Textbook - MATTER IN OUR SURROUNDINGS Questions in English

(A) Matter is defined as anything that has mass and occupies space.
$1$. Chair: Has mass and occupies space (Matter).
$2$. Air: Has mass and occupies space (Matter).
$3$. Love: An emotion,not matter.
$4$. Smell: The sensation of smell is not matter,but the particles of perfume causing the smell are matter.
$5$. Hate: An emotion,not matter.
$6$. Almonds: Have mass and occupy space (Matter).
$7$. Thought: $A$ mental process,not matter.
$8$. Cold: $A$ sensation,not matter.
$9$. Lemon water: Has mass and occupies space (Matter).
$10$. Smell of perfume: The particles of perfume in the air have mass and occupy space (Matter).
Therefore,the items that are matter are: Chair,air,almonds,lemon water,and smell of perfume.

(N/A) The particles of matter are constantly moving. The rate of diffusion of particles increases with an increase in temperature.
In hot sizzling food,the kinetic energy of the particles is high,which causes them to diffuse rapidly into the air.
Consequently,these particles can travel over a longer distance and reach you from several metres away.
In contrast,the particles in cold food have lower kinetic energy,resulting in a slower rate of diffusion.
Therefore,you need to go close to the cold food to detect its smell.

(B) The phenomenon of a diver cutting through water in a swimming pool demonstrates that the particles of water have spaces between them. Because these spaces exist,the diver is able to move through the water by displacing the particles.

(N/A) The characteristics of the particles of matter are as follows:
$1.$ Particles of matter have space between them.
$2.$ Particles of matter are continuously moving.
$3.$ Particles of matter attract each other.
$4.$ Particles of matter are extremely small in size.

(N/A) Density is defined as the mass per unit volume of a substance. Generally, the density of states of matter follows the order: $Gas < Liquid < Solid$.
$1$. Air and exhaust from chimneys are gases, which have the lowest density.
$2$. Water and honey are liquids, which have a higher density than gases.
$3$. Cotton, chalk, and iron are solids, which have the highest density.
Within these categories, the specific order of increasing density is:
Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron.

(N/A) The characteristics of the three states of matter are as follows:
$1.$ $\text{Solid}:$
- Solids have a definite volume.
- Solids do not flow.
- Solids are rigid.
- Solids have a definite shape (with few exceptions like sponge or rubber band).
- Solids are generally incompressible.
$2.$ $\text{Liquid}:$
- Liquids have a definite volume.
- Liquids tend to flow (fluids).
- Liquids are not rigid.
- Liquids do not have a definite shape; they take the shape of the container.
- Liquids are almost incompressible.
$3.$ $\text{Gas}:$
- Gases do not have a definite volume; they occupy the entire space of the container.
- Gases flow easily.
- Gases are not rigid.
- Gases do not have a definite shape.
- Gases are highly compressible.

(N/A) $Rigidity$: The property by which an object retains its shape and size is called rigidity. Solids are rigid, whereas liquids and gases are not.
$Compressibility$: This is the property due to which a substance can be compressed, meaning its volume can be decreased. Gases are highly compressible, whereas solids and liquids are generally considered incompressible.
$Fluidity$: The tendency of a substance to flow is called fluidity. Gases and liquids are fluids, while solids are not.
$Filling \text{ } a \text{ } gas \text{ } container$: $A$ large volume of gas can be filled into a small container by compressing it under very high pressure. This is possible due to the high compressibility of gases.
$Shape$: The property of having a definite geometry is called the shape of a substance. Solids have a definite shape, whereas liquids and gases take the shape of the container.
$Kinetic \text{ } energy$: The energy possessed by moving particles or molecules is called kinetic energy. On increasing the temperature, the kinetic energy of molecules increases. Gas molecules possess the highest kinetic energy.
$Density$: The mass per unit volume of a substance is called density. Density = $\frac{\text{Mass}}{\text{Volume}}$.

