Class 9 Science chapter 2 syllabus is based on different types of matter. It covers the definition and examples of a mixture, solution, suspension, colloids, etc. The features of these substances are explained and compared in detail in this chapter. Details explanation of this chapter already uploaded as a video format available on YouTube you can watch for better understanding.
Pure substance: – The substance in which all the particles present in it are of the same chemical nature, then it is scientifically called a pure substance. That is, pure matter is made up of only one type of particles.
Elements: An element is the purest and simplest substance of matter which cannot be divided into two or more simpler substances by any physical or chemical method. Like – hydrogen, oxygen, nitrogen, phosphorus, sulphur, copper, silver, gold, platinum etc.
Note :- All metals, non-metals and sub-metals come under the category of elements.
Classification of Elements
1. metal
2. nonmetal
3. Metalloids
Properties of metal
- It is shiny.
- It is a good conductor of heat and electricity.
- Metals are malleable and ductile.
- It is acoustic (resonant)
properties of nonmetals
- it does not shine
- It is a poor conductor of heat and electricity.
- Non-metals are not malleable and ductile.
- It is not acoustic (resonant)
Metalloids: – Some elements exhibit properties both metals and nonmetals, such elements are called metalloids. For example, Boron, Silicon and Germanium etc.
Compound: A substance formed by a chemical process by the combination of two or more elements in a certain ratio is called a compound. For example, water, salt, sugar, alcohol and carbon-dioxide are compounds.
Properties of the compound
- The constituent elements of a compound cannot be separated by any mechanical or physical method.
- The properties of a compound are completely different from the properties of its constituent elements.
- Energy is usually emitted or absorbed in the form of heat or light in the formation of a compound.
- The idea of weight of its constituent elements remains in the compound.
- The melting point and boiling point of the compound are fixed
- A compound is a homogeneous substance; That is, the composition and properties of the compound always remain the same.
Mixture:- A mixture is that substance which is formed by mixing two or more elements or compounds together in any proportion and its components. It can be separated by simple mechanical methods. For example – mixture of sugar, blood, air and sand salt in water etc.
Difference between element and compound
| Elements | Compounds |
| 1. An element is a substance which is made up of two or more different elements. Cannot be divided into substances. | 1. A compound can be separated into two or more substances with different properties by chemical methods. |
| 2. An element is made up of only one type of atoms. | 2. Compounds are made up of different types of atoms. |
| 3. An element is made of only one substance | 3. Compound is made of two or more different substances. |
| 4. The smallest particle of an element is called an atom. | 4. The smallest particle of a compound is called a molecule |
Types of Mixtures
There are two types of mixtures
1.Homogeneous Mixture: A mixture in which all the components are present equally in the whole mixture is called homogeneous mixture and the components present in the mixture are in same phase.
2.Heterogeneous Mixture: A mixture in which all the components are not present equally in the whole mixture is called heterogeneous mixture. Its structure is not uniform. Like: Mixture of iron filings
The mixture can be divided into the following three parts according to the texture of their constituents and the size of the constituents:
- Solutions
- Suspension
- Colloidal solutions
Solutions :- Homogeneous mixture of two or more substances is called solution.Example: Solution of water and sugar, solution of salt and water, air, etc. Solutions are found in all the three states of matter.
a) Solid solution : Alloy.
b) Liquid solution : Lemon-water.
c) Gaseous solution : Air.
Composition of a Solution
The two components of a solution are the solute and the solvent.
solution = solvent + solute
Solvent: – The component of the solution which is present in the largest amount in the solution and it Adds other components to the solution, is called solvent. For example: water, alcohol, etc. are solvents.
Solute: – That component of the solution which is present in the least amount in the solution and remains dissolved in the solvent. For example: sugar, salt, soda, etc.
Types of solutions based on the amount of solute present in the solution:-
1.Saturated Solution :- The solution formed at a certain temperature in which the maximum amount of solute is dissolved in solution is called saturated solution.In other words – if no more solute can dissolve in a solution at a given temperature, then only as much solute can dissolve as the capacity of the solution.
2.Unsaturated Solution :- A solutions in which the amount of dissolved solute is less than the saturation point of the solvent that any temperature is called unsaturated solution.
3. Supersaturated Solution :- A saturated solution in which the amount of solute dissolved in it is more than the amount of solute needed to saturate that solution is called supersaturated solution.
Solubility: The amount of solute present in a saturated solution at a given temperature is called the solubility of the solution.
Concentration of a solution
The amount of solute present in a unit volume of a solution called concentration.In other words, the ratio of the amount of the solute to that of the solution is called the concentration of the solution.
Concentration of Solution = Amount of Solute Amount of Solution
Suspension :- Such heterogeneous mixtures in which solid particles are dispersed in the liquid without dissolving, suspension are called Example: mixture of flour and water, mixture of chalk and water, mixture of dust particles in the air, etc.
Properties of Suspensions
- It is a heterogeneous mixture.
- These particles can be seen with eyes.
- Their suspended particles scatter the beam of light.
- They are temporary.
- They can be separated by the method of filtration.
Colloidal Solution: It is a heterogeneous mixture, whose particles are not visible due to being very fine, but the colloidal particles are spread evenly in the solution and they easily scatter the rays of light. Such a solution is called a colloidal solution.For example – milk, smoke, fog, etc.
Properties of a Colloid
- It is a heterogeneous mixture.
- Due to their small size, they cannot be seen with eyes.
Components of Colloidal Solution: Colloidal solution has two components,
colloidal solution = dispersed phase + dispersion medium
a. Dispersed Phase: The component of the solute which remains in colloidal form is called the dispersed phase. That is, the solute particles are called the dispersed phase.
b. Dispersing Medium: The component in which the dispersed phase remains suspended is called the dispersion medium. That is, the solvent in which they are completely distributed is called the dispersion medium.
Tyndall Effect :- Small particles of colloidal scatter the beam of light thus dotes aerosol, fog, fluid, foam, shaving cream. The dispersion of a ray of light is called Tyndall Effect.
Usage : floating solute particles can be easily seen in a beam of light through a small hole in a room. These dust particles act as colloids suspended in the air, which scatter the beam of light, thus making the path of light visible.
The Separation of components of Mixture
There are various methods are used to separate the components of a mixture.
- Evaporation method
- Centrifugation method
- Separation method
- Sublimation method
- chromatography method
- Distillation Method or Fractional Aswan Method
- Crystallization method
1. Evaporation method:- The components of a mixture in which one component is solid and the other liquid, can be separated by evaporation method. In this method, the liquid substance is vaporized by heating and the rest of the particles of the mixture remain otestre.
Applications :
- In obtaining salt from sea water.
- To separate black colored ink from water.
2. Centrifugation method: – This is the method in which a centrifugal device is used which is a type of churner or mixer, which is rotated rapidly in the mixture, then heavy particles settle down and light particles remains above.
Application :
- In the examination of blood and urine in the laboratory.
- In the process of extracting butter from dairy and cream.
- in a washing machine.
3. Separation method: By this method, a mixture of two immiscible liquids is separated. According to the principle of separation, immiscible liquids separate into different layers according to their density.
Application
- To separate an insoluble mixture of oil and water.
- in the separation of iron during metallurgy.
4. Sublimation method: This method is used to separate the sublimated substances from the non-sublimated impurities. Some sublimating substances such as ammonia chloride, camphor, naphthalene and anthracene are examples.
Application :