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All questions of Matter in Our Surroundings for Class 9 Exam

What is the physical state of water at 100°C?
  • a)
    both gaseous and liquid state
  • b)
    solid state
  • c)
    liquid state
  • d)
    gaseous state
Correct answer is option 'A'. Can you explain this answer?

Arvind Singh answered
At 100°C, water exists in both the liquid state as well as in gaseous state. This is special condition because 100°C is the boiling point of water and as well as liquefaction temperature of the water vapour

What is the physical state of water at100C?
  • a)
    Liquid
  • b)
    Solid
  • c)
    gas
  • d)
    All of these
Correct answer is 'B'. Can you explain this answer?

Arjun Sharma answered
The answer is a .
The physical state of water at its boiling point temperature of 100 degree Celsius will be both liquid state as well as gaseous state. This is because at its boiling point of 100 degree celsius the liquid state of water starts changing into its Gaseous state (steam).

An Almirah is a solid because its
  • a)
    hard and rigid
  • b)
    shape doesn’t change when pressed
  • c)
    density is very high
  • d)
    All of these
Correct answer is 'D'. Can you explain this answer?

An almirah is solid because it is hard and rigid, have fixed shape and have very high density. All these properties are possessed by solid substance only.

Find the incorrect statement
  • a)
    Low boiling liquids evaporate faster than high boiling liquids.
  • b)
    Cooling is caused during boiling
  • c)
    The normal room temperature is 298K and 293K both.
  • d)
    Evaporation is a surface phenomenon but boiling is not
Correct answer is option 'B'. Can you explain this answer?

Raghav Bansal answered
The normal room temperature is 298K or 25C.  Other common values are 293 K (20 C or 68 F). Evaporation is a surface phenomenon but boiling is bulk phenomenon. Liquid having low boiling points evaporate faster. Cooling is not caused during boiling.

Arrange the following substances in increasing order of attraction between the particles: water, sugar, oxygen.
  • a)
    water < sugar < oxygen
  • b)
    oxygen < water < sugar
  • c)
    sugar < oxygen < water
  • d)
    none
Correct answer is option 'B'. Can you explain this answer?

Ravi Verma answered
Sugar is a solid; the forces of attraction between the particles of sugar are strong. Water is a liquid; the forces of attraction here are weaker than sugar. Oxygen is a gas; the forces of attraction are the weakest in gases.
Thus, the increasing order of forces of attraction between the particles of water, sugar and oxygen is
Oxygen < Water < Sugar

Which of the following does not affect rate of evaporation?
  • a)
    Wind speed
  • b)
    Surface area      
  • c)
    Temperature
  • d)
    Insoluble heavy impurities
Correct answer is option 'D'. Can you explain this answer?

Subham Gupta answered
Factors Affecting Rate of Evaporation

Wind Speed: Higher wind speeds can increase the rate of evaporation by carrying away the water vapor molecules from the surface, creating a lower concentration of water vapor around the liquid. This allows more water molecules to evaporate.

Surface Area: A larger surface area can increase the rate of evaporation as more liquid molecules are exposed to the air, allowing for more evaporation to occur.

Temperature: Higher temperatures can increase the rate of evaporation as the kinetic energy of the liquid molecules increases, leading to more molecules escaping into the air.

Insoluble Heavy Impurities: Insoluble heavy impurities do not affect the rate of evaporation. These impurities remain in the liquid and do not impact the evaporation process. The rate of evaporation is primarily influenced by factors such as wind speed, surface area, and temperature.

Which of the following is not correct? 
  • a)
    SI unit of temperature is kelvin 
  • b)
    SI unit of pressure is Newton
  • c)
    SI unit of density is kg/m3 
  • d)
    1 litre = 1000 cm3 - 1 dm3 
Correct answer is option 'B'. Can you explain this answer?

Kritika Bose answered
SI Units of Measurement

SI units are the International System of Units, which is the modern form of the metric system. It is used in scientific and technical fields as a standard system of measurement. The SI system has seven base units, which are used to derive all other units of measurement.

SI Units of Temperature, Pressure, Density and Volume

Temperature: The SI unit of temperature is Kelvin (K), not Celsius (°C).

Pressure: The SI unit of pressure is Pascal (Pa), not atm (atmosphere).

Density: The SI unit of density is kilograms per cubic meter (kg/m3).

Volume: The SI unit of volume is cubic meter (m3). However, liter (L) is also commonly used as a non-SI unit of volume. 1 L = 1000 cm3 = 1 dm3.

