CHAPTER – 1

MATTER IN OUR SURROUNDINGS

All matters in the universe exist in three states. There are two ways of classification of matter.
1. According to physical state as solid, liquid or gas.
2. According to its composition as element, compound or mixture.

CHARACTERISTICS OF PARTICLES OF MATTER

PARTICLES OF MATTER HAVE SPACE BETWEEN THEM- when we make tea,

coffee or lemonade (nimbu paani ), particles of one type of matter get into the spaces between
particles of the other. This shows that there is enough space between particles of matter.
Similarly particles of sugar, salt, Dettol, or potassium permanganate get evenly distributed in
water.

PARTICLES OF MATTER ARE CONTINUOUSLY MOVING- Particles of matter are

continuously moving, that is, they possess what we call the kinetic energy. As the temperature
rises, particles move faster. So, we can say that with increase in temperature the kinetic energy
of the particles also increases.

PARTICLES OF MATTER ATTRACT EACH OTHER- Particles of matter have force

acting between them. This force keeps the particles together. The strength of this force of
attraction varies from one kind of matter to another.

INTEXT QUESTIONS PAGE NO. 3

Q1. Which of the following are matter?

Chair, air, love, smell, hate, almonds, thought, cold, colddrink, smell of perfume.
Answer: Chair, air, smell, almonds, cold-drink and smell of perfume are matter because they
have some weight and occupy space.

Q2. Give reasons for the following observation:

The smell of hot sizzling food reaches you several metres away, but to get the smell from
cold food you have to go close.
Answer: Hot food evaporates easily. Its vapours diffuse between the air molecules and reach
within a short time to a distant place. But the case is different with the cold food because it
remains in solid form and does not mix with air molecules, so we have to go close to smell it.
Q3. A diver is able to cut through water in a swimming pool. Which property of matter
does this observation show?
Answer: The phenomena of cutting the water by the diver show that matter has space between
its particles.

Q4. What are the characteristics of the particles of matter?

Answer: Characteristics of particles of matter :
1. Particles of matter have space between them.
2. Particles of matter are continuously moving.
3. Particles of matter have an attraction force between them.
4. Particles of matter are very small in size.

STATES OF MATTER

1. THE SOLID STATE- all solids have a definite shape, distinct boundaries and fixed
volumes, that is, have negligible compressibility. Solids have a tendency to maintain their
shape when subjected to outside force. Solids may break under force but it is
difficult to change their shape, so they are rigid.

2. THE LIQUID STATE- Liquids have no fixed shape but have a fixed volume. They take up
the shape of the container in which they are kept. Liquids flow and change shape, so they are
not rigid but can be called fluid. The rate of diffusion of liquids is higher than that of solids.
This is due to the fact that in the liquid state, particles move freely and have greater space
between each other as compared to particles in the solid state.

3. THE GASEOUS STATE- Gases are highly compressible as compared to solids and liquids.
The liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen
supplied to hospitals in cylinders is compressed gas. In the gaseous state, the particles move
about randomly at high speed. Due to this random movement, the particles hit each other and
also the walls of the container.
INTEXT QUESTIONS PAGE NO. 6

Q1. The mass per unit volume of a substance is called density. (density = mass/volume).
Arrange the following in order of increasing density – air, exhaust from chimneys, honey,
water, chalk, cotton and iron.
Answer: The order of density is gas< liquid< solid. Thus,

Q2. (a) Tabulate the differences in the characteristics of states of matter.

Answer:
(a) The differences in the characteristics of states of matter are given in the following table.
S. No. Solids Liquids Gases
No definite shape. Liquids Gases have neither a
Definite shape and
1 attain the shape of the vessel in definite shape nor a
volume.
which they are kept. definite volume.
2 Incompressible Compressible to a small extent. Highly compressible
There is little space
These particles have a greater The space between gas
3 between the particles of a
space between them. particles is the greatest.
solid.
These particles attract The force of attraction between The force of attraction is
4 each other very strongly. liquid particles is less than least between gaseous
solid particles. particles.
Gaseous particles are in a
Particles of solid cannot
5 These particles move freely. continuous, random
move freely.
motion.

(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container,
shape, kinetic energy and density.
Answer:
(i) Rigidity The property due to which an object retains its shape and size is known as rigidity.
Solids are rigid whereas liquids and gases are not.

(ii) Compressibility Compressibility is the property due to which a substance can be

compressed, i.e., its volume can be decreased. Gases are compressible whereas solids and
liquids are not.

(iii) Fluidity The property due to which a substance tends to flow is called fluidity. Gases and
liquids are fluids, solids are not.

(iv) Filling a gas container A gas can be filled in a gas container by compressing it under high
pressure. The property of compressibility (of gases) helps them in this regard.

(v) Shape The property of having a definite geometry is called shape of a particular substance.
Solids have a definite shape whereas gases and liquids do not have.

(vi) Kinetic energy The energy possessed by an object or by the molecules of an object due to
its state of motion is called kinetic energy. Molecules of gases posses highest kinetic energy.
Increasing the temperature also increases the kinetic energy of a substance (or its molecules).
(vii) Density The mass per unit volume of a substance is called density.