(N/A) The force of attraction between the molecules of gases is negligible.
As a result,gas molecules are free to move in all directions and occupy the maximum space available to them.
Additionally,the high kinetic energy possessed by gas molecules allows them to move rapidly and fill the entire volume of the container.

(N/A) In the gaseous state,particles move randomly at very high speeds. Due to this random movement,the particles collide with each other and also strike the walls of the container. The pressure exerted by the gas is defined as the force exerted by these particles per unit area on the walls of the container.

(N/A) wooden table is classified as a solid because it possesses a fixed shape and a definite volume. In solids,the constituent particles are held together by strong intermolecular forces of attraction,which keeps them in fixed positions. Additionally,the intermolecular space between these particles is negligible. Due to these properties,a wooden table maintains its structure and does not flow,which are the defining characteristics of a solid state.

(C) Air molecules are very far from each other due to the negligible force of attraction working between them. Therefore,our hand gets sufficient space to move through the air,and we can easily displace air molecules by applying a small force.
In contrast,a solid block of wood has particles that are very closely packed with strong intermolecular forces of attraction. Because of this rigid structure,our hand cannot move through it without applying a massive amount of force in a precise direction,which is why a karate expert is required.

(B) Generally,solids have a higher density than liquids. However,water is an exception.
When water freezes to form ice,the molecules arrange themselves in a specific cage-like structure due to hydrogen bonding.
This structure creates vacant spaces between the water $(H_2O)$ molecules.
Because of these vacant spaces,the volume of ice increases for the same mass,which decreases its density compared to liquid water.
Since ice is less dense than liquid water,it floats on the surface.

(A) To convert temperature from the Kelvin scale to the Celsius scale,we use the following formula:
$t \, ^\circ C = T \, K - 273$
$(a)$ For $300 \, K$:
$300 - 273 = 27 \, ^\circ C$
$(b)$ For $573 \, K$:
$573 - 273 = 300 \, ^\circ C$
Therefore,the correct answer is $27 \, ^\circ C$ and $300 \, ^\circ C$.

(N/A) The boiling point of water is $100\,^{\circ}\text{C}$.
$(a)$ At $250\,^{\circ}\text{C}$,which is above the boiling point,water exists as steam or water vapour,i.e.,in a gaseous state.
$(b)$ At $100\,^{\circ}\text{C}$,water is at its boiling point where a phase transition occurs. Therefore,at this temperature,water exists in both liquid and gaseous states simultaneously.

(B) During the change of state of a substance,the temperature remains constant.
This happens because the heat energy supplied is used to overcome the forces of attraction between the particles of the substance.
This hidden heat is known as latent heat.
Since this energy is consumed in changing the state rather than increasing the kinetic energy of the particles,the temperature does not rise during the phase transition.

(B) Atmospheric gases can be liquefied by applying high pressure and simultaneously reducing the temperature.
This process works because increasing pressure brings gas particles closer together,while decreasing the temperature reduces their kinetic energy,allowing intermolecular forces to hold the particles together in a liquid state.

(N/A) desert cooler functions on the principle of evaporative cooling.
The rate of evaporation is directly proportional to the temperature and inversely proportional to the humidity of the air.
On a hot and dry day,the temperature is high and the humidity is low,which significantly increases the rate of evaporation.
Since evaporation causes a cooling effect,the increased rate of evaporation leads to better cooling by the desert cooler.

(B) An earthen pot (matka) has a large number of tiny pores on its surface.
Water seeps through these pores and reaches the outer surface of the pot.
This water evaporates continuously due to the heat of the surroundings.
Since the process of evaporation is an endothermic process that requires energy (latent heat of vaporization),it absorbs this heat from the remaining water inside the pot.
As a result,the temperature of the water inside the pot decreases,making it cool.

(A) Acetone,petrol,and perfume are volatile substances that evaporate rapidly when exposed to air.
During the process of evaporation,these substances absorb the necessary latent heat of vaporization from the surface of the palm.
Since the palm loses heat to the liquid,the temperature of the palm decreases,causing a cooling sensation.

