02 Structure of Atom
03 Formular and Equations
04 Periodic Table
05 Chemical Bond
06 Electrochemistry
07 Acids and Bases
08 Salts
09 Manufactured Substances in Industry
10 Rate of Reaction
11 Carbon Compounds
12 Oxidation and Reduction
13 Thermochemistry
14 Chemicals for Consumers

2.1.2 Changes in the State of Matter

3 States of Matter

Matter exists in 3 states of matter, namely, solid state, liquid state and gaseous state.

Characteristics of Matter in Solid, Liquid and Gaseous State

Arrangement of Particles

Solid
Particles are arranged in an orderly manner and close to one another.
Liquid
Particles are not arranged in order. The space between particles is moderately large.
Gas
The particles are very far apart and randomly arranged.
Movement of Particles
Solid Particles vibrate at fixed positions.
Liquid Particles move randomly and slowly and sometimes will collide against each other.
Gas The particles move randomly in all directions at great speed.

The force of Attraction Between Particles

Solid very strong
Liquid Strong but weaker than in the solid state.
Gas very weak

Ability to be compressed

Solid Very difficult to be compressed because the particles are packed closely.
Liquid Not easily compressed because the particles are packed quite closely.
Gas Easily compressed because the particles are very far apart.

Heat Energy content

Solid Lowest Energy Content
Liquid Moderate energy content.
Gas Highest energy content
Volume and Shape
Volume Shape
Solid Fixed Fixed
Liquid Fixed Follows the container
Gas Follows the container Fills the whole container

Inter-conversion between the States of Matter

Change in Heat and Kinetic Energy of Particles

  1. The change in temperature will influences the kinetic energy or the speed of the motion of the particles.
  2. When a substance is heated, the kinetic energy of the particles in the substance increases. This causes the particles to move or vibrate faster.
  3. Likewise, when a substance is cooled, the kinetic energy of the particles in the substance decreases. This causes the particles to move or vibrate slower.
  4. The kinetic energy of the particles in a substance is directly proportional to the temperature of the substance.
Inter-conversion between States of Matter

Heating Curve

 
The graph above shows the heating curve of a substance.
  • Naphthalene is in solid state at any temperature below its melting point.
  • The particles are very closely packed together in an orderly manner.
  • The forces between the particles are very strong. The particles can only vibrate at a fixed position.
  • As the naphthalene is heated, heat energy is converted to kinetic energy.
  • Kinetic energy increases and the molecules vibrate faster about their fixed positions and the temperature increases.
  • Naphthalene is still in solid state.
  • Naphthalene molecules have received enough energy to overcome the forces of attraction between them.
  • Some of the particles that gain enough energy begin to move freely.
  • Naphthalene starts to melt and changes into a liquid.
  • Naphthalene exists in both solid and liquid states.
  • The temperature remains constant because the heat that supplied to naphthalene is used to overcome the forces of attraction that hold the particles together.
  • The constant temperature is called the melting point.
  • The heat energy that absorbed to overcome the intermolecular forces is named as the latent heat of fusion.
  • All the naphthalene has completely melted.
  • Solid naphthalene has turned into liquid.
  • Naphthalene is in liquid state.
  • As the liquid naphthalene is heated, the molecules gain more heat energy and the temperature continues to increase.
  • The particles move faster and faster because their kinetic energy is increasing.
  • Naphthalene still exists in liquid state.
  • Naphthalene molecules have received enough energy to overcome the forces of attraction between the particles in the liquid.
  • Some of the naphthalene molecules start to move freely and liquid naphthalene begin to change into gas.
  • Naphthalene exists in both liquid and gaseous states.
  • The temperature remains unchanged.
  • The is because the heat energy absorbed is used to overcome the intermolecular forces between the particles of the liquid rather than increase the temperature of the liquid.
  • This constant temperature is the boiling point.
  • All the naphthalene has turn into gas.
  • The gas particles continue to absorb more energy and move faster.
  • The temperature increases as heating continues.

Cooling Curve


The graph above shows the cooling curve of a substance.

  • The substance exists in gaseous state.
  • The particles have very high energy and are moving randomly.
  • The intermolecular forces between the particles are very weak and can be ignored.
  • The substance is in gaseous state.
  • The particles lose kinetic energy during cooling, the particles getting closer to each other and the temperature drops.
  • The substance still exists as a gas.
  • As the molecules are close enough, stronger forces of attraction result in forming of intermolecular bonds.
  • The gas begins to condense and become liquid.
  • The process of condensation going on.
  • Stronger bonds form as gas changes into liquid.
  • The substance exists in both gaseous and liquid states.
  • The temperature remains unchanged.
  • This is because the energy produced during the formation of bonds is equal to the heat energy released to the surroundings during cooling.
  • This constant temperature is the boiling point.
  • The heat energy that releases during this condensation process is called the latent heat of vaporization.
  • The substance exists only in liquid state as all the gas particles have condensed into liquid.
  • The substance exists as a liquid.
  • As the temperature falls, the naphthalene molecules lose heat energy. Their movement shows down and they move closer to each other.
  • The substance still in liquid state.
  • The particles have very little energy and begin to move closer towards one another as it starts to freeze into solid.
  • The liquid is changing into solid form.
  • Molecules rearrange to form the molecular arrangement of a solid.
  • The substance exists as both liquid and solid.
  • The temperature remains constant until all the liquid changes to solid.
  • This is because the energy released is the same as the energy lost to the surroundings during cooling.
  • This constant temperature is the freezing point.
  • The heat energy that releases during this freezing process is called the latent heat of fusion.
  • All the liquid freezes into solid. The particles are now closely packed in an orderly manner.
  • Once all the liquid has become solid, the temperature falls once again until it reaches room temperature. The substance is in the solid state here.
  • The substance reaches room temperature and remain at this temperature as long as the room temperature remain the same.

Melting Point, Boiling Point and State of Matter

  1. The physical state of a substance at a certain temperature and pressure depends on the values of its melting and boiling points.
  2. A substance is in solid state if it exists at a temperature below its melting point.
  3. A substance is in liquid state if it exists at a temperature above its melting point but below its boiling point.
  4. A substance is in gaseous state if it exists at a temperature above its boiling point.