Q3. Give reasons

(a) A gas fills completely the vessel in which it is kept.
Answer: There is little attraction between particles of gas. Thus, gas particles movefreely in all
directions. Therefore, gas completely fills the vessel in which it is kept.

(b) A gas exerts pressure on the walls of the container.

Answer: Particles of gas move randomly in all directions at high speed. As a result,
theparticles hit each other and also hit the walls of the container with a force. Therefore, gas
exerts pressure on the walls of the container.

(c) A wooden table should be called a solid.

Answer: A wooden table has a definite shape and volume. It is very rigid and cannot be
compressed i.e., it has the characteristics of a solid. Hence, a wooden table should be called a
solid.
(d) We can easily move our hand in air but to do the same through a solid block of wood
we need a karate expert.
Answer: Particles of air have large spaces between them. On the other hand, wood has little
space between its particles. Also, it is rigid. For this reason, we can easily move our hands in
air, but to do the same through a solid block of wood, we need a karate expert.

Q4. Liquids generally have lower density as compared to solids. But you must have
observed that ice floats on water. Find out why.
Answer: The mass per unit volume of a substance is called density (density = mass/volume).
As the volume of a substance increases, its density decreases. Though ice is a solid, it has large
number of empty spaces between its particles. These spaces are larger as compared to the
spaces present between the particles of water. Thus, the volume of ice is greater than that of
water. Hence, the density of ice is less than that of water. A substance with lower density than
water can float on water. Therefore, ice floats on water.
PROCESS OF CHANGE OF STATES OF MATTER:
• Vaporization
• Condensation
• Freezing
• Melting
• Sublimation
• Evaporation

VAPORIZATION:(CHANGE OF LIQUID INTO GAS):

The process of change of water into vapor is called vaporization. When water is heated after
reaching at 1000C water starts boiling. At this temperature water turns into vapour. Since,
water boils at 1000C, hence 1000C is called the boiling point of water.

BOILING POINTS
The common definition of boiling point is, the temperature at which a liquid boils is called its
boiling point. Different liquid boils at different temperatures.

CONDENSATION:(CHANGE OF GAS INTO LIQUID)-

The change of vapor into water because of decrease in temperature is called condensation.
Condensation is the reverse process of vaporization. When the temperature of vapor decreases
it changes into water, this process is known as condensation.
Distilled water is manufactured by the condensation of vapor. The process of making of
distilled water is known as distillation. In distillation first water is boiled to vaporize and the
vapor is cooled, i.e. condensed to get distilled water.

FREEZING:(CHANGE OF LIQUID INTO SOLID) -

The change of liquid into solid because of decrease in temperature is called freezing. Water
change into ice because of decrease in temperature, in other words water freezes into ice
because of decrease in temperature. Water freezes at 00C.
MELTING:(CHANGE OF SOLID INTO LIQUID)
The change of solid into liquid due to increase in temperature is known as melting. Ice, which
is a solid melts, i.e. changes into water at 00C.

LATENT HEAT

When water is heated up-to 1000C it starts boiling and changes into vapor. But we see that
even after continuous supply of heat temperature does not rise above the 100C while boiling of
water.
Temperature supplied after 100C to boiling water is used to change the water into vapor and
temperature of water does not rise.
On the other hand we see that when heat is supplied to ice, temperature does not rise above the
00C, until all ice melts. In this process also the heat supplied to ice after 00C is used to change
of ice into water and temperature of ice does not rise.
Heat is used in these processes without rise in temperature is known as Latent Heat. The
latent heat is used in change of states of matter, such as from solid to liquid or from liquid
to gas without rising in temperature.
Hence, Latent heat is the heat released or absorbed by a body during the process without
change in temperature of the system. This happens while change of state of matter meaning
a phase transition. Example - Melting of ice, boiling of water.
The particles of solid and liquid are bonded together with great force of attraction, because of
which a matter exists in a particular state. When we supply heat to a solid or liquid, the heat is
supplied without come in notice is used to break the force of attraction between particles and
this heat is not used to increase the kinetic energy of particles. Since, kinetic energy of particles
do not increase we do not see any rise in temperature of the system.
The word ‘latent’ is derived from the Latin word ‘Latere” which means “to lie hidden”. Joseph
Black introduced the term Latent heat around 1762.
TYPES OF LATENT HEAT :
• Latent heat of fusion
• Latent heat of vaporization

LATENT HEAT OF FUSION (MELTING OR FREEZING):

When solid changes into liquid, the head required changing the state without rising in
temperature is called the Latent Heat of Fusion.
The change of solid to liquid state is an endothermic reaction as heat is required in it. The
reaction in which heat is supplied or used is called endothermic reaction or process.
Let us take the example of melting of ice.
When heat is supplied to melt ice, temperature does not rise from 00C even after continuous
supply of heat till all ice melts. After melting of all ice temperature starts rising. The additional
heat is required to melt the ice without coming into notice is the latent heat of fusion.
The latent heat of fusion of ice is the energy which is used to change the state of ice (solid)
to water (liquid).
The quantity of heat required to convert I kilogram of solid to liquid without any change in
temperature is called Latent Heat of fusion.
The heat required is measured in joules (J).

3.34 x 105 joules of heat is required to convert 1 kilogram of ice into water at its melting point.
Thus, the heat of fusion of ice at its melting point = 3.34 x 105 joules.

