NOTES OF IS MATTER AROUND US PURE?
Matter
Anything which has mass and occupies space is called matter. It may be solid, liquid or gas.
Matter is of 2 types -
1. Pure Matter
2. Impure substances
Pure Matter
Pure substances may be defined as material which contains only one kind of atoms or
molecules.
Pure substances are of 2 kinds: -
1. Elements -Pure substances which are made up of only one kind of atoms are known
as elements. All atoms in an element are identical. Atoms of different elements are
different.
2. Compounds -Pure substances which are made up of only one kind of molecules are
known as compounds. Atoms constituting are from two or more different elements.
The different elements are combined in fixed proportion in a compound.
Impure Matter
Impure matters are also called mixture. A mixture is a material which contains two or more
different kinds of particles (atoms or molecules) which do not react chemically but are
physically mixed together in any proportion.
Mixtures are of 2 types:
1. Homogeneous mixtures -A mixture is said to be homogeneous if all the
components of the mixture are uniformly mixed and there are no boundaries of
separation between them. For example- Salt in water etc.
2. Heterogeneous mixtures -A mixture is sad to be heterogeneous if all the
components of the mixture are not thoroughly mixed and there are visible
boundaries of separation between them. For example- Sand in water etc.
Before we proceed further we should know the difference between the properties of compounds
and mixtures.
Properties of Compounds -
1. A compound is a homogeneous substance.
2. A compound has a definite composition.
3. A compound has definite melting point or boiling point.
4. Energy is absorbed or evolved in the form of heat or light during the formation of a
compound.
5. The properties of compound are entirely different from those of its constituents.
For example – If we mix Iron and Sulphur in a watch glass, we get a mixture. This is then
heated till a black mass is formed. This leads to formation of compound called Iron
Sulphide.
On bringing magnet near to it, no Iron is attracted towards it. Also, Sulphur does not
dissolve on adding carbon disulphide, thus, not showing the properties of its constituents.
, 6. The constituents of a compound cannot be separated by simple physical means.
Properties of Mixtures -
1. A mixture may be homogenous or heterogeneous.
2. The composition of a mixture is variable.
3. A mixture does not have a definite melting point or boiling point.
4. Energy is neither absorbed nor evolved during the formation of a mixture.
5. The properties of mixture are the properties of its constituents.
For example- If we mix Iron and Sulphur in a watch glass, we obtain a mixture. Now, if we
bring a magnet near it, it attracts the iron-filings which is the property of its constituent
(Iron) whereas if we dissolve it in carbon disulphide, then Sulphur gets dissolved leaving the
iron-filings unchanged, thus showing the property of its constituent (Sulphur).
6. The constituents of mixture can be separated by simple physical methods.
Physical and Chemical Changes
Physical Change -
Those changes in which only physical properties of the substances change but no new
substances are formed are called physical changes.
For example – Melting of ice to form water, breaking of glass, preparing a solution etc.
Chemical Change -
Those changes in which new substances are formed are called chemical changes and
chemical properties of a substance gets changed in a chemical change. For example -
Rusting of iron, burning a piece of paper etc.
NOTE: There are many features which distinguish a physical and a chemical change. They
are as follows: -
Physical Change Chemical Change
1. A physical change brings about
1. A chemical change brings about change in
change in physical properties such as
chemical properties.
physical state, shape, size etc.
2. There is no change in chemical
2. There is always a change in chemical composition
composition of a substance during
of a substance during chemical change.
physical change.
3. No new substance is formed. 3. A new substance is always formed.
4. It is temporary and hence
4. It is permanent and hence irreversible.
reversible.
Matter
Anything which has mass and occupies space is called matter. It may be solid, liquid or gas.
Matter is of 2 types -
1. Pure Matter
2. Impure substances
Pure Matter
Pure substances may be defined as material which contains only one kind of atoms or
molecules.
Pure substances are of 2 kinds: -
1. Elements -Pure substances which are made up of only one kind of atoms are known
as elements. All atoms in an element are identical. Atoms of different elements are
different.
2. Compounds -Pure substances which are made up of only one kind of molecules are
known as compounds. Atoms constituting are from two or more different elements.
The different elements are combined in fixed proportion in a compound.
Impure Matter
Impure matters are also called mixture. A mixture is a material which contains two or more
different kinds of particles (atoms or molecules) which do not react chemically but are
physically mixed together in any proportion.
Mixtures are of 2 types:
1. Homogeneous mixtures -A mixture is said to be homogeneous if all the
components of the mixture are uniformly mixed and there are no boundaries of
separation between them. For example- Salt in water etc.
2. Heterogeneous mixtures -A mixture is sad to be heterogeneous if all the
components of the mixture are not thoroughly mixed and there are visible
boundaries of separation between them. For example- Sand in water etc.
Before we proceed further we should know the difference between the properties of compounds
and mixtures.
Properties of Compounds -
1. A compound is a homogeneous substance.
2. A compound has a definite composition.
3. A compound has definite melting point or boiling point.
4. Energy is absorbed or evolved in the form of heat or light during the formation of a
compound.
5. The properties of compound are entirely different from those of its constituents.
For example – If we mix Iron and Sulphur in a watch glass, we get a mixture. This is then
heated till a black mass is formed. This leads to formation of compound called Iron
Sulphide.
On bringing magnet near to it, no Iron is attracted towards it. Also, Sulphur does not
dissolve on adding carbon disulphide, thus, not showing the properties of its constituents.
, 6. The constituents of a compound cannot be separated by simple physical means.
Properties of Mixtures -
1. A mixture may be homogenous or heterogeneous.
2. The composition of a mixture is variable.
3. A mixture does not have a definite melting point or boiling point.
4. Energy is neither absorbed nor evolved during the formation of a mixture.
5. The properties of mixture are the properties of its constituents.
For example- If we mix Iron and Sulphur in a watch glass, we obtain a mixture. Now, if we
bring a magnet near it, it attracts the iron-filings which is the property of its constituent
(Iron) whereas if we dissolve it in carbon disulphide, then Sulphur gets dissolved leaving the
iron-filings unchanged, thus showing the property of its constituent (Sulphur).
6. The constituents of mixture can be separated by simple physical methods.
Physical and Chemical Changes
Physical Change -
Those changes in which only physical properties of the substances change but no new
substances are formed are called physical changes.
For example – Melting of ice to form water, breaking of glass, preparing a solution etc.
Chemical Change -
Those changes in which new substances are formed are called chemical changes and
chemical properties of a substance gets changed in a chemical change. For example -
Rusting of iron, burning a piece of paper etc.
NOTE: There are many features which distinguish a physical and a chemical change. They
are as follows: -
Physical Change Chemical Change
1. A physical change brings about
1. A chemical change brings about change in
change in physical properties such as
chemical properties.
physical state, shape, size etc.
2. There is no change in chemical
2. There is always a change in chemical composition
composition of a substance during
of a substance during chemical change.
physical change.
3. No new substance is formed. 3. A new substance is always formed.
4. It is temporary and hence
4. It is permanent and hence irreversible.
reversible.