Conclusion

Option B is not correct because the SI unit of pressure is Pascal (Pa), not atm (atmosphere). Atm is a non-SI unit of pressure. Therefore, the correct answer is option B.

Which of the following statements is incorrect?
  • a)
    Matter is made up of particles
  • b)
    Particles of matter are always in state of motion
  • c)
    Matter is continuous in nature
  • d)
    Particles of matter attract each other
Correct answer is option 'C'. Can you explain this answer?

Incorrect Statement: Matter is continuous in nature.

Explanation:

Matter is made up of small particles called atoms and molecules that have mass and occupy space. These particles are not continuous but are separated by empty spaces. Therefore, the statement that "matter is continuous in nature" is incorrect.

Evidence Supporting the Correct Statements:

a) Matter is made up of particles:

The concept of matter being made up of small particles was first proposed by the Greek philosopher Democritus in the 5th century BC. This idea was later supported by scientists like John Dalton, who proposed the atomic theory of matter in the 19th century. Today, we know that matter is made up of atoms and molecules.

b) Particles of matter are always in a state of motion:

Particles of matter are always in motion, even when they appear to be at rest. This motion can be either random or organized. The kinetic theory of matter explains that the temperature of matter is related to the speed of its particles. When matter is heated, the particles move faster and vice versa.

d) Particles of matter attract each other:

Particles of matter attract each other due to the presence of forces like gravitational, electric, and magnetic forces. These forces allow particles to stick together and form larger structures like molecules, crystals, and even planets.

Conclusion:

In conclusion, the statement that "matter is continuous in nature" is incorrect. Matter is made up of small particles that are separated by empty spaces. These particles are always in motion and attract each other due to the presence of forces.

Assertion (A): Water droplets form on the outer surface of a glass containing ice-cold water.
Reason (R): Water evaporates from the glass and condenses on the outside.
  • a)
    If both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • b)
    If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • c)
    If Assertion is true but Reason is false
  • d)
    If both Assertion and Reason are false
Correct answer is option 'C'. Can you explain this answer?

- Assertion (A) is true: Water droplets form on the outer surface of a glass containing ice-cold water because the cold temperature of the glass causes moisture in the air to condense.
- Reason (R) is false: Water does not evaporate from the glass and condense on the outside. Instead, the moisture in the surrounding air condenses on the cooler surface of the glass.
- Therefore, the correct option is C: The assertion is true, but the reason is false.

What is the physical state of water at 1000C?
  • a)
    gaseous
  • b)
    Solid
  • c)
    Liquid
  • d)
    All of these
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
The boiling point of water is 100°C. The physical state of water at its boiling point temperature of 100 degree Celsius will be both liquid state as well as gaseous state.

Which one of the following sets of phenomenon would increase on raising the temperature?
  • a)
    Evaporation, diffusion, compression of gases 
  • b)
    Evaporation, compression of gases, solubility 
  • c)
    Evaporation, diffusion, expansion of gases 
  • d)
    Evaporation, solubility, diffusion, compression of gases.
Correct answer is option 'C'. Can you explain this answer?

Mihir Shah answered
The correct answer is option 'C': Evaporation, diffusion, expansion of gases.

Explanation:
When the temperature is increased, several physical processes tend to increase. These processes include evaporation, diffusion, and expansion of gases. Let's understand each of these phenomena in detail:

1. Evaporation:
Evaporation is the process by which a liquid changes into a vapor or gas at temperatures below its boiling point. When the temperature is increased, the kinetic energy of the molecules in the liquid also increases. As a result, more molecules gain enough energy to overcome the attractive forces of the liquid and escape into the gas phase. Therefore, evaporation increases with an increase in temperature.

2. Diffusion:
Diffusion is the process of movement of particles from an area of higher concentration to an area of lower concentration. It occurs due to the random motion of particles. When the temperature is increased, the kinetic energy of the particles also increases. This increased kinetic energy leads to faster and more frequent collisions between particles, resulting in an increased rate of diffusion.

3. Expansion of gases:
When gases are heated, their molecules gain kinetic energy and move faster. This increased molecular motion leads to an increase in the volume of the gas because the molecules now occupy a larger space. Therefore, gases expand when the temperature is raised.

These three phenomena - evaporation, diffusion, and expansion of gases - all increase with an increase in temperature.

Let's summarize the answer:

- Evaporation, the process by which a liquid changes into a vapor or gas, increases with an increase in temperature.
- Diffusion, the movement of particles from an area of higher concentration to an area of lower concentration, increases with an increase in temperature.
- Expansion of gases occurs when the temperature is raised, as the increased kinetic energy of the gas molecules causes them to move faster and occupy a larger volume.