LATENT HEAT OF VAPORIZATION:

When liquid changes into gas because of rise in temperature, the heat required changing the
state without rising in temperature is called the Latent Heat of vaporization.
The change of liquid to gaseous state is an endothermic reaction as heat is required in it.
Let us take the example of boiling of water.
Water boils at 1000C. When heat is supplied to water temperature does not rise after 1000C
even after continuous supply of heat. The heat supplied at this stage is used to change water
into vapor and hence does not come into notice. The additional heat is required to change the
water into vapor without coming into notice is the latent heat of vaporization.
The latent heat of vaporization of water is the energy which is used to change the state of
water (liquid) to vapor (gas).
22.5 x 105 J energy is required to convert 1 kilogram of water into vapor. Hence, the latent
heat of water is equal to 22.5 x 105 J per kilogram or it is written as 22.5 x 105 J/kg.
Different liquid has different latent heat of vaporization.
SUBLIMATION:
The process in which a solid changes into vapor without changing into liquid and from vapor
changes into solid without changing into liquid is known as sublimation.
Generally solid first changes into liquid and then changes into gas because of rise in
temperature. But there are many substances, which change into gas without changing into
liquid and changes into solid from gas without changing into liquid. Such substances, which go
under sublimation, are known as sublime.
For example – camphor, naphthalene balls, ammonium chloride, iodine, dry ice, etc.
The solid obtained after cooling of the gas of sublime is called Sublimate. The process of
cooling of vapor of sublime to get sublimate is also known as ‘sublimation’ although it is also
known as deposition.
When camphor is heated it changes into vapor without changing into liquid. When the vapor of
camphor is cooled it changes into solid without changing into liquid.

SUBLIMATION IN EVERYDAY LIFE:

The dry ice (solid carbon dioxide) turns into vapor without changing into liquid and is
considered as sublime. Because of this property dry ice is used to give the illusion of smoke or
cloud on the stage in movies and stage shows.

Naphthalene balls are kept with cloths and documents to protect them from insects. Since
naphthalene balls go under sublimation, hence it changes into vapor without changing into
liquid and its vapor prevent the insects to come or stay in cloths or documents. This protects
the documents and cloths to get destroyed.

We usually see that the size of naphthalene balls decrease gradually and finally disappeared
when they are kept in open. This happens because of sublimation of naphthalene.
Naphthalene balls are used in toilets also as disinfectant and air freshener.
INTEXT QUESTIONS PAGE NO. 3

Q1. Convert the following temperature to celsius scale:

a) 300 K b) 573 K.
Answer: (a) 300 K = (300 − 273)°C = 27°C
(b)573 K = (573 − 273)°C = 300°C

Q2. What is the physical state of water at:

a) 2500C b) 1000C ?
Answer:
(a) Water at 250°C exists in gaseous state.
(b) At 100°C, water can exist in both liquid and gaseous form. At this temperature, after
getting the heat equal to the latent heat of vaporization, water starts changing from liquid state
to gaseous state.

Q3. For any substance, why does the temperature remain constant during the change of
state?
Answer: During a change of state, the temperature remains constant. This is because all the
heat supplied to increase the temperature is utilised in changing the state by overcoming the
forces of attraction between the particles. Therefore, this heat does not contribute in increasing
the temperature of the substance.
Q4. Suggest a method to liquefy atmospheric gases.
Answer: Applying high pressure and cooling a gas to low temperature helps in the liquifaction
of atmospheric gases. The reason is that under such conditions of temperature and pressure, the
molecules of gases come closer, their kinetic energy becomes less and the gas is liquefied.

EVAPORATION
The change of liquid into vapor without reaching at its boiling point is called Evaporation.
Evaporation takes place only at the surface of liquid while vaporization takes place on the
whole mass of liquid.
Evaporation takes place even at room temperature also. Evaporation speeds up with rise in
temperature.
When water or other liquid is left in open, gradually its volume decreases. If you left some
water in a pot in open, after two or three days water disappears. If the water left in garden or in
a open balcony, it disappears quickly than kept in a room. This happens because of
evaporation.
PROCESS OF EVAPORATION
Molecules at the surface of water, when exposed some temperature, their kinetic energy
increases. Because of increase in kinetic energy those molecules become able to overcome the
force of attraction between the particles of liquid. After getting required kinetic energy and
decrease in force of attraction, they escape in the air in the form of vapor. Additionally those
kinetic energy get some of the required kinetic energy from their neighboring molecules also
because of which the temperature of the adjacent molecules decrease, which finally result in
decrease of the temperature of surface of liquid.

FACTORS AFFECTING THE EVAPORATION

• Temperature
• Pressure
• Surface area
• Humidity in air
• Wind speed

TEMPERATURE
Evaporation increases with increase in temperature and decreases with decrease in temperature.
This means rate of evaporation is directly proportional to the temperature.
With increase in temperature the particles of liquid at surface get required kinetic energy to
overcome the force of attraction and escape in air quickly. Hence, the increase in temperature
increases the rate of evaporation.
PRESSURE
Evaporation decreases with increase in pressure and increases with decrease in pressure. This
means the rate of evaporation is indirectly proportional to the pressure.
Particles at the surface of liquid require more kinetic energy to escape in air when there is more
pressure over it and hence rate of evaporation will decrease. While if there is less pressure over
the surface of liquid, the particles would require less kinetic energy to escape in air and hence
rate of evaporation will increase. Therefore, increase in pressure slows down the rate of
evaporation and decrease in pressure speeds up the rate of evaporation.

