All questions of Matter in Our Surroundings for Class 9 Exam

Condensation and Freezing Release Heat

- Condensation is the process by which a gas or vapor changes into a liquid state. When water vapor condenses, it releases heat energy to the surroundings. This occurs because the molecules in the gas phase have higher kinetic energy compared to the liquid phase. As they lose energy and slow down, they release heat. For example, when water vapor condenses on a cold surface to form dew, heat is released.

- Freezing is the process by which a liquid changes into a solid state. When a substance freezes, it releases heat energy. This is because the molecules in the liquid phase lose energy and slow down, releasing heat as they arrange themselves into a more ordered solid structure. For example, when water freezes into ice, heat is released.

Vaporization and Melting Absorb Heat

- Vaporization is the process by which a liquid changes into a gas or vapor. When a substance vaporizes, it absorbs heat energy from the surroundings. This occurs because the molecules in the liquid phase gain energy and speed up to overcome intermolecular forces and transition into the gas phase. For example, when water boils and turns into steam, heat is absorbed from the surroundings.

- Melting is the process by which a solid changes into a liquid state. When a substance melts, it absorbs heat energy. This is because the molecules in the solid phase gain energy and vibrate more rapidly, breaking the intermolecular forces holding them together and transitioning into the liquid phase. For example, when ice melts into water, heat is absorbed from the surroundings.

Conclusion

- The processes of condensation and freezing release heat, while vaporization and melting absorb heat.

To convert temperatures from Kelvin (K) to Celsius (°C), we use the formula:

°C = K - 273.15

Let's apply this formula to the given temperatures:

1. For 308 K:
°C = 308 - 273.15 = 34.85 ≈ 35°C

2. For 329 K:
°C = 329 - 273.15 = 55.85 ≈ 56°C

3. For 391 K:
°C = 391 - 273.15 = 117.85 ≈ 118°C

Hence, the correct sequence of temperatures in Celsius scale is:

35°C, 56°C, and 118°C.

Explanation:
To convert temperatures from Kelvin to Celsius, we subtract 273.15 from the given temperature in Kelvin. This is because 0 K is the absolute zero temperature, which is equivalent to -273.15°C. So, to convert any temperature above absolute zero from Kelvin to Celsius, we need to subtract 273.15.

In the given question, we have three temperatures: 308 K, 329 K, and 391 K.

By applying the conversion formula, we find that 308 K is approximately equal to 35°C, 329 K is approximately equal to 56°C, and 391 K is approximately equal to 118°C.

Therefore, the correct sequence of temperatures in Celsius scale is 35°C, 56°C, and 118°C, which corresponds to option B.

Molecules have arrangement

Plasma and BEC (Bose-Einstein condensate) are also considered as states of matter because plasma is mixture of free atoms and ions and BEC occupies space and has mass.

Answer:

When heat is constantly supplied by a burner to boiling water, the temperature of the water does not rise at all. This is because during the process of vaporization, the heat energy supplied is used to convert the liquid water into water vapor rather than increasing the temperature of the water.

Explanation:

When heat is supplied to boiling water, it undergoes the process of vaporization. Vaporization is the phase transition from a liquid to a gas, and it occurs at the boiling point of the substance. In the case of water, the boiling point is 100 degrees Celsius (212 degrees Fahrenheit) at atmospheric pressure.

During the process of vaporization, the heat energy supplied to the water is used to break the intermolecular forces between the water molecules, allowing them to escape into the surrounding air as water vapor. This process requires a large amount of energy, known as the latent heat of vaporization.

As the heat energy is absorbed by the water molecules and used for vaporization, the temperature of the water remains constant at the boiling point. This is because the energy is being used to change the state of the water rather than increase its temperature.

Once all the liquid water has been converted into water vapor, the temperature of the water can start to rise again as the heat energy supplied by the burner is no longer being used for vaporization.

Summary:

When heat is constantly supplied by a burner to boiling water, the temperature of the water does not rise at all. This is because the heat energy is used for the process of vaporization, converting the liquid water into water vapor, rather than increasing the temperature of the water.

When surface area increases and the temperature rises, evaporation of water also increases, because the area which is exposed to the outer atmosphere is more and increasing the temperature, leads to an increase in the kinetic energy, due to which the rate of evaporation also increases.

Understanding Kinetic Energy in States of Matter
Kinetic energy is the energy of motion, and in the context of particles in different states of matter, it varies significantly depending on temperature and state.

States of Matter and Temperature
- **Steam at 100°C:**
- Particles are in a gaseous state, moving rapidly and freely.
- High kinetic energy due to increased temperature.
- **Water at 0°C:**
- Particles are in a liquid state, moving but less freely than in gas.
- Moderate kinetic energy.
- **Water at 100°C:**
- Particles are in a liquid state, but transitioning to gas.
- Higher kinetic energy, similar to steam.
- **Ice below 0°C:**
- Particles are in a solid state, vibrating in fixed positions.
- Minimal kinetic energy as the temperature is low.