Hence, the correct answer is option 'C': Evaporation, diffusion, expansion of gases.

Which state of matter has particles that move freely and has maximum space between them?
  • a)
    Solid
  • b)
    Liquid
  • c)
    Gas
  • d)
    Plasma
Correct answer is option 'C'. Can you explain this answer?

Pranjal Gupta answered
Understanding States of Matter
Matter exists in different states, primarily solid, liquid, gas, and plasma. Each state has unique characteristics based on the arrangement and movement of its particles.
Characteristics of Gases
- Particle Movement: In gases, particles move freely and rapidly. They do not have a fixed position, allowing them to spread out in any direction.
- Spacing: There is maximum space between gas particles compared to solids and liquids. This spacing allows gases to expand and fill the entire volume of their container.
Comparison with Other States
- Solids: In solids, particles are tightly packed and vibrate in fixed positions. This results in a definite shape and volume.
- Liquids: In liquids, particles are close together but can slide past one another. Liquids have a definite volume but take the shape of their container.
- Plasma: Plasma consists of ionized gases with free-moving charged particles. While particles in plasma can also move freely, they are significantly affected by electric and magnetic fields.
Conclusion
The correct answer is option C: Gas because gases have particles that move freely with a maximum distance between them, allowing for the properties of expansion and compressibility. This unique arrangement makes gases distinct from solids and liquids, which have more structured particle arrangements.

Statement A: Celsius scale is the best scale for measuring temperature. 
Statement B: CO2 (liquid state) is stored under high pressure.
Which of the two statements is true?
  • a)
    Statement A
  • b)
     Neither a nor b
  • c)
    Statement B
  • d)
    Both a and b
Correct answer is option 'C'. Can you explain this answer?

Yashika Gupta answered
Understanding the Statements
Statement A: "Celsius scale is the best scale for measuring temperature."
Statement B: "CO2 (liquid state) is stored under high pressure."
Analysis of Statement A
- The Celsius scale is widely used for everyday temperature measurement, particularly in most countries.
- However, it may not be the best scale for all scientific applications.
- For example, the Kelvin scale is preferred in scientific contexts as it starts from absolute zero, providing a more accurate representation of thermal energy.
Analysis of Statement B
- Carbon dioxide (CO2) in its liquid state must be stored under high pressure.
- This is necessary because CO2 only becomes liquid at pressures above 5.1 atmospheres at room temperature.
- Hence, storing liquid CO2 requires specialized high-pressure containers to maintain its liquid form.
Conclusion
- Statement A is subjective and not universally true; thus, it is not entirely accurate to claim it is the best scale.
- Statement B is a factual statement regarding the storage of liquid CO2 under high pressure.
Final Answer
- Therefore, the correct answer is option 'C': Statement B is true, while Statement A is not necessarily the best.

Which of the following does not undergo sublimation? 
  • a)
    Ammonium chloride 
  • b)
    Sodium chloride 
  • c)
    Solid carbon dioxide 
  • d)
    Iodine
Correct answer is option 'B'. Can you explain this answer?

Ananya Das answered
Sublimation is when a solid changes directly to gas without changing into liquid.
NaCl when heated does not change its state when heated , while all the other options sublime. Hence sodium chloride is the right answer.

Latent heat of fusion is amount of 
  • a)
    heat energy required to change 1 kg solid into liquid completely at its melting point
  • b)
    heat energy required to convert 1 kg solid into liquid at room temperature
  • c)
    heat energy required to change 1 g of solid into liquid completely
  • d)
    heat energy required to change 1 kg of solid into liquid at any temperature
Correct answer is option 'A'. Can you explain this answer?

Sara Khanna answered
Latent Heat of Fusion

Latent heat of fusion refers to the amount of heat energy required to change 1 kg of solid into a liquid completely at its melting point. This is a specific type of heat energy that is required for a substance to change phases from a solid to a liquid.

Explanation

When a solid substance is heated, its temperature increases until it reaches its melting point. Once the substance reaches its melting point, the heat energy being added is used to break the bonds between the molecules in the solid, allowing the molecules to move more freely and become a liquid. This process requires a certain amount of heat energy, which is known as the latent heat of fusion.

The latent heat of fusion is a specific amount of heat energy that is required to change 1 kg of a substance from a solid to a liquid at its melting point. It is a characteristic property of each substance and is typically measured in units of J/kg.

For example, the latent heat of fusion of water is 334 kJ/kg. This means that it takes 334 kJ of heat energy to melt 1 kg of ice into liquid water at 0°C.

