TNPSC Chemistry - Elements and compounds (Compounds)
COMPOUNDS:
When two or more elements combine in a fixed ratio by mass, they form compound.
For example, water is a compound made of two Hydrogen atoms and one Oxygen atom on the ratio 2:1 by volume or 1:8 by mass.
A compound is a pure substance composed of two or more elements combined together chemically in a fixed ratio by mass.
Elements + Element → Compound
N2 + 3H2 → 2NH3
Characteristics of a compound:
1. Chemical reaction between two or more elements in a fixed proportion by mass.
2. Compounds of the compound cannot be separated by simple physical methods.
3. Formation of a compound is associated with evolution or absorption of heat.
4. Compound has a fixed melting and boiling point.
5. The properties of a compound are different from those of its component elements.
6. Compound is homogeneous.
CLASSIFICATION OF COMPOUND:
Let us learn to classify the compounds based on the origin or chemical components as
1. Inorganic compounds:
Compounds obtained from non living sources such as rock, minerals, etc., are called inorganic compounds. eg. Chalk, marble, baking powder, etc.,
2. Organic compounds:
Compounds obtained from living sources such as plants, animals etc., are called organic compound. eg. Protein, waxes, oil, carbohydrates, etc.,
Uses of compounds:
a. Water - For drinking and as solvent.
b. Table salt - Essential components of our daily diet, preservative for meat and fish.
c. Sugar - Preparation of sweets, toffees and fruit juices.
d. Baking soda - Fire extinguisher, Preparation of baking powder and preparation of cakes and bread.
e . Washing soda - As cleaning agent in soap and softening of hard water.
f. Bleaching powder - As bleaching agent, disinfectant and sterilisation of drinking water.
g. Quick lime - Manufacture of cement and glass.
h. Slaked lime - White washing of walls.
i . Lime stone - Preparation of chalk pieces.
Molecule of compound:
The molecule of a contains two or more different types of atoms. For example, the molecule of hydrogen chlorine contains one atom of hydrogen and one atom of chlorine. Similarly, one molecule of water contains two hydrogen atoms and one atom of Oxygon.
COMPARE AND CONTRAST BETWEEN
ELEMENTSS: AND COMPOUNDS:
ELEMENTS. COMPOUNDS
1.Contains only one Contains more than
kind of atoms. one kind of atoms.
2. It is a pure substance It is not a pure
Substance
3. Has definite Has definite
physical and chemical physical and
Properties. chemical properties
When two or more elements combine in a fixed ratio by mass, they form compound.
For example, water is a compound made of two Hydrogen atoms and one Oxygen atom on the ratio 2:1 by volume or 1:8 by mass.
A compound is a pure substance composed of two or more elements combined together chemically in a fixed ratio by mass.
Elements + Element → Compound
N2 + 3H2 → 2NH3
Characteristics of a compound:
1. Chemical reaction between two or more elements in a fixed proportion by mass.
2. Compounds of the compound cannot be separated by simple physical methods.
3. Formation of a compound is associated with evolution or absorption of heat.
4. Compound has a fixed melting and boiling point.
5. The properties of a compound are different from those of its component elements.
6. Compound is homogeneous.
CLASSIFICATION OF COMPOUND:
Let us learn to classify the compounds based on the origin or chemical components as
1. Inorganic compounds:
Compounds obtained from non living sources such as rock, minerals, etc., are called inorganic compounds. eg. Chalk, marble, baking powder, etc.,
2. Organic compounds:
Compounds obtained from living sources such as plants, animals etc., are called organic compound. eg. Protein, waxes, oil, carbohydrates, etc.,
Uses of compounds:
a. Water - For drinking and as solvent.
b. Table salt - Essential components of our daily diet, preservative for meat and fish.
c. Sugar - Preparation of sweets, toffees and fruit juices.
d. Baking soda - Fire extinguisher, Preparation of baking powder and preparation of cakes and bread.
e . Washing soda - As cleaning agent in soap and softening of hard water.
f. Bleaching powder - As bleaching agent, disinfectant and sterilisation of drinking water.
g. Quick lime - Manufacture of cement and glass.
h. Slaked lime - White washing of walls.
i . Lime stone - Preparation of chalk pieces.
Molecule of compound:
The molecule of a contains two or more different types of atoms. For example, the molecule of hydrogen chlorine contains one atom of hydrogen and one atom of chlorine. Similarly, one molecule of water contains two hydrogen atoms and one atom of Oxygon.
COMPARE AND CONTRAST BETWEEN
ELEMENTSS: AND COMPOUNDS:
ELEMENTS. COMPOUNDS
1.Contains only one Contains more than
kind of atoms. one kind of atoms.
2. It is a pure substance It is not a pure
Substance
3. Has definite Has definite
physical and chemical physical and
Properties. chemical properties
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