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NOTES

CH-1 MATTER IN OUR
SURROUNDINGS
CLASS 9th
PREPARED BY- HENA KOUSER
11/8/2020

CH-1 MATTER IN OUR
SURROUNDINGS
KEY POINTS:
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Matter:
Anything that occupies space and has mass is called matter
...

For example: Chair, bed, river, mountain, dog, tree, building, etc
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These particles are too small to be observed with naked eye
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These particles have spaces between them
...

Diffusion:
Particles of matter intermix on their own with each other
...
This intermixing of particles of two different types of matter on their own is
called diffusion
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By changing the temperature
2
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Effect of Change of Temperature:
Solid to liquid:
On increasing the temperature of solids, the kinetic energy of the particles increases which
overcomes the forces of attraction between the particles thereby solid gets converted to a liquid
...

Melting point: The temperature at which a solid melts to become a liquid at the atmospheric
pressure is called its melting point
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(a) Liquid to gas:

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On heating a liquid like water, the kinetic energy of its particles increases as high as in a gas,
thus causing the liquid to change to a gas
...

Boiling point: The temperature at which a liquid boils and changes rapidly into a gas at the
atmospheric pressure is called its boiling point
...

(b) Gas to liquid:
On cooling a gas like steam (or water vapour), the kinetic energy of its particles is lowered down,
causing them to move slowly and bringing them closer, forming a liquid
...

(c) Liquid to solid:
When a liquid is cooled down by lowering its temperature, its particles lose the kinetic energy and
come to a stationary position, causing the liquid to turn to solid
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Freezing point: The temperature at which the state of a substance changes from a liquid to a
solid is called the freezing point of that substance
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Latent heat: The heat energy that is required to change the state of a substance without causing
any ruse in the temperature of the substance is called latent heat
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Latent heat of fusion: The heat energy required to convert 1 kilogram of a solid into liquid at
atmospheric pressure, at its melting point, is known as the latent heat of fusion
Latent heat of vaporisation: The heat energy required to convert 1 kilogram of liquid into gas, at
atmospheric pressure, at its boiling point, is known as the latent heat of vaporisation
Note: Water vapour at 373 K have more energy than water at the same temperature because
particles in steam have absorbed extra energy in the form of latent heat of vaporisation
...

2
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When
a high pressure is applied to a gas, it gets compressed and if the temperature is lowered, the gas
is liquefied
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This is the reason that solid carbon dioxide is also known as dry
ice
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Factors affecting the rate of evaporation:
Surface area: The rate of evaporation increases on increasing the surface area of the liquid
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Humidity: Decrease in the humidity increases the rate of evaporation
...

Evaporation causes cooling:
During the process of evaporation, the particles of liquid absorb energy or latent heat of
vaporisation from the surrounding to get converted to gaseous state
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For example: The perspiration or sweating in our body keep the body temperature constant by
taking away the extra heat from body as the latent heat of vaporisation
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1-1
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Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, lemon
water, smell of perfume
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2
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Solution:
Particles in the air, if fuelled with higher temperatures, acquire high kinetic energy which aids them
to move fast over a stretch
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3
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Which property of matter does
this observation show?
Solution:
The diver is able to easily cut through the water in the swimming pool because of the weak forces of
attraction between water molecules
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3 Page: 6
1
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(density=mass/volume)
...

