9th Science Notes Chapter 1 Matter In Our Surrounding
Matter In Our Surrounding
When we dissolve salt in water, the
particles of salt get into the spaces
between particles of water
Particles are varying and have spaces
between them
Matter
The matter is the material of which
everything in this universe, in and around us is made up of in different
shapes. It is anything that occupies space and
has mass and offers resistance to any applied force.
Physical Nature of Particles
1️⃣ Matter is made up of tiny particles
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All matter (solid, liquid, gas) is made up of very small particles.
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These particles are so small that we cannot see them with the naked eye.
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Example: When we dissolve a small crystal of potassium permanganate or salt in water, it spreads throughout — showing particles are tiny and evenly distributed.
2️⃣ Particles of matter have space between them
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The spaces between particles are called inter-particle spaces.
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This is why:
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Water can mix with sugar or salt (they fill in the spaces).
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Gases can be compressed (particles are far apart).
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3️⃣ Particles of matter are constantly moving
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Particles are in continuous motion, having kinetic energy.
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This movement increases with temperature.
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Example: Fragrance of perfume spreads in a room — due to the movement of gas particles.
4️⃣ Particles of matter attract each other
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There is a force of attraction between particles.
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This force is:
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Strong in solids
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Moderate in liquids
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Weak in gases
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That's why solids hold shape, liquids flow, and gases spread out freely.
🧠 Summary:
| Property | Explanation |
|---|---|
| Tiny size | Cannot be seen with naked eyes |
| Space between particles | Allows mixing, compression |
| Constant motion | Shows energy, helps in diffusion |
| Attraction between particles | Strong in solids, weaker in gases |
States of Matter
The physical states of a matter are :
(i) Solid, (ii) Liquid, (iii) Gas.
1️⃣ Solid
Examples: Ice, Wood, Brick
| Property | Description |
|---|---|
| Shape | Fixed |
| Volume | Fixed |
| Particle arrangement | Tightly packed |
| Movement of particles | Very slow (vibrate in place) |
| Force of attraction | Strong |
| Compressibility | Cannot be compressed |
Example : Rubber band is a solid
because it can change its shape under force and regains its shape when force is
removed. If excessive force is applied, it
breaks.
The solids have fixed and rigid shape. The
kinetic energy of the particles in the solid state is very less and therefore,
solids have fixed and rigid shape.
• We can compress sponge as its pores
are filled with air but it is solid.
• Salt and sugar take the shape of
the container in which they are placed
but shape of their crystals do not change, so they are solids.
2️⃣ Liquid
Examples: Water, Oil, Milk
| Property | Description |
|---|---|
| Shape | Not fixed (takes shape of container) |
| Volume | Fixed |
| Particle arrangement | Loosely packed |
| Movement of particles | Free to move around |
| Force of attraction | Moderate |
| Compressibility | Almost incompressible |
• Force of attraction between the
particles of liquid keeps its volume same.
• Liquids are substances having fixed
(definite volume) and no fixed shape. They take the shape of the container in
which they are stored.
• The gases (oxygen and carbon
dioxide) from the atmosphere diffuse and dissolve in water. Due to these gases
aquatic plants and animals are able to survive. Diffusion is much more in
liquids than in solids due to free movement of particles of liquids.
3️⃣ Gas
Examples: Air, Oxygen, Carbon dioxide
| Property | Description |
|---|---|
| Shape | No fixed shape |
| Volume | No fixed volume |
| Particle arrangement | Far apart |
| Movement of particles | Very fast |
| Force of attraction | Very weak |
| Compressibility | Highly compressible |
• The particles in a gas are free to
move in any direction hence gases can flow.
• Gases are substances that do not
have fixed volume and occupy all the volume available to them.
• Pressure of gas is the force
applied on the walls of vessel by the irregular moving gas particles.
🔄 Changes Between States of Matter
Matter can change from one state to another through:
| Process | Change |
|---|---|
| Melting | Solid → Liquid (by heating) |
| Freezing | Liquid → Solid (by cooling) |
| Evaporation | Liquid → Gas (by heating) |
| Condensation | Gas → Liquid (by cooling) |
| Sublimation | Solid → Gas (directly) |
| Deposition | Gas → Solid (directly) |
• Water can exist in three states of
matter i.e., solid – ice, liquid – water,
gas – water vapour.