Conclusion

In conclusion, the latent heat of fusion is the amount of heat energy required to change a substance from a solid to a liquid at its melting point. It is a characteristic property of each substance and is typically measured in units of J/kg.

Why does the smell of food reach us in seconds?
  • a)
    Because the particles of food are very small
  • b)
    Because of the high speed of particles in gases
  • c)
    Because the food particles are heavy
  • d)
    Because food particles dissolve in water
Correct answer is option 'B'. Can you explain this answer?

Shruti Rao answered
Understanding the Smell of Food
The rapid detection of food aromas can be attributed to the properties of gases and how they interact with our sensory systems.
High Speed of Gas Particles
- Gases consist of particles that are in constant motion.
- These particles travel at high speeds, allowing them to disperse quickly in the air.
- When food is cooked or heated, volatile compounds are released.
- These compounds are tiny particles that move rapidly, reaching our noses almost instantaneously.
Diffusion of Odors
- The process by which these particles spread out is known as diffusion.
- In the case of gases, diffusion occurs quickly due to the high energy levels of the particles.
- As the food particles collide with air molecules, they disperse throughout the surrounding environment.
Human Sensory Response
- Our olfactory receptors, located in the nasal cavity, are highly sensitive to these odor particles.
- When these particles reach our noses, they bind to the receptors, sending signals to our brain that interpret the smell.
- This system is extremely efficient, enabling us to detect food odors within seconds.
Conclusion
In summary, the reason we can smell food almost instantly is primarily due to the high speed of particles in gases. The rapid motion and diffusion of these tiny particles allow their scent to reach us quickly, stimulating our sense of smell and enhancing our experience of food.

As the temperature of a solid increases, the particles gain more kinetic energy and start vibrating vigorously. Eventually, the forces of attraction between the particles are overcome and the solid changes into a liquid. The minimum temperature at which this happens (at atmospheric pressure) is called the:
  • a)
    Sublimation point
  • b)
    Melting point
  • c)
    Boiling point
  • d)
    Evaporation point
Correct answer is option 'B'. Can you explain this answer?

When a solid is heated, its particles absorb energy and start vibrating faster and faster. As the temperature rises, these vibrations become strong enough to overcome the attractive forces holding the particles together.
At the exact temperature where those forces finally break and the solid transforms into a liquid — that magical threshold is called the melting point.

It’s the lowest temperature at which a solid becomes a liquid at normal atmospheric pressure.
Boiling point is for liquid → gas, sublimation is solid → gas, evaporation is slow liquid → gas…
But solid → liquid?
That’s 100% the melting point. 🌡️✨

What is the latent heat of fusion?
  • a)
    The heat energy required to change a liquid into gas
  • b)
    The heat energy required to change a solid into liquid
  • c)
    The heat energy required to increase the temperature of a solid
  • d)
    The heat energy required to change a gas into liquid
Correct answer is option 'B'. Can you explain this answer?

The latent heat of fusion refers to the amount of heat energy needed to convert a solid into a liquid at its melting point, without changing its temperature. Here are some key points:
  • The process occurs at the melting point of the solid.
  • During this change, the temperature remains constant.
  • The heat energy is used to overcome the forces of attraction between the particles.
  • For example, when ice melts, it absorbs heat without an increase in temperature.
  • The latent heat of fusion is typically measured in joules per kilogram (J/kg).
In summary, the latent heat of fusion is essential for understanding how solids transition to liquids while maintaining a stable temperature.

Name the state of matter that ‘has minimum interparticle attraction’
  • a)
    Liquid
  • b)
    Solid
  • c)
    gas
  • d)
    All of these
Correct answer is option 'C'. Can you explain this answer?

Gases have not definite shape and volume and highly incompressible. solid posses rigidity and liquid and gases posses fluidiy .

What is the main reason gases exert pressure on the walls of their container?
  • a)
    Due to their high density
  • b)
    Due to their random movement and collision with container walls
  • c)
    Due to the fixed position of particles
  • d)
    Due to the solid state of the gas
Correct answer is option 'B'. Can you explain this answer?

