Important Points and Formulas: Is Matter Around Us Pure? | Science Class 9 PDF Download

 Page 1


 
 
IS MATTER AROUND US PURE 
 
 
 
A pure substance consists of particles of only one kind of matter which are similar to one 
another and which cannot be separated into other kinds of matter by any physical process. 
Furthermore, a pure substance has a uniform composition throughout. Pure substances are 
classified into two categories, i.e., elements and compounds. 
 
 
 
 Element, Compound and Mixture 
• An element is defined as the simplest form of a pure substance which can neither be 
broken into nor built from simpler substances by any physical or chemical method. For 
example, hydrogen, oxygen, mercury, gold, iron, copper, etc. 
 Elements are further classified into metals, non-metals and metalloids or semi-metals. 
 (a) Metals possess luster. They are malleable and ductile, good conductors of heat 
and electricity and are sonorous. For example, iron, copper, mercury, sodium, etc. 
 (b) Non-metals are neither malleable nor ductile. They are not lustrous and are non-
conductors of heat and electricity. For example, hydrogen, oxygen, bromine, sulphur, 
phosphorus, etc. 
 (c) Metalloids or semi-metals have properties in between those of metals and non-
metals. For example, silicon, germanium, arsenic, antimony and tellurium. 
• A compound is defined as a pure substance made up of two or more elements 
chemically combined in a fixed proportion by mass. For example, water, carbon dioxide, lime 
stone, etc. 
• Mixtures. A mixture contains two or more substances (elements or compounds), 
 
Matter 
(Solid, Liquid or Gas) 
Pure Substance 
(Fixed Composition) 
Elements 
Mixtures 
(No Fixed Composition) 
Cannot be broken down 
to simpler substances 
for example- copper, 
oxygen, iron, hydrogen, 
mercury etc. 
Compounds 
Have fixed composition 
Can be broken down into 
elements by chemical or 
electrochemical reactions 
for example-  water, 
methane, sugar, salt etc. 
Homogeneous 
 
Uniform composition. 
(Solutions) 
for example- salt in 
water, alcohol etc. 
Heterogeneous 
 
Non-uniform composition. 
(Suspension and 
colloids) 
 
for example- water in oil, 
blood etc. 
Page 2


 
 
IS MATTER AROUND US PURE 
 
 
 
A pure substance consists of particles of only one kind of matter which are similar to one 
another and which cannot be separated into other kinds of matter by any physical process. 
Furthermore, a pure substance has a uniform composition throughout. Pure substances are 
classified into two categories, i.e., elements and compounds. 
 
 
 
 Element, Compound and Mixture 
• An element is defined as the simplest form of a pure substance which can neither be 
broken into nor built from simpler substances by any physical or chemical method. For 
example, hydrogen, oxygen, mercury, gold, iron, copper, etc. 
 Elements are further classified into metals, non-metals and metalloids or semi-metals. 
 (a) Metals possess luster. They are malleable and ductile, good conductors of heat 
and electricity and are sonorous. For example, iron, copper, mercury, sodium, etc. 
 (b) Non-metals are neither malleable nor ductile. They are not lustrous and are non-
conductors of heat and electricity. For example, hydrogen, oxygen, bromine, sulphur, 
phosphorus, etc. 
 (c) Metalloids or semi-metals have properties in between those of metals and non-
metals. For example, silicon, germanium, arsenic, antimony and tellurium. 
• A compound is defined as a pure substance made up of two or more elements 
chemically combined in a fixed proportion by mass. For example, water, carbon dioxide, lime 
stone, etc. 
• Mixtures. A mixture contains two or more substances (elements or compounds), 
 
Matter 
(Solid, Liquid or Gas) 
Pure Substance 
(Fixed Composition) 
Elements 
Mixtures 
(No Fixed Composition) 
Cannot be broken down 
to simpler substances 
for example- copper, 
oxygen, iron, hydrogen, 
mercury etc. 
Compounds 
Have fixed composition 
Can be broken down into 
elements by chemical or 
electrochemical reactions 
for example-  water, 
methane, sugar, salt etc. 
Homogeneous 
 
Uniform composition. 
(Solutions) 
for example- salt in 
water, alcohol etc. 
Heterogeneous 
 
Non-uniform composition. 
(Suspension and 
colloids) 
 
for example- water in oil, 
blood etc. 
  