SURFACE AREA
Evaporation increases with increase in surface area and decreases with decrease in surface
area.
Since evaporation takes place at the surface of liquid only, hence if the more surface of liquid
is exposed to atmosphere more particles will receive the required temperature to get the
required kinetic energy to escape in air. Therefore, evaporation takes place more rapidly with
larger surface area. This means rate of evaporation increases with increase in surface area and
decreases with decrease in surface area.

After rain roads are dried up quickly than pot holes. This happens because of increase in
surface area of water. On roads water is spread over a large area, because of that large area of
water exposed to atmosphere, and evaporation of water takes place quickly resulting in quickly
drying of the roads. While in pot holes less water surface is exposed to air because of that less
water area could come in contact with air and receives less temperature, resulting in delayed
evaporation. That’s why water dried from road quickly than in pot holes.
Wet clothes are spread up over the laundry line to get them dried up quickly. More surface area
of water exposes to the air because of spreading of clothes this speeds up the rate of
evaporation and clothes are dried up quickly. On the other hand if wet clothes are left even in
the sun without spreading, they take more time to get dried because of less surface area
exposed to air. That’s why wet clothes are kept spread over laundry line to get dried up
quickly.
Water kept in a plate evaporates quickly than water kept in a tumbler (glass). This happens
because in plate more surface area of water exposed to atmosphere which receives more heat
and evaporates quickly. While in a glass less surface area of water exposed to atmosphere
because of that less molecules of water receives heat from the atmosphere and evaporates
slowly compare to the water exposed with large surface area.
Hence, rate of evaporation increases with increase in surface area and decreases with decrease
the surface area.

HUMIDITY IN AIR AND EVAPORATION

Evaporation decreases with increase in humidity and increases with decrease in humidity
present in air. This means rate of evaporation is indirectly proportional to the humidity present
in air.
Humidity is the amount of water vapor present in air. In weather reports, which are published
in news paper or given on the TVs channels, the humidity percent is given, which shows the
percent of water vapor present in air.
Because of more water vapor present in air the water holding capacity of atmosphere decreases
which decrease the rate of evaporation. If air is dry then it can holds more water and thus in dry
air rate of evaporation increases.
This is the cause that our cloths get dried up quickly in summer and winter than in rainy
season. Because in rainy season there is more water vapor present in air, which decrease the
water holding capacity of atmosphere resulting in decrease the rate of evaporation and our
cloths do not dry up quickly in the rainy season.
Our sweat does not dry up quickly in rainy season. Because of that we feel uneasiness because
of damp. This is because of higher percent of humidity present in air decreases the rate of
evaporation in rainy season and our sweat does not evaporate quickly and we feel uneasy
because of damp.

WIND SPEED AND EVAPORATION

Evaporation increases with the increase in wind speed and decreases with decrease in wind
speed. This means rate of evaporation is directly proportional to the speed of wind.
Speedy wind propelled away some of the particles of water with it which speeds up the rate of
evaporation. That’s why speedy wind speeds up the rate of evaporation.
We see that wet cloth is dried up quickly in a windy day since the wind speeds up the rate of
evaporation.
The wet clothes are given jerks before hanging them on laundry line because by giving jerks
some of the water droplets propelled out. This reduces the presence of water in the wet cloths
and they dried up quickly.

EVAPORATION IN EVERYDAY LIFE:

(a) Water from the surface of oceans, seas and other large water bodies evaporate continuously
as they are exposed to atmosphere. The water vapor because of evaporation rises up in air and
cumulates in the form of cloud, which makes the rain. Hence, evaporation is one of the
essential parts of water cycle. Thus we can say that evaporation is one of the most natural
phenomena for us.
(b) In summer days sweats come out to regulate the temperature of our body. The sweat
evaporates because of increase in surface area and getting the temperature from atmosphere.
This is resulting in decrease in temperature of skin and finally our body, which gives relief to
us in hot days. Sweating is a natural mechanism to keep cool the surface of our body in hot
days. This is the cause that with increase in temperature our body sweats a lot especially in hot
summer days.
(c) Water is kept in earthen pots to keep them cool. Earthen pot has lot of pores. Water kept in
earthen pots evaporates from the pores of pots, which cools the neighboring molecules of
water. This process continues and whole of the water kept in the earthen pots become cooler.
Hence, water is kept in the earthen pot to keep them cool for drinking purpose.
(d) Wet clothes on the laundry lines are dried up because of evaporation.
(e) Sea water has lot of salt. Sea water is left in shallow pond. The water evaporates gradually
because of heat of sun leaving the salt in the shallow pond. These salts are collected and used
for with food after purification.
(f) Evaporative coolers are widely used in hot summer days. In evaporative coolers, dry air is
blow over husk saturated of water. From the surface of husk water is evaporated resulted in
cooling of husk. The water particles at the surface of wet husk evaporate and cool the rest
portion of wet husk. Air blown from the cool husk is sent in the room, which cools the room.
INTEXT QUESTIONS PAGE NO. 6
Q1. Why does a desert cooler cool better on a hot dry day?
Answer: The rate of evaporation increases with increase in temperature and decrease in
humidity. A desert cooler functions on the basis of evaporation. As evaporation increases when
the day is hot and dry, so the desert cooler functions to a better extent.
Q2. How does the water kept in an earthen pot (matka) become cool during summer?
Answer: The surface of the earthen pot (matka) has tiny pores. The water stored in the earthen
pot (matka) evaporates faster through these pores due to the increased exposed surface area. As
the process of evaporation causes cooling, the stored water inside the earthen pot (matka)
becomes cool.
Q3. Why does our palm feel cold when we put some acetone or petrol or perfume on it?
Answer: Acetone, petrol, perfume, etc., being volatile, evaporate very fast when exposed to
larger surfaces. During the process they absorb the required latent heat of vaporisation from the
palm (if kept on palm). So, the process causes cooling and the palm feels cool.

