ICSE – Grade 8 – Physics – Ch 01 – QA

Questions & Answers

ICSE - Grade - 8

Subject: Physics

Chapter - 01 - Matter

Types of Questions

MCQ

Fill in the Blanks

  1. Anything that has mass and occupies space is called __________.

Answer: Matter

  1. The smallest unit of a substance that retains its chemical properties is called a __________.

Answer: Molecule

  1. The force of attraction between molecules is called __________ force.

Answer: Intermolecular

  1. The amount of space occupied by a substance is called its __________.

Answer: Volume

  1. The three states of matter are __________, __________, and __________.

Answer: Solid, Liquid, Gas

  1. Solids have a definite __________ and __________.

Answer: Shape, Volume

  1. Liquids have a definite __________ but no definite __________.

Answer: Volume, Shape

  1. Gases have neither a definite __________ nor a definite __________.

Answer: Shape, Volume

  1. The process by which a solid changes directly into gas is called __________.

Answer: Sublimation

  1. The process by which a gas changes directly into solid is called __________.

Answer: Deposition

  1. The process by which a liquid changes into gas at any temperature below its boiling point is called __________.

Answer: Evaporation

  1. The process by which a liquid changes into gas at its boiling point is called __________.

Answer: Vaporization

  1. The boiling point of pure water at sea level is __________ °C.

Answer: 100

  1. The melting point of ice is __________ °C.

Answer: 0

  1. The process by which a liquid changes into solid is called __________.

Answer: Freezing

  1. The process of conversion of gas into liquid is called __________.

Answer: Condensation

  1. The temperature at which a substance changes from solid to liquid is called its __________ point.

Answer: Melting

  1. The temperature at which a liquid changes into gas is called its __________ point.

Answer: Boiling

  1. The temperature at which a liquid changes into solid is called its __________ point.

Answer: Freezing

  1. The state of matter with the least intermolecular space is __________.

Answer: Solid

  1. The state of matter with the most intermolecular space is __________.

Answer: Gas

  1. __________ is an example of a substance that undergoes sublimation.

Answer: Camphor

  1. The energy possessed by molecules due to their motion is called __________ energy.

Answer: Kinetic

  1. As temperature increases, the kinetic energy of molecules __________.

Answer: Increases

  1. As temperature decreases, the kinetic energy of molecules __________.

Answer: Decreases

  1. The rate of evaporation increases with an increase in __________.

Answer: Temperature

  1. The rate of evaporation decreases with an increase in __________.

Answer: Humidity

  1. The rate of evaporation increases when the surface area of the liquid is __________.

Answer: Increased

  1. The rate of evaporation increases when wind speed is __________.

Answer: Increased

  1. The process by which a liquid changes into gas due to the absorption of heat is called __________.

Answer: Evaporation

  1. The cooling effect of evaporation is due to the absorption of __________ from the surroundings.

Answer: Heat

  1. Water boils at a lower temperature at __________ altitudes.

Answer: Higher

  1. The molecules of gases move in __________ directions.

Answer: Random

  1. The property of matter due to which it resists changes in its state is called __________.

Answer: Inertia

  1. The process by which a substance absorbs heat but its temperature remains constant is called __________.

Answer: Latent heat

  1. When heat is supplied to a solid at its melting point, its temperature __________.

Answer: Remains constant

  1. The process of heating a liquid until it changes into vapor is called __________.

Answer: Boiling

  1. The conversion of water vapor into tiny water droplets is called __________.

Answer: Condensation

  1. A __________ takes the shape of its container but has a fixed volume.

Answer: Liquid

  1. A __________ has neither a fixed shape nor a fixed volume.

Answer: Gas

  1. A gas can be compressed easily due to large __________ between its molecules.

Answer: Intermolecular space

  1. The force of attraction between solid molecules is __________ than that between liquid molecules.

Answer: Greater

  1. __________ is the process in which a liquid turns into a solid.

Answer: Freezing

  1. __________ is the process by which a gas turns into a liquid.

Answer: Condensation

  1. The change of state from solid to liquid requires __________.

Answer: Heat

  1. The change of state from gas to liquid releases __________.

Answer: Heat

  1. The expansion of matter on heating is called __________.

Answer: Thermal expansion

  1. The contraction of matter on cooling is called __________.

Answer: Thermal contraction

  1. The ability of gases to spread and mix with other gases is called __________.

Answer: Diffusion

  1. The process in which a liquid absorbs heat and changes into gas without reaching its boiling point is called __________.

