Matter.

Matter is anything that occupies space and has weight. Matter is made up of very tiny particles known as ions, atoms or molecules.
An atom is the smallest electrically neutral particles of an element that takes part in a chemical reaction.
A molecule is the smallest electrically neutral particle of a compound or element that can exist on its own.
An ion is an electrically charged particle of an atom or a group of chemically combined atoms after losing or gaining electrons.
Matter exists in three state i.e. liquid, solid and gas.

Properties of the states of matter
Solids

  • Consist of particles that are fixed together i.e. particles that are not mobile.
  • The particles are held by very strong forces of attraction.
  • Solids have fixed shape.
  • Solids have very high density.
  • Solids are practically incompressible.
    Arrangement of particles in a solid
1 9

Liquids

  • A liquid has a definite volume but no definite shape i.e. it takes up the shape of the container in which it is placed.
  • Particles in a liquid are held together by weak intermolecular forces of attraction making the particles to move freely to some extent around each other.
  • Liquids are slightly compressible
  • Liquids are less dense compared to solids.
  • Particles in a solid are relatively spread apart

Arrangement of particles in a liquid

1 10

Gases

  • Particles in a gas are far apart from each other.
  • Particles in a gas are free to move randomly as they have negligible forces of attraction.
  • Gases are easily compressible
  • Gases have no definite shape and volume.
  • Gases are very light.
    Arrangement of particles in a gas
1 11

KINETIC THEORY OF MATTER

Kinetic theory of matter states that; Particles that make up matter have kinetic energy and they are always in motion. The extent of the movement of the particles depends on the amount of kinetic energy the particles have.

In solids, the particles are held together by very strong intermolecular forces of attraction; the particles donot have enough kinetic energy to make them move from one place to another but they can vibrate in their mean position. When a solid is heated, the kinetic energy of the particles increase as they absorb the heat energy which weakens the forces of attraction between the particles. When the melting point is reached, the molecules break free and the solid changes to liquid.

In liquids, the particles are held together by weak forces of attraction. However, they have enough kinetic energy to enable the particles move from one place to another within the liquid. When a liquid is heated, the forces of attraction between the particles are weakened further until when they are completely broken and at this point, the liquid changes to a gas. This is the boiling point of the liquid.

In a gas, the particles are free to move randomly as they posses much kinetic energy and the particles are not held together by any particular forces of attraction(or negligible forces of attraction)

CHANGE OF STATES

  • The process by which a solid changes into a liquid is the melting.
  • The constant temperature at which a solid changes into a liquid is called melting point
  • The process by which a liquid changes into a gas is called boiling or evaporation.
  • The constant temperature at which a liquid changes into a gas is the boiling point.
  • The process by which a liquid changes to a solid is freezing or solidification.
  • The constant temperature at which a liquid changes into a solid is referred to as freezing point.
  • The process by which a gas changes into a liquid is called condensation.
  • The process by which a gas changes directly to a solid is referred to as sublimation and vice versa
changes of states

Experiments to demonstrate that particles in liquids and gases move

a)Brownian motion

This is the continuousrandom movement/motion of solid particles in liquids and gases.

1.Demonstration of Brownian motion in Liquids

When pollen grains are poured in water, they are seen to be moving in a continuous random zigzag manner. The movement of the pollen grain is due to bombardment of the particles by the moving particles of water.

2.Demonstration of Brownian motion in gases

When smoke particles are trapped in a glass cell and observed under a microscope, the particles are seen to be moving in a random zigzag manner. The movement of the smoke particles is due to bombardment by the moving gas particles.

Or

When a beam of light is directed into a dark room, the dust particles are seen to be moving in a continuous random manner. The movement of the dust particles is due to the bombardment of these particles by gas particles.

b)Diffusion

This is the spreading of particles or molecules from aregion of high concentrationto a region of low concentration.

1.Demonstration of diffusion in liquids

Place a crystal of potassium permanganate in a beaker of water and watch. After sometimes, the water turns pink due to the particles of potassium permanganate spreading through out the water.

2.Demonstration of diffusion in gas

Open a bottle of concentrated ammonia solution and place the bottle at the corner of aroom. After sometimes, ammonia smell will spread through out the room due to diffusion of the ammoniaparticles.

Rate of diffusion of gases

The rate of diffusion of a gas depends on;

  • -Density of the gas. The lighter the gas, the higher the rate of diffusion.
  • -Density of the diffusion medium. The lighter the density of the diffusion medium, the faster is the rate of diffusion.
  • -Concentration gradient. The steeper the concentration gradient, the higher the rate of diffusion.
  • -Surface area. The smaller the surface area of diffusion, the higher the rate of diffusion.
  • -Temperature of the diffusion medium. The higher the temperature, the faster is the rate of diffusion of the particles.
  • -Size of the particles. Smaller particles diffuse faster the larger particles.
  • -Distance through which diffusion occurs. The smaller the diffusion distance, the faster is the diffusion.
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