Matter - Compulsory Test - Class 9 MCQ

To determine the strongest interparticle force at room temperature, we need to consider the type of bonding or forces present in each substance.
Nitrogen:
- Nitrogen exists as diatomic molecules (N2) held together by triple covalent bonds.
- The interparticle forces in nitrogen are relatively weak van der Waals forces.
Mercury:
- Mercury is a liquid at room temperature and consists of individual mercury atoms.
- The interparticle forces in mercury are also weak van der Waals forces.
Iron:
- Iron is a solid at room temperature and has metallic bonding.
- Metallic bonding involves the sharing of delocalized electrons between metal atoms.
- The interparticle forces in iron are strong metallic bonds.
Chalk:
- Chalk is a solid composed mainly of calcium carbonate (CaCO3).
- The interparticle forces in chalk are primarily ionic bonds between calcium and carbonate ions.
Based on the analysis above, the substance with the strongest interparticle force at room temperature is Iron due to its strong metallic bonding.

The change of state from solid to liquid known as melting.
Melting is the process in which a substance changes from a solid state to a liquid state. It occurs when the temperature of the substance reaches its melting point.
Explanation:
When a solid substance is heated, it absorbs energy in the form of heat. This added energy increases the kinetic energy of the particles within the solid, causing them to vibrate more rapidly.
As the temperature continues to rise, the particles gain enough energy to overcome the attractive forces holding them in a fixed position. At this point, the solid starts to lose its rigid structure and the particles begin to move more freely.
The temperature at which this transition occurs is known as the melting point. It is a characteristic property of each substance and remains constant under normal conditions of pressure.
During the process of melting, the solid substance gradually changes into a liquid state. The particles move more randomly and are able to flow and take the shape of their container.
Some examples of melting include ice melting into water when heated and wax melting when exposed to heat.
In summary, melting is the change of state from solid to liquid, and it occurs when the substance reaches its melting point and the particles gain enough energy to break free from their fixed positions.

Introduction:
Dry ice is a unique substance that is commonly used in various applications, such as preserving food, creating special effects, and industrial cleaning. It is important to understand the properties of dry ice to ensure safe handling and usage.
Explanation:
Dry ice is not water, but rather carbon dioxide (CO2) in its solid state. Here is a detailed explanation of why each of the given options is incorrect, and why the correct answer is D:
A. Water in solid state:
- This option is incorrect because dry ice is not water; it is made of CO2, not H2O.
- Water in a solid state is commonly known as ice, and dry ice is not ice made of water.
B. Water in gaseous state:
- This option is incorrect because dry ice is not water vapor or steam.
- Water in a gaseous state is commonly known as water vapor, and dry ice is not water vapor.
C. CO2 in liquid state:
- This option is incorrect because dry ice is not CO2 in its liquid state.
- CO2 in a liquid state is commonly known as carbon dioxide liquid, and dry ice is not a liquid.
D. CO2 in solid state:
- This option is correct because dry ice is indeed CO2 in its solid state.
- Dry ice is formed when carbon dioxide gas is cooled and compressed, resulting in the formation of solid CO2.
Conclusion:
Dry ice is not water, but rather carbon dioxide in its solid state. It is important to correctly identify the properties of dry ice to ensure proper handling and usage, as it can be hazardous if not handled with care.

To find the boiling point of water on the Kelvin scale, we need to convert the boiling point of water from Celsius to Kelvin.
The boiling point of water in Celsius is 100°C.
To convert Celsius to Kelvin, we use the formula:
Kelvin = Celsius + 273.15
Using this formula, we can calculate the boiling point of water in Kelvin:
Kelvin = 100 + 273.15 = 373.15 K
Hence, the boiling point of water on the Kelvin scale is 373 K.
Therefore, the correct answer is option C: 373 K.

