Matter In Our Surroundings - Practice Test, Class 9 Science - Class 9 MCQ

Explanation:
To determine the correct answer, let's analyze the properties of liquids:
1. Definite volume: Liquids have a fixed amount of matter and therefore have a definite volume.
2. No definite shape: Unlike solids, liquids do not have a fixed shape. They take the shape of the container they are placed in.
Based on these properties, we can conclude that the correct answer is A: definite volume and no definite shape.
Here is a breakdown of the options:
A: definite volume and no definite shape
- This is the correct answer. Liquids have a fixed volume, but they take the shape of the container they are in.
B: no definite volume and no definite shape
- This is incorrect. Liquids have a definite volume, but they do not have a fixed shape.
C: definite shape and volume
- This is incorrect. Liquids do not have a fixed shape, as they take the shape of the container they are in.
D: definite shape but no definite volume
- This is incorrect. Liquids have a definite volume, but they do not have a fixed shape.
In summary, the correct answer is A: definite volume and no definite shape.

Gas Properties:
- Gas is one of the three states of matter, along with solid and liquid.
- It is characterized by its unique properties, including volume and shape.
Definite Volume:
- A gas does not have a definite volume.
- Unlike solids and liquids, gases can expand or contract to fill the available space.
- This property allows gases to take the shape and volume of their containers.
No Definite Shape:
- Gases do not have a definite shape.
- They can diffuse and spread out freely in all directions, filling the space they occupy.
- This is because gas particles are in constant motion and have a high degree of freedom.
Answer Explanation:
- option A: "definite volume and no definite shape" is incorrect because gases do not have a definite volume.
- option B: "no definite volume and no definite shape" is the correct answer as it accurately describes the properties of gases.
- option C: "definite shape and volume" is incorrect because gases do not have a definite shape.
- option D: "definite shape but no definite volume" is incorrect because gases do not have a definite volume.
Conclusion:
- The correct answer is option B: "no definite volume and no definite shape" because gases lack both a definite volume and shape.

Explanation:
The correct answer is C: The particles of matter are in a stationary state.
Here is a detailed explanation of each property of particles of matter:
A: The particles of matter are extremely small:
- Matter is made up of tiny particles such as atoms, molecules, or ions.
- These particles are so small that they cannot be seen with the naked eye.
B: The particles of matter have spaces between them:
- The particles of matter are not tightly packed together.
- There are spaces or gaps between the particles.
- These spaces allow for movement and give matter its volume.
C: The particles of matter are in a stationary state:
- This statement is incorrect.
- The particles of matter are constantly moving.
- They have kinetic energy and are in a constant state of motion.
- The motion can be in the form of vibration, rotation, or translation.
D: The particles of matter attract each other:
- Particles of matter do attract each other.
- This attraction is due to various forces, such as gravitational forces or intermolecular forces.
- These forces hold particles together and give matter its cohesive properties.
To summarize, the property that is NOT true for particles of matter is that they are in a stationary state (option C).

Explanation:
To determine which of the following has minimum spaces among the particles, we need to understand the nature of solids, liquids, and gases.
Solids:
- Solids have tightly packed particles.
- The particles in solids are arranged in a fixed pattern and are close to each other.
- The intermolecular forces between particles are strong, keeping them in a fixed position.
- As a result, solids have minimum spaces among the particles.
Liquids:
- Liquids have particles that are close to each other but not as tightly packed as solids.
- The intermolecular forces between particles in liquids are weaker than in solids, allowing particles to move around and flow.
- However, liquids still have some spaces between the particles.
Gases:
- Gases have particles that are widely spaced apart.
- The intermolecular forces between particles in gases are very weak, allowing them to move freely and occupy a larger volume.
- As a result, gases have the maximum spaces among the particles.
Conclusion:
Based on the above explanations, we can conclude that solids have the minimum spaces among the particles. Therefore, option A is correct.

Explanation:
Evaporation is the process by which a liquid, in this case water, changes into a vapor or gas state. When water is kept in an earthen pot during summer, it undergoes evaporation, leading to the cooling effect. The phenomenon can be explained as follows:
1. Earthen pot:
- An earthen pot is made of clay, which is a porous material.
- The pores in the clay allow air to pass through, facilitating evaporation.
2. Water:
- Water molecules have kinetic energy, which causes them to move randomly.
- Some water molecules near the surface of the liquid gain enough energy to escape into the air as vapor.
3. Evaporation:
- As the water molecules evaporate, they take away heat energy from the remaining water.
- This loss of heat energy reduces the temperature of the water, making it cool.
4. Cooling effect:
- The evaporation process continues until the water reaches an equilibrium with the surrounding air.
- The constant evaporation of water from the earthen pot results in a continuous cooling effect on the remaining water inside the pot.
Therefore, the phenomenon responsible for the cooling of water kept in an earthen pot during summer is evaporation.

