Q: Question 4Arrange the following in increasing order of forces of attraction between the particles –water, sugar, oxygen.

Oxygen (gas) < water (liquid) < sugar (solid)

Q: Question 5What is the physical state of water at?(a) 25°C(b) 0°C(c) 100°C?

(a) At 25°C (normal room temperature) — liquid state(b) At 0°C (freezing point) — Both solid and liquid phases are observed(c) At 100°C (boiling point) — Both liquid and gaseous phases are observed

Q: Question 6Give two reasons to justify –(a) water at room temperature is a liquid.(b) an iron almirah is a solid at room temperature.

(a) Water at room temperature is a liquid because of the following reasons:At room temperature, water does not have a fixed shape and flows to fit the container's shape.A fixed volume is occupied by a fixed mass of water.(b) An iron almirah is a solid at room temperature because of the following reasons:It has a definite shape and volume at room temperature.It is rigid.

Q: Question 7Why is ice at 273 K more effective in cooling than water at the same temperature?

The latent heat of fusion of ice is 336 J g-1 so it absorbs 336 J of heat and changes to water at 0°C and then water at 0°C absorbs heat and temperature is raised. Therefore, ice at 0°C absorbs extra heat in comparison to water at 0°C (due to latent heat of fusion). Hence, ice at 0°C has greater cooling effect than water at 0°C.

Q: Question 8What produces more severe burns, boiling water or steam?

Steam has a higher heat content on account of high specific latent heat of condensation that is 2268 J g-1. Hence, steam at 100°C carries more heat than water. Therefore, burns caused by steam are more severe than burns caused by boiling water.

Q: Question 9Name A, B, C, D, E and F in the following diagram showing a change in its state.

(A) Solid to Liquid — Melting or liquefaction(B) Liquid to Gas — Evaporation or vaporization(C) Gas to liquid — Condensation(D) Liquid to Solid — Solidification(E) Solid to Gas — Sublimation(F) Gas to Solid — Deposition

Q: Question 1Which of the following are matter?Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of perfume.

The following substances are matter:ChairAirAlmondsLemon waterSmell of perfume (due to the presence of some volatile substances in air that occupy space & have mass.)

Question 1

Question 1Convert the following temperatures to Celsius scale.(a) 293 K(b) 470 K

Accepted Answer

(a) °C = Kelvin - 273 = 293 - 273 = 20°C(b) °C = Kelvin - 273 = 470 - 273 = 197°C

Question 2

Question 2Convert the following temperatures to the Kelvin scale.(a) 25°C(b) 373°C

Accepted Answer

(a) Kelvin = (°C + 273) K = 25 + 273 = 298 K(b) Kelvin = (°C + 273) K = 373 + 273 = 646 K

Question 3

Question 3Give reason for the following observations:(a) Naphthalene balls disappear with time without leaving any solid.(b) We can get the smell of perfume sitting several metres away.

Accepted Answer

(a) Naphthalene balls when left open, directly change into vapour without heating due to sublimation. Hence, with time they become small in size and finally disappear.(b) Perfumes comprise substances that are volatile, and diffuse rapidly into the air. Hence, we are able to smell perfume sitting several metres away.

Question 4

Question 4Arrange the following in increasing order of forces of attraction between the particles –water, sugar, oxygen.

Accepted Answer

Oxygen (gas) < water (liquid) < sugar (solid)

Question 5

Question 5What is the physical state of water at?(a) 25°C(b) 0°C(c) 100°C?

Accepted Answer

(a) At 25°C (normal room temperature) — liquid state(b) At 0°C (freezing point) — Both solid and liquid phases are observed(c) At 100°C (boiling point) — Both liquid and gaseous phases are observed

Question 6

Question 6Give two reasons to justify –(a) water at room temperature is a liquid.(b) an iron almirah is a solid at room temperature.

Accepted Answer

(a) Water at room temperature is a liquid because of the following reasons:At room temperature, water does not have a fixed shape and flows to fit the container's shape.A fixed volume is occupied by a fixed mass of water.(b) An iron almirah is a solid at room temperature because of the following reasons:It has a definite shape and volume at room temperature.It is rigid.

Question 7

Question 7Why is ice at 273 K more effective in cooling than water at the same temperature?

Accepted Answer

The latent heat of fusion of ice is 336 J g-1 so it absorbs 336 J of heat and changes to water at 0°C and then water at 0°C absorbs heat and temperature is raised. Therefore, ice at 0°C absorbs extra heat in comparison to water at 0°C (due to latent heat of fusion). Hence, ice at 0°C has greater cooling effect than water at 0°C.

Question 8

Question 8What produces more severe burns, boiling water or steam?

Accepted Answer

Steam has a higher heat content on account of high specific latent heat of condensation that is 2268 J g-1. Hence, steam at 100°C carries more heat than water. Therefore, burns caused by steam are more severe than burns caused by boiling water.

Question 9

Question 9Name A, B, C, D, E and F in the following diagram showing a change in its state.

Accepted Answer

(A) Solid to Liquid — Melting or liquefaction(B) Liquid to Gas — Evaporation or vaporization(C) Gas to liquid — Condensation(D) Liquid to Solid — Solidification(E) Solid to Gas — Sublimation(F) Gas to Solid — Deposition

Question 10

Question 1Which of the following are matter?Chair, air, love, smell, hate, almonds, thought, cold, lemon water, the smell of perfume.