Process of Change of Liquid into Vapour: Evaporation
Evaporation is the process by which a liquid changes into its gaseous state, usually at a temperature below its boiling point. Here is a detailed explanation of the process of evaporation:
1. Definition of Evaporation:
- Evaporation is the process in which the molecules of a liquid gain enough energy to escape from the liquid phase and enter the gas phase.
- It occurs at the surface of the liquid.
2. Energy Requirement for Evaporation:
- Evaporation requires energy in the form of heat.
- The energy is used to overcome the attractive forces between the liquid molecules and allow them to break away and enter the gas phase.
3. Factors Affecting Evaporation:
- Temperature: Higher temperatures provide more energy to the liquid molecules, increasing the rate of evaporation.
- Surface Area: Larger surface areas allow more liquid molecules to be exposed to the surrounding air, increasing the rate of evaporation.
- Humidity: Higher humidity levels in the surrounding air reduce the rate of evaporation, as the air is already saturated with water vapor.
4. Role of Kinetic Energy:
- Evaporation occurs due to the kinetic energy of the liquid molecules.
- As the temperature increases, the average kinetic energy of the molecules also increases, leading to more frequent and energetic collisions.
- Some of these collisions provide enough energy for the molecules to escape from the liquid surface and enter the gas phase.
5. Cooling Effect of Evaporation:
- Evaporation is an endothermic process, meaning it absorbs heat from the surroundings.
- As the more energetic molecules leave the liquid, the average kinetic energy of the remaining molecules decreases, resulting in a cooling effect.
6. Examples of Evaporation:
- When a wet cloth is hung out to dry, the water evaporates from the cloth, leaving it dry.
- Water bodies, such as lakes, rivers, and oceans, undergo evaporation due to the heat from the sun.
In conclusion, the process of change of a liquid into vapor at any temperature is called evaporation. It is a natural process that occurs due to the kinetic energy of the liquid molecules and is influenced by factors like temperature, surface area, and humidity. Evaporation is an essential part of the water cycle and has various practical applications in our daily lives.

Factors Affecting Evaporation:
Evaporation is the process by which a liquid substance is converted into a gaseous state. Several factors can influence the rate of evaporation. In this case, the factors affecting evaporation are:
A: Temperature:
- Higher temperatures lead to increased evaporation rates. This is because higher temperatures provide more energy to the liquid molecules, causing them to move faster and escape into the atmosphere as gas.
- Increasing the temperature of a liquid also increases the average kinetic energy of its molecules, leading to an increase in the number of molecules with enough energy to overcome the intermolecular forces and evaporate.
B: Surface Area:
- A larger surface area facilitates faster evaporation. This is because a larger surface area provides more space for liquid molecules to escape into the gas phase.
- When the surface area is increased, more liquid molecules are exposed to the air, allowing them to evaporate more quickly.
C: Both (A) & (B):
- Both temperature and surface area have an impact on the rate of evaporation. Increasing both factors simultaneously can lead to even faster evaporation rates.
- Higher temperatures increase the kinetic energy of the liquid molecules, while a larger surface area provides more space for the molecules to escape.
D: None of these:
- This option is not applicable in this case, as both temperature and surface area are factors that affect evaporation.
In conclusion, the factors affecting evaporation are temperature and surface area. Increasing both factors can lead to a faster rate of evaporation.

Explanation:
When the temperature of a liquid is increased, the kinetic energy of the molecules in the liquid also increases. This leads to an increase in the rate of evaporation. The higher kinetic energy allows more molecules to overcome the attractive forces holding them in the liquid phase and escape into the gas phase.
Reasoning:
The rate of evaporation depends on several factors, including temperature, surface area, and the presence of other substances in the liquid. In this case, we are only considering the effect of temperature.
Conclusion:
Based on the explanation provided, the correct answer is A. The rate of evaporation increases when the temperature of the liquid is increased.

Fluids are:
- Liquids and gases
Explanation:
- Fluids are substances that have the ability to flow and take the shape of their containers.
- Liquids and gases are both examples of fluids.
- Liquids have a definite volume but no definite shape, while gases have neither a definite volume nor a definite shape.
- Examples of liquids include water, oil, and milk, while examples of gases include air, oxygen, and carbon dioxide.
- Solids, on the other hand, do not flow like fluids and have a definite shape and volume. Examples of solids include rocks, wood, and metals.
- Therefore, the correct answer is option A: Liquids and gases.

