1 STOICHIOMETRIC RELATIONSHIPS
1.1 INTRODUCTION TO THE PARTICULATE NATURE OF MATTER AND
CHEMICAL CHANGE
THE PARTICULATE NATURE OF MATTER
The three states of matter are solid, liquid and gas.
They differ in terms of the arrangement and movement of particles.
Sublimation is the change of state when a substance goes directly from the solid state to the
gaseous state
The reverse process (gas → solid) is often called deposition
Figure 1 Names of the changes of state
Figure 2 The properties of the three states of matter
As a solid is heated, its particles vibrate more violently – they gain kinetic energy and the
temperature of the solid rises
All the heat energy being supplied is used to partially overcome the forces of attraction
between particles so that they can move around each other
, CHEMICAL CHANGE
ELEMENTS AND COMPOUNDS
Element: is a pure substance that contains only one type of atom
Atom: is the smallest part of an element that can still be recognised as that element
Compound: is a pure substance formed when two or more elements combine chemically.
THE PHYSICAL AND CHEMICAL PROPERTIES OF A COMPOUND ARE VERY
DIFFERENT TO THOSE OF THE ELEMENTS FROM WHICH IT IS FORMED
Chemical properties dictate how something reacts in a chemical reaction.
Physical properties are basically all the other properties of a substance – such as melting
point, density, hardness, electrical conductivity…
When atoms combine to form compounds they do so in fixed ratios
State symbols are often used to indicate the physical state of substances involved in a
reaction:
• (s) = solid
• (l) = liquid
• (g) = gas
• (aq)=aqueous (dissolved in water)
MIXTURES
Mixtures : contains two or more substances mixed together
The components of a mixture are not chemically bonded together and so retain their
individual properties
The components of a mixture can be mixed together in any proportion
Solutions are mixtures
The components of a mixture can be separated from each other by physical means
HOMOGENEOUS AND HETEROGENEOUS
Homogeneous mixture : has the same (uniform) composition throughout the mixture and
consists of only one phase.
- No individual particles can be seen in the solution
- Example : water and salt
1.1 INTRODUCTION TO THE PARTICULATE NATURE OF MATTER AND
CHEMICAL CHANGE
THE PARTICULATE NATURE OF MATTER
The three states of matter are solid, liquid and gas.
They differ in terms of the arrangement and movement of particles.
Sublimation is the change of state when a substance goes directly from the solid state to the
gaseous state
The reverse process (gas → solid) is often called deposition
Figure 1 Names of the changes of state
Figure 2 The properties of the three states of matter
As a solid is heated, its particles vibrate more violently – they gain kinetic energy and the
temperature of the solid rises
All the heat energy being supplied is used to partially overcome the forces of attraction
between particles so that they can move around each other
, CHEMICAL CHANGE
ELEMENTS AND COMPOUNDS
Element: is a pure substance that contains only one type of atom
Atom: is the smallest part of an element that can still be recognised as that element
Compound: is a pure substance formed when two or more elements combine chemically.
THE PHYSICAL AND CHEMICAL PROPERTIES OF A COMPOUND ARE VERY
DIFFERENT TO THOSE OF THE ELEMENTS FROM WHICH IT IS FORMED
Chemical properties dictate how something reacts in a chemical reaction.
Physical properties are basically all the other properties of a substance – such as melting
point, density, hardness, electrical conductivity…
When atoms combine to form compounds they do so in fixed ratios
State symbols are often used to indicate the physical state of substances involved in a
reaction:
• (s) = solid
• (l) = liquid
• (g) = gas
• (aq)=aqueous (dissolved in water)
MIXTURES
Mixtures : contains two or more substances mixed together
The components of a mixture are not chemically bonded together and so retain their
individual properties
The components of a mixture can be mixed together in any proportion
Solutions are mixtures
The components of a mixture can be separated from each other by physical means
HOMOGENEOUS AND HETEROGENEOUS
Homogeneous mixture : has the same (uniform) composition throughout the mixture and
consists of only one phase.
- No individual particles can be seen in the solution
- Example : water and salt
