Matter in our surroundings class 9 notes- Chapter 1:  All about chemistry which help to prepare for class 9th examination. It improves your ability to be the best. 

What is Matter?

  • Anything that occupies space and has mass is matter. Everything in this
    universe is made up of matter.
  • For example, the air we breathe, the food we eat, clouds, stars, plants,
    animals, stones, even a small drop of water or a particle of sand- everything is
    matter.
  • Matter is made up of particles & the particles of matter are very small.

CHARACTERISTICS OF PARTICLES OF MATTER: –

1. Particles of matter have space between them –

  • The space between particles of matter is minimum in solids, medium in liquids
    and maximum in gases.

2. Particles of matter are continuously moving –
• Particles of matter possess `kinetic energy’. As the temperature rises the
kinetic energy of particles also increases thus the particles move faster.

3. Particles of matter attract each other-

  • The particles of matter have force acting between them. This force keeps the
    particle together.
  • The strength of this force of attraction varies from one kind of matter to
    another.
  • It is high in solids, medium in liquids and very less in gases.

STATES OF MATTER: –

Matter exists in three different states- solid, liquid and
gas.

matter in our surroundings class 9 notes
1. SOLID-

  • In solid particles are packed closely.
  • Solids have definite shape, distinct boundaries & fixed volumes i.e. they have
    negligible compressibility.
  • The solid have the capability to maintain their shape even when some outside
    force is applied.
  • Solid may break under force but it is difficult to change their shape, so they
    are rigid.

2. LIQUID

  • The particles are packed less closely.
  • Liquids don’t have fixed shape but have a fixed volume. They takes the shape
    of the container in which they are kept.
  • Liquids can flow and change shape due to large space between the particles
    and weaker force of attraction than solid.
  • The particles of liquid can move more freely than solid due to large space between
    particles. So, solid, liquid and gases all can diffuse into liquids.

3. GASES-

  • Interparticle spaces is very large.
  • Gases have neither have definite shape nor definite volume. Gases can
    acquire the shape and volume of the vessel in which they are placed.
  • They have large interparticle space and weak interparticle force of attraction.
  • Gases are highly compressible as compared to solid & liquid due to large space
    between the particle. gases can be compressed by applying pressure. For
    example, LIQUIFIED PETROLEUM GAS (LPG) which is used at homes are
    supplied in the form of cylinders by compressing the gases.

Later on scientists discovered two another states of matter, Plasma state & Bose- Einstein condensate (BEC).

# Plasma State of matter:

  • This state doesn’t fit in the three state of matter, so it is called as fourth state of matter.
  • It consists of highly ionized gas in which the particle exist in super energetic and super excited states.
  • Ex- Fluorescent tube contains helium & other gas. when electricity is passed through these gas, the gas gets ionized & produce a glowing colour (depending upon the nature of the gas) which is essentially plasma.

# Bose- Einstein Condensate (BEC):

  • In 1920, the indian scientist Satyendra Nath Bose gave the concept of 5th state of matter on the basis of his statistical calculations.
  • Einstein also predicted the possibility of such a state.
  • In 1995, Bose-Einstein condensates were made with the help of the advancements in technology.
  • BECs are used to study quantum mechanics on a macroscopic level.
  • Light appears to slow down as it passes through a BEC.
  • BECs are also used to simulate conditions that might exist in black holes.

CHANGE OF STATE OF MATTER: –

The states of matter can be converted from one state to another by the
following two ways.
1. By changing temperature
2. By changing pressure

matter in our surroundings class 9 notes

EFFECTS OF CHANGE OF TEMPERATURE
❖ MELTING POINT –

  • The change of state from solid to liquid is called melting or fusion.
  • The temperature at which solids changes into liquid at the atmospheric
    pressure is called melting point of the solid.
  • For Example: Melting point of ice is 0˙C or 273.15 k(kelvin)
  • Different substances have different melting points.
  • The melting point of a solid is an indication of the strength of the force of
    attraction between its particles.
  • Higher the melting point, greater is the strength of interparticle force of
    attraction.

❖ LATENT HEAT OF FUSION –

  •  The amount of heat energy required to convert 1 kg of a solid into liquid at
    the atmospheric pressure at its melting point is known as LATENT HEAT OF
    FUSION of substance.
  •  For Example: water in liquid state at 273K has more energy than water in solid
    state (ice) at 273K.

❖ BOILING POINT –

  • The temperature at which liquid starts boiling at the atmospheric pressure is
    known as its boiling point.
  • Boiling is a bulk phenomenon. Particles from the bulk of the liquid gain enough
    energy to change into vapour state.
  • Boiling point of water is 100˙C (373K).

❖ LATENT HEAT OF VAPORIZATION –

  • The amount of heat energy required to convert one kilogram of a liquid into
    gas at the atmospheric pressure at its boiling point is known as LATENT HEAT
    OF VAPORIZATION of the liquid.

❖ SUBLIMATION –

  • It is the change of solid state directly to gaseous state without going to the
    liquid state.

❖ DEPOSITION –

  • It is the change of gaseous state directly to solid state without going to the
    liquid state.

EFFECT OF CHANGE OF PRESSURE
By applying a pressure physical state of matter can also be changed.
Gas can be liquified by applying pressure and by reducing
temperature.
❖ DRY ICE:

matter in our surroundings class 9 notes

  • When carbon dioxide gas is cooled under high pressure, it directly gets
    converted into solid carbon dioxide called DRY ICE.
  • DRY ICE is stored under high pressure.

EVAPORATION –

matter in our surroundings class 9 notes

The process of change of a liquid into vapours at any temperature below its boiling point is called EVAPORATION.

❖ FACTORS AFFECTING EVAPORATION

1. SURFACE AREA OF THE LIQUID –

matter in our surroundings class 9 notes

  • Evaporation is a surface phenomenon. If the surface area is increased the rate
    of evaporation increases.
  • For example: tea becomes cold at a faster rate in a saucer than in a cup due
    large surface area of the liquid in saucer.

2. TEMPERATURE –

matter in our surroundings class 9 notes

  • The rate of evaporation increases with increase in temperature.
  • for example: clothes dry faster in summer than in winters.

3. A DECREASE IN HUMIDITY –

  • Humidity is the amount of water vapour present in air.
  • If the amount of water in air is already high, the rate of evaporation
    decreases.

4. AN INCREASE IN WIND SPEED –

  • With the increase in wind, the particles of water vapour move away with the
    wind, decreasing the amount of water vapour in the surrounding.
  • For example: clothes dry faster on windy day.

❖ COOLING CAUSED BY EVAPORATION: –

  • When the liquid is kept in an open vessel the particle of liquid absorbs energy
    from surrounding to regain the energy lost during evaporation. This
    absorption of energy makes the surrounding cold.
  • For example: when you pour some Acetone (Nail polish remover) on your
    palm the particles gain energy from your palm or surroundings and evaporate
    causing the palm to feel cool.

Related Links

Science Chapter List

 

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