Accepted Answer

The following substances are matter:ChairAirAlmondsLemon waterSmell of perfume (due to the presence of some volatile substances in air that occupy space & have mass.)

Question 11

Question 2Give reasons for the following observation:The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food, you have to go close.

Accepted Answer

Particles of matter are continuously moving as they possess kinetic energy. An increase in temperature increases the kinetic energy of particles hence they start moving faster and can move several meters quickly. Therefore, the smell of hot sizzling food reaches a person even at a distance of several meters but to get the smell from cold food, we have to go close.

Question 12

Question 3A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Accepted Answer

The observation that a diver can cut through water in a swimming pool indicates that the particles of liquid matter have spaces between them, and the intermolecular forces of attraction are relatively weak. Consequently, the force exerted by the diver is sufficient to overcome these forces of attraction, allowing the diver to move through the water.

Question 13

Question 4What are the characteristics of the particles of matter?

Accepted Answer

The characteristics of the particles of matter are:Particles of matter have space between them.Particles of matter are always in random motion.Particles of matter attract each other.

Question 14

Question 1The mass per unit volume of a substance is called density. (Density = Mass/Volume ). Arrange the following in order of increasing density – air, exhaust from the chimneys, honey, water, chalk, cotton and iron.

Accepted Answer

The following substances are arranged in increasing density:Air < exhaust from chimney < cotton < water < honey < chalk < iron

Question 15

Question 2(a) Tabulate the differences in the characteristics of states of matter.(b) Comment upon the following:rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density.

Accepted Answer

(a) The difference in the characteristics of the three states of matter are:CharacteristicsSolidLiquidGasShapeFixed shapeNo Fixed shapeNo Fixed shapeVolumeFixed volumeFixed volumeNo Fixed volumeIntermolecular forceMaximumLess than solidsVery lessIntermolecular spaceVery lessMore than solidsMaximumCompressibilityNegligibleCompressibleHighly compressible(b) (i) Rigidity — It is the property of matter to continue to remain in its shape when treated with an external force.(ii) Compressibility — It is the property of the particles of matter to contract their intermolecular space when exposed to an external force, thereby increasing its density.(iii) Fluidity — It is the ability of a substance to flow or move about freely.(iv) Filling a gas container — The particles of gas fill the entire container as the intermolecular spaces between the gas molecules is very large and hence the particles are free to move about in all directions.(v) Shape — It is the definite structure of an object within an external boundary(vi) Kinetic energy — Motion allows particles to possess energy which is referred to as kinetic energy.K.E = 12\dfrac{1}{2}21​ mv2, where'm' is the mass and'v' is the velocity of the particle.(vii) Density — It is the mass of a unit volume of a substance.d = mv\dfrac{	ext{m}}{	ext{v}}vm​, whered is the density,m is the mass andv is the volume of the substance

Question 16

Question 3Give reasons(a) A gas fills completely the vessel in which it is kept.(b) A gas exerts pressure on the walls of the container.(c) A wooden table should be called a solid.(d) We can easily move our hand in the air, but to do the same through a solid block of wood, we need a karate expert.

Accepted Answer

(a) Gas is a state of matter in which intermolecular attraction is very weak and intermolecular space is so large that the particles become completely free to move randomly in the entire available space. Hence, it fills completely the vessel in which it is kept.(b) Gas molecules have negligible intermolecular forces and possess high kinetic energy, enabling them to move rapidly in all directions. This random motion leads to collisions among particles and with the container walls, resulting in the exertion of pressure by gas particles on the container.(c) A solid is characterized by a fixed shape and volume, and a wooden table also has these properties with its definite shape and volume, minimal intermolecular spaces, and rigidity. Therefore, it is appropriately called as a solid.(d) Air particles have very weak intermolecular force of attraction and hence very large intermolecular spaces. As a result, we can move our hands freely in the air. The particles in a solid block, on the other hand, are bound together by a strong force of attraction. As a result, there is no space between them. Hence, we will require a karate expert.

Question 17

Question 4Liquids generally have a lower density than solids. But you must have observed that ice floats on water. Find out why.

Accepted Answer

Water shows unique behaviour as it is one of the few substances that expands on freezing resulting in a decrease in its density. Therefore, the ice formed is less dense than the liquid water, causing it to float on water.

Question 18

Question 1Convert the following temperature to Celsius scale:(a) 300 K(b) 573 K

Accepted Answer

(a) °C = Kelvin - 273 = 300 - 273 = 27°C(b) °C = Kelvin - 273 = 573 - 273 = 300°C

Question 19

Question 2What is the physical state of water at?(a) 250°C(b) 100°C

Accepted Answer

(a) At 250°C water is in gaseous state since it is beyond its boiling point.(b) At 100°C water is in the transition state as the water is at its boiling point. Hence it would be present in both liquid and gaseous states.

Question 20

Question 3For any substance, why does the temperature remain constant during the change of state?

Accepted Answer

The temperature remains constant during a change of state because the heat energy supplied or released is used to overcome the intermolecular forces between particles rather than increasing the kinetic energy of the particles. This heat energy that is supplied or released without showing any change in temperature is known as the latent heat.

Matter in Our Surroundings

Exercises

Intext Questions 1

Intext Questions 2

Intext Questions 3

Intext Questions 4