Q4. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Answer: In a saucer, the exposed surface area of tea or milk is greater as compared to the cup.
Therefore, the evaporation is faster and it is easier to sip colder tea or milk.

Q5. What type of clothes should we wear in summer?

Answer: We should wear cotton clothes in summers. During summers, we sweat more. On the
other hand, cotton is a good absorber of water. Thus, it absorbs sweat from our body and
exposes the liquid to the atmosphere, making evaporation faster. During this evaporation,
particles on the surface of the liquid gain energy from our body surface, making the body cool.

EXERCISE QUESTIONS PAGE NO. 12

Q1. Convert the following temperatures to the Celsius scale.
(a) 300 K (b) 573 K.
Answer: Kelvin is an SI unit of temperature, where 0°C = 273 K
(a) 300 K = (300 − 273) °C = 27 °C
(b) 573 K = (573 − 273) °C = 300 °C
Q2. Convert the following temperatures to the Kelvin scale.
(a) 25°C (b) 373°C.
Answer: Kelvin is an SI unit of temperature, where 0°C = 273 K
(a) 25 °C = (25 + 273) K = 298 K
(b) 373 °C = (373 + 273) K = 646 K

Q3. Give 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.
Answer:
(a) Naphthalene undergoes sublimation easily i.e., the change of state of naphthalene from
solid to gas takes place easily. Thus, naphthalene balls disappear with time without leaving any
solid.
(b) Gaseous particles possess high speed and large spaces between them. Particles of perfume
diffuse into these gaseous particles at a very fast rate and reach our nostrils. This enables us to
smell the perfume from a distance.
Q4. Arrange the following substances in increasing order of forces of attraction between
the particles—
water, sugar, oxygen.
Answer:
Sugar is a solid; the forces of attraction between the particles of sugar are strong. Water is a
liquid; the forces of attraction here are weaker than sugar. Oxygen is a gas; the forces of
attraction are the weakest in gases.
Thus, the increasing order of forces of attraction between the particles of water, sugar and
oxygen is
Oxygen < Water < Sugar

Q5. What is the physical state of water at—

(a) 25°C (b) 0°C (c) 100°C ?
Answer:
(a) Water at 25°C is present in the liquid state.

(b) At 0 °C, water can exist as both solid and liquid. At this temperature, after getting the heat
equal to the latent heat of fusion, the solid form of water i.e., ice starts changing into its liquid
form i.e., water.

(c) At 100 °C, water can exist as both liquid and gas. At this temperature, after getting the heat
equal to the latent heat of vaporization, water starts changing from its liquid state to its gaseous
state, i.e., water vapours.

Q6. Give two reasons to justify—

(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.
Answer:
(a) At room temperature (25 °C), water is a liquid because it has the following characteristic of
liquid:
i). At room temperature, water has no shape but has a fixed volume that is, it occupies the
shape of the container in which it is kept.
ii). At room temperature, water flows.

(b) An iron almirah is a solid at room temperature (25 °C) because:

i). it has a definite shape and volume like a solid at room temperature.
ii). it is rigid as solid at room temperature.

Q7. Why is ice at 273 K more effective in cooling than water at the same temperature?
Answer: When ice melts, it absorbs the energy equal to the latent heat of fusion too from the
surroundings so it causes cooling more effectively than the water at same temperature (because
water does not absorb energy from the surroundings).

Q8. What produces more severe burns, boiling water or steam?

Answer: Steam causes more severe burns than boiling water. The reason is that it releases the
extra amount of heat (latent heat) which it has already taken during vaporisation (when the
steam was formed from water).
Q9. Name A,B,C,D,E and F in the following diagram showing change in its state

Answer:

A = Melting or fusion, here the solid changes into liquid.

B = Evaporation or vaporisation, here the liquid changes into gas.
C = Condensation or liquification, here the gas changes into liquid.
D = Freezing or solidification, here the liquid changes into solid.
E = Sublimation, here solid directly changes into gas without coming in liquid state.
F = Sublimation, here gas changes into solid without coming to liquid state.
 ASSIGNMENT QUESTIONS SET – 1
CHAPTER – 1
MATTER IN OUR SURROUNDINGS

1. Fill in the blanks

a. The process of ________ causes cooling.
b. The process of cooling glass is known as ____.
c. Liquids have no fixed ______ but have fixed _____.
d. ____ exists in all three states of matter.
e. Carbon dioxide is a white solid called _____ at temperature below ______.