Why Ice Below 0°C Has Minimum Kinetic Energy
- **Solid State Characteristics:**
- In solids like ice, particles are closely packed and primarily vibrate in place rather than moving freely.
- **Low Temperature Effect:**
- Below 0°C, the temperature decreases the energy of the particles, resulting in lower kinetic energy.
- **Comparison with Other States:**
- The kinetic energy of particles in steam and water (both at higher temperatures) is significantly greater than that of ice, making ice the state with minimum kinetic energy.

Conclusion
In summary, the particles of ice below 0°C have the minimum kinetic energy among the given options due to their solid-state arrangement and lower temperature, which restricts their motion compared to liquids and gases at higher temperatures.

Explanation:

When a gas jar full of air is placed upside down on a gas jar full of bromine vapours, the red–brown vapours of bromine from the lower jar go upward into the jar containing air. This phenomenon can be explained by the difference in density between bromine and air.

Density of Bromine:
Bromine is a dense liquid, with a density of about 3.1 grams per cubic centimeter. This means that a given volume of bromine is much heavier than the same volume of air.

Density of Air:
Air, on the other hand, is a mixture of gases, primarily nitrogen (N2) and oxygen (O2), with a density of about 1.2 grams per cubic centimeter. This means that a given volume of air is lighter than the same volume of bromine.

Why does bromine go upward into the jar containing air?
The movement of bromine vapours from the lower jar into the jar containing air can be explained by the principle of diffusion. Diffusion is the process by which particles move from an area of higher concentration to an area of lower concentration.

In this case, the jar containing bromine vapours has a higher concentration of bromine molecules compared to the jar containing air. As a result, the bromine molecules tend to spread out or diffuse into the jar with lower bromine concentration, which is the jar containing air.

Since bromine is heavier than air, it might be expected that the bromine vapours would sink down instead of rising up. However, diffusion is driven by the random motion of particles, and the motion of gas particles is influenced by factors such as temperature and pressure.

In this experiment, the movement of bromine vapours upwards against gravity can be explained by the fact that the bromine molecules are highly volatile and have a higher vapor pressure compared to the air molecules. As a result, the bromine molecules are able to overcome the force of gravity and rise up into the jar containing air.

Therefore, the correct answer to the question is option 'A': Bromine is heavier than air.

When water freezes into its solid form, the molecules can form more stable hydrogen bonds, locking them into positions. As the molecules are not moving, they cannot form as many hydrogen bonds as other water molecules. This leads to ice water molecules not being as close together as in liquid water, thus reducing its density.

When salt is dissolved in water, the particles of salt disappear in water. This happen because particles of salt get adjusted in the space b/w the particles of water.

Understanding Helium Gas as Matter
Helium gas is classified as matter due to its fundamental properties. Here's a detailed breakdown:

Mass and Volume
- Helium has a definite mass, even though it is a light gas.
- All matter possesses mass, which is a key characteristic that defines it as matter.
- Additionally, helium occupies space, which is another essential property of matter.

Definite Volume
- Although helium gas does not have a definite volume in the sense of a fixed shape, it still occupies space within a container.
- Gases expand to fill the volume of their containers, but they are still considered to have volume since they displace air and other gases.

Compressibility
- Helium can be compressed easily, which is a characteristic of gases.
- While compressibility is notable, it does not define matter; rather, it describes the behavior of gases.

Conclusion
- The key reason helium is classified as matter is its mass and the ability to occupy space.
- Thus, the correct answer is option 'A': "It has mass and occupies volume," highlighting the essential properties of all matter.

Breathing involves the exchange of gases in the lungs, a process which occurs by diffusion. The oxygen is then transported throughout the body. Carbon dioxide is the waste gas produced by respiration.

Separation of sulphur and sodium chloride mixture

Introduction:
The mixture of sulphur and sodium chloride can be separated by various methods based on the physical properties of the components. One of the most effective methods is to dissolve the mixture in water followed by filtration and evaporation.

Method:
The following steps can be followed to separate sulphur and sodium chloride using this method:

1. Dissolving in water:
- The mixture of sulphur and sodium chloride is added to a beaker containing water.
- Both sulphur and sodium chloride are soluble in water, so they dissolve in the solvent.

2. Filtration:
- Once the mixture is dissolved, it is poured through a filter paper placed in a funnel.
- The filter paper allows the water to pass through, but retains the solid particles.

3. Evaporation:
- The filtrate containing the dissolved sodium chloride and sulphur is collected in a separate container.
- The water is then evaporated from the filtrate using a heating source like a Bunsen burner or hot plate.
- As the water evaporates, the dissolved sodium chloride and sulphur crystallize and separate from the solution.

4. Separation:
- The solid crystals of sodium chloride and sulphur can be separated from each other using various methods such as decantation or filtration.
- Decantation can be used if the crystals are large and settle at the bottom of the container. The liquid can be carefully poured out, leaving the solid behind.
- Filtration can be used if the crystals are small and mixed with impurities. The crystals can be collected on a filter paper and washed with a suitable solvent to remove impurities.

Conclusion:
By dissolving the mixture of sulphur and sodium chloride in water, followed by filtration and evaporation, we can separate the two components. This method takes advantage of the difference in solubility of sulphur and sodium chloride in water. While sodium chloride is highly soluble, sulphur has limited solubility and can be easily separated from the solution.