Solution:
The following substances are arranged in the increasing density:
Air
Exhaust from chimney
Cotton
Water
Honey
Chalk
Iron
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a) Tabulate the differences in the characteristics of matter
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Solution:
(a) The difference in the characteristics of the three states of matter
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Force of attraction between
particles is very strong
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Have definite shape and
volume
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Incompressible
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Force of attraction between
particles is less strong
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Do not have definite shape but
definite volume
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Almost incompressible
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Force of attraction between
particles is negligible
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Neither have definite shape
nor definite volume
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Highly compressible
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(ii) Compressibility: It is the attribute of the particles to contract its intermolecular space when
exposed to an external force thereby escalating its density
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(iv) Filling the gas container: The particles in a container take its shape as they randomly vibrate in
all possible directions
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The increasing order of kinetic energy possessed by various states of matter are:
Solids < Liquids < Gases
Mathematically, it can be expressed as K
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(vii) Density: It is the mass of a unit volume of a substance
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Give reasons
a) A gas fills completely the vessel in which it is kept
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c) A wooden table should be called a solid
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Solution:
a) Kinetic energy possessed by gas particles is very high which allows them to randomly move
across all directions when contained, hence the particles fills the gas vessel entirely
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These collisions with the walls of the container generate pressure
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• It is rigid and cannot be compressed
d) Molecules in gases are loosely packed as compared to solid molecules which are densely packed
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But you must have observed that ice
floats on water
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Solution:
Density of ice is less than the density of water
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Exercise-1
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Convert the following temperature to Celsius scale:
a
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573K

Solution:
a
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573K= (573-273)°C = 300°C
2
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250°C

b
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(b) At 100°C – It is at the transition state as the water is at its boiling point
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3
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4
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Solution:
It can be achieved by either increasing the pressure or decreasing the temperature which ultimately
leads to the reduction of spaces between molecules
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5 Page: 10
1
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High levels of this evaporation provide better cooling effects
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How does the water kept in an earthen pot (matka) become cool during summer?
Solution:
An earthen pot is porous in nature
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The process of evaporation requires energy which is contributed by
water in the pot as a result of which water turns cooler
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Why does our palm feel cold when we put on some acetone or petrol or perfume on it?
Solution:
Acetone, petrol, and perfume are volatile substances that get evaporated when they come in contact
with air
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4
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5
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Exercise Page: 12
1
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(a) 293K

(b) 470K

Solution:
0°C=273K
(a) 293K= (293 – 273)°C = 20°C
(b) 470K= (470 – 273)°C = 197°C
2
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(a) 25°C

(b) 373°C

Solution:
0°C = 273K
(a) 25°C = (25+273)K = 298K
(b) 373°C = (373+273)K = 646K
3
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(b) We can get the smell of perfume while sitting several metres away
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e
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(b) Molecules of air move at a higher speed and have large intermolecular spaces
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Hence we are able to smell perfume sitting several metres away
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Arrange the following in increasing order of forces of attraction between the particles – water,
sugar, oxygen
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What is the physical state of water at –
(a) 25°C (b) 0°C (c) 100°C?
Solution:
(a) At 25°C, the water will be in liquid form (normal room temperature)
(b) At 0°C, the water is at its freezing point, hence both solid and liquid phases are observed
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(b) An iron almirah is a solid at room temperature
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At room temperature, water
is in the liquid state, thereby exhibiting all the properties of a liquid such as
•
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Water flows at this temperature
It has a fixed volume and it takes the shape of its container