(B) Evaporation is a surface phenomenon.
When tea or milk is poured into a saucer,it spreads out,providing a larger surface area compared to a cup.
$A$ larger surface area allows more particles of the liquid to escape into the atmosphere as vapor,thereby increasing the rate of evaporation.
Since evaporation causes cooling,the liquid in the saucer cools down much faster than in a cup,allowing us to sip it more quickly.

(B) We should wear light-colored cotton clothes in summer because:
$1.$ Cotton is a good absorber of water/sweat. It provides more surface area for the sweat to evaporate.
$2.$ Light colors absorb less heat.
Therefore,wearing light-colored cotton clothes helps us feel cool and comfortable.

(B) To convert temperature from the Kelvin scale to the Celsius scale,we subtract $273$ from the given value,as the relationship is defined by the formula: $^\circ C = K - 273$.
$(a)$ For $293 \, K$: $293 - 273 = 20 \, ^\circ C$.
$(b)$ For $470 \, K$: $470 - 273 = 197 \, ^\circ C$.

(C) To convert temperature from the Celsius scale to the Kelvin scale,we add $273$ to the given Celsius value,as the relationship is defined by the formula:
$K = ^{\circ}C + 273$
$(a)$ For $25\,^{\circ}C$:
$25 + 273 = 298\, K$
$(b)$ For $373\,^{\circ}C$:
$373 + 273 = 646\, K$
Therefore,the correct values are $298\, K$ and $646\, K$.

(N/A) Naphthalene is a substance that undergoes sublimation,meaning it changes directly from a solid to a gas without passing through the liquid state. As it absorbs heat from the surroundings,the naphthalene balls sublime and disappear over time.
$(b)$ The smell of perfume is due to the presence of volatile aromatic compounds. These particles diffuse rapidly through the air,allowing us to detect the scent even when sitting several metres away.

(A) The forces of attraction between particles are strongest in solids,moderate in liquids,and weakest in gases.
Sugar is a solid,water is a liquid,and oxygen is a gas.
Therefore,the increasing order of forces of attraction is: Oxygen < Water < Sugar.

(N/A) At $0\,^oC$,water exists in a state of equilibrium between solid (ice) and liquid phases. At $100\,^oC$,water exists in a state of equilibrium between liquid and gaseous (steam) phases. Between $0\,^oC$ and $100\,^oC$,water remains in the liquid state.
$(a)$ At $25\,^oC$: Liquid state.
$(b)$ At $0\,^oC$: Solid and liquid state (melting point).
$(c)$ At $100\,^oC$: Liquid and gaseous state (boiling point).

(N/A) Water is a liquid at room temperature because:
$1$. It has a tendency to flow (fluidity).
$2$. It takes the shape of the container in which it is kept,but its volume remains fixed.
$(b)$ An iron almirah is a solid at room temperature because:
$1$. It has a definite shape and a fixed volume.
$2$. It is hard and rigid,meaning it resists change in shape when subjected to external force.

(A) At $273 \ K$,ice and water are at the same temperature,but they differ in their energy content.
Ice requires additional energy,known as the latent heat of fusion,to change its state from solid to liquid.
When ice is used for cooling,it absorbs this latent heat from the substance being cooled,thereby providing more effective cooling compared to water at the same temperature,which does not have this additional heat-absorbing capacity.

(B) Steam causes more severe burns than boiling water.
This is because steam contains an additional amount of heat known as latent heat of vaporization.
When steam comes into contact with the skin,it condenses into water and releases this extra latent heat,causing more intense damage to the skin tissues compared to boiling water at the same temperature.

(N/A) $A =$ Melting or fusion,where solid changes into liquid.
$B =$ Evaporation or vaporization,where liquid changes into gas.
$C =$ Condensation,where gas changes into liquid.
$D =$ Freezing or solidification,where liquid changes into solid.
$E =$ Sublimation,where solid directly changes into gas without passing through the liquid state.
$F =$ Deposition,where gas directly changes into solid without passing through the liquid state.