 
2 
 
which are physically mixed in any proportion but not chemically combined. Thus, mixtures 
have variable composition and hence no definite formula can be assigned to a mixture. 
• Properties of compounds are different from those of its constituent elements, whereas 
a mixture shows the properties of its constituent elements or compounds. 
 Homogeneous and heterogeneous mixtures 
• Homogeneous and heterogeneous mixtures. A mixture is said to be homogeneous 
if its composition is uniform throughout. For example, air (free from suspended impurities), 
diesel, natural gas, soda-water, etc. 
 The particles of a homogeneous mixture are so small (< 1 nm or 10
–9
 m or 10
–7
 cm) 
that they cannot be seen by the naked eye or even under a microscope. 
 A homogeneous mixture has only one phase. 
 In contrast, a mixture is said to be heterogeneous if its composition is not uniform 
throughout. For example, iron filings and powdered sulphur, sand and salt, sand and sugar, 
kerosene oil and water, etc. 
 Physical and Chemical Change  
• A change in which only the physical properties of a substance change but no new 
substance is formed is called a physical change. The inter-conversion of states of matter 
(i.e., ice to water or water to steam) is a physical change because these changes occur without 
any change in composition or the chemical nature of the substance. These changes are 
reversible. 
• A chemical change brings about changes in the chemical properties of the substance. 
During a chemical change, the original substances lose their identity to form new substances. 
A chemical change is also called a chemical reaction. These changes are irreversible. 
 Solution, Solvent and Solute 
• A solution is a homogeneous mixture of two or more substances. The major 
component of the solution is called the solvent and the minor component is called the solute. 
Depending upon whether the solvent is a solid, liquid or a gas, the solutions are classified as 
solid, liquid and gaseous solutions. Thus, there are in all nine types of binary solutions. 
 The nine types of solutions discussed above are summarized in the following table :  
 
Name of the solution Solute Solvent Examples 
Solid solutions 
 1. Solid in solid 
  
 
Solid 
 
 
Solid 
 
 
Alloys like brass, bronze, German silver, 
etc. 
Page 3


 
 
IS MATTER AROUND US PURE 
 
 
 
A pure substance consists of particles of only one kind of matter which are similar to one 
another and which cannot be separated into other kinds of matter by any physical process. 
Furthermore, a pure substance has a uniform composition throughout. Pure substances are 
classified into two categories, i.e., elements and compounds. 
 
 
 
 Element, Compound and Mixture 
• An element is defined as the simplest form of a pure substance which can neither be 
broken into nor built from simpler substances by any physical or chemical method. For 
example, hydrogen, oxygen, mercury, gold, iron, copper, etc. 
 Elements are further classified into metals, non-metals and metalloids or semi-metals. 
 (a) Metals possess luster. They are malleable and ductile, good conductors of heat 
and electricity and are sonorous. For example, iron, copper, mercury, sodium, etc. 
 (b) Non-metals are neither malleable nor ductile. They are not lustrous and are non-
conductors of heat and electricity. For example, hydrogen, oxygen, bromine, sulphur, 
phosphorus, etc. 
 (c) Metalloids or semi-metals have properties in between those of metals and non-
metals. For example, silicon, germanium, arsenic, antimony and tellurium. 
• A compound is defined as a pure substance made up of two or more elements 
chemically combined in a fixed proportion by mass. For example, water, carbon dioxide, lime 
stone, etc. 
• Mixtures. A mixture contains two or more substances (elements or compounds), 
 
Matter 
(Solid, Liquid or Gas) 
Pure Substance 
(Fixed Composition) 
Elements 
Mixtures 
(No Fixed Composition) 
Cannot be broken down 
to simpler substances 
for example- copper, 
oxygen, iron, hydrogen, 
mercury etc. 
Compounds 
Have fixed composition 
Can be broken down into 
elements by chemical or 
electrochemical reactions 
for example-  water, 
methane, sugar, salt etc. 
Homogeneous 
 
Uniform composition. 
(Solutions) 
for example- salt in 
water, alcohol etc. 
Heterogeneous 
 
Non-uniform composition. 
(Suspension and 
colloids) 
 
for example- water in oil, 
blood etc. 
  