Sublimation Process:
Sublimation is the process in which a substance transitions directly from a solid phase to a gaseous phase without passing through the liquid phase. This occurs when the vapor pressure of the solid substance exceeds atmospheric pressure.
Substances that undergo sublimation:
A few examples of substances that undergo sublimation include:
1. Naphthalene: Naphthalene is a white crystalline solid that commonly undergoes sublimation. It is commonly found in mothballs and can transition from a solid to a gas when heated.
2. CO₂ (Carbon Dioxide): CO₂ is another substance that undergoes sublimation. Solid carbon dioxide, also known as dry ice, can transition directly to a gaseous state at temperatures and pressures below its triple point.
3. Ice: While ice typically melts to form liquid water when heated, under certain conditions, it can also undergo sublimation. This occurs at low temperatures and pressures, where ice can transition directly to water vapor without melting.
4. N₂ (Nitrogen): Nitrogen gas can undergo sublimation. At low temperatures and pressures, solid nitrogen can transition directly to its gaseous phase.
Conclusion:
In summary, substances that undergo sublimation include naphthalene, CO₂ (carbon dioxide), ice, and N₂ (nitrogen). These substances can transition directly from a solid state to a gaseous state without passing through the liquid phase.

Condensation process is:
The condensation process refers to the change of state from gas to liquid. It occurs when a gas is cooled down, causing its particles to lose energy and come together to form a liquid.
Explanation:
During the condensation process, several key points should be noted:
1. Change of state: Condensation is a physical change of state where a substance transitions from a gaseous state to a liquid state. This transition occurs due to a decrease in temperature.
2. Gas to liquid: The condensation process specifically involves the transformation of a gas into a liquid. The gas particles lose energy and slow down, leading to the formation of liquid droplets.
3. Cooling: Condensation usually occurs when a gas is cooled down. By reducing the temperature, the kinetic energy of the gas particles decreases, allowing intermolecular forces to bring the particles closer together and form a liquid.
4. Liquid formation: As the gas particles cool and come closer together, they start to form liquid droplets. These droplets can be seen as fog, dew, or even clouds in the atmosphere.
In conclusion, the condensation process involves the change of state from gas to liquid. It occurs when a gas is cooled down, causing the gas particles to lose energy and form liquid droplets.

Key Point: The melting point of ice is the temperature at which ice changes from a solid to a liquid state.
Explanation:
To determine the melting point of ice, we need to consider the temperature at which ice transforms into water. The correct answer is A: 0°C.
Here is a detailed explanation:
1. Definition:
The melting point of a substance is the temperature at which it changes from a solid to a liquid state. In the case of ice, it is the temperature at which solid ice converts into liquid water.
2. Ice and Water:
Ice is the solid form of water, and water is the liquid form of H2O. Ice consists of water molecules arranged in a specific pattern called a crystal lattice. At low temperatures, water molecules in the lattice have low kinetic energy and remain in a solid state.
3. Melting Point of Ice:
As the temperature increases, the kinetic energy of the water molecules also increases. At the melting point of ice, the water molecules have enough energy to break free from the crystal lattice and transition into a liquid state. This transition occurs at 0°C.
4. Freezing and Melting:
The freezing point of water is the same as the melting point of ice, which is 0°C. This means that water freezes into ice at 0°C and ice melts back into water at the same temperature.
5. Importance of 0°C:
The melting point of ice at 0°C is a significant value in many practical applications. It is used as a reference point for temperature scales and is often used as a standard for calibrating thermometers.
In conclusion, the melting point of ice is 0°C.

To determine the physical state of matter that can be easily compressed, we need to consider the properties of each state.
Liquid:
- Liquids have a definite volume but no definite shape.
- They are not easily compressed because their particles are already close together.
Solid:
- Solids have a definite shape and volume.
- They are difficult to compress because their particles are tightly packed.
Gas:
- Gases have no definite shape or volume.
- They can be easily compressed because their particles are far apart.
None of these:
- If none of the given options were correct, it would imply that there is another physical state of matter that can be easily compressed. However, this is not the case.
Answer:
The correct answer is B: Gas. Gases have the property of being easily compressible due to the large distance between their particles.

