7.12 (b)
   • A mixture of Fig. 7.12 (b) and Fig. 7.12 (c) (correct)
   • Fig. 7.12 (c)

   Why: At boiling point, both liquid and gaseous phases coexist, represented by a mix of their particle arrangements.

8. Observe the diagram showing the melting of a solid. Which panel best represents the state where the solid has just begun to melt, with some particles gaining enough energy to move from fixed positions?
   • Fig. 7.4 (a)
   • Fig. 7.4 (b) (correct)
   • Fig. 7.4 (c)
   • None of the above

   Why: Fig. 7.4 (b) shows particles vibrating more vigorously and starting to lose their fixed positions, indicating the onset of melting.

9. Which of the following statements are true regarding the properties of matter?
   • The interparticle attractions are strongest in solids. (correct)
   • Gases have a definite volume but no fixed shape.
   • Liquids are generally less compressible than solids.
   • Particles in gases move completely freely. (correct)

   Why: Solids have the strongest attractions, and gas particles move freely; gases have no definite volume, and liquids are more compressible than solids.

10. Which two statements correctly describe the behavior of particles in different states of matter?
    • In liquids, particles can move freely, but only within a limited space. (correct)
    • When solids are heated, their particles stop vibrating and become fixed.
    • The particles in gases have maximum interparticle spacing. (correct)
    • Interparticle forces in liquids are stronger than in solids.

    Why: Liquid particles move within limits, and gas particles have maximum spacing. Heating increases vibrations, and liquid forces are weaker than solid forces.