 
2 
 
which are physically mixed in any proportion but not chemically combined. Thus, mixtures 
have variable composition and hence no definite formula can be assigned to a mixture. 
• Properties of compounds are different from those of its constituent elements, whereas 
a mixture shows the properties of its constituent elements or compounds. 
 Homogeneous and heterogeneous mixtures 
• Homogeneous and heterogeneous mixtures. A mixture is said to be homogeneous 
if its composition is uniform throughout. For example, air (free from suspended impurities), 
diesel, natural gas, soda-water, etc. 
 The particles of a homogeneous mixture are so small (< 1 nm or 10
–9
 m or 10
–7
 cm) 
that they cannot be seen by the naked eye or even under a microscope. 
 A homogeneous mixture has only one phase. 
 In contrast, a mixture is said to be heterogeneous if its composition is not uniform 
throughout. For example, iron filings and powdered sulphur, sand and salt, sand and sugar, 
kerosene oil and water, etc. 
 Physical and Chemical Change  
• A change in which only the physical properties of a substance change but no new 
substance is formed is called a physical change. The inter-conversion of states of matter 
(i.e., ice to water or water to steam) is a physical change because these changes occur without 
any change in composition or the chemical nature of the substance. These changes are 
reversible. 
• A chemical change brings about changes in the chemical properties of the substance. 
During a chemical change, the original substances lose their identity to form new substances. 
A chemical change is also called a chemical reaction. These changes are irreversible. 
 Solution, Solvent and Solute 
• A solution is a homogeneous mixture of two or more substances. The major 
component of the solution is called the solvent and the minor component is called the solute. 
Depending upon whether the solvent is a solid, liquid or a gas, the solutions are classified as 
solid, liquid and gaseous solutions. Thus, there are in all nine types of binary solutions. 
 The nine types of solutions discussed above are summarized in the following table :  
 
Name of the solution Solute Solvent Examples 
Solid solutions 
 1. Solid in solid 
  
 
Solid 
 
 
Solid 
 
 
Alloys like brass, bronze, German silver, 
etc. 
 
3 
 
 2. Liquid in solid 
 
Liquid 
 
Solid 
 
Hydrated crystals such as blue vitriol 
(hydrated copper sulphate). 
 3. Gas in solid 
 
Gas 
 
Solid 
 
Gases adsorbed over the surface of metals 
(such as nickel, palladium, platinum, etc.) 
under pressure. 
Liquid solutions 
 4. Solid in liquid 
 
Solid 
 
Liquid 
 
Sugar, common salt or other salts 
dissolved in water. 
 5. Liquid in liquid Liquid Liquid Mixture of two miscible liquids such as 
acetone and water, alcohol and water, etc. 
 
 6. Gas in liquid 
 
 
Gas 
 
 
Liquid 
 
 
Aerated drinks (here carbon dioxide is 
dissolved in water under pressure). 
Gaseous solutions 
 7. Solid in gas 
 
Solid 
 
Gas 
 
Camphor in air or iodine in air. 
 
 8. Liquid in gas Liquid 
 
Gas 
 
Clouds and fog [here, water drops (liquid) 
are dispersed in gas (air)]. 
 9. Gas in gas 
 
Gas Gas Air is a mixture of gases like nitrogen, 
oxygen, carbon dioxide, inert gases, etc. 
 