Process by which a drop of ink spreads in a beaker of water:
Diffusion:
- Diffusion is the process by which particles move from an area of higher concentration to an area of lower concentration.
- When a drop of ink is added to a beaker of water, it undergoes the process of diffusion.
- The ink particles, which are initially concentrated in the drop, spread out and mix with the water molecules.
Explanation:
- Initially, the ink particles are concentrated in the drop, while the water molecules are evenly distributed in the beaker.
- As soon as the drop of ink is added to the water, the ink particles start to move randomly due to their kinetic energy.
- The ink particles collide with the water molecules and transfer some of their kinetic energy to them.
- This causes the water molecules to move faster and spread out, while the ink particles slow down and disperse.
- Over time, the ink particles continue to collide with the water molecules, causing them to spread even further.
- Eventually, the ink particles become evenly dispersed throughout the beaker of water, resulting in a uniform color.
Key Points:
- The process by which a drop of ink spreads in a beaker of water is called diffusion.
- Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
- The ink particles in the drop initially have a higher concentration compared to the water molecules in the beaker.
- Through random motion and collisions, the ink particles gradually disperse and mix with the water molecules.
- This process continues until the ink particles become evenly distributed throughout the beaker, resulting in a uniform color.

To convert the temperature from Celsius to Kelvin, we need to add 273.15 to the Celsius temperature. Here is the step-by-step solution:
1. Given temperature: 373°C
2. Add 273.15 to the Celsius temperature to convert to Kelvin:
- 373 + 273.15 = 646.15 K
Therefore, the temperature of 373°C is equivalent to 646.15 K.
Answer: A. 646 K

To convert the temperature from Kelvin to Celsius, we need to subtract 273.15 from the given temperature.
Given:
Temperature in Kelvin = 270 K
To convert Kelvin to Celsius, we use the formula:
Celsius = Kelvin - 273.15
Substituting the given values:
Celsius = 270 - 273.15
Calculating:
Celsius = -3.15
So, the temperature of 270 K is -3.15°C.
Therefore, the correct answer is A. -3°C.

Plasma is the Fourth state of matter -
Plasma is often referred to as the fourth state of matter because it is distinct from the other three states: solid, liquid, and gas. Here is a detailed explanation of why plasma is the fourth state of matter:
1. Introduction:
- Plasma is a state of matter where the atoms are ionized, meaning they have lost or gained electrons and become charged particles.
- It is a highly ionized gas consisting of positively charged ions and free electrons.
2. Characteristics of Plasma:
- Plasma is electrically conductive, meaning it can carry an electric current.
- It is highly reactive and can interact with electromagnetic fields.
- Plasma can be found naturally in certain environments, such as stars, lightning, and the Earth's ionosphere.
- Artificially created plasma can be seen in fluorescent light bulbs, plasma displays, and plasma torches.
3. How Plasma is Different from Other States:
- Solid: In the solid state, atoms are tightly packed and have a fixed shape and volume. Plasma, on the other hand, has no fixed shape and can expand or contract based on the environment.
- Liquid: Liquids have a definite volume but no fixed shape. Plasma, unlike liquids, can conduct electricity and is affected by magnetic fields.
- Gas: Gases have no fixed shape or volume, but they do not conduct electricity like plasma does.
4. Energy Required to Create Plasma:
- To create plasma, a significant amount of energy is required to ionize the atoms and free the electrons.
- This energy can be provided by heating a gas to a high temperature or applying an electric field to a gas.
- Once the atoms are ionized, they can freely move and interact with other charged particles.
In conclusion, plasma is considered the fourth state of matter because it has distinct characteristics and behaviors that differentiate it from solids, liquids, and gases. It is an electrically conductive and highly reactive state of matter that exists naturally in certain environments and can be artificially created.

The process for the change of a solid directly into its vapour is called Sublimation.
Explanation:
Sublimation is the process in which a solid substance directly converts into its gaseous form without passing through the liquid phase. Here is a detailed explanation of sublimation:
1. Definition: Sublimation is a phase transition process where a solid substance changes into its vapor form without melting into a liquid first.
2. Process: During sublimation, the solid substance absorbs heat energy from its surroundings, causing the particles to gain enough energy to break free from their fixed positions and directly transform into a gaseous state.
3. Examples: Sublimation is commonly observed in substances like dry ice (solid carbon dioxide) and mothballs (naphthalene). In both cases, the solid directly converts into a gas without undergoing the intermediate liquid phase.
4. Conditions: Sublimation occurs under specific conditions of temperature and pressure. The temperature at which sublimation occurs is called the sublimation point or sublime point.
5. Uses: Sublimation has various practical applications. It is used in freeze-drying processes to preserve food, in the purification of substances, and in the production of certain pharmaceuticals.
In conclusion, sublimation is the process by which a solid substance transforms directly into its gaseous form without passing through the liquid state. It is an essential concept in chemistry and has various practical applications in different industries.