Rajdeep Das answered
Understanding Gas Pressure
Gases exert pressure on the walls of their container primarily due to the random movement and collisions of their particles. Here’s a detailed breakdown of why this occurs:
Random Movement of Gas Particles
- Gas particles are in constant, rapid motion.
- They move freely in all directions, resulting in a wide range of velocities.
Collisions with Container Walls
- As gas particles travel, they frequently collide with the walls of their container.
- Each collision exerts a small force on the wall.
Accumulation of Forces
- The total pressure exerted by the gas is the cumulative effect of countless collisions occurring per second.
- The more frequent and forceful these collisions, the higher the pressure exerted on the walls.
Key Factors Influencing Gas Pressure
- Temperature: Higher temperatures increase particle speed, leading to more frequent and forceful collisions.
- Volume: Reducing the volume of the container can increase the rate of collisions, thereby increasing pressure.
- Number of Particles: More particles in a given volume increase the likelihood of collisions, raising the pressure.
Conclusion
In essence, the pressure exerted by gases is a direct result of their dynamic nature and the interactions between the particles and the container walls. Understanding this concept is fundamental in the study of gas behavior and properties.

The temperature at which a liquid starts boiling is called its:
  • a)
    Melting point
  • b)
    Freezing point
  • c)
    Boiling point
  • d)
    Sublimation point
Correct answer is option 'C'. Can you explain this answer?

Geetika Menon answered
Understanding Boiling Point
The boiling point of a liquid is a fundamental concept in thermodynamics and chemistry. It refers to the specific temperature at which a liquid transitions into a gas.
Definition of Boiling Point
- The boiling point is defined as the temperature at which the vapor pressure of a liquid equals the atmospheric pressure surrounding it.
- At this temperature, the molecules within the liquid gain enough energy to overcome intermolecular forces, allowing them to escape into the gas phase.
Comparison with Other Points
- Melting Point: This is the temperature at which a solid turns into a liquid. It is different from the boiling point, as it deals with the solid-liquid phase transition.
- Freezing Point: The temperature at which a liquid becomes a solid. Like the melting point, it involves a change of state but in the opposite direction.
- Sublimation Point: This refers to the temperature and pressure at which a solid changes directly into a gas without passing through the liquid state, which is not applicable in the context of liquids boiling.
Importance of Boiling Point
- The boiling point is crucial for various applications, including cooking, industrial processes, and the formulation of chemical substances.
- It also helps in identifying and characterizing substances, as different liquids have distinct boiling points.
In summary, option 'C' is correct because the boiling point specifically refers to the temperature at which a liquid begins to boil and transition into vapor, differentiating it from other thermal transitions such as melting and freezing.

Choose the correctly matched pair.
  • a)
    Boiling Point of Water - 273 K
  • b)
    Melting Point of Ice - 373 K
  • c)
    Latent Heat of Fusion - Energy required to change 1 kg of solid to liquid
  • d)
    Latent Heat of Vaporisation - Temperature at which a liquid starts boiling
Correct answer is option 'C'. Can you explain this answer?

  • Option A: Boiling Point of Water - 273 K
    • This is incorrect because the boiling point of water is 373 K, not 273 K. 273 K is the melting point of ice.
  • Option B: Melting Point of Ice - 373 K
    • This is incorrect because the melting point of ice is 273 K, not 373 K. 373 K is the boiling point of water.
  • Option C: Latent Heat of Fusion - Energy required to change 1 kg of solid to liquid
    • This is correct. The latent heat of fusion is defined as the amount of heat energy required to change 1 kg of a solid into a liquid at atmospheric pressure at its melting point.
  • Option D: Latent Heat of Vaporisation - Temperature at which a liquid starts boiling
    • This is incorrect. The latent heat of vaporisation is the amount of heat energy required to change 1 kg of a liquid into a gas at atmospheric pressure at its boiling point. The temperature at which a liquid starts boiling is known as its boiling point.
  • Therefore, the correctly matched pair is Option C: (c) Latent Heat of Fusion - Energy required to change 1 kg of solid to liquid.

What property of matter allows gases to be highly compressible compared to solids and liquids?
  • a)
    Definite shape
  • b)
    Fixed volume
  • c)
    Random movement of particles
  • d)
    Rigid structure
Correct answer is option 'C'. Can you explain this answer?

Understanding Gas Compressibility
Gases exhibit a unique property of high compressibility, which sets them apart from solids and liquids. The key reason for this phenomenon lies in the behavior of gas particles.
Random Movement of Particles
- Gases consist of particles (atoms or molecules) that are in constant, random motion.
- This movement is not restricted, allowing particles to spread out and occupy a larger volume.
- The distance between gas particles is significantly greater than in solids and liquids, where particles are more tightly packed.
Low Density
- Because gas particles are spread out, gases have a lower density compared to solids and liquids.
- This low density contributes to the ease with which gases can be compressed.
Interactions Between Particles
- In gases, the forces of attraction between particles are minimal, allowing them to move freely.
- When pressure is applied to a gas, the particles can be pushed closer together, resulting in compression.
Comparison with Solids and Liquids
- Solids have a definite shape and fixed volume due to closely packed particles that vibrate in place.
- Liquids have a fixed volume but take the shape of their container; however, their particles are still closer together than in gases.
- In both solids and liquids, particle movement is restricted, making them less compressible.
Conclusion
In summary, the high compressibility of gases compared to solids and liquids is primarily due to the random movement of particles, which allows them to occupy more space and be compressed easily under pressure. This fundamental characteristic is crucial in various applications, from industrial processes to understanding atmospheric behavior.