2. State True or False

a. Evaporation of water is a bulk phenomenon.
b. Diffusion takes place in haphazard and random way.
c. SI unit of pressure is Pascal.
d. A gas is highly incompressible fluid.
e. Solids and liquids can be identified from their characteristic melting and boiling points.

3. Zig-zag movement of the solute particle in a solution is known as

(a) Linear motion
(b) Circular motion
(c) Brownian motion
(d) Curved motion.

4. Gases can be liquified by

(a) increasing pressure
(b) decreasing temperature
(c) both (a) and (b)
(d) decreasing pressure

5. Density of a substance is defined as

(a) ratio of mass and volume
(b) product of mass and volume
(c) ratio of mass and temperature
(d) product of mass and temperature

6. Which of the following is not matter

(a) Blood
(b) Humidity
(c) Electron
(d) Moon rock

7. Which is more effective in cooling?

(a) Ice at 0° C
(b) Water at 0° C
(c) Water at 100° C
(d) Ice at 100° C
8. 0° C temperature is equal to
(a) 0 K
(b) 273 K
(c) -273 K
(d) 300 K

9. The process involving the change of state from solid to gas is called
(a) melting
(b) boiling
(c) sublimation
(c) fusion

10. A solid has

(a) definite volume and no definite shape
(b) no definite volume no definite shape
(c) definite shape and volume
(d) definite shape but no definite volume

11. A liquid has

(a) definite volume and no definite shape
(b) no definite volume no definite shape
(c) definite shape and volume
(d) definite shape but no definite volume

12. A gas has

(a) definite volume and no definite shape
(b) no definite volume no definite shape
(c) definite shape and volume
(d) definite shape but no definite volume

13. Which of the following is NOT a property of particles of a matter?

(a) The particles of matter are extremely small
(b) The particles of matter have spaces between them.
(c) The particles of matter are in stationery state.
(d) The particles of matter attract each other.

14. Which of the following has minimum spaces among the particles?
(a) Solids
(b) Liquids
(c) Gases
(d) None of these
15. During summer, water kept in an earthen pot becomes cool because of the phenomenon of
(a) diffusion
(b) transpiration
(c) osmosis
(d) evaporation
16. Rate of diffusion is the fastest in
(a) Solids
(b) Liquids
(c) Gases
(d) None of these
17. Thermal conduction takes places in
(a) solids only
(b) liquids only
(c) gases only
(d) solids, liquids and gases.

18. Evaporation always causes

(a) thermal expansion
(b) Liquification
(c) Cooling down
(d) all of these

19. A change of state directly from solid to gas without changing into liquid state (or vice
versa) is called
(a) Evalopartion
(b) Sublimation
(c) Diffusion
(d) Condensation

20. The rate of evaporation decreases with

(a) increase in humidity
(b) increase of temperature
(c) increase in wind speed
(d) increase of surface area

21. Expand CNG and LPG.

22. Arrange the following substances in increasing order of force of attraction between the
particles. (i) milk (ii) salt (iii) oxygen
23. Why is sponge a solid though compressible?
24. Write one important characteristic of matter.
25. Why does a desert cooler cool better in a hot dry day?
26. Convert: (a) 25°C into kelvin scale (b) 500 K into celsius scale
27. Why does the smell of hot sizzling food reach you several metres away but to get the smell
from cold food you have to go close?
28. What is the term used for change of solid state to liquid state?
29. Name the temperature at which solid and liquid states of matter can coexist.
30. Define evaporation.
31. "The wool being knitted into a sweater is a physical change." Justify the statement.
32. Mention two ways to liquefy atmospheric gases.
33. What is the value of boiling point of water on Kelvin Scale of temperature?
34. What is dry ice?
35. (a) Dry ice is compressed at high pressure. What happens when pressure is released?
(b) Suggest a method to liquefy atmospheric gases.
36. (a) The melting points of 2 substances A & B are 280 K and 320 K respectively. Are these
substances liquid at room temperature? Justify your answer.
(b) Give an example that shows the state of matter can be changed into another state by
changing the temperature.

37. How will you show that matter is composed of tiny particles?

38. Define (i) Latent heat of fusion and (ii) latent heat of vapourisation.

39. Explain how the following factors affect the rate of evaporation of a liquid:
(i) temperature of the liquid.
(ii) area of the exposed surface.
(iii) moisture in the surrounding air.
(iv) increase in wind speed.

40. When a bottle of scent is opened in one corner of a room, it immediately spreads
throughout the room. What property of matter is responsible for this observation? Explain.

41. (a) Conversion of solid to vapour is called sublimation. Name the term used to denote the
conversion of vapour to solid.
(b) Conversion of solid state to liquid state is called fusion; what is meant by latent heat of
fusion?

42. Both boiling and evaporation convert a liquid into vapours. What is the difference between
the two processes?

43. A sample of water under study was found to boil at 102°C at normal pressure. Is the
water pure? Will this water freeze at 0°C? Comment.

44. Why does the temperature of a substance remain constant during its m.pt. or boiling point?

45. Answer the following questions:

(i) Arrange the following substances in increasing order of force of attraction between the
particles.
(i) water (ii) hydrogen (iii) sand

(ii) Why does the temperature remain constant at the melting point?