(b) The melting and boiling points of iron are as high as 1538°C and 2862°C respectively
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Hence iron almirah is a solid at room temperature
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Why is ice at 273K more effective in cooling than water at the same temperature?
Solution:
Water at this temperature(273K) is less effective than ice as ice can readily form water through
absorption of ambient heat energy as opposed to water which does not exhibit this property as it already
possesses additional latent heat of fusion so does not require extra heat
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It is because it is an exothermic reaction that releases a high amount of
heat which it had consumed during vaporization
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Name A, B, C, D, E and F in the following diagram showing a change in its state
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What happens when you pour some acetone (nail polish remover) on your palm?
ANS : The particles gain energy from your palm or surroundings and evaporate causing the palm to feel
cool
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After a hot sunny day, people sprinkle water on the roof or open ground
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3
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We
know that during evaporation, the particles at the surface of the liquid gain energy from the surroundings
or body surface and change into vapour
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Cotton, being a good absorber of water helps in
absorbing the sweat and exposing it to the atmosphere for easy evaporation
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Why do we see water droplets on the outer surface of a glass containing ice-cold water?
Let us take some ice-cold water in a tumbler
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The water
vapour present in air, on coming in contact with the cold glass of water, loses energy and gets converted
to liquid state, which we see as water droplets
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When a crystal of potassium permanganate is placed in a beaker containing water, its purple
colour spreads throughout the water
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After few minutes, pink colour
spreads and whole solution turns pink due to diffusion
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Water molecules due to liquid state, collide with solid
particles and intermix due to sufficient space between molecules
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Why do solids have a regular geometrical shape?
Answer:
In solids, the particles have highly ordered arrangement because the intermolecular forces between the
particles are very strong
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It breaks on applying excessive force
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The latent heat of fusion
of ice in SI unit is 3
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This is because it directly gets converted into gaseous state without
passing through liquid state on decreasing the pressure to 1 atmosphere
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Suggest an activity to show that the rate of diffusion of liquids decreases with increase in
density of the liquid
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Put a drop of blue ink slowly along the sides of the first beaker and honey in the same way in
another beaker
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We observe that honey diffuses slowly as compared to ink
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Answer:
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Take crystals of ammonium chloride in a china dish
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Put an inverted funnel on the china dish and insert a cotton plug in the stem of the funnel
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In the inside of the funnel white deposits of ammonium chloride is seen which directly converts into
gaseous state and then solidifies
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To which physical state of matter, do the following statements apply ? (CBSE 2013)
1
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3
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incompressible, no fixed shape
incompressible, high melting point
compressible, no definite volume
incompressible, highly fluid
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2
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4
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Which of the two
will spread faster ? Give reason for your answer
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The density of honey is more than that of ink
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(b) List four factors which affect the rate of evaporation
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Latent heat of vaporisation of water is 226 kj kg-1
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(b)
1
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3
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Surface area available for evaporation
Increase in temperature
Decrease in humidity
Increase in the speed of wind

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(a) 373 K
(b) 300 K
(c) 200 K (CBSE 2015)
Answer:
(a) Gas or Vapours
(b) Liquid
(c) Ice
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Why does perspiration keep our body cool ? (CBSE 2015)
Answer:
Actually, we perspire a lot in the hot and humid weather
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We feel more comfortable
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The synthetic clothes are less porous and do
not absorb sweat so quickly
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The temperature of the body gets lowered and we feel more
comfortable
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(CBSE 2015)
Answer:

19
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2
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4
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A liquid has a fixed volume but not a fixed shape
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A wooden table is called a solid at room temperature
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This happens because of diffusion
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2
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A
liquid cannot be compressed on applying pressure
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Liquids therefore
keep their volume
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Ice (solid state) floats over water (liquid state)
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Actually, the structure of ice is more porous* as compared to that of water
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As a
result, ice floats over water
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different containers
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(b) Write any one similarity between three states of matter
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The particles of common salt will occupy inter particle empty
spaces present in the molecules of water
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(b) All the three states of matter consist of particles which have specific mass
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Out of boiling and evaporation, which is a surface phenomenon ? Explain
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In a liquid, the
particles or molecules experience mutual forces of attraction
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The particles of a liquid are also colliding with one another
and exchanging energy during the collisions
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The particles of the liquid present on the surface have a tendency to
come out from the surface so that they may acquire more freedom to move and become part of the
atmosphere
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To overcome the interparticle forces of attraction, they
need some energy which they take up from the rest of the particles or molecules of the liquid
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Write down the boiling point of water on Celcius scale and Kelvin scale
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For example, the boiling point temperature of water is 100°C or 373 K
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It means that once the liquid starts boiling, its temperature does not change although it is still
being heated
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As long as the liquid has not boiled, the heat energy which
is supplied increases the kinetic energy of the particles (or H2O molecules) present in the liquid
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Once the liquid starts boiling, the heat energy is now being used to bring
about a change in state from liquid to gas or vapours
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Latent heat of vaporisation of water is 226 kj kg-1
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23
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Compare their properties and show that
they can flow easily
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e
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This is due to
lesser inter particle or intermolecular forces that are present in the liquid state as compared to the solid
state
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For example, water flows at a faster rate than
honey because in honey, the particles are heavier and also more closely packed
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Since the inter particle spaces are the maximum in the gaseous state, the attractive forces are the least
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Rigidity
2
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Density
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Rigidity: We have seen that rigidity is maximum in the solid state and fluidity or particle motion is
negligible
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The liquids are less rigid than the solids and the molecular motion is also comparatively
more
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Kinetic energy: The kinetic energy is linked with movement of the particles from one place to the
other
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That is why solids do not flow
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Density: Mass occupied by a solid per unit volume and is obtained by dividing the mass of a
particular solid by the volume occupied by that mass of the solid
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0°C to Kelvin
(b) 775 K to °C
(c) 489 K to °C
(d) 24°C to Kelvin
Answer:
(a) – 78 + 273 = 195 K
(b) 775 – 273 = 502°C
(c) 489-273 = 216°C
(d) 24 + 273 = 297 K
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a
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295 K
c
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225 K
Answer
a
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220C
c
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-480C