Answer:

Introduction:
When determining the boiling point of a liquid using a thermometer, it is important to follow certain guidelines to ensure accurate measurements. The correct option in this case is option 'B', which states that the thermometer should be above the liquid and remain vertical. Let's explore why this is the correct choice.

Explanation:
To measure the boiling point of a liquid, the thermometer should be positioned in a way that allows it to accurately measure the temperature of the vapor being produced. Placing the thermometer in different positions can lead to inaccurate readings. Here's why option 'B' is the correct choice:

Above the liquid:
Placing the thermometer above the liquid ensures that it measures the temperature of the vapor rather than being influenced by the temperature of the liquid itself. The boiling point of a liquid is the temperature at which its vapor pressure equals the atmospheric pressure. By positioning the thermometer above the liquid, it can accurately measure the temperature of the vapor as it escapes from the liquid.

Remain vertical:
Keeping the thermometer vertical ensures that it is immersed in the rising vapor and not tilted towards any particular direction. This helps in obtaining a more precise reading as the thermometer is evenly exposed to the vapor and can measure its temperature uniformly. Tilting the thermometer could lead to uneven temperature measurements, affecting the accuracy of the boiling point determination.

Other options:
- Option 'A': Dipping the thermometer into the liquid would measure the temperature of the liquid itself, not the boiling point. This would not provide accurate results.
- Option 'C': Touching the bottom of the container could lead to the thermometer measuring the temperature of the container rather than the vapor. This would result in inaccurate readings.
- Option 'D': Placing the thermometer slanting in the liquid would likely lead to inaccurate measurements as the thermometer would not be fully immersed in the rising vapor.

Conclusion:
To determine the boiling point of a liquid accurately, it is important to position the thermometer above the liquid and keep it vertical. This ensures that the thermometer measures the temperature of the vapor being produced, leading to more precise and reliable results.

The important characteristics of particles of matter are the following

Decreasing Order of Force of Attraction Between Particles

Sugar, alcohol, and nitrogen have intermolecular forces of attraction that are stronger than those between water, air, and chalk. Sulphur dioxide, carbon disulphide, and sulphur have even stronger forces of attraction than the former three, while oxygen, water, and sugar have the weakest forces of attraction.

Explanation:

Intermolecular forces of attraction refer to the forces that hold the particles of a substance together. These forces include Van der Waals forces, dipole-dipole interactions, and hydrogen bonding. The strength of these forces varies depending on the type of particles involved and their arrangement.

The correct arrangement of decreasing order of force of attraction between particles is option B (sugar, alcohol, nitrogen). Sugar and alcohol have strong intermolecular forces of attraction due to the presence of hydrogen bonding between their molecules. Nitrogen also has strong intermolecular forces of attraction due to the presence of Van der Waals forces between its molecules.

Option A (water, air, chalk) has weaker intermolecular forces of attraction than option B. Water has hydrogen bonding between its molecules, but air and chalk have weaker Van der Waals forces between their particles.

Option C (sulphur dioxide, carbon disulphide, sulphur) has even stronger intermolecular forces of attraction than option B. Sulphur dioxide and carbon disulphide have dipole-dipole interactions and Van der Waals forces between their molecules, while sulphur has strong Van der Waals forces between its particles.

Option D (oxygen, water, sugar) has the weakest intermolecular forces of attraction among the given options. Oxygen has weak Van der Waals forces between its molecules, while water and sugar have weaker hydrogen bonding than sugar and alcohol.

In summary, the correct arrangement of decreasing order of force of attraction between particles is:

1. Sulphur dioxide, carbon disulphide, sulphur
2. Sugar, alcohol, nitrogen
3. Water, air, chalk
4. Oxygen, water, sugar.

When the liquid water turns to solid ice we find that water freezes without getting any colder. That's because the latent heat of fusion is being lost from the liquid as it solidifies and the temperature of the water does not fall so quickly.

Fluids are the substances that have the ability to flow. Gases and liquids can flow easily because their particles are free to move. Hence, gases and liquids behave as fluids is the correct option.

Ammonia is a weak base and it combines with HCl to form ammonium chloride. But moisture is necessary to bring out this reaction. So when exposed to air they combine to form dense fumes of ammonium chloride. The salts produced by the action of ammonia on acids are known as the ammonium salts and all contain the ammonium ion.

Solid carbon dioxide can be changed into vapour or gaseous state by decreasing the pressure and increasing the temperature. Both the processes increase the inter-particle spaces in the solid carbon dioxide.

Temperature remains constant during change of state

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Iodine and ammonium chloride produces fumes on gentle heating while sodium chloride does not sublime.

An earthen pot (matka) has small pores in it. Water seeps through these pores and reaches the outer surface of the earthen pot. This water then evaporates by taking heat from the earthen pot, thereby making it cooler.

Latent heat is absorbed during the change of state of a substance because it is the heat energy that has to be supplied to change the state of a substance, while the specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius.

Particles of matter are continuously moving.