matter in our surroundings extra questions

(A) Only gases behave like fluids.
(B) Gases and solids behave like fluids.
(C) Gases and liquids behave like fluids.
(D) Only liquids are fluids.

Answer: (C) is correct. Liquids and gases can flow easily due to weaker intermolecular forces.

(A) Sugar < water < oxygen
(B) Oxygen < water < sugar
(C) Water < sugar < oxygen
(D) Water < oxygen < sugar

Answer: (B). Forces of attraction increase from gases → liquids → solids.

(A) Diffusion
(B) Evaporation
(C) Expansion of gases
(D) All of the above

Answer: (D). Higher temperature increases kinetic energy, so all these processes increase.

(A) Low pressure, low temperature
(B) High temperature, low pressure
(C) Low temperature, high pressure
(D) High temperature, high pressure

Answer: (C). High pressure brings particles closer, and low temperature removes kinetic energy.

(A) Celsius
(B) Kelvin
(C) Fahrenheit
(D) Joule

Answer: (B) Kelvin

(A) Conversion of solid into vapours without passing through the liquid state is called vaporisation
(B)Conversion of solid into vapour withoutpassing through the liquid state is called sublimation.
(C)Conversion of solid into liquid is called sublimation.
(D) Conversion of vapours into solid without passing through the liquid state is called freezing.

Answer: (B) : The conversion of liquid into gas(vapour) is called vaporisation. The conversion of liquid into solid is called freezing. The conversion of solid into liquid is called melting

Answer: (A) Both A and R are true, and R is the correct explanation of A.
Explanation: The constant and random motion of gas particles causes them to collide with the container walls, exerting pressure.

Answer: (A) Both A and R are true, and R is the correct explanation of A.
Explanation: This process is called sublimation. Naphthalene sublimes into vapour, hence no liquid or residue is observed.

Answer: (A) Both A and R are true, and R is the correct explanation of A.
Explanation: Ice uses latent heat of fusion to melt, taking more energy and thus providing better cooling.

Answer: (B) Both A and R are true but R is not the correct explanation of A.
Explanation: Gas molecules intermix because they move randomly and fill space; diffusion is the general process that results (R), but A’s intermixing specifically occurs due to particle motion.

Answer: (A) Both A and R are true, and R is the correct explanation of A.
Explanation: Supplying heat increases particle kinetic energy, weakening attractions and causing melting (fusion).

Particles of matter are extremely small — so tiny that they cannot be seen without a microscope. Their size is in the nanometer range, far beyond the resolving power of the human eye.

Gases have negligible intermolecular forces, allowing their particles to move freely and randomly in all directions. This results in the gas spreading out to occupy the entire volume of its container.

°C = K − 273
300 − 273 = 27 °C

The melting point of ice is 273 K (which equals 0°C).

The boiling point of water is 373 K (which equals 100°C).

At 0°C, water exists as a mixture of solid (ice) and liquid (water), since it is the melting point.

Oxygen < water < sugar, Gases have the weakest intermolecular forces, then liquids, then solids (sugar).

Perfume molecules diffuse through air. The perfume particles spread out into air (fill the space) and reach our nose, so we smell them at a distance

This shows that water’s particles have space between them. The diver moves between molecules, indicating water molecules are not tightly locked.

Matter is anything that occupies space and has mass.
Example: water (it fills a volume and has mass).

Gases have large spaces between their particles and very weak intermolecular forces. When pressure is applied, these particles can be pushed closer together. In solids and liquids, the particles are already tightly packed, offering very little room for compression.

Evaporation is the process by which a liquid changes into vapour at temperatures below its boiling point. It occurs at the surface and leads to cooling. Two factors affecting evaporation are:

• Temperature – Higher temperature increases the rate of evaporation.
• Surface Area – A larger surface area allows more particles to escape quickly.

Sweat evaporates by absorbing heat energy from the skin. This heat is used to break intermolecular bonds in the sweat. As a result, our body loses heat, which produces a cooling effect.