Thermal Conduction
Thermal conduction is the process of heat transfer through direct contact between particles of a substance. It occurs in solids, liquids, and gases, but the extent of conduction varies depending on the nature of the material. Here is a detailed explanation of thermal conduction in different states of matter:
1. Solids:
- In solids, thermal conduction is the most efficient due to the close arrangement of particles.
- The particles in solids are tightly packed and vibrate in fixed positions.
- When heat is applied to one end of a solid, the energy is transferred from one particle to another through collisions, causing the particles to vibrate more rapidly.
- This increased kinetic energy is then transferred throughout the solid, resulting in the conduction of heat.
2. Liquids:
- Thermal conduction in liquids is less efficient compared to solids due to the relatively looser arrangement of particles.
- Although the particles in liquids are still in contact with each other, they have more freedom to move and slide past one another.
- When heat is applied to a liquid, the particles gain kinetic energy and move more vigorously.
- However, the transfer of heat in liquids mainly occurs through convection, where the heated particles rise and the cooler particles sink, creating a circulation of heat.
3. Gases:
- Thermal conduction in gases is the least efficient because the particles are widely spaced and have high mobility.
- The particles in gases move randomly and are not held together strongly.
- When heat is applied to a gas, the particles gain kinetic energy and move faster, but the transfer of heat primarily occurs through convection and radiation rather than conduction.
Conclusion:
In summary, thermal conduction takes place in solids, liquids, and gases. However, the efficiency of conduction varies among these states of matter. Solids have the highest thermal conductivity, followed by liquids, while gases have the lowest conductivity.

Evaporation is the process of a liquid turning into a gas. It occurs when the molecules in a liquid gain enough energy to break free from the liquid's surface and become vapor. Evaporation is an important natural process that happens constantly in the environment, and it has several effects and consequences.
Effects of evaporation:
- Cooling down: When a liquid evaporates, it takes energy from its surroundings in the form of heat. This results in a cooling effect in the environment. For example, sweating helps to cool down our bodies by evaporation of sweat from the skin.
- Loss of liquid volume: Evaporation leads to a decrease in the volume of the liquid. As the liquid molecules convert to gas and escape into the atmosphere, the liquid level gradually decreases.
- Concentration of solutes: When a liquid evaporates, the solutes or dissolved substances in it become more concentrated. This is because only the liquid molecules evaporate, leaving behind the solutes in a smaller volume of liquid.
- Separation of mixtures: Evaporation can be utilized to separate mixtures of liquids with different boiling points. By heating the mixture, the liquid with the lower boiling point will evaporate first, leaving behind the liquid with the higher boiling point.
Therefore, the correct answer is C: evaporation always causes cooling down.

Answer:
The change of state directly from solid to gas without going through the liquid state (or vice versa) is called sublimation. Here is a detailed explanation of sublimation:
Sublimation:
- Sublimation is a physical process where a substance transforms from a solid state directly into a gaseous state without passing through the intermediate liquid state.
- It occurs when the vapor pressure of the solid substance exceeds the atmospheric pressure at a given temperature.
- During sublimation, the solid molecules gain enough energy to break the intermolecular forces holding them together and transform into a gas.
- The reverse process, where a gas directly transforms into a solid, is also called sublimation.
- Sublimation is commonly observed in substances like dry ice (solid carbon dioxide) and mothballs (naphthalene).
- The sublimation process is endothermic, meaning it requires energy input to break the intermolecular forces.
Examples of Sublimation:
- Dry ice: Solid carbon dioxide sublimes directly into carbon dioxide gas at temperatures below -78.5°C (-109.3°F).
- Mothballs: Naphthalene, commonly used as mothballs, sublimes directly from a solid into a gas at room temperature.
- Iodine: Solid iodine sublimes when heated, producing a violet gas.
In conclusion, sublimation is the process by which a substance directly changes from a solid to a gas without passing through the liquid state (or vice versa). It is an interesting phenomenon observed in various substances and has practical applications in fields like chemistry and physics.

