THE NATURE OF MATTER
Matter is anything that has mass and occupies space. The mass of an object is the quantity of matter contained in such object.
PROPERTIES OF MATTER.
1. Physical properties :
These are the properties of matter associated with physical change.
When a particular aspect of matter undergoes a physical change,no new substances are formed.
Examples of physical properties of matter are boiling and melting point, density, colour, odour,taste, malleability,change of state,etc.
Examples of physical changes are the dissolution of salt in water, freezing of liquid to solid,eg,water to ice,the sublimation of solid to gas,the vaporization of liquid to gas,etc.
2. Chemical properties:
These are the properties of matter associated with chemical changes.
A chemical change is the one which cannot be easily reversed and in which new substances are formed.
Examples of chemical changes the dissolution of metals and limestone in acid, the rusting of iron, the addition of water to quicklime, the fermentation and decay of substances, etc.
CLASSIFICATIONS OF MATTER.
Matter is basically classified into two groups namely:
1. Pure substances:
These are substances that has constant chemical composition and properties.
It is further divided into ELEMENTS (metals, non-metals metalloids and Noble gases),
and COMPOUNDS
(Ionic and molecular compounds).
2.Impure substances:
These are substances formed from the combination of two or more pure substances which could be elements and/ or compounds.
Impure substances are also called MIXTURES.
Mixtures can be homogeneous (solution or colloids) or
Heterogeneous
(Suspension or colloids).
DEFINITION OF TERMS.
ELEMENTS:
An element is a substance that cannot be separated into simpler units by chemical methods.
There are 118 known elements in the world.
Elements are grouped into:
(a) METALS:
Metals are elements that ionize by losing electrons to form cations.
examples are calcium,sodium, magnesium, potassium, etc.
PROPERTIES OF METALS.
1.They are malleable, ductile or sonorous (produces sound)
2.They are lustrous.
3.Good conductors of heat and electricity.
4.High melting and boiling point.
5.High density
6.They have great tensile strength (hardness)
7.They are reducing agents.
8.They form basic oxides when they react with oxygen.examples are Magnesium oxide (MgO), sodium oxide, potassium oxide, etc.
9.They form ionic compounds.
(b) NON-METALS
Non-metals are elements that ionize by gaining electrons to form negative ions.
examples are chlorine, oxygen, Nitrogen,Iodine,etc.
Properties of non-metals:
1.They are oxidizing agents.
2.They form acidic oxides when they react with oxygen.eg.
Carbon(iv)oxide, sulphur (vi) oxide,etc.
3.The physical properties of non-metals are the opposite of that of metals, except for the case of melting and boiling point in carbon,a non-metal which has high melting and boiling point like metals.
(C) METALLOIDS.
These are elements that has intermediate properties between those of metals and non-metals.
It is also called a SEMI-METAL.
Examples are Antimony,Boron, Silicon,Germanium
Arsenic,and tellurium.etc.
Metalloids tends to be semi- conductors,since they share the properties of metals and non-metals, silicon is a very good example of a semiconductor.
(D)NOBLE GASES.
These are elements that have low chemical reactivity and are the most stable elements because they have maximum number of valence electrons.
They rarely reacts with other elements because they are already stable.
They are odourless,colourless and
can conduct electricity.
Examples of Noble gases are helium, argon,neon, Krypton,xedon,and radon.
COMPOUNDS.
A compound is a substance which is formed when two or more elements are chemically combined together.
When a compound is formed,it is a new substance with properties entirely different from those of the components elements combined together to form the compound.
For example, the properties of water,a compound which is formed from the combination of Hydrogen and Oxygen,is entirely different from that of Hydrogen and Oxygen.
Examples of compounds are water,sand, caustic soda, Ethanol, sugar,salt, limestone,etc.
MIXTURES.
This is a substance formed by the physical combination of two or more components (elements and/or compounds),which can easily be separated by physical methods.
No chemical change is involved in the formation of mixtures and the proportions of each components in a particular mixture varies.
TYPES OF MIXTURES.
1.Homogenous mixtures.
These are mixtures that are uniform in composition throughout any of it's given sample in which the components cannot be distinguished from one another.
Examples are alloys,salt and water mixture,
Cement,air,powder,milk, bitumen, plastics,blood plasma,wine,wood,etc.
2.Heterogenous mixtures.
An heterogeneous mixture is a substance in which the components parts can be differentiated from one another,ie,we can easily identify the components that combined together to form it.
Examples are the mixture of sand and water,concrete formed by combining cement and water,sugar and sand mixture, salt and pepper mixture,etc.
DIFFERENCES BETWEEN MIXTURES AND COMPOUNDS.
1.Mixtures can be homogeneous or heterogeneous while compounds are always homogeneous.
2.The constituents in mixtures can easily be separated by physical method because they're not chemically combined while in compounds,the components are chemically combined together and cannot be separated by physical means.
3.The components in a mixture are not fixed in quantity,so they can't be represented by a chemical formula,while in compounds,the quantity of each elements combined together are in fixed ratio to one another,no matter the mass, therefore,a compound can be represented by a chemical formula.
For example,The ratio of Hydrogen to Oxygen in water is always 2:1,in every quantity of water.
4.The properties of a mixture are the sum of those of it's components,while in compounds,the properties of each individual components elements are entirely different from that of the compound formed.
5.No new substance is formed in mixtures but new substances are formed in compounds.
6.Mixtures have variable melting and boiling point while compounds have fixed melting and boiling point.
7.In the formation of mixtures, there's no loss of heat and energy while in compounds, there's loss of heat and energy when they
are formed.
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