1. Liquids have a definite volume (they occupy a fixed amount of space).
2. They flow and take the shape of their container.
3. They are almost incompressible (very low compressibility).
4. Liquids have weaker intermolecular forces than solids but stronger than gases.

In solids, particles are tightly packed with very little space between them. There is no extra space for particles to move closer under pressure. Hence, solids cannot be easily compressed (their volume hardly changes).

A gas is a substance in its gaseous state at room temperature (e.g. O₂, H₂) and is stable. A vapor is gaseous form of a liquid/solid below its boiling/melting point; it is unstable and condenses on cooling (e.g. water vapor).

(i) Gas particles have negligible attraction and move freely in all directions; they spread out to occupy all available space.
(ii) Fast-moving gas particles collide with container walls; these collisions per unit area exert a force called pressure

Liquids flow and take the shape of their container because their particles are loosely packed and can move past each other. However, they have a definite volume because particles are still close enough that volume doesn’t change. Liquids diffuse faster than solids because their particles have more kinetic energy and more space to move. The greater kinetic energy in liquids (compared to solids) lets particles mix more quickly

The three states are solid, liquid, gas. Solids have a definite shape, distinct boundary and fixed volume.
Liquids take the container’s shape and fixed volume; gases fill the container and have no fixed volume.

In terms of compressibility:

1. solids are essentially incompressible (negligible space between particles)
2. liquids are slightly compressible (very small space between particles)
3. gases are highly compressible (large spaces between particles allow volume to decrease greatly)

Changing pressure can change the state of matter by forcing particles closer or allowing them apart. For gases, increasing pressure squeezes particles closer. If we also lower temperature, a gas can liquefy (e.g. turning natural gas into liquid under high pressure and cooling). Conversely, decreasing pressure allows gases to expand or even solids to sublimate.

For example, solid CO₂ (dry ice) at high pressure directly becomes gas when pressure drops to 1 atm

(a) This process is sublimation – solid camphor/naphthalene turns directly into vapour without melting.

(b) It is a physical change , because the substance changes state (solid → gas) without forming a new substance.

(i) Gas particles move randomly and fill all available space because intermolecular attraction is negligible.
(ii) Rapidly moving gas particles collide with and push on container walls; these collisions produce pressure
(iii) A wooden table has a definite shape and fixed volume under normal conditions. Its particles are closely packed in a rigid structure, so it is a solid.

(i) The particles of matter have spaces between them.
(ii) The particles of matter are constantly moving.
(iii) The particles of matter attract one another.

Matter exists in three main physical states: solids, liquids, and gases. Each has different particle arrangements and behaviors:

The phenomenon of change of matter from one state to another and back to the original state is called interconversion of states of matter.

• Melting: The process of changing a solid into a liquid is called melting.The melting point is the temperature at which a solid changes into a liquid.
  Example: When we heat an ice cube, it melts and turns into liquid water. The melting point of ice is 0°C.


• Freezing: The process of changing a liquid into a solid is called freezing. The freezing point is the temperature at which a liquid changes into a solid.
  Example:When we put liquid water in the freezer, it loses heat and freezes, forming ice. The freezing point of water is also 0°C.


• Boiling:The process of changing a liquid into a gas at a specific temperature throughout the liquid is called boiling. The temperature at which a liquid boils is known as its boiling point.
  Example: When we heat water in a kettle, it reaches its boiling point and starts boiling, forming steam. The boiling point of water is 100°C.


• Condensation: The process of changing a gas into a liquid is called condensation. It occurs when a gas loses heat energy and turns into a liquid.
  Example: When steam comes in contact with a cold surface, such as a mirror, it condenses and forms water droplets. This phenomenon is commonly observed in when you put a plate covering hot bowl if maggie, the vapours forms droplets.


• Sublimation:It is the process in which a solid directly changes into a gas without passing through the liquid state.
  Example: Camphor(kapur), when heated, undergoes sublimation. It changes from a solid to a gas without forming a liquid in between.