(iii) Which property of gases makes it possible to fill large volume of gases in small
cylinders?

46. Answer the following questions:

(a) Why is ice at 273 K more effective in cooling than water at the same temperature?
(b) Name the two gases which are supplied in compressed form in homes and hospitals.
47. You want to wear your favourite shirt to a party but the problem is that it is still wet after a
wash. What steps would you take to dry it fast?

48. Give reasons:

(a) Steam produces more severe burns than boiling water.
(b) We are able to sip hot tea faster from a saucer rather than from a cup.
(c) Water kept in an earthen pot becomes cool during summer.
49. Why do cotton clothes suit best in summer?

50. Classify the following into osmosis and diffusion:

(a) Swelling up of a resin on keeping in water.
(b) Spreading of virus on sneezing.
(c) Earthworm dying on coming in contact with common salt.
(d) Shrinking of grapes kept in thick sugar syrup.
(e) Preserving pickles in salt.
(f) Aquatic animals using oxygen dissolved in water during respiration.
 ASSIGNMENT QUESTIONS SET – 2
CHAPTER – 1
MATTER IN OUR SURROUNDINGS

1. What is a matter?
2. Sodium chloride and sugar have same appearance. Are they same or different?
3. All substances around us are alike. How?
4. How can we say that air is a matter?
5. State the characteristics of matter?
6. What are the intensive properties of matter?
7. What are the extensive properties of matter?
8. State the characteristics of particles of matter.
9. What is the effect of temperature on a matter?
10. The smell of hot sizzling food reaches us several metres away. Why?
11. What is diffusion?
12. If a bottle of perfume is opened in one corner of a room, it immediately spreads throughout
the room. Why?
13. Name the three states of matter with examples.
14. State the characteristics of solids.
15. What are the characteristics of liquids?
16. What are the characteristics of gases?
17. What are fluids?
18. Which of the following substances is most compressible?CO2, H2O, NaCl.
19. Which property of a gas results in steady pressure of the gas ?
20. In which of the following substances, weakest inter molecular force is expected: H2O,
CH3OH,
21. One gas mixes with another gas easily. What is this property called ?
22. Describe briefly (i) Melting point and (ii) Boiling point.
23. How would you find out whether a sample of sodium chloride is pure or impure ?
24. How will you find out whether a sample of water is pure or impure ?
25. Why do solids have a fixed shape and gases have neither a fixed shape nor a fixed volume?
26. What is Vaporization ?
27. What is Sublimation ?
28. What is Condensation ?
29. What is Deposition ?
30. What is Liquefaction ?
31. What is Solidification ?
32. What is difference between vapour and gas.
33. Why do the three states of matter differ ?
34. Why does the temperature remain constant until whole of the solid changes into liquid,
though the heat energy is constantly supplied ?
35. Why does the temperature remain constant during boiling though heat is constantly
supplied ?
36. Why does a gas fill a vessel completely ?
37. How does the state of matter changes from solid to liquid and then to gas on heating ?
38. Why evaporation is called surface phenomenon?
39. List two processes from which it may be concluded that the particles of a gas move
continuously.
40. At what temperature does solid ice and liquid water co-exist together?
41. What is common among the three states of matter?
42. Which property of gas is used in supplying oxygen cylinders to hospitals?
43. A substance x was highly compressible and could easily be liquefied. it could also take the
shape of the container. Predict the nature of the substance
44. What is the state of water at 100 degree celsius, zero degree celsius and 4 degree celsius?
45. Can a liquid turn into vapor without heating?
46. What do you mean by Latent heat of Fusion?
47. What is compressibility? How it is negligible in solids?
48. Two cubes of ice are pressed hard between two palms. After releasing the pressure, the
cubes join together. Why?
49. Explain why ice has lower density than water?
50. Give one similarity between a liquid and a gas and one dissimilarity.
51. What property of gas is utilized when natural gas is supplied for vehicles.
52. What are ‘intermolecular forces’? How are these related to the three states of matter ?
53. Separate the following substances in groups of high and low intermolecular force: Ice,
sulphur vapour, nitrogen, sugar, copper, air, salt, plastic.
54. Which of the following substances you expect strongest and in which weakest
intermolecular force: Water, alcohol, sugar, sodium chloride, carbon dioxide.
55. Why are gases compressible but liquids not ?
56. Compare the process of boiling and vaporization.
57. How is pressure developed in a container full of a gas ?
58. What are the applications of interconversion of states of matter ?
59. What happens to a gas if its inter molecular space is reduced ?
60. Explain how lumps of ice are more effective cooling than water at 273K.
 ASSIGNMENT QUESTIONS SET – 3
CHAPTER – 1
MATTER IN OUR SURROUNDINGS

1. Conversion of solid to vapour is called sublimation. Name the term used to denote the
conversion of vapour to solid.

2. Conversion of solid state to liquid state is called fusion; what is meant by latent heat of
fusion?

3. Fill in the blanks:

(a) Evaporation of a liquid at room temperature leads to a——— effect.
(b) At room temperature the forces of attraction between the particles of solid substances
are———than those which exist in the gaseous state.
(c) The arrangement of particles is less ordered in the ——— state. However, there is no
order in the ——— state.
(d) ——— is the change of gaseous state directly to solid state without going through the
———state.
(e) The phenomenon of change of a liquid into the gaseous state at any temperature below
its boiling point is called———.