• On heating ice melts into water and
then converts into water vapours.
Change in the physical state of
matter can be done in two ways :
(A) By Changing the Temperature :
(i) Melting Point :
The temperature at which a solid melts to form liquid at atmospheric pressure is called its melting point.
- At the melting point, both solid and liquid states exist in equilibrium.
- The substance absorbs heat, but its temperature does not increase during the actual melting.
- This heat is used to break the force of attraction between the particles of the solid.
Melting point of ice is 273.16 K (0º C). During melting the temperature of ice does not rise even though heat is being supplied continuously due to latent heat of fusion.
This latent heat of fusion is used up to overcome the forces of attraction between ice particles.
At 0º C energy
of water particles is much more than the energy of particles of ice at 0º C.
• Latent Heat of Fusion :
The amount of heat required to change 1 kg solid to its liquid state (at its melting point) at
atmospheric pressure.
Latent Heat "Hidden" heat — used for change of state, not raising temperature
Fusion Melting (Solid → Liquid)
Latent Heat of Fusion Heat required to melt 1 kg of solid at melting point
(ii) Boiling Point :
The temperature at which a liquid boils to form vapours at atmospheric pressure is called its boiling point.
liquid changes into a gas (vapor) throughout the entire liquid, not just from the surface.
Boiling point of water is 373
K (100º C + 273 = 373 K).
• Latent Heat of Vapourization :
The amount of heat required to change 1 kg liquid to its gaseous
state (at its boiling point) at atmospheric pressure.
• During boiling the temperature of
water does not rise even though heat is being supplied continuously as this
heat of vapourization is used up to over the forces of attraction between water
particles.
At 100º C, energy of water vapours is
much more than the energy of water at 100º C.
So, we can change one state of matter
to another state by changing temperature.
At 25ºC, water is liquid. At 0º C,
water is solid (ice). At 100º C, water is gaseous state (steam).
(iii) Sublimation :
The change of solid directly into vapours on heating and of vapours
into solid on cooling without passing through the intervening liquid state is
called sublimation.
Example : When camphor or ammonium
chloride is heated in a China dish covered by a inverted funnel (with cotton
plug in its upper open end), the vapours of ammonium chloride are converted
into solid ammonium chloride on coming in contact with the cold inner walls of
the funnel
. 
(B) Effect of Change of Pressure :
If we compress a gas in a cylinder,
the distance between the particles of gas is reduced and finally gas is
liquefied on lowering temperature.
• By applying high pressure, the
particles of a gas can be brought close together.
• Solid carbon dioxide (dry ice) is
changed into carbon dioxide gas directly without changing into liquid when
pressure is reduced to one atmospheric pressure.
• Thus, states of matter i.e., solid,
liquid, gas are determined by temperature & pressure.
Evaporation :
A surface phenomenon in which liquid changes into vapours at any temperature below its boiling point is called evaporation.
Particles on the surface of a liquid
have higher kinetic energy than others, so they break. The forces of attraction
between the particles & escape from the surface of liquid in the form of
vapours.
Factors affecting evaporation : Rate of evaporation depends on :
(a) Exposed surface area :
On
increasing surface area of liquid, rate of evaporation increases.
(b) Increase in temperature :
Increases kinetic energy of particles
hence rate of evaporation increases.
(c) Humidity :
When the
humidity of air (degree of dampness of air) is low, evaporation rate is
increased. More humidity, less evaporation.
(d) Wind :
When wind speed
increases, rate of evaporation also increases.
Evaporation always causes cooling :
The cooling caused by evaporation is based on the fact that when a
liquid evaporates, it takes latent heat of vaporization from surroundings which
on losing heat get cooled.
Examples :
(i) When we put acetone on our hand,
it gets evapourized by taking heat from our hand and our hand feels cool.
(ii) We should wear cotton clothes in
summer to keep cool and comfortable as cotton is good absorber of water, so it
absorbs the sweat from our body and exposes it to air for evaporation of sweat thus
cools our body
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