Answer: Evaporation

Name the Following

  1. Anything that has mass and occupies space.

Answer: Matter

  1. The smallest unit of a substance that retains its chemical properties.

Answer: Molecule

  1. The force of attraction between molecules.

Answer: Intermolecular force

  1. The three states of matter.

Answer: Solid, Liquid, Gas

  1. The state of matter that has a definite shape and volume.

Answer: Solid

  1. The state of matter that has a definite volume but no definite shape.

Answer: Liquid

  1. The state of matter that has neither a definite shape nor a definite volume.

Answer: Gas

  1. The process by which a solid changes directly into gas.

Answer: Sublimation

  1. The process by which a gas changes directly into solid.

Answer: Deposition

  1. The process by which a liquid changes into gas below its boiling point.

Answer: Evaporation

  1. The process by which a liquid changes into gas at its boiling point.

Answer: Vaporization

  1. The boiling point of water at sea level.

Answer: 100°C

  1. The melting point of ice.

Answer: 0°C

  1. The process by which a liquid changes into solid.

Answer: Freezing

  1. The process of conversion of gas into liquid.

Answer: Condensation

  1. The temperature at which a substance changes from solid to liquid.

Answer: Melting point

  1. The temperature at which a liquid changes into gas.

Answer: Boiling point

  1. The temperature at which a liquid changes into solid.

Answer: Freezing point

  1. The state of matter with the least intermolecular space.

Answer: Solid

  1. The state of matter with the most intermolecular space.

Answer: Gas

  1. A solid that undergoes sublimation.

Answer: Camphor

  1. The energy possessed by molecules due to their motion.

Answer: Kinetic energy

  1. The factor that increases when temperature rises.

Answer: Kinetic energy of molecules

  1. The factor that increases evaporation.

Answer: Temperature

  1. The factor that decreases evaporation.

Answer: Humidity

  1. The term for the amount of space occupied by a substance.

Answer: Volume

  1. The term for the mass per unit volume of a substance.

Answer: Density

  1. The ability of a liquid to take the shape of its container.

Answer: Fluidity

  1. The property of gases that allows them to fill their container.

Answer: Compressibility

  1. The process by which a solid turns into a liquid.

Answer: Melting

  1. The process by which a gas turns into a liquid.

Answer: Condensation

  1. The process by which a liquid turns into a gas at any temperature below its boiling point.

Answer: Evaporation

  1. The process by which a liquid turns into a gas at its boiling point.

Answer: Vaporization

  1. The type of energy absorbed during melting.

Answer: Latent heat of fusion

  1. The type of energy absorbed during vaporization.

Answer: Latent heat of vaporization

  1. The change of state from liquid to gas at a fixed temperature.

Answer: Boiling

  1. The energy required to convert 1 kg of solid to liquid without changing temperature.

Answer: Latent heat of fusion

  1. The energy required to convert 1 kg of liquid to gas without changing temperature.

Answer: Latent heat of vaporization

  1. The type of process in which no heat is lost or gained by the system.

Answer: Adiabatic process

  1. The state of matter that has the highest kinetic energy.

Answer: Gas

  1. The state of matter that has the highest density.

Answer: Solid

  1. The state of matter that can be compressed the most.

Answer: Gas

  1. The temperature at which water boils at normal atmospheric pressure.

Answer: 100°C

  1. The temperature at which ice melts at normal atmospheric pressure.

Answer: 0°C

  1. The process of heating a solid until it becomes a liquid.

Answer: Melting

  1. The process of cooling a liquid until it becomes a solid.

Answer: Freezing

  1. The process of cooling a gas until it becomes a liquid.

Answer: Condensation

  1. The process in which a gas expands without gaining heat.

Answer: Adiabatic expansion

  1. The term for gases spreading and mixing with other gases.

Answer: Diffusion

  1. The reason why steam causes more severe burns than boiling water.

Answer: Latent heat of vaporization

Answer in One Word

  1. Anything that has mass and occupies space.

Answer: Matter

  1. The smallest unit of a substance that retains its chemical properties.

Answer: Molecule

  1. The force of attraction between molecules.

Answer: Intermolecular

  1. The state of matter with the highest intermolecular force.

Answer: Solid

  1. The state of matter with the highest kinetic energy.

Answer: Gas

  1. The process of a solid changing directly into gas.

Answer: Sublimation

  1. The process of a gas changing directly into solid.

Answer: Deposition

  1. The process by which a liquid changes into gas below its boiling point.

Answer: Evaporation

  1. The process by which a liquid changes into gas at its boiling point.

Answer: Vaporization

  1. The boiling point of water at sea level (in °C).

Answer: 100

  1. The melting point of ice (in °C).

Answer: 0

  1. The process of changing liquid into solid.

Answer: Freezing

  1. The process of changing gas into liquid.

Answer: Condensation

  1. The temperature at which a solid changes into a liquid.

Answer: Melting

  1. The temperature at which a liquid changes into gas.

Answer: Boiling

  1. The temperature at which a liquid changes into solid.

Answer: Freezing

  1. The state of matter that can be compressed the most.

Answer: Gas

  1. A solid that undergoes sublimation.

Answer: Camphor

  1. The energy possessed by molecules due to their motion.

Answer: Kinetic

  1. The term for the amount of space occupied by a substance.

Answer: Volume

  1. The term for mass per unit volume.

Answer: Density

  1. The ability of a liquid to take the shape of its container.

Answer: Fluidity

  1. The property of gases that allows them to fill their container.

Answer: Compressibility

  1. The change of state from liquid to gas at a fixed temperature.

Answer: Boiling

  1. The energy absorbed during melting.

Answer: Latent

  1. The energy absorbed during vaporization.

Answer: Latent

  1. The expansion of matter on heating.

Answer: Thermal

  1. The contraction of matter on cooling.

Answer: Thermal

  1. The ability of gases to mix with other gases.

Answer: Diffusion

  1. The process of heating a liquid until it becomes gas.

Answer: Boiling

  1. The state of matter with a fixed volume but no fixed shape.

Answer: Liquid

  1. The process of water droplets forming on a cold glass.

Answer: Condensation

  1. The process in which a gas expands without gaining heat.

Answer: Adiabatic

  1. The cooling effect observed during evaporation is due to loss of __________ energy.

Answer: Heat

  1. The type of heat that does not raise temperature but changes state.

Answer: Latent

  1. The phenomenon where a liquid turns into a gas without boiling.

Answer: Evaporation

  1. The state of matter with the least intermolecular space.

Answer: Solid

  1. The process where a liquid cools to form a solid.

Answer: Freezing

  1. The state of matter that does not have a fixed shape or volume.

Answer: Gas

  1. The rate of evaporation increases with increasing __________.

Answer: Temperature

  1. The rate of evaporation decreases with increasing __________.

Answer: Humidity

  1. The temperature at which a liquid turns into a gas.

Answer: Boiling

  1. The term for the resistance of a liquid to flow.

Answer: Viscosity

  1. The state of matter with a definite volume but no definite shape.

Answer: Liquid

  1. The process in which a substance absorbs heat but its temperature remains constant.

Answer: Latent

  1. The gas law that relates pressure and volume at constant temperature.

Answer: Boyle’s

  1. The gas law that relates volume and temperature at constant pressure.

Answer: Charles’

  1. The law stating that mass is conserved in a chemical reaction.

Answer: Conservation

  1. The ability of solids to change their shape under force and return to their original shape.

Answer: Elasticity

  1. The energy stored in a substance due to its temperature.

Answer: Heat

ICSE - Grade 8 - Physics

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  • Chapter 1: Matter
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  • Chapter 3: Force and Pressure
  • Chapter 4: Energy
  • Chapter 5: Light Energy
  • Chapter 6: Heat Transfer
  • Chapter 7: Sound
  • Chapter 8: Electricity

ICSE - Grade 8 - Chemistry

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  • Chapter 1: Matter
  • Chapter 2: Physical and Chemical Changes
  • Chapter 3: Elements, Compounds and Mixtures
  • Chapter 4: Atomic Structure
  • Chapter 5: Language of Chemistry
  • Chapter 6: Chemical Reactions
  • Chapter 7: Hydrogen
  • Chapter 8: Water
  • Chapter 9: Carbon and its compounds

ICSE - Grade 8 - Mathematics

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  • Chapter 1: Rational Numbers
  • Chapter 2: Exponents
  • Chapter 3: Squares and Square Roots
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  • Chapter 5: Playing with Numbers
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  • Chapter 7: Percent and Percentage
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  • Chapter 9: Interest
  • Chapter 10: Direct and Inverse Variations
  • Chapter 11: Algebraic Expressions
  • Chapter 12: Identities
  • Chapter 13: Factorization
  • Chapter 14: Linear Equation in One Variable
  • Chapter 15: Linear Inequalities
  • Chapter 16: Understanding Shapes
  • Chapter 17: Special Types of Quadrilaterals
  • Chapter 18: Constructions
  • Chapter 19: Representing 3-D in 2-D
  • Chapter 20: Area of Trapezium and a Polygon
  • Chapter 21: Surface Area, Volume and Capacity
  • Chapter 22: Data Handling
  • Chapter 23: Probability

