CLASS-9

SUBJECT- SCIENCE

CHAPTER-1

MATTER IN OUR SURROUNDINGS

 

MATTER – Anything that occupies space and has mass is matter. Everything in this universe is made up of matter. EG. - clouds, stars, plants, animals, stones etc.

CLASSIFICATION OF MATTER

1.    PHYSICAL CLASSIFICATION

·      Solid

·      Liquid

·      Gases

2.    CHEMICAL CLASSIFICATION

·      Element

·      Compounds

·      Mixture

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 possess `kinetic energy’. As the temperature rises the kinetic energy of particles also increases thus particles move faster.

 

3.    Particles of matter attract each other- The particles of matter have force acting between them which 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.

 

1.    SOLID- In solid particles are packed closely.

 

PROPERTIES OF SOLID

·      Solids have definite shape- Solids have definite shape and they do not change their shape when they are put in different containers like pen, book, table etc. Solid have definite shape due to close packing of particles and strong attractive force between them.

·      SOLIDS ARE RIGID- The solid have the capability to maintain shape even when some outside force is applied.

·      SOLID HAVE A DEFINITE VOLUME- This is due to very less space between the particles some solids can be compressed such as sponge which has small holes in which air is trapped. Sponge gets compressed on pressing it as air expelled out of it.

·      SOLID DO NOT GO UNDER DIFFUSION- This is because of less space between the particles and absence of any movement of particles of solids.

 

2.    LIQUID- The particles are packed less closely.

PROPERTIES OF LIQUID

·      LIQUID DO NOT HAVE DEFINITE VOLUME SHAPE BUT HAVE DEFINITE VOLUME- Due to strong force of attraction in particles of liquids they have a definite volume but liquids do not have a definite shape. Liquids takes the shape of the container in which they are placed.

·      LIQUIDS ARE NOT RIGID BUT HAVE THE TENDENCY TO FLOW-Liquids can flow and change shape due to large space between the particles and weaker force of attraction than solid.

·      LIQUIDS CAN UNDERGO DIFFUSION-The particles of liquid can move more freely due to large interparticle space. So, solid, liquid and gases all can diffuse into liquids.

3.    GASES- Interparticle spaces is very large.

PROPERTIES OF GASES

·      GASES HAVE NEITHER HAVE DEFINITE SHAPE NOR DEFINITE VOLUME- Gases can acquire the shape and volume of the vessel in which they are placed.

·      GASES HAVE MAXIMUM FLUIDITY- Fluidity of gases is maximum due to large interparticle space and weak interparticle force of attraction.

·      GASES ARE HIGHLY COMPRESSIBLE-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.

 

 

 

 

COMPARISION BETWEEN SOLIDS, LIQUIDS AND GASES

PROPERTY	SOLIDS	LIQUIDS	GASES
Packing of particles	Close packing	Less close packing	Very -very loose
Space between the particles	Very Small	Larger than solids; smaller than gases	Very Large
Attractive forces between the particles	Very Strong	Not so strong	Very weak
Volume	definite	definite	Take the volume of container
Diffusion	do not diffuse	Diffuse slowly	Diffuse rapidly

 

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

EFFECTS OF CHANGE OF TEMPERATURE

GASESOUS STATE

SOLID STATE

LIQUID STATE

 

 

1.    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.

·      Higher the melting point, greater is the strength of interparticle force of attraction.

LATENT HEAT OF FUSION- The amount of heat required to convert one kilogram 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 273 k has more energy than water in solid state (ice) at 273 k.

2.    BOILING POINT-The temperature at which liquid starts boiling at the atmospheric pressure is known as its boiling point.

 

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

 

3.    SUBLIMATION- It is the process where some substances on heating directly change from solid state to gaseous state without passing through the liquid state and vice-versa on cooling. For Example: ammonium chloride, camphor, iodine, naphthalene etc.

 

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: 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: 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- 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- 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 on your palm the particles gain energy from your palm or surroundings and evaporate causing the palm to feel cool.