• Deposition: Deposition is the process that converts a gaseous state directly into a solid state without first going through a liquid phase.
  Example:Frost is a common example of deposition because, without ever-changing into a liquid phase, water vapour from humid air are directly deposited on the solid and crystalline frost pattern on windows or on a leaf.

    Temperature: Increases kinetic energy and helps particles overcome forces of attraction.

    Pressure: Brings particles closer; used to liquefy gases.

Latent heat of fusion The amount of heat energy that is required tochange 1 kg of a solid into liquid at atmospheric pressure at its melting point is known as the latent heat of fusion.

Latent heat of vaporization The amount of heat energy that is required to change 1 kg of a liquid into gas at boiling point without any rise in temperature is known as the latent heat of fusion.

For example, ice melts at 0°C; heat absorbed breaks bonds and lets particles move freely, but temperature stays constant until all ice melts. Only after the phase change is complete does temperature rise again. Thus during melting/boiling, heat is “hidden” in changing the state, keeping temperature constant.

Evaporation is the vaporization of surface particles at temperatures below boiling. When particles evaporate, they absorb energy (latent heat) from the surroundings to overcome attractions. This energy absorption lowers the temperature of the remaining liquid and surroundings.
For example,
sweat on the skin evaporates and draws heat from the body, cooling us. Likewise, water sprinkled on a hot floor evaporates and removes heat, cooling the surface. Sitting under a fan increases air flow, which removes humid air and accelerates evaporation of sweat, enhancing the cooling effect

(a) Acetone is volatile; its particles evaporate quickly at room temperature. As they evaporate from the skin, they absorb heat (latent heat of vaporization) from the palm, lowering its temperature. Thus the palm feels cold.

(b) Airflow from the fan increases the evaporation rate of sweat from our skin. Faster evaporation means more heat is drawn from the body into the sweat, causing a cooling effect. The moving air also carries away the humid air, maintaining a low humidity that favors further evaporation

Diffusion is the mixing of particles of different substances by spontaneous motion, filling the available space.
Gaseous diffusion is very rapid because gas particles move randomly and quickly. Increasing temperature increases kinetic energy; particles move faster and spread out more quickly, so diffusion rate increases

Q1: Why does water under the fan become cooler?
Answer: The moving air increases the rate of evaporation. As water evaporates, it absorbs heat from the remaining water and surroundings, making it cooler.

Q2: What property of gases allows perfume to spread across the room?
Answer: The rapid and random motion of gas particles (diffusion) allows perfume to spread quickly.

Q3: Which phenomenon is responsible for the cooling effect of evaporation?
Answer: Absorption of latent heat from the surroundings during evaporation.

Q1: What process causes camphor to disappear?
Answer: Sublimation – camphor changes directly from solid to gas.

Q2: Why does the floor become cooler after sprinkling water?
Answer: The water evaporates, absorbing heat from the floor, leading to a cooling effect.

Q1: Why did the ice melt faster on the metal plate than on the wooden plank?
Answer: Metal is a good conductor of heat. It transfers more heat to the ice, making it melt faster. Wood is an insulator, so less heat reaches the ice.

Q2: Why does petrol give off a strong smell quickly?
Answer: Petrol is volatile. Its molecules evaporate quickly and mix with the air.

Q3: What property of particles does this demonstrate?
Answer: This demonstrates diffusion and that particles of matter are constantly moving.

Q1: What is the scientific name of dry ice?
Answer: Dry ice is solid carbon dioxide (CO₂).

Q2: What is the process observed by Arjun called?
Answer:The process is called sublimation.

Q3: Why is dry ice used in making artificial fog?
Answer: When dry ice sublimes, it produces thick white fog-like vapour used for stage effects and refrigeration without liquid residue.

Q1: Why does water boil at a lower temperature at high altitude?
Answer: Atmospheric pressure is lower at high altitudes, so water needs less energy to boil.

Q2:How does atmospheric pressure affect boiling point?
Answer:Lower pressure means particles escape more easily, thus lowering boiling point.

Q3: What implication does this have for cooking at high altitudes?
Answer: It takes longer to cook food in boiling water, so pressure cookers are commonly used in such regions.