27
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a
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-15 0C
c
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3 0C
Answer
a
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258K
c
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276K

28
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Melting point
b
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Boiling point
Answer
a
...

b
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c
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Revision Notes on Matter in Our Surroundings
❖ What is Matter?
Air, water, stones, sand, clouds, pencils, books – Everything is made up of matter
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Constituents of Matter
According to the early Indian philosophers, every living and non-living thing is made of five basic
elements called the Panchtatava – Air, Water, Earth, Sky, and Fire
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❖ Physical Nature of Matter:
Is matter continuous or particulate?

Matter is particulate in nature
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For Example, If we put a drop of red colour in water the colour of the water turns red
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What is the size of these particles?

•

The size of the particles of matter is very small
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For Example, On dilution of a colourful solution,
as shown in the figure below, we can still see the colour
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Which of these is matter – happiness, air, sandwich, thoughts, juice, and eraser? Air, sandwich, juice,
and eraser as they have mass, they occupy space and can be broken into further particles
...
Particles of matter have spaces between them
2
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Particles of matter attract each other

Particles of Matter have spaces between them
Have you ever wondered what causes salt to get dissolved in water?
Salt gets dissolved in water because their particles have spaces between them
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•

We cannot see these particles through naked eyes
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Hence, they possess kinetic energy
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For Example, Salt
in water, Various gases in the air, Ink in water
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Diffusion becomes faster on heating
...


Particles of Matter attract each other
• The particles of matter are always held together because of a force of attraction between them
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That is why we cannot move our hands thro ugh a solid
object
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•

Similarly, particles of gases have the least force of attraction in them
...


•

We can arrange the force of attraction between different types of matter (solids, liquids, and
gases) in increasing order as:

•

We can also move our hands through water or liquid matter but not as freely as we can in the air
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Gas < Liquid < Solids
❖ States of Matter:
Now we know that particles of matter have a force of attraction between them
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The Solid State
• Solids are the objects that have these three properties:
o They have a specific shape
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o

They have a volume
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They are generally arranged in an
order
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They cannot be compressed
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There is not much space
between the particles
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•

Which of these are solids: Rubber band, Sponge, Salt?
o All of them are solids
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A rubber band and sponge
change their shape only when we apply force on to them
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The Liquid State
• Liquids have the following properties:

•

o

Liquids have a fixed volume

o

Liquids do not have a fixed shape
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Therefore, there is a space between
the particles of liquids and they can flow easily
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That is why they are
also called fluids
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You might have seen that liquids t ake the
shape of the container in which we put them
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•

Can other matter diffuse into liquids?
o Yes, other matter can diffuse into liquids whether it is solids, liquids, or gases
...

o
o
o

Diffusing solids into liquids: Mixing sugar in tea
Diffusing liquids into liquids: Mixing ink in water
Diffusing gases into liquids: The presence of oxygen and carbon dioxide in water