Assertion (A): Evaporation causes cooling in an open vessel.
Reason (R): Energy is absorbed from the surroundings during evaporation, leading to a decrease in temperature.
  • a)
    If both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • b)
    If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • c)
    If Assertion is true but Reason is false
  • d)
    If both Assertion and Reason are false
Correct answer is option 'A'. Can you explain this answer?

C K Academy answered
Explanation:
  • The Assertion that evaporation causes cooling in an open vessel is correct. When liquid evaporates, the particles of the liquid absorb energy from the surroundings to compensate for the energy lost during the process. This absorption of energy results in a cooling effect, making the surroundings feel colder.
  • The Reason provided explains this phenomenon accurately. Energy absorption during evaporation is a key factor that leads to the cooling effect. Therefore, the Reason is a correct explanation for the Assertion.
Conclusion:
  • Both the Assertion and Reason are true, and the Reason accurately explains why the Assertion is valid. Hence, Option A is the correct answer choice.

Why does ice float on water despite having a lower density than water?
  • a)
    Ice has more particles than water
  • b)
    Ice is made up of larger particles
  • c)
    Ice has air trapped inside, making it less dense than water
  • d)
    Ice and water have the same density
Correct answer is option 'C'. Can you explain this answer?

C K Academy answered
Ice floats on water because it is less dense than liquid water.
The reason for this lies in the molecular structure of ice:
  • Ice forms a crystalline structure that creates gaps between its molecules.
  • These gaps trap air, contributing to its lower density.
  • This allows ice to float on water, which has a higher density.
This unique property of ice is vital for aquatic life, as it insulates the water below and helps maintain a stable environment.

What is the melting point of ice?
  • a)
    373 K
  • b)
    277 K
  • c)
    273.15 K
  • d)
    100 K
Correct answer is option 'C'. Can you explain this answer?

C K Academy answered
The melting point of ice is 273.15 K, which is equivalent to 0°C. This is the temperature at which solid ice transforms into liquid water.
Key points about the melting process:
  • The melting point indicates the strength of the forces between the particles in a solid.
  • During melting, the temperature remains constant until all the ice has converted to water.
  • Heat energy supplied during this process is used to overcome the attractive forces between particles.
This process is also referred to as fusion.

Which of the following is true about the latent heat of vaporization?
  • a)
    It is the heat energy required to melt a solid
  • b)
    It is the heat energy required to convert a liquid into gas
  • c)
    It is the heat energy required to solidify a liquid
  • d)
    It is the heat energy required to increase the temperature of a gas
Correct answer is option 'B'. Can you explain this answer?

Imk Pathshala answered
The latent heat of vaporization is the amount of heat energy needed to convert a liquid into a gas without changing its temperature. Here are some key points:
  • This process occurs at the boiling point of the liquid.
  • During vaporization, heat energy is absorbed, which allows particles to break free from each other.
  • The term "latent" means hidden, as this heat does not raise the temperature.
  • For water, the latent heat of vaporization is significant, as it requires a considerable amount of energy to change from liquid to gas.

Which of the following is a characteristic of solids?
  • a)
    Have no definite shape
  • b)
    Have a fixed volume and shape
  • c)
    Flow easily
  • d)
    Can easily change shape
Correct answer is option 'B'. Can you explain this answer?

Solids have distinct characteristics that set them apart from other states of matter. Here are the key features:
  • Fixed Shape: Solids maintain a definite shape and do not change unless a significant force is applied.
  • Fixed Volume: They occupy a specific volume and do not expand or contract easily.
  • Packed Particles: The particles in solids are tightly packed in a fixed arrangement, making them rigid.
  • Resistance to Change: While solids can break under excessive force, they resist changes in shape.
Examples of solids include: Rubber Bands, Crystals and Sponge.

What happens when the temperature of a solid is increased?
  • a)
    Its particles vibrate more quickly
  • b)
    It turns into a gas immediately
  • c)
    Its particles slow down
  • d)
    It becomes more rigid
Correct answer is option 'A'. Can you explain this answer?