The Rate of Evaporation Decreases with:
There are several factors that can affect the rate of evaporation. In this case, we are looking for the factor that causes a decrease in the rate of evaporation. The correct answer is A: increase in humidity. Let's break down the factors and explain why humidity affects the rate of evaporation.
1. Increase in Humidity:
- Humidity refers to the amount of moisture or water vapor present in the air.
- When the humidity is high, the air already contains a significant amount of water vapor.
- As a result, the air is less able to hold additional moisture, which slows down the evaporation process.
- The concentration gradient between the liquid and the air is reduced, leading to a decrease in the rate of evaporation.
2. Increase of Temperature:
- Higher temperatures generally increase the rate of evaporation.
- When temperature rises, the kinetic energy of water molecules increases, causing them to move faster and escape from the liquid phase more easily.
- This leads to an increase in the rate of evaporation.
3. Increase in Wind Speed:
- Wind can enhance the rate of evaporation by removing the water vapor near the surface of the liquid.
- When wind blows over the liquid, it carries away the saturated air and replaces it with drier air, maintaining a higher concentration gradient for evaporation.
- This results in an increased rate of evaporation.
4. Increase of Surface Area:
- A larger surface area of the liquid allows for more water molecules to be exposed to the air, increasing the rate of evaporation.
- This is because a larger surface area provides more sites for water molecules to escape from the liquid phase.
- Consequently, an increase in surface area leads to an increased rate of evaporation.
In conclusion, the rate of evaporation decreases with an increase in humidity. This is because high humidity reduces the concentration gradient between the liquid and the air, making it more difficult for water molecules to evaporate.

The Zigzag Movement of Solute Particles in a Solution
The zigzag movement of solute particles in a solution is known as Brownian motion. This phenomenon was first observed and described by the Scottish botanist Robert Brown in 1827. Brownian motion is a result of the random collisions between solute particles and solvent molecules in a solution.
Explanation of Brownian Motion
Brownian motion occurs due to the constant and random motion of solvent molecules, such as water molecules, in a solution. The solvent molecules collide with the solute particles, causing them to move in a zigzag pattern. This motion is characterized by the following key points:
1. Random Movement: The solute particles move in a random, irregular, and unpredictable manner. They change their direction and speed continuously due to the collisions with solvent molecules.
2. Zigzag Trajectory: The solute particles do not move in a straight line. Instead, they exhibit a zigzag trajectory as they are pushed and pulled by the solvent molecules.
3. Molecular Collisions: The solute particles experience countless collisions with the solvent molecules. These collisions are responsible for the erratic movement of the solute particles.
4. Continuous Motion: Brownian motion is a continuous process. The solute particles do not come to rest unless there is an external force acting on them.
Importance of Brownian Motion
Brownian motion has several important implications and applications in various fields:
1. Particle Size Determination: The study of Brownian motion has enabled scientists to determine the size of particles in a solution. By analyzing the random movement of solute particles, researchers can estimate the size of the particles based on their diffusion rate.
2. Diffusion and Mixing: Brownian motion plays a crucial role in the process of diffusion and mixing in solutions. The random movement of solute particles helps in the even distribution of substances in a solution.
3. Drug Delivery: Understanding Brownian motion is essential in the field of drug delivery. The random movement of drug particles in a solution allows for their efficient distribution and absorption in the body.
4. Nanotechnology: Brownian motion is also significant in the field of nanotechnology. The movement of nanoparticles in a solution can be utilized for various applications, such as self-assembly and targeted drug delivery.
In conclusion, the zigzag movement of solute particles in a solution is known as Brownian motion. This phenomenon results from the random collisions between solute particles and solvent molecules. Brownian motion has important applications in various scientific and technological fields.

Explanation:
To liquify gases, there are two main methods: increasing pressure and decreasing temperature. Let's break down each method:
1. Increasing Pressure:
- When the pressure exerted on a gas is increased, the gas molecules come closer together.
- This reduces the space between the gas molecules, leading to greater intermolecular forces.
- The increased intermolecular forces cause the gas molecules to condense and form a liquid state.
2. Decreasing Temperature:
- When the temperature of a gas is decreased, the kinetic energy of the gas molecules decreases.
- As a result, the gas molecules slow down and lose energy.
- At lower temperatures, the intermolecular forces become stronger, causing the gas molecules to come closer together.
- Eventually, the gas molecules condense and transition into a liquid state.
Conclusion:
- Both increasing pressure and decreasing temperature can be used to liquify gases.
- Increasing pressure forces the gas molecules closer together, while decreasing temperature reduces their kinetic energy.
- Combining both methods, by increasing pressure and decreasing temperature simultaneously, can further enhance the liquification process.
Note: It is important to follow safety guidelines and proper procedures when handling gases under high pressures or low temperatures.

