Basic Concept of Matter

Definition of Matter

Tiny and discrete particles

2.1

Basic Concept of Matter

Matter can be divided into two;
- Element
- Compound
Element: substances that only consist of one type of atom, such as pure iron metal.
Compound: substances that consist of more than one element that form a molecule.
A compound is made up of either molecules or ions.
An example of a compound is carbon dioxide, \(CO_2\) where there are two types of elements in one molecule.
Atom: smallest and indivisible particles of an element.
Molecule: compound made up of two or more atoms (different or same kind of atoms).
Ion: particles that carry charges [cation(+) or anion(-)].

Solid	Liquid	Gas
Arrangement of particle
Packed very closely	Packed closely but have empty space between them	Particle very far apart
Movement of particles
Vibrate at a fixed position	Move randomly and slowly	Move randomly and rapidly at all directions
Kinetic energy
Low	High on average	High speed
Rate of diffusion
Low	Average	High

Melting

Solid is heated, the particles obtain energy and vibrate at a faster rate.
The vibration keeps increasing as the temperature increase until it reaches the melting point.
At the melting point, the particles obtain enough energy to overcome the attractive forces between the particles.
Therefore, the matter in solid state changes to a liquid.
During melting, the temperature remains constant. This is because the heat energy is used to break the bond

Vaporisation

Occurs in two conditions: either evaporation or boiling.
Evaporation occurs only on the surface of the liquid and at a slower rate.
Boiling occurs to the whole liquid and happens very fast.
Both will cause the attractive forces between particles to break and change the state from liquid to gas.

Freezing

Temperature drops and the heat energy is released.
As the heat is released, the kinetic energy decreases, the movement of particles are slower and the particles are pulled closer by the strong forces between particles.
Therefore, the physical state of the matter will change from liquid to solid.
The temperature stays at the freezing point because the heat is released constantly.

Condensation

A process by which a gas or vapour changes to liquid state at a certain temperature.
When the temperature drops, the gas loses its kinetic energy, and therefore it will change the physical state of matter to the liquid.
Condensation occurs at or below the boiling point of the substance

Sublimation

A process of conversion of a substance from the solid to the vapour state without its becoming liquid.

Heating curve of naphthalene

A	The particle are very closely packed together in an orderly manner The force between the particles is very strong.
A-B	The naphthalene is heated the energy is converted to kinetic energy The temperature increase, the kinetic energy increase and the molecules vibrate faster about their fixed position.
B	The naphthalene molecules have received enough energy to overcome the force of attraction between them. Some of the molecules begin to move freely. The naphthalene starts to melt and changes into a liquid.
B-C	Naphthalene exists in both state, solid and liquid. The temperature remains constant because the heat is used to overcome the force of attraction. The constant temperature is called the melting point.
C	The napthalene has turned into liquid completely
C-D	The naphthalene is in the liquid state The temperature keeps increasing and gain more energy. The particle is then moving faster because the kinetic energy is increasing.

Cooling curve of naphthalene

P	The substance exists in the gaseous state Have very high energy and moving randomly The intermolecular force is weak.
P-Q	The particles lose kinetic energy during cooling, The particle getting closer to each other and the temperature drops.
S	The substance is still in the gas state The gas begins to condense and become liquid.
Q-R	Stronger bonds form as gas change into a liquid. The substances exist both in gas and liquid. The energy produced during the formation of bonds is equal to the heat released to the surroundings during cooling. This is known as the freezing point.
R	The substances exist fully in the liquid state
R-S	The temperature keeps decreasing, causing the naphthalene molecules to lose heat energy. The movement of the particles slow down and move close to each other.