C K Academy answered
When the temperature of a solid increases:
  • The kinetic energy of its particles rises.
  • Particles begin to vibrate more quickly.
  • This increased vibration can lead to a phase change, such as melting.
  • As the solid continues to heat, particles may overcome the forces holding them in place, transitioning into a liquid state.
In summary, heating a solid causes its particles to move faster, which can eventually result in melting.

Choose the correctly matched pair.
  • a)
    Panch Tatva - Five Basic Elements
  • b)
    SI unit of mass - Litre
  • c)
    Particles of matter - Continuous
  • d)
    SI unit of volume - metre
Correct answer is option 'A'. Can you explain this answer?

EduRev Class 9 answered
  • Option A: Panch Tatva - Five Basic Elements: This is correctly matched. The Panch Tatva includes air, earth, fire, sky, and water, which are considered the fundamental elements of all matter.
  • Option B: SI unit of mass - Litre: This is incorrect. The SI unit of mass is kilogram (kg), while litre is a unit of volume.
  • Option C: Particles of matter - Continuous: This is incorrect. Matter is made up of discrete particles, not a continuous substance.
  • Option D: SI unit of volume - metre: This is incorrect. The SI unit of volume is cubic metre (m³), not metre.

Which state of matter has particles tightly packed in fixed positions?
  • a)
    Solid
  • b)
    Liquid
  • c)
    Gas
  • d)
    Plasma
Correct answer is option 'A'. Can you explain this answer?

C K Academy answered
In solids, particles are closely packed in a fixed arrangement. This structure gives solids their definite shape and volume. Key characteristics include:
  • Particles are tightly packed, making solids rigid.
  • They maintain their shape unless a significant force is applied.
  • Examples include items like wood, metal, and glass.
When subjected to force, solids may break, but their shape remains unchanged under normal conditions. This rigidity is a defining feature of the solid state of matter.

What happens when a sponge is compressed?
  • a)
    It stays the same size
  • b)
    The air trapped in the sponge is expelled
  • c)
    It becomes solid
  • d)
    It dissolves
Correct answer is option 'B'. Can you explain this answer?

C K Academy answered
When a sponge is compressed, the following occurs:
  • The air trapped inside the sponge is forced out.
  • This action reduces the sponge's volume.
  • As a result, the sponge becomes denser and easier to handle.
In summary, compressing a sponge expels air, allowing it to be compacted.

Shivam visited an LPG unit and found that the gas can be liquified at specific conditions of temperature and pressure. Help him to identify the correct set of conditions.
  • a)
    High temperature and high pressure
  • b)
    Low temperature and low pressure
  • c)
    Low temperature and high pressure
  • d)
    High temperature and low pressure
Correct answer is option 'C'. Can you explain this answer?

EduRev Class 9 answered
For liquefying gas, the correct conditions involve:
  • Low temperature - This reduces the kinetic energy of gas molecules, making them easier to condense.
  • High pressure - This forces gas molecules closer together, promoting liquefaction.
Combining low temperature and high pressure is ideal for converting gas to liquid.

Which of the following can change its shape under force?
  • a)
    A rubber band
  • b)
    A piece of wood
  • c)
    A metal rod
  • d)
    A stone
Correct answer is option 'A'. Can you explain this answer?

Shreya Bajaj answered
Understanding Shape Change Under Force
When evaluating which materials can change their shape under force, it's essential to consider their physical properties and behavior when subjected to stress.
Characteristics of Materials
  • Rubber Band:
    - Rubber bands are elastic materials, meaning they can stretch and return to their original shape when the force is removed.
    - This elasticity allows them to deform significantly under tension.
  • Piece of Wood:
    - Wood is a rigid material.
    - While it can bend slightly under a significant force, it typically breaks or splinters rather than returning to its original shape.
  • Metal Rod:
    - Metal rods are generally strong but also rigid.
    - They can bend under enough force, but like wood, they are likely to remain in that deformed state or fracture if the force exceeds their yield strength.
  • Stone:
    - Stone is an extremely rigid material.
    - It does not change shape easily under force and will typically break or shatter instead.

Conclusion
Among the options provided, only the rubber band can change its shape under force and return to its original form once the force is removed. This characteristic is due to its elastic nature, which allows for significant deformation without permanent change. In contrast, the other materials mentioned have rigid structures that resist deformation and do not revert to their original shapes once the force is applied.

Under what conditions does diffusion occur faster?
  • a)
    Low temperature
  • b)
    Low pressure
  • c)
    High temperature
  • d)
    High pressure
Correct answer is option 'C'. Can you explain this answer?