• Alloys are homogeneous mixtures. They may also be regarded as solid in solid 
solutions. For example, brass is an alloy of approximately 30% zinc and 70% copper. 
• The particles of a true solution are so small (less than 10
–9
 m in diameter) that they 
cannot be seen even under a microscope. They do not scatter light. 
 Saturated, Unsaturated and Supersaturated Solutions 
• Concentration of a solution is the amount of solute present per unit volume or per 
unit mass of the solution/solvent. 
   Concentration of solution =     
  Or, Concentration of solution =     
• Solubility of a solute in a given solvent at a particular temperature is the amount of 
the solute in grams that can be dissolved in 100 grams of the solvent at that temperature. 
• Saturated solution. A solution which contains the maximum amount of the solute 
dissolved in a given quantity of the solvent at the given temperature and which cannot dissolve 
any more solute at that temperature is called a saturated solution. In other words, 
concentration of solute in a saturated solution is the same as the solubility of the solute at 
that temperature. 
solution of Amount
solute of Amount
solvent of Amount
solute of Amount
Page 4


 
 
IS MATTER AROUND US PURE 
 
 
 
A pure substance consists of particles of only one kind of matter which are similar to one 
another and which cannot be separated into other kinds of matter by any physical process. 
Furthermore, a pure substance has a uniform composition throughout. Pure substances are 
classified into two categories, i.e., elements and compounds. 
 
 
 
 Element, Compound and Mixture 
• An element is defined as the simplest form of a pure substance which can neither be 
broken into nor built from simpler substances by any physical or chemical method. For 
example, hydrogen, oxygen, mercury, gold, iron, copper, etc. 
 Elements are further classified into metals, non-metals and metalloids or semi-metals. 
 (a) Metals possess luster. They are malleable and ductile, good conductors of heat 
and electricity and are sonorous. For example, iron, copper, mercury, sodium, etc. 
 (b) Non-metals are neither malleable nor ductile. They are not lustrous and are non-
conductors of heat and electricity. For example, hydrogen, oxygen, bromine, sulphur, 
phosphorus, etc. 
 (c) Metalloids or semi-metals have properties in between those of metals and non-
metals. For example, silicon, germanium, arsenic, antimony and tellurium. 
• A compound is defined as a pure substance made up of two or more elements 
chemically combined in a fixed proportion by mass. For example, water, carbon dioxide, lime 
stone, etc. 
• Mixtures. A mixture contains two or more substances (elements or compounds), 
 
Matter 
(Solid, Liquid or Gas) 
Pure Substance 
(Fixed Composition) 
Elements 
Mixtures 
(No Fixed Composition) 
Cannot be broken down 
to simpler substances 
for example- copper, 
oxygen, iron, hydrogen, 
mercury etc. 
Compounds 
Have fixed composition 
Can be broken down into 
elements by chemical or 
electrochemical reactions 
for example-  water, 
methane, sugar, salt etc. 
Homogeneous 
 
Uniform composition. 
(Solutions) 
for example- salt in 
water, alcohol etc. 
Heterogeneous 
 
Non-uniform composition. 
(Suspension and 
colloids) 
 
for example- water in oil, 
blood etc. 
  
 
2 
 
which are physically mixed in any proportion but not chemically combined. Thus, mixtures 
have variable composition and hence no definite formula can be assigned to a mixture. 
• Properties of compounds are different from those of its constituent elements, whereas 
a mixture shows the properties of its constituent elements or compounds. 
 Homogeneous and heterogeneous mixtures 
• Homogeneous and heterogeneous mixtures. A mixture is said to be homogeneous 
if its composition is uniform throughout. For example, air (free from suspended impurities), 
diesel, natural gas, soda-water, etc. 
 The particles of a homogeneous mixture are so small (< 1 nm or 10
–9
 m or 10
–7
 cm) 
that they cannot be seen by the naked eye or even under a microscope. 
 A homogeneous mixture has only one phase. 
 In contrast, a mixture is said to be heterogeneous if its composition is not uniform 
throughout. For example, iron filings and powdered sulphur, sand and salt, sand and sugar, 
kerosene oil and water, etc. 
 Physical and Chemical Change  
• A change in which only the physical properties of a substance change but no new 
substance is formed is called a physical change. The inter-conversion of states of matter 
(i.e., ice to water or water to steam) is a physical change because these changes occur without 
any change in composition or the chemical nature of the substance. These changes are 
reversible. 
• A chemical change brings about changes in the chemical properties of the substance. 
During a chemical change, the original substances lose their identity to form new substances. 
A chemical change is also called a chemical reaction. These changes are irreversible. 
 Solution, Solvent and Solute 
• A solution is a homogeneous mixture of two or more substances. The major 
component of the solution is called the solvent and the minor component is called the solute. 
Depending upon whether the solvent is a solid, liquid or a gas, the solutions are classified as 
solid, liquid and gaseous solutions. Thus, there are in all nine types of binary solutions. 
 The nine types of solutions discussed above are summarized in the following table :  
 