The Gaseous State
• Gases have the following properties:
o

They do not have a fixed volume
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•

The particles of gases have the least or almost no force of attraction between them
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•

Also, they can be easily compressed and put into a small container, unlike solids and liquids
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•

The kinetic energy between the particles is the maximum in the case of gases
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Difference in the characteristic of states of matter
Solid

Liquid

Gas

Definite shape

Indefinite shape

Indefinite shape

Definite volume

Definite volume

Indefinite volume

Maximum force of attraction
between particles

Less forces of attraction
Negligible force of
between particles compare to attraction between
solid
particles

Cannot be compressed

Cannot be compressed

Can be compressed

Kinetic energy of particles is
minimum

Kinetic energy of particles is
more than solid

Kinetic energy of
particles is maximum

Particles cannot move rather
they vibrate only at their fixed
position

Particles can slide over one
another

Particles can move
freely

Highest density

Density is lower than solid

Lowest density

Cannot flow

Flow

Flow

❖ Can Matter Change its State?
Water exists in three states:
•

Ice – solid

•

Water – liquid

•

Water Vapour – Gas
This is an indication that matter can change its states
...
Solids:
• As we heat solids, the kinetic energy between the particles of solids increases which decreases
the force of attraction between them
...
Slowly, due to heat the particles become free
and a solid converts into liquid
...
For Example, the melting point of ice is 273
...

Fusion – The process of melting of a solid into liquid is called Fusion
...
So where does all the heat go? The heat present in the solid at time of melting is used by
the particles to diminish the force of attraction between each other
...


•

Latent Heat – The heat energy which is used to break the force of attraction between the particles
of matter is known as latent heat
...

• Latent Heat of Fusion – The amount of heat energy required to change 1 kg of a solid into liquid
at atmospheric pressure at its melting point is known as the Latent Heat of Fusion
...

2
...

•

As we keep on supplying the heat, a point comes when the particles overcome the forces of
attraction completely
...


•

Boiling Point - The temperature at which a liquid starts boiling at the atmospheric pressure is
known as its Boiling Point
...

Latent Heat of Vaporization – the amount of heat energy required to change 1 kg of a liquid into a
gas at atmospheric pressure at its boiling point is known as Latent Heat of Vaporization
...
Gases:
• The kinetic energy between the particles decreases and they turn into a liquid state
...
For Example, The formation of clouds is due to condensation of water vapor from
Earth
...
Liquids:
• The kinetic energy between the particles decreases and they turn into a solid state
...

• Sublimation – change of state of a gas directly into solid and vice-versa is known as
sublimation
...

Therefore, by increasing or decreasing the temperature we can change the states of matter into one
another
...


Effect of change of Pressure
• By applying pressure, we can bring the particles of matter close to each other thereby, increasing
the force of attraction among the particles
...


•

Dry Ice – Carbon dioxide in solid form is known as Dry Ice
...

❖ Evaporation:

•

We already know that –
o

Particles of matter are never at rest

o

Particles of matter possess different amounts of kinetic energy

•

The particles of liquids have more kinetic energy
...


•

Evaporation – The phenomenon of change of a liquid into vapours at any given temperature
below its boiling point is called Evaporation
...


Factors Affecting Evaporation
Condition

Rate of Evaporation

Reason

Increase in Surface Area

Increases

Particles have more space and
thus can evaporate easily

Increase in temperature

Increases

Kinetic energy among the
particles increases

Increase in humidity

Decreases

Water content in air increases
and so evaporation decreases

Increase in wind speed

Increases

Water vapours are blown away
by winds allowing more
evaporation

❖ How evaporation causes cooling?
The process of evaporation uses the energy of the liquid particles
...
This results in cooling of the surrounding area
...
As the sweat evaporates it takes energy from our body surface and
keeps our body cool
...
This, in turn, keeps us cool in summer days
...
When they come in contact with the walls of the glass
that has ice-cold water in it they condense
...




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