4. Match the physical quantities given in column A to their S I units given in column B :
(A) (B)
(a) Pressure (i) cubic metre
(b) Temperature (ii) kilogram
(c) Density (iii) pascal
(d) Mass (iv) kelvin
(e) Volume (v) kilogram per cubic metre
5. The non S I and S I units of some physical quantities are given in column A and column B
respectively. Match the units belonging to the same physical quantity:
(A) (B)
(a) degree celsius (i) kilogram
(b) centimetre (ii) pascal
(c) gram per centimetre cube (iii) metre
(d) bar (iv) kelvin
(e) milligram (v) kilogram per metre cube
6. Classify the following into osmosis/diffusion
(a) Swelling up of a raisin on keeping in water.
(b) Spreading of virus on sneezing.
(c) Earthworm dying on coming in contact with common salt.
(d) Shrinking of grapes kept in thick sugar syrup.
(e) Preserving pickles in salt.
(f) Spreading of smell of cake being baked through out the house.
(g) Aquatic animals using oxygen dissolved in water during respiration.
7. Which one of the following sets of phenomena would increase on raising the temperature?
(a) Diffusion, evaporation, compression of gases
(b) Evaporation, compression of gases, solubility
(c) Evaporation, diffusion, expansion of gases
(d) Evaporation, solubility, diffusion, compression of gases

8. Seema visited a Natural Gas Compressing Unit and found that the gas can be liquefied
under specific conditions of temperature and pressure. While sharing her experience with
friends she got confused. Help her to identify the correct set of conditions
(a) Low temperature, low pressure
(b) High temperature, low pressure
(c) Low temperature, high pressure
(d) High temperature, high pressure

9. The property to flow is unique to fluids. Which one of the following statements is correct?
(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

10. During summer, water kept in an earthen pot becomes cool because of the phenomenon of
(a) diffusion
(b) transpiration
(c) osmosis
(d) evaporation

11. A few substances are arranged in the increasing order of ‘forces of attraction’ between their
particles. Which one of the following represents a correct arrangement?
(a) Water, air, wind
(b) Air, sugar, oil
(c) Oxygen, water, sugar
(d) Salt, juice, air

12. On converting 25°C, 38°C and 66°C to kelvin scale, the correct sequence of temperature
will be
(a) 298 K, 311 K and 339 K
(b) 298 K, 300 K and 338 K
(c) 273 K, 278 K and 543 K
(d) 298 K, 310 K and 338 K
13. The boiling points of diethyl ether, acetone and n-butyl alcohol are 35°C, 56°C and 118°C
respectively. Which one of the following correctly represents their boiling points in kelvin
scale?
(a) 306 K, 329 K, 391 K
(b) 308 K, 329 K, 392 K
(c) 308 K, 329 K, 391 K
(d) 329 K, 392 K, 308 K
14. Which condition out of the following will increase the evaporation of water?
(a) Increase in temperature of water
(b) Decrease in temperature of water
(c) Less exposed surface area of water
(d) Adding common salt to water
15. Choose the correct statement of the following
(a) conversion of solid into vapours without passing through the liquid state is called
vapourisation.
(b) conversion of vapours into solid without passing through the liquid state is called
sublimation.
(c) conversion of vapours into solid without passing through the liquid state is called
freezing.
(d) conversion of solid into liquid is called sublimation.

16. In which of the following conditions, the distance between the molecules of hydrogen gas
would increase?
(i) Increasing pressure on hydrogen contained in a closed container
(ii) Some hydrogen gas leaking out of the container
(iii) Increasing the volume of the container of hydrogen gas
(iv) Adding more hydrogen gas to the container without increasing the volume of the
container
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)

17. A student heats a beaker containing ice and water. He measures the temperature of the
content of the beaker as a function of time. Which of the following graph would correctly
represent the result? Justify your choice.

18. A glass tumbler containing hot water is kept in the freezer compartment of a refrigerator
(temperature < 0°C). If you could measure the temperature of the content of the tumbler,
which of the following graphs would correctly represent the change in its temperature as a
function of time.

19. A sample of water under study was found to boil at 102°C at normal temperature and
pressure. Is the water pure? Will this water freeze at 0°C? Comment.

20. ‘Osmosis is a special kind of diffusion’. Comment.

21. Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain
these observations.
22. Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam
gushing out of the spout of the kettle. She wondered whether the temperature of the steam
was higher than that of the water boiling in the kettle. Comment.

23. Look at below figure and suggest in which of the vessels A,B, C or D the rate of
evaporation will be the highest? Explain.

24. You are provided with a mixture of naphthalene and ammonium chloride by your teacher.
Suggest an activity to separate them with well labelled diagram.

25. It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon clothes respectively.
Who do you think would be more comfortable and why?

26. You want to wear your favourite shirt to a party, but the problem is that it is still wet after a
wash. What steps would you take to dry it faster?

27. Comment: Evaporation produces cooling.

28. Comment: Rate of evaporation of an aqueous solution decreases with increase in humidity.

29. Comment: Sponge though compressible is a solid.

30. Why does the temperature of a substance remain constant during its melting point or
boiling point?