Name of the solution Solute Solvent Examples 
Solid solutions 
 1. Solid in solid 
  
 
Solid 
 
 
Solid 
 
 
Alloys like brass, bronze, German silver, 
etc. 
 
3 
 
 2. Liquid in solid 
 
Liquid 
 
Solid 
 
Hydrated crystals such as blue vitriol 
(hydrated copper sulphate). 
 3. Gas in solid 
 
Gas 
 
Solid 
 
Gases adsorbed over the surface of metals 
(such as nickel, palladium, platinum, etc.) 
under pressure. 
Liquid solutions 
 4. Solid in liquid 
 
Solid 
 
Liquid 
 
Sugar, common salt or other salts 
dissolved in water. 
 5. Liquid in liquid Liquid Liquid Mixture of two miscible liquids such as 
acetone and water, alcohol and water, etc. 
 
 6. Gas in liquid 
 
 
Gas 
 
 
Liquid 
 
 
Aerated drinks (here carbon dioxide is 
dissolved in water under pressure). 
Gaseous solutions 
 7. Solid in gas 
 
Solid 
 
Gas 
 
Camphor in air or iodine in air. 
 
 8. Liquid in gas Liquid 
 
Gas 
 
Clouds and fog [here, water drops (liquid) 
are dispersed in gas (air)]. 
 9. Gas in gas 
 
Gas Gas Air is a mixture of gases like nitrogen, 
oxygen, carbon dioxide, inert gases, etc. 
 
• Alloys are homogeneous mixtures. They may also be regarded as solid in solid 
solutions. For example, brass is an alloy of approximately 30% zinc and 70% copper. 
• The particles of a true solution are so small (less than 10
–9
 m in diameter) that they 
cannot be seen even under a microscope. They do not scatter light. 
 Saturated, Unsaturated and Supersaturated Solutions 
• Concentration of a solution is the amount of solute present per unit volume or per 
unit mass of the solution/solvent. 
   Concentration of solution =     
  Or, Concentration of solution =     
• Solubility of a solute in a given solvent at a particular temperature is the amount of 
the solute in grams that can be dissolved in 100 grams of the solvent at that temperature. 
• Saturated solution. A solution which contains the maximum amount of the solute 
dissolved in a given quantity of the solvent at the given temperature and which cannot dissolve 
any more solute at that temperature is called a saturated solution. In other words, 
concentration of solute in a saturated solution is the same as the solubility of the solute at 
that temperature. 
solution of Amount
solute of Amount
solvent of Amount
solute of Amount
4 
 
• Unsaturated solution. A solution which can dissolve more solute in it at the given 
temperature is called the unsaturated solution. 
• Supersaturated solution. A solution which temporarily contains more solute than the 
saturation level is called a supersaturated solution. Unlike saturated solution, it is not stable. 
When it is disturbed either mechanically or by addition of a few crystals of the dissolved solute, 
precipitation of some additional solute occurs. 
 Suspension and Colloids  
• A suspension is a heterogeneous mixture in which the solute particles do not 
dissolve but remain suspended throughout the bulk of the medium. The particles of a 
suspension are big enough (> 100 nm) to be seen by the naked eye. For example, lime-
water used for white wash is a suspension of calcium hydroxide in water