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  • Chapter 5: Endocrine Systems and Adolescence
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  • Chapter 7: Nervous System
  • Chapter 8: Diseases and First Aid
  • Chapter 9: Food Production

ICSE - Grade 8 - History

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  • A Period of Transition
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  • The American War of Independence
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  • Traders to Rulers
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Find the Odd One Out

  1. Solid, Liquid, Gas, Energy

Odd One Out: Energy (Others are states of matter)

  1. Ice, Water, Steam, Oxygen

Odd One Out: Oxygen (Others are different states of water)

  1. Melting, Boiling, Freezing, Expansion

Odd One Out: Expansion (Others are phase changes)

  1. Camphor, Naphthalene, Water, Ammonium chloride

Odd One Out: Water (Others undergo sublimation)

  1. Density, Volume, Mass, Temperature

Odd One Out: Temperature (Others are related to matter’s measurement)

  1. Solid, Liquid, Plasma, Gas

Odd One Out: Plasma (Not a classical state of matter in school-level study)

  1. Boiling, Freezing, Condensation, Diffusion

Odd One Out: Diffusion (Others are state changes)

  1. Water, Mercury, Alcohol, Iron

Odd One Out: Iron (Others are liquids at room temperature)

  1. Wood, Rubber, Plastic, Mercury

Odd One Out: Mercury (Only liquid at room temperature)

  1. Air, Hydrogen, Oxygen, Ice

Odd One Out: Ice (Others are gases)

  1. Freezing, Melting, Boiling, Diffusion

Odd One Out: Diffusion (Others are phase changes)

  1. Boyle’s Law, Charles’ Law, Pascal’s Law, Newton’s Law

Odd One Out: Newton’s Law (Others are gas laws)

  1. Vaporization, Evaporation, Condensation, Sublimation

Odd One Out: Condensation (Others involve conversion to gas)

  1. Petrol, Alcohol, Water, Iron

Odd One Out: Iron (Others are liquids at room temperature)

  1. Pressure, Temperature, Volume, Mass

Odd One Out: Mass (Others affect gas behavior)

  1. Camphor, Naphthalene, Ice, Dry Ice

Odd One Out: Ice (Does not sublime)

  1. Rubber, Plastic, Steel, Copper

Odd One Out: Plastic (Not a metal)

  1. Evaporation, Condensation, Freezing, Radiation

Odd One Out: Radiation (Others are state changes)

  1. Petrol, Alcohol, Water, Iron

Odd One Out: Iron (Others are liquids)

  1. Nitrogen, Oxygen, Carbon dioxide, Ice

Odd One Out: Ice (Others are gases at room temperature)

  1. Solid, Liquid, Gas, Energy

Odd One Out: Energy (Not a state of matter)

  1. Water, Oil, Alcohol, Sugar

Odd One Out: Sugar (Others are liquids)

  1. Ice, Water, Mercury, Alcohol

Odd One Out: Ice (Only solid)

  1. Iron, Copper, Mercury, Oxygen

Odd One Out: Oxygen (Others are metals)

  1. Solidification, Fusion, Vaporization, Diffusion

Odd One Out: Diffusion (Others are phase changes)

  1. Water, Mercury, Oxygen, Alcohol

Odd One Out: Oxygen (Others are liquids)

  1. Plasma, Solid, Liquid, Gas

Odd One Out: Plasma (Not a classical state of matter)

  1. Melting, Freezing, Boiling, Dissolving

Odd One Out: Dissolving (Not a state change)

  1. Ice, Steam, Water, Salt

Odd One Out: Salt (Others are forms of water)

  1. Air, Steam, Smoke, Iron

Odd One Out: Iron (Others are gases or vapors)

  1. Evaporation, Condensation, Freezing, Filtration

Odd One Out: Filtration (Not a state change)

  1. Kinetic energy, Potential energy, Heat energy, Oxygen

Odd One Out: Oxygen (Others are forms of energy)

  1. Diamond, Graphite, Sand, Charcoal

Odd One Out: Sand (Others are forms of carbon)

  1. Copper, Gold, Aluminium, Oxygen

Odd One Out: Oxygen (Not a metal)

  1. Boiling, Freezing, Melting, Radiation

Odd One Out: Radiation (Not a phase change)

  1. Silver, Mercury, Gold, Ice

Odd One Out: Ice (Not a metal)

  1. Water, Oil, Mercury, Glass

Odd One Out: Glass (Not a liquid)

  1. Neon, Argon, Oxygen, Helium

Odd One Out: Oxygen (Not a noble gas)

  1. Melting, Boiling, Condensation, Reflection

Odd One Out: Reflection (Not a state change)

  1. Expansion, Contraction, Freezing, Sublimation

Odd One Out: Expansion (Others involve state changes)

  1. Steam, Fog, Ice, Water vapor

Odd One Out: Ice (Only solid)

  1. Wood, Plastic, Rubber, Iron

Odd One Out: Iron (Only conductor)

  1. Alcohol, Water, Mercury, Ice

Odd One Out: Ice (Only solid)

  1. Boiling, Evaporation, Condensation, Diffusion

Odd One Out: Diffusion (Not a phase change)

  1. Water, Steel, Alcohol, Mercury

Odd One Out: Steel (Not a liquid)

  1. Diamond, Gold, Graphite, Charcoal

Odd One Out: Gold (Not a form of carbon)

  1. Water, Petrol, Mercury, Rock

Odd One Out: Rock (Not a liquid)

  1. Kinetic energy, Potential energy, Latent heat, Sublimation

Odd One Out: Sublimation (Not a form of energy)

  1. Steam, Smoke, Fog, Cloud

Odd One Out: Smoke (Contains solid particles)

  1. Melting, Freezing, Condensation, Photosynthesis

Odd One Out: Photosynthesis (Not a phase change)

Match the Pair

Set 1

  1. Solid → (a) Molecules move freely
  2. Liquid → (b) Has a definite shape
  3. Gas → (c) Freezing
  4. Change of state from liquid to solid → (d) Sublimation
  5. Direct conversion of solid to gas → (e) Takes the shape of the container

Answers (Set 1)

1 – (b)
2 – (e)
3 – (a)
4 – (c)
5 – (d)

 

 

Set 2

  1. Boiling point of water (at 1 atm) → (a) 1000°C
  2. Evaporation → (b) Occurs at any temperature
  3. Boiling → (c) Occurs only at a fixed temperature
  4. Freezing point of water → (d) 100°C
  5. Ice floats on water → (e) Due to lower density than water

Answers (Set 2)

1 – (d)
2 – (b)
3 – (c)
4 – (a)
5 – (e)

 

 

Set 3

  1. Water at 0°C → (a) Steam burns are more severe
  2. Water at 100°C → (b) Ice
  3. Water vapor → (c) Liquid phase
  4. Steam burns → (d) Gas phase
  5. Solid form of water → (e) Feels colder than liquid water at 0°C

Answers (Set 3)

1 – (e)
2 – (c)
3 – (d)
4 – (a)
5 – (b)

 

 

Set 4

  1. Intermolecular force in solids → (a) Weakest
  2. Intermolecular force in liquids → (b) Very strong
  3. Intermolecular force in gases → (c) Weak
  4. Shape of solids → (d) Fixed
  5. Shape of liquids → (e) Indefinite

Answers (Set 4)

1 – (b)
2 – (c)
3 – (a)
4 – (d)
5 – (e)

 

 

Set 5

  1. Latent heat of fusion → (a) Liquid to gas
  2. Latent heat of vaporization → (b) Solid to liquid
  3. Process of boiling → (c) Temperature remains constant
  4. Evaporation rate → (d) Increases with surface area
  5. Condensation → (e) Gas to liquid

Answers (Set 5)

1 – (b)
2 – (a)
3 – (c)
4 – (d)
5 – (e)

 

 

Set 6

  1. Naphthalene balls disappear over time → (a) Boiling
  2. Water turning to ice → (b) Sublimation
  3. Water forming droplets on a cool glass → (c) Condensation
  4. Water changing into steam → (d) Freezing
  5. Formation of mist in winter → (e) Evaporation

Answers (Set 6)

1 – (b)
2 – (d)
3 – (c)
4 – (a)
5 – (e)

 

 

Set 7

  1. Higher temperature → (a) Slower evaporation
  2. Lower humidity → (b) Faster evaporation
  3. Windy conditions → (c) Increases evaporation rate
  4. More surface area → (d) Decreases evaporation
  5. Lower pressure → (e) Faster boiling

Answers (Set 7)

1 – (b)
2 – (d)
3 – (c)
4 – (a)
5 – (e)

 

 

Set 8

  1. Deposition → (a) Conversion of gas into liquid
  2. Freezing → (b) Conversion of gas into solid
  3. Boiling point → (c) Liquid to solid
  4. Condensation → (d) 100°C for water
  5. Latent heat → (e) Heat required to change state

Answers (Set 8)

1 – (b)
2 – (c)
3 – (d)
4 – (a)
5 – (e)

 

 

Set 9

  1. Matter → (a) Solid, liquid, gas
  2. Solid → (b) Definite shape and volume
  3. Liquid → (c) Flows and takes the shape of container
  4. Gas → (d) Highly compressible
  5. Plasma → (e) Fourth state of matter

Answers (Set 9)

1 – (a)
2 – (b)
3 – (c)
4 – (d)
5 – (e)

 

 

Set 10

  1. Water at 4°C → (a) Has maximum density
  2. Water expands → (b) On freezing
  3. Steam burns → (c) Cause more severe injuries
  4. Ice floats → (d) Due to hydrogen bonding
  5. Boiling and evaporation → (e) Are different processes

Answers (Set 10)

1 – (a)
2 – (b)
3 – (c)
4 – (d)
5 – (e)

Short Answer Questions  

  1. What is matter?
    Matter is anything that has mass and occupies space.
  2. Name the three states of matter.
    Solid, Liquid, and Gas.
  3. What is diffusion?
    The intermixing of particles of one substance with another due to their motion is called diffusion.
  4. Why do gases exert pressure?
    Gas molecules move randomly and collide with the walls of the container, exerting pressure.
  5. Why are solids rigid?
    Solids have strong intermolecular forces that hold particles in fixed positions.
  6. What is the physical state of water at 0°C?
    Water can exist as both solid (ice) and liquid at 0°C.
  7. What happens to the intermolecular force when a solid melts?
    The intermolecular force weakens as particles gain energy and move apart.
  8. Define melting point.
    The temperature at which a solid changes into a liquid is called the melting point.
  9. What is the boiling point of water at sea level?
    100°C.
  10. Why does evaporation cause cooling?
    Particles with higher energy escape, reducing the average kinetic energy and causing cooling.
  11. Define latent heat.
    The heat energy absorbed or released during a phase change without a temperature change.
  12. Why does water take the shape of a container but not a fixed shape?
    Liquids have weak intermolecular forces that allow molecules to flow.
  13. What is condensation?
    The process in which gas changes into a liquid upon cooling.
  14. What is the difference between boiling and evaporation?
    Boiling occurs at a fixed temperature, whereas evaporation occurs at any temperature.
  15. What is the freezing point of pure water?
    0°C.
  16. Why does boiling occur only at a specific temperature?
    At boiling point, molecules gain enough energy to overcome intermolecular forces and escape as vapor.
  17. What is sublimation?
    The direct conversion of a solid into gas without passing through the liquid state.
  18. Give an example of a substance that undergoes sublimation.
    Naphthalene.
  19. Why does ice float on water?
    Ice is less dense than water due to the expansion of molecules during freezing.
  20. Why do gases expand more than solids and liquids?
    Gases have weak intermolecular forces, allowing particles to move freely.
  21. What is the effect of pressure on the boiling point of a liquid?
    Higher pressure increases the boiling point, and lower pressure decreases it.
  22. What happens to the energy of particles during melting?
    Particles absorb heat energy and move more freely.
  23. What is the latent heat of fusion?
    The heat required to convert a solid into a liquid without temperature change.
  24. Why does a wet cloth dry faster on a windy day?
    Wind removes water vapor, increasing the rate of evaporation.
  25. Why does camphor disappear over time?
    Camphor undergoes sublimation.
  26. Why does steam cause more severe burns than boiling water?
    Steam has more energy due to the latent heat of vaporization.
  27. Why does a balloon burst when heated?
    Gas molecules inside the balloon move faster and exert more pressure.
  28. What is deposition?
    The process in which gas directly changes into a solid without becoming a liquid.
  29. Why is evaporation a surface phenomenon?
    Only surface molecules with enough energy escape into vapor.
  30. How does temperature affect the rate of evaporation?
    Higher temperature increases evaporation rate by giving more energy to particles.
  31. What is the role of humidity in evaporation?
    Higher humidity slows down evaporation.
  32. Why do we see droplets on the outside of a cold bottle?
    Water vapor condenses into liquid due to cooling.
  33. What is an example of deposition in nature?
    Frost formation.
  34. What happens to the intermolecular spaces during condensation?
    The spaces decrease as particles come closer.
  35. Why is latent heat important in phase changes?
    It provides the energy needed to change states without altering temperature.
  36. Why does water boil at a lower temperature on a mountain?
    The atmospheric pressure is lower, requiring less energy for molecules to escape.
  37. What happens to the volume of water when it freezes?
    It increases.
  38. What is the relationship between pressure and gas volume?
    As pressure increases, gas volume decreases (Boyle’s Law).
  39. What is the difference between solid and liquid in terms of compressibility?
    Solids are incompressible, while liquids are slightly compressible.
  40. What is the effect of wind speed on the rate of evaporation?
    Higher wind speed increases evaporation.
  41. Why does mercury remain liquid at room temperature?
    It has a very low melting point.
  42. Why do liquids flow but solids do not?
    Liquids have weaker intermolecular forces than solids.
  43. What happens to the boiling point of a liquid in a vacuum?
    It decreases.
  44. Why does petrol evaporate faster than water?
    Petrol has weaker intermolecular forces than water.
  45. What is the SI unit of temperature?
    Kelvin (K).
  46. Why does dry air feel cooler than humid air?
    Less humidity allows faster evaporation of sweat, causing cooling.
  47. What happens to the energy of a substance during freezing?
    It is released into the surroundings.
  48. Why do gases have no definite volume?
    Gas molecules move freely and occupy available space.
  49. What is the process of converting a gas into a liquid called?
    Condensation.
  50. What is the role of pressure in solidification?
    Increased pressure helps in converting a liquid into a solid.

Puzzles

Difference Between:

  1. Difference between Solid and Liquid

Solid:

  • Has a fixed shape and volume.
  • Particles are tightly packed with strong intermolecular forces.
  • Cannot flow; rigid in nature.
  • Low compressibility.

Liquid:

  • Has a fixed volume but no fixed shape.
  • Particles are loosely packed with moderate intermolecular forces.
  • Can flow and take the shape of the container.
  • Slightly compressible.
  1. Difference between Liquid and Gas

Liquid:

  • Has a definite volume but no fixed shape.
  • Moderate intermolecular force.
  • Cannot be compressed easily.
  • Flows but does not expand to fill the container completely.

Gas:

  • No fixed volume or shape.
  • Weak intermolecular force.
  • Highly compressible.
  • Expands to fill the entire container.
  1. Difference between Boiling and Evaporation

Boiling:

  • Occurs at a fixed temperature (boiling point).
  • Happens throughout the liquid.
  • Produces bubbles.
  • Rapid process.

Evaporation:

  • Occurs at any temperature below the boiling point.
  • Happens only at the surface of the liquid.
  • No bubble formation.
  • Slow process.
  1. Difference between Melting and Freezing

Melting:

  • Process of changing from solid to liquid.
  • Heat is absorbed.
  • Occurs at the melting point.

Freezing:

  • Process of changing from liquid to solid.
  • Heat is released.
  • Occurs at the freezing point.
  1. Difference between Vaporization and Condensation

Vaporization:

  • Liquid changes to gas.
  • Heat is absorbed.
  • Increases kinetic energy of particles.

Condensation:

  • Gas changes to liquid.
  • Heat is released.
  • Decreases kinetic energy of particles.
  1. Difference between Diffusion in Solids and Gases

Diffusion in Solids:

  • Very slow process.
  • Particles move slightly due to strong intermolecular forces.

Diffusion in Gases:

  • Very fast process.
  • Particles move freely due to weak intermolecular forces.
  1. Difference between Latent Heat of Fusion and Latent Heat of Vaporization

Latent Heat of Fusion:

  • Heat required to convert solid into liquid without temperature change.
  • Example: Ice melting into water.

Latent Heat of Vaporization:

  • Heat required to convert liquid into gas without temperature change.
  • Example: Water turning into steam.
  1. Difference between Physical and Chemical Change

Physical Change:

  • No new substance is formed.
  • Reversible process.
  • Example: Ice melting.

Chemical Change:

  • New substance is formed.
  • Irreversible process.
  • Example: Rusting of iron.
  1. Difference between Intermolecular Space in Solids and Gases

Solids:

  • Very little intermolecular space.
  • Particles are closely packed.

Gases:

  • Large intermolecular space.
  • Particles are widely spaced apart.
  1. Difference between Expansion and Contraction

Expansion:

  • Increase in volume due to heat.
  • Particles move farther apart.

Contraction:

  • Decrease in volume due to cooling.
  • Particles come closer.
  1. Difference between Sublimation and Deposition

Sublimation:

  • Solid changes directly into gas.
  • Example: Camphor evaporating.

Deposition:

  • Gas changes directly into solid.
  • Example: Frost formation.
  1. Difference between Boyle’s Law and Charles’ Law

Boyle’s Law:

  • Pressure and volume are inversely related at constant temperature.
  • P ∝ 1/V

Charles’ Law:

  • Volume and temperature are directly related at constant pressure.
  • V ∝ T
  1. Difference between Heating and Cooling Effect

Heating Effect:

  • Increases kinetic energy.
  • Leads to expansion or phase change.

Cooling Effect:

  • Decreases kinetic energy.
  • Leads to contraction or phase change.
  1. Difference between Kinetic Energy in Solids and Gases

Solids:

  • Low kinetic energy.
  • Particles vibrate in fixed positions.

Gases:

  • High kinetic energy.
  • Particles move freely.
  1. Difference between Real Gas and Ideal Gas

Real Gas:

  • Intermolecular forces exist.
  • Does not follow gas laws at high pressure and low temperature.

Ideal Gas:

  • No intermolecular forces.
  • Follows gas laws perfectly.
  1. Difference between Atmospheric Pressure and Gas Pressure

Atmospheric Pressure:

  • Exerted by air around us.
  • Decreases with altitude.

Gas Pressure:

  • Exerted by gas molecules inside a container.
  • Increases with temperature.
  1. Difference between Evaporation and Condensation in Daily Life

Evaporation:

  • Cooling effect.
  • Example: Sweat evaporating.

Condensation:

  • Heating effect.
  • Example: Water droplets on a cold glass.
  1. Difference between Cohesion and Adhesion

Cohesion:

  • Attraction between same kind of molecules.
  • Example: Water forming droplets.

Adhesion:

  • Attraction between different substances.
  • Example: Water sticking to glass.
  1. Difference between Miscible and Immiscible Liquids

Miscible Liquids:

  • Liquids that mix completely.
  • Example: Water and alcohol.

Immiscible Liquids:

  • Liquids that do not mix.
  • Example: Oil and water.
  1. Difference between Plasma and Bose-Einstein Condensate

Plasma:

  • High-energy ionized gas.
  • Found in the Sun, lightning.

Bose-Einstein Condensate:

  • Supercooled state of matter near absolute zero.
  • Used in quantum physics experiments.

Assertion and Reason

Instructions:

  • Mark (A) if both Assertion and Reason are true, and the Reason correctly explains the Assertion.
  • Mark (B) if both Assertion and Reason are true, but the Reason does not correctly explain the Assertion.
  • Mark (C) if Assertion is true, but the Reason is false.

Mark (D) if Assertion is false, but the Reason is true.

 

  1. Assertion: Solids have a definite shape.

Reason: Intermolecular forces in solids are very strong.
Answer: A

  1. Assertion: Gases can be compressed easily.

Reason: Gases have large intermolecular spaces.
Answer: A

  1. Assertion: Liquids do not have a fixed shape but have a fixed volume.

Reason: The intermolecular forces in liquids are weaker than in solids but stronger than in gases.
Answer: A

  1. Assertion: Ice floats on water.

Reason: Ice is denser than water.
Answer: C

  1. Assertion: Water takes the shape of the container in which it is kept.

Reason: The molecules of water are held together by weak intermolecular forces.
Answer: A

  1. Assertion: Gases exert pressure on the walls of the container.

Reason: Gas molecules are in continuous random motion.
Answer: A

  1. Assertion: Evaporation causes cooling.

Reason: During evaporation, molecules with higher kinetic energy escape, leaving behind molecules with lower kinetic energy.
Answer: A

  1. Assertion: Liquids have a fixed volume.

Reason: Liquids have high intermolecular attraction.
Answer: B

  1. Assertion: Boiling and evaporation are the same process.

Reason: Both involve the conversion of a liquid to a gas.
Answer: C

  1. Assertion: During boiling, the temperature of a liquid remains constant.

Reason: The heat supplied is used to break intermolecular bonds rather than increasing temperature.
Answer: A

  1. Assertion: Mercury is a liquid metal.

Reason: Mercury has weak metallic bonding.
Answer: A

  1. Assertion: Sublimation occurs in camphor and naphthalene.

Reason: Sublimation is the direct conversion of a solid into a gas without passing through the liquid state.
Answer: A

  1. Assertion: Solids expand when heated.

Reason: On heating, the kinetic energy of molecules increases, causing them to move apart.
Answer: A

  1. Assertion: Water boils at 100°C at all altitudes.

Reason: Atmospheric pressure does not affect the boiling point of a liquid.
Answer: D

  1. Assertion: Gases diffuse faster than liquids.

Reason: Gas molecules have higher kinetic energy and weaker intermolecular forces than liquids.
Answer: A

  1. Assertion: The volume of a gas decreases when compressed.

Reason: Gases have large intermolecular spaces.
Answer: A

  1. Assertion: Solids can flow like liquids.

Reason: The intermolecular forces in solids are weak.
Answer: D

  1. Assertion: Evaporation takes place only at the boiling point of a liquid.

Reason: Evaporation occurs only when heat is supplied continuously.
Answer: D

  1. Assertion: Humidity reduces the rate of evaporation.

Reason: Higher humidity reduces the difference in vapor pressure between liquid and air.
Answer: A

  1. Assertion: Dry ice sublimes when exposed to air.

Reason: Dry ice is solid carbon dioxide.
Answer: B

  1. Assertion: Water has a higher boiling point than alcohol.

Reason: Water molecules have strong hydrogen bonds.
Answer: A

  1. Assertion: Liquids expand more than solids when heated.

Reason: The intermolecular forces in liquids are weaker than in solids.
Answer: A

  1. Assertion: Solids diffuse faster than gases.

Reason: The intermolecular spaces in solids are larger than in gases.
Answer: D

  1. Assertion: A gas fills the entire volume of a container.

Reason: Gas molecules move randomly in all directions.
Answer: A

  1. Assertion: Steam burns are more severe than boiling water burns.

Reason: Steam contains more latent heat than boiling water.
Answer: A

  1. Assertion: The density of ice is lower than that of water.

Reason: Ice has an open lattice structure due to hydrogen bonding.
Answer: A

  1. Assertion: Solids can be compressed easily.

Reason: The particles in solids are tightly packed with strong intermolecular forces.
Answer: D

  1. Assertion: Gases have definite shape and volume.

Reason: Gases have strong intermolecular forces.
Answer: D

  1. Assertion: When water boils, bubbles are formed.

Reason: The bubbles consist of air from the surroundings.
Answer: C

  1. Assertion: Freezing is an exothermic process.

Reason: Heat is released when a liquid turns into a solid.
Answer: A

  1. Assertion: The melting point of ice and freezing point of water are the same.

Reason: At equilibrium, both solid and liquid phases coexist at the same temperature.
Answer: A

  1. Assertion: Solids have a definite shape.

Reason: Solid particles are arranged in a fixed pattern.
Answer: A

  1. Assertion: Water vapor is visible.

Reason: Water vapor condenses into tiny droplets forming mist.
Answer: C

  1. Assertion: Boiling occurs at a fixed temperature.

Reason: The boiling point of a liquid depends on atmospheric pressure.
Answer: A

  1. Assertion: Ice at 0°C feels colder than water at 0°C.

Reason: Ice absorbs heat during melting without changing temperature.
Answer: A

  1. Assertion: Liquids do not have a fixed shape.

Reason: Liquid molecules can move past each other.
Answer: A

  1. Assertion: Water expands on freezing.

Reason: The density of ice is less than that of water.
Answer: A

  1. Assertion: Air is a mixture of gases.

Reason: Air has a fixed composition of gases.
Answer: C

  1. Assertion: The mass of a substance remains unchanged during a change of state.

Reason: The number of molecules remains constant.
Answer: A

  1. Assertion: Carbon dioxide dissolves in water.

Reason: Carbon dioxide is a non-polar gas.
Answer: B

  1. Assertion: Diffusion is slower in liquids than in gases.

Reason: Liquids have weaker intermolecular forces than gases.
Answer: C

  1. Assertion: All gases are compressible.

Reason: Gases have high intermolecular attraction.
Answer: C

  1. Assertion: Plasma is a state of matter.

Reason: Plasma consists of free electrons and ions.
Answer: A

  1. Assertion: Water vaporization occurs only at 100°C.

Reason: Water can evaporate at any temperature.
Answer: D

  1. Assertion: The boiling point of a liquid decreases with altitude.

Reason: Atmospheric pressure decreases with altitude.
Answer: A

True or False

  1. Solids have a fixed shape and volume. (True)
  2. Liquids have a fixed shape but not a fixed volume. (False)
  3. Gases can be compressed easily due to large intermolecular spaces. (True)
  4. The intermolecular force in gases is stronger than in solids. (False)
  5. Water exists only in the liquid state under normal conditions. (False)
  6. The process of converting a solid into a liquid is called freezing. (False)
  7. Melting and fusion refer to the same process. (True)
  8. The boiling point of water at sea level is 100°C. (True)
  9. Evaporation occurs only at the boiling point of a liquid. (False)
  10. Humidity affects the rate of evaporation. (True)
  11. Increasing the surface area of a liquid increases the rate of evaporation. (True)
  12. Ice melts at a temperature below 0°C. (False)
  13. Water can exist in all three states of matter. (True)
  14. Gases do not exert pressure on the walls of a container. (False)
  15. Steam burns are less severe than boiling water burns. (False)
  16. A gas can expand to fill any container. (True)
  17. The density of ice is greater than that of water. (False)
  18. Boiling is a bulk phenomenon, whereas evaporation is a surface phenomenon. (True)
  19. Water evaporates faster on a humid day. (False)
  20. The temperature remains constant during a change of state. (True)
  21. Solids can be easily compressed like gases. (False)
  22. Freezing is an exothermic process. (True)
  23. Plasma is the fourth state of matter. (True)
  24. Evaporation occurs more rapidly at lower temperatures. (False)
  25. Sublimation is the direct conversion of a gas to a solid. (False)
  26. Boiling occurs at a fixed temperature, while evaporation can occur at any temperature. (True)
  27. Ice at 0°C feels colder than water at 0°C. (True)
  28. The melting point of a substance is the same as its freezing point. (True)
  29. Solids can flow like liquids. (False)
  30. Gases have strong intermolecular forces. (False)
  31. Condensation is the process of gas turning into a liquid. (True)
  32. Diffusion is slower in gases than in liquids. (False)
  33. The boiling point of water decreases with altitude. (True)
  34. Water vapor is visible. (False)
  35. Naphthalene undergoes sublimation. (True)
  36. The latent heat of fusion is the heat energy required to convert a solid into a liquid without a temperature change. (True)
  37. Water boils at a higher temperature on a mountain than at sea level. (False)
  38. Liquids have a definite volume but not a definite shape. (True)
  39. The particles in gases are closely packed. (False)
  40. A substance must reach its boiling point before evaporation can occur. (False)
  41. Freezing is the reverse of melting. (True)
  42. Intermolecular spaces are the smallest in solids. (True)
  43. The kinetic energy of particles decreases as temperature increases. (False)
  44. The latent heat of vaporization is the energy required to change a liquid into a gas at its boiling point. (True)
  45. Dry ice is the solid form of oxygen. (False)
  46. Boiling and evaporation are the same processes. (False)
  47. Water expands when it freezes. (True)
  48. Steam has more energy than boiling water at the same temperature. (True)
  49. Matter is made up of molecules. (True)
  50. The rate of evaporation increases with an increase in humidity. (False)

Long Answer Questions

Give Reasons

  1. Solids have a definite shape and volume.
    → The particles in solids are tightly packed with strong intermolecular forces, keeping them fixed in position.
  2. Liquids take the shape of the container but have a definite volume.
    → The intermolecular forces in liquids are weaker than solids, allowing them to flow, but strong enough to maintain a fixed volume.
  3. Gases do not have a fixed shape or volume.
    → Gas particles are far apart with negligible intermolecular forces, allowing them to expand and fill any container.
  4. Solids are incompressible, whereas gases are highly compressible.
    → Solid particles are tightly packed with no space for compression, while gas particles have large spaces between them, allowing compression.
  5. A gas exerts pressure on the walls of its container.
    → Gas molecules move randomly and collide with the container walls, exerting pressure.
  6. When salt is dissolved in water, the water level does not rise significantly.
    → Salt particles occupy spaces between water molecules, so the overall volume change is negligible.
  7. Sugar dissolves faster in hot water than in cold water.
    → Heat increases molecular motion, making sugar molecules disperse quickly in hot water.
  8. Gases diffuse faster than liquids.
    → Gas particles have more kinetic energy and larger intermolecular spaces, allowing them to diffuse quickly.
  9. A sponge can be compressed despite being a solid.
    → A sponge has tiny air-filled pores, which get compressed when pressed.
  10. Perfume spreads quickly in a room even if sprayed at one corner.
    → The gaseous particles of the perfume diffuse rapidly in air due to random motion.
  11. Boiling occurs at a fixed temperature, but evaporation occurs at all temperatures.
    → Boiling requires enough energy to convert the entire liquid into vapor, while evaporation happens when surface molecules gain sufficient energy.
  12. Evaporation causes cooling.
    → During evaporation, liquid molecules absorb heat from their surroundings, causing a cooling effect.
  13. Water stored in an earthen pot remains cool.
    → Water seeps out through the tiny pores of the pot and evaporates, taking away heat.
  14. Wet clothes dry faster on a windy day.
    → Wind removes the saturated air around wet clothes, increasing the rate of evaporation.
  15. Water boils at a lower temperature at higher altitudes.
    → Atmospheric pressure is lower at higher altitudes, so water molecules require less heat to escape as vapor.
  16. LPG cylinders contain liquefied gas instead of gaseous fuel.
    → Liquefied gas occupies less space and can be stored under high pressure for convenience.
  17. Naphthalene balls disappear after some time.
    → Naphthalene undergoes sublimation, directly changing from solid to gas.
  18. Camphor disappears when left open.
    → Camphor sublimes, converting directly into vapor without becoming liquid.
  19. Water droplets form on the outer surface of a cold glass.
    → Water vapor from the air condenses on the cold surface of the glass.
  20. Steam causes more severe burns than boiling water.
    → Steam contains additional latent heat of vaporization, releasing extra energy when it condenses.
  21. Melting and freezing occur at the same temperature.
    → The temperature at which a solid melts into liquid is the same at which a liquid freezes into solid.
  22. Gases expand on heating.
    → Heat increases the kinetic energy of gas molecules, making them move apart and expand.
  23. Pressure cookers cook food faster.
    → Increased pressure raises the boiling point of water, allowing food to cook at a higher temperature.
  24. Dry ice does not melt into a liquid but directly turns into gas.
    → Dry ice is solid CO₂, which undergoes sublimation instead of melting.
  25. A balloon bursts when taken to high altitude.
    → Atmospheric pressure decreases with altitude, causing the gas inside the balloon to expand until it bursts.
  26. Boiling water remains at 100°C even when heated further.
    → Extra heat is used to convert liquid into vapor (latent heat of vaporization).
  27. A piece of iron expands on heating.
    → Heating increases molecular motion, causing expansion.
  28. A metal lid of a jar expands when heated.
    → Metal expands on heating due to increased molecular vibrations, making it easier to open.
  29. Air pressure inside a car tire increases on a hot day.
    → Heat increases gas molecule movement, raising pressure.
  30. Milk overflows when boiled but water does not.
    → Milk contains proteins and fats that trap steam, forming foam that spills over.
  31. Smell of hot food spreads faster than cold food.
    → Heat increases kinetic energy, allowing gas molecules to diffuse faster.
  32. Why does ice float on water?
    → Ice is less dense than water due to its open crystalline structure.
  33. Why does mercury in a thermometer rise when heated?
    → Mercury expands on heating, moving up the scale.
  34. Condensation is the reverse of vaporization.
    → In condensation, gas molecules lose energy and come closer to form a liquid.
  35. Aerosol sprays contain compressed gas.
    → Compressed gas expands rapidly when released, creating a fine mist.
  36. Water evaporates faster in a dry climate than in a humid climate.
    → Low humidity allows more water to evaporate since the air can hold more moisture.
  37. When ice melts, the temperature remains constant.
    → Heat energy is used to break intermolecular bonds instead of raising temperature.
  38. Why do ice packs help reduce swelling?
    → Ice absorbs heat from the swollen area, reducing temperature and inflammation.
  39. We can smell petrol from an open bottle even from a distance.
    → Petrol has high volatility, allowing its molecules to diffuse quickly.
  40. During a hot day, the road appears wet from a distance.
    → This is due to the mirage effect, where hot air bends light rays, creating an illusion of water.
  41. Alcohol feels cool when applied to the skin.
    → Alcohol evaporates quickly, absorbing heat from the skin.
  42. A cooling unit is placed at the top of a refrigerator.
    → Cold air is denser and sinks, allowing efficient cooling of the entire space.
  43. Clouds form due to condensation.
    → Water vapor cools at high altitudes, condensing into tiny droplets that form clouds.
  44. Frost forms on the ground during winter nights.
    → Water vapor directly freezes into solid ice due to low temperatures.
  45. Air conditioners work better in dry regions.
    → In dry air, water evaporates faster, enhancing the cooling effect.
  46. Glass cracks when hot water is poured into it on a cold day.
    → Sudden temperature change causes uneven expansion, leading to cracks.
  47. When a gas is compressed, its temperature increases.
    → Compression reduces intermolecular space, increasing collisions and temperature.
  48. Water boils faster in a vacuum than under normal conditions.
    → Reduced pressure lowers the boiling point, requiring less heat to boil.
  49. Railway tracks have gaps between them.
    → Metal expands in hot weather, preventing deformation due to thermal expansion.
  50. Household refrigerators cool faster when not overloaded.
    → Proper air circulation allows even cooling, improving efficiency.