Diffusion becomes faster at high temperatures. This is because, at higher temperatures, the particles of matter gain more kinetic energy, allowing them to move more rapidly and intermix more quickly. As temperature increases, the kinetic energy overcomes the forces of attraction between particles, facilitating faster diffusion.

On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperature will be
  • a)
    298 K, 311 K and 339 K
  • b)
    298 K, 300 K and 338 K
  • c)
    273 K, 278 K and 543 K
  • d)
    298 K, 310 K and 338 K
Correct answer is option 'A'. Can you explain this answer?

Chirag Desai answered
Kelvin is the SI Unit of measurement of temperatures. It is represented with the Unit Kelvin 'K'.
Temperatures can be converted from Celsius to Kelvin by adding 273 to the the Celsius Scale.
We have been given 3 temperatures here which are in the Celsius Scale.
25°C, 38°C and 66°C
To convert all of them to the Kelvin Scale, add 273 to all of them.
25 + 273 = 298 K
38 + 273 = 311 K
66 + 273 = 339 K
Read more on Brainly.in - https://brainly.in/question/12484519#readmore

Which process involves the transformation of gas directly into a solid?
  • a)
    Vaporization
  • b)
    Sublimation
  • c)
    Condensation
  • d)
    Deposition
Correct answer is option 'D'. Can you explain this answer?

Tara Singh answered
Understanding Deposition
Deposition is a fascinating phase transition where a gas transforms directly into a solid without passing through the liquid state. This process is crucial in various natural and industrial phenomena.
Key Characteristics of Deposition:
- Direct Transition: In deposition, gas molecules lose energy and directly condense into a solid form. This bypasses the liquid phase entirely, making it unique among other phase changes.
- Examples in Nature: A common example of deposition is the formation of frost. When water vapor in the air comes into contact with a cold surface, it transforms directly into ice crystals, creating frost without becoming liquid water first.
- Role in Sublimation: Deposition is essentially the reverse of sublimation, where a solid transitions directly into a gas. Together, these processes illustrate the dynamic nature of matter and energy.
Comparison with Other Processes:
- Vaporization: This process involves the conversion of a liquid into a gas, which is the opposite of deposition.
- Sublimation: While sublimation refers to a solid becoming a gas, deposition does the reverse, indicating that they are complementary processes.
- Condensation: This is the transformation of a gas into a liquid, which again is distinct from deposition.
Significance of Deposition:
- Environmental Impact: Deposition plays a vital role in weather patterns and the formation of snowflakes, emphasizing its importance in atmospheric science.
- Industrial Applications: Understanding deposition can aid in processes like freeze-drying and the manufacturing of certain materials where direct solid formation is beneficial.
In summary, deposition is a critical process in both nature and industry, highlighting the intricate behaviors of materials under varying conditions.

Convert 300K into Celsius
  • a)
    2730C
  • b)
    5730C
  • c)
    270C
  • d)
    3000C
Correct answer is option 'C'. Can you explain this answer?

Zero on the Celsius scale is the equivalent to 273.15K  . 1- degree rise in Celsius scale is equivalent to the 1- degree rise in the kelvin scale. So , the correct answer is 
27� C

What are the three states of matter?
  • a)
    Solid, Liquid, Plasma
  • b)
    Solid, Liquid, Gas
  • c)
    Solid, Liquid, Energy
  • d)
    Gas, Liquid, Air
Correct answer is option 'B'. Can you explain this answer?

Understanding the Three States of Matter
Matter is anything that has mass and occupies space. The three classical states of matter are:
Solid
- Solids have a definite shape and volume.
- The particles in solids are closely packed together, creating a rigid structure.
- They vibrate in place but do not move freely, which gives solids their fixed form.
Liquid
- Liquids have a definite volume but take the shape of their container.
- The particles are less tightly packed than in solids, allowing them to slide past each other.
- This fluidity enables liquids to flow and take the shape of their surroundings.
Gas
- Gases have neither a definite shape nor a fixed volume.
- The particles are far apart and move freely, resulting in gases expanding to fill any available space.
- This characteristic makes gases compressible and easily adjustable to changes in temperature and pressure.
Why Option B is Correct
- Option 'b' (Solid, Liquid, Gas) correctly identifies the three fundamental states of matter.
- While other options may include terms like "Plasma" and "Energy," they do not represent the three primary states of matter.
- Plasma, for example, is a state of matter formed at extremely high temperatures, but it is not one of the classical states typically taught at the basic level.
Conclusion
Understanding these three states is crucial for grasping the behavior of matter in different physical conditions. Each state has unique properties that determine how substances interact in our world.

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