Density of a substance is defined as:
The density of a substance is defined as the ratio of its mass to its volume. It is a fundamental property of matter that describes how much mass is packed into a given volume.
Explanation:
To understand the concept of density, it is important to consider the following points:
1. Definition: Density is the measure of how much mass is contained in a given volume of a substance. It is calculated by dividing the mass of the substance by its volume.
2. Mathematical formula: The mathematical formula for density is: Density = Mass/Volume. This formula shows that density is the ratio of mass to volume.
3. Units: The SI unit for density is kilograms per cubic meter (kg/m³). However, in practice, other units such as grams per cubic centimeter (g/cm³) or grams per milliliter (g/mL) are commonly used.
4. Relationship with mass and volume: Density is directly proportional to mass and inversely proportional to volume. This means that as the mass of a substance increases, its density increases, and as the volume of a substance increases, its density decreases.
5. Importance: Density is an important property in various scientific fields, including physics, chemistry, and engineering. It helps in identifying substances, determining their purity, and understanding their behavior under different conditions.
In conclusion, the density of a substance is defined as the ratio of its mass to its volume. It is a fundamental property that helps in characterizing and comparing different substances.

Answer: B

Humidity is not matter because:

• Humidity is the amount of water vapor present in the air or a gas.


• It is a measure of the moisture content in the atmosphere.


• Unlike the other options, humidity does not have mass or occupy space, which are characteristics of matter.


• Humidity is a property or condition rather than a physical substance.


• It cannot be separated into different components or substances.


• Humidity is an important factor in weather and can affect how we feel, but it is not considered matter in the same way as blood, electrons, or moon rock.

In summary, humidity is a measure of the moisture content in the air or a gas, but it is not considered matter because it does not have mass or occupy space like other physical substances.

To determine which substance is more effective in cooling, we need to consider their specific heat capacities and the amount of energy required to change their temperature.
Specific heat capacity:
- Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by 1 degree Celsius (or Kelvin).
- The substance with a higher specific heat capacity will require more energy to change its temperature.
Now let's analyze each option:
A: Ice at 0°C
- Ice has a specific heat capacity of 2.09 J/g°C.
- When ice is at 0°C, it requires energy to melt (latent heat of fusion), but its temperature remains constant.
- Ice at 0°C will absorb heat from its surroundings to melt, thus providing a cooling effect.
B: Water at 0°C
- Water has a specific heat capacity of 4.18 J/g°C.
- Water at 0°C will require more energy to change its temperature compared to ice at the same temperature.
- However, like ice, water at 0°C can absorb heat from its surroundings to freeze, providing a cooling effect.
C: Water at 100°C
- Water at 100°C has a specific heat capacity of 4.18 J/g°C.
- Water at its boiling point will require a significant amount of energy to change its phase from liquid to gas (latent heat of vaporization).
- This phase change absorbs heat from its surroundings, resulting in a cooling effect.
D: Ice at 100°C
- Ice at 100°C has a specific heat capacity of 2.09 J/g°C.
- Similar to water at 100°C, ice at 100°C will require a significant amount of energy to change its phase from solid to gas (sublimation).
- The phase change absorbs heat from its surroundings, resulting in a cooling effect.
Conclusion:
- Ice (option A) and water at 0°C (option B) are more effective in cooling as they can absorb heat energy from their surroundings to change their phase.
- Water at 100°C (option C) and ice at 100°C (option D) also have a cooling effect due to the energy required for phase changes, but their specific heat capacities are the same as ice and water at 0°C, respectively.
- Therefore, option A, ice at 0°C, is the most effective substance for cooling.

0°C temperature is equal to 273 K

To understand why 0°C is equal to 273 K, we need to know the conversion formula between Celsius and Kelvin temperature scales. The Kelvin scale is an absolute temperature scale, where 0 K represents absolute zero, the point at which all molecular motion ceases. The Celsius scale, on the other hand, is based on the freezing and boiling points of water.

Conversion Formula:

To convert Celsius to Kelvin, we add 273 to the Celsius temperature.

Explanation:

Since 0°C is the freezing point of water, we can use the conversion formula to find the corresponding temperature in Kelvin:

0°C + 273 = 273 K

Conclusion:

Therefore, 0°C is equal to 273 K.

Answer: B

The process involving the change of state from solid to gas is called:
The correct answer is C: sublimation.
Explanation:

Melting: Melting is the process of changing a solid into a liquid state.

Boiling: Boiling is the process of changing a liquid into a gas state.

Sublimation: Sublimation is the process of directly changing a solid into a gas state without passing through the liquid state. In this process, the solid substance bypasses the liquid phase and transforms into a gas when heated.

Fusion: Fusion is another term for melting, which refers to the process of changing a solid into a liquid state.

Therefore, in this context, the process involving the change of state from solid to gas is referred to as sublimation.

Because 25degree is room temperature. So,water remains in liquid state.At 0degree water freezes to form ice(solid) because of lowered temperature. At 100 degree water boils to form vapours because of rising temperature.Latent heat plays a crucial role In it .