Arrange the Words 

Case Studies

Case Study 1: Ice Cream Melting

Ravi bought an ice cream and stood in the sun for a long time. He noticed that the ice cream started melting.

Q1: Which process is responsible for this change?
A: Melting

Q2: What happens to the intermolecular force during this process?
A: The intermolecular force decreases as the solid turns into a liquid.

Q3: Which form of energy is absorbed during melting?
A: Latent heat of fusion

 

 

Case Study 2: Water Boiling in a Kettle

Aisha placed a kettle of water on the stove. After a few minutes, she saw bubbles forming and steam escaping from the spout.

Q1: What is the process occurring in the kettle?
A: Boiling

Q2: At what temperature does pure water boil at sea level?
A: 100°C

Q3: What happens to the kinetic energy of water molecules during boiling?
A: It increases, causing the molecules to move apart and turn into vapor.

 

 

Case Study 3: Wet Clothes Drying on a Windy Day

Rahul hung his wet clothes outside. He noticed that they dried faster on a windy day compared to a humid day.

Q1: What process is responsible for the drying of clothes?
A: Evaporation

Q2: Why do clothes dry faster on a windy day?
A: Wind removes the moist air around the clothes, increasing the evaporation rate.

Q3: How does humidity affect the rate of evaporation?
A: Higher humidity decreases the rate of evaporation.

 

 

Case Study 4: Pressure Cooker Whistle

While cooking rice, Priya heard the pressure cooker whistle after some time.

Q1: Why does the pressure inside the cooker increase?
A: The trapped steam increases the pressure inside the cooker.

Q2: How does the increased pressure affect the boiling point of water?
A: The boiling point of water increases under high pressure.

Q3: What is the advantage of using a pressure cooker?
A: It cooks food faster by increasing the boiling point of water.

 

 

Case Study 5: Camphor Disappearing Over Time

A piece of camphor was kept in an open dish. After a few days, it became smaller without leaving any liquid behind.

Q1: Which process is responsible for this change?
A: Sublimation

Q2: What state change occurs during sublimation?
A: Solid directly changes into gas.

Q3: Name another substance that undergoes sublimation.
A: Naphthalene

 

 

Case Study 6: Water Droplets on a Cold Glass

Sonia poured chilled juice into a glass. After some time, she saw water droplets forming on the outer surface of the glass.

Q1: What is the phenomenon occurring here?
A: Condensation

Q2: Why do water droplets form on the glass?
A: Water vapor in the air loses heat and condenses into liquid.

Q3: What role does temperature play in condensation?
A: Lower temperatures increase the rate of condensation.

 

 

Case Study 7: Balloon Bursting at High Altitude

A helium-filled balloon was released into the sky. After reaching a high altitude, it burst.

Q1: Why did the balloon burst at a high altitude?
A: Air pressure decreases with altitude, causing the balloon to expand and burst.

Q2: Which law explains this phenomenon?
A: Boyle’s Law (Pressure is inversely proportional to volume).

Q3: What happens to the density of air as altitude increases?
A: The density of air decreases.

 

 

Case Study 8: Refrigeration and Cooling

A refrigerator keeps food cool even when the room temperature is high.

Q1: What principle does a refrigerator work on?
A: Evaporation and condensation cycle.

Q2: Why does evaporation cause cooling?
A: It absorbs heat from the surroundings.

Q3: What fluid is used in refrigerators for cooling?
A: Refrigerant (commonly Freon or other cooling gases).

 

 

Case Study 9: Mercury in a Thermometer

Rohan measured his body temperature using a mercury thermometer.

Q1: Why is mercury used in thermometers?
A: It expands uniformly with temperature changes.

Q2: What property of mercury makes it a good liquid for thermometers?
A: It has high thermal conductivity and does not stick to glass.

Q3: What is the normal body temperature of a human?
A: 37°C (98.6°F)

 

 

Case Study 10: Steam Causing Severe Burns

Neha accidentally touched boiling water and steam. She noticed that the steam caused more pain than the hot water.

Q1: Why does steam cause more severe burns than boiling water?
A: Steam contains latent heat of vaporization.

Q2: What happens when steam condenses on the skin?
A: It releases heat, causing more burns.

Q3: What is the boiling point of water?
A: 100°C

Numericals

Numeric problems are not available for this chapter.

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