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All questions of Matter for Class 8 Exam

Why do liquids take the shape of their container?
  • a)
    Because they are always in motion
  • b)
    Because their particles are loosely packed and can flow
  • c)
    Because their particles are tightly packed
  • d)
    Because they have a fixed shape
Correct answer is option 'B'. Can you explain this answer?

Liquids take the shape of their container because their particles are loosely packed, allowing them to flow and move around each other. This characteristic differentiates liquids from solids, which maintain a fixed shape.

What happens to the energy of particles in a solid when it is heated?
  • a)
    They gain energy and move more
  • b)
    They remain unchanged
  • c)
    They stop moving
  • d)
    They decrease in energy
Correct answer is option 'A'. Can you explain this answer?

When a solid is heated, the energy of its particles increases, causing them to move more vigorously. This added energy can eventually lead to a change in state from solid to liquid, demonstrating the relationship between temperature and particle motion.

What can be concluded from the law of conservation of mass regarding chemical reactions?
  • a)
    The total mass can change freely
  • b)
    Chemical reactions create mass
  • c)
    Mass can disappear during reactions
  • d)
    Mass remains constant before and after reactions
Correct answer is option 'D'. Can you explain this answer?

The law of conservation of mass concludes that mass remains constant before and after chemical reactions. This principle is fundamental to chemistry, ensuring that the total mass of reactants equals the total mass of products, regardless of the changes that occur during the reaction.

Which of the following is an example of condensation?
  • a)
    Solid carbon dioxide turning into gas
  • b)
    Water vapor turning into liquid water
  • c)
    Ice melting into water
  • d)
    Water boiling into steam
Correct answer is option 'B'. Can you explain this answer?

Condensation is the process where water vapor (a gas) cools and turns back into liquid water. This is commonly observed when dew forms on grass in the morning, showcasing the transition from gas to liquid.

Which of the following correctly describes the behavior of gas particles?
  • a)
    They are tightly packed and vibrate in place
  • b)
    They move freely and have weak intermolecular forces
  • c)
    They do not move at all
  • d)
    They have a fixed shape and size
Correct answer is option 'B'. Can you explain this answer?

Gas particles move freely with significant energy and have very weak intermolecular forces. This allows them to spread out and fill any container they are in, demonstrating the distinct properties of gases compared to solids and liquids.

What does the term "melting" refer to?
  • a)
    Solid turning into gas
  • b)
    Liquid turning into solid
  • c)
    Solid turning into liquid
  • d)
    Gas turning into liquid
Correct answer is option 'C'. Can you explain this answer?

Melting refers to the process where a solid turns into a liquid when heated. During this change, the energy of the particles increases, allowing them to overcome their rigid structure and move more freely.

What is the main idea of the kinetic molecular theory?
  • a)
    All matter is made of water
  • b)
    Matter is made of large, stationary particles
  • c)
    Matter cannot change states
  • d)
    Matter is composed of tiny, moving particles
Correct answer is option 'D'. Can you explain this answer?

The kinetic molecular theory states that matter is composed of tiny particles that are constantly in motion. This movement and the energy associated with it determine the state of matter and its properties, forming a foundational concept in physical science.

Which of the following correctly describes solids?
  • a)
    Are always in motion
  • b)
    Have a fixed shape and size
  • c)
    Have no fixed shape or size
  • d)
    Take the shape of their container
Correct answer is option 'B'. Can you explain this answer?

Solids are characterized by having a fixed shape and size because their particles are closely packed together and strongly bonded. This strong attraction prevents them from changing shape when moved, which is a fundamental property of solids.

What is meant by "intermolecular space"?
  • a)
    The space between particles in matter
  • b)
    The space occupied by solids
  • c)
    The area where chemical reactions occur
  • d)
    The total volume of a solid
Correct answer is option 'A'. Can you explain this answer?

Intermolecular space refers to the empty space between particles in matter. This space varies depending on the state of matter—solid, liquid, or gas—affecting how particles interact and their overall properties.

What does the law of conservation of mass state?
  • a)
    Mass cannot change during physical changes
  • b)
    Mass is only found in solids
  • c)
    The total mass before a chemical reaction equals the total mass after
  • d)
    Mass can be created or destroyed
Correct answer is option 'C'. Can you explain this answer?

The law of conservation of mass states that the total mass of matter remains constant before and after a chemical reaction. This principle is crucial in chemistry as it ensures that atoms are neither created nor destroyed, only rearranged.

Which of the following describes adhesion?
  • a)
    No interaction between particles
  • b)
    Attraction between different types of particles
  • c)
    Repulsion between particles
  • d)
    Attraction between the same type of particles
Correct answer is option 'B'. Can you explain this answer?

Adhesion refers to the attraction between different types of particles. This property is important in various phenomena, such as water spreading on a surface, highlighting the interactions between different materials.

How does the kinetic energy of particles change during melting?
  • a)
    It decreases
  • b)
    It stays the same
  • c)
    It increases
  • d)
    It becomes zero
Correct answer is option 'C'. Can you explain this answer?

During melting, the kinetic energy of particles increases as they absorb heat. This added energy allows solid particles to overcome the strong intermolecular forces that hold them in a fixed position, enabling them to move more freely as a liquid.

What causes matter to change from one state to another?
  • a)
    Changes in color
  • b)
    Changes in size
  • c)
    Changes in temperature and pressure
  • d)
    Changes in shape
Correct answer is option 'C'. Can you explain this answer?

Matter changes its state (solid, liquid, gas) primarily due to changes in temperature and pressure. When energy is added (like heating), particles move faster, potentially changing from solid to liquid or gas, while cooling can reverse these changes.

In liquids, how do the particles behave compared to solids?
  • a)
    They are tightly packed and do not move
  • b)
    They are scattered and have no attraction
  • c)
    They are fixed in place
  • d)
    They are loosely packed and can move around
Correct answer is option 'D'. Can you explain this answer?

In liquids, particles are loosely packed, allowing them to move around each other. This property enables liquids to take the shape of their container while maintaining a fixed volume, which distinguishes them from solids.

What happens to gas particles when they cool down?
  • a)
    They lose energy and move slower
  • b)
    They gain energy and move faster
  • c)
    They become solids
  • d)
    They become liquids
Correct answer is option 'A'. Can you explain this answer?

When gas particles cool down, they lose energy and move slower. This decrease in kinetic energy can lead to condensation, where gas transforms into a liquid as the particles come closer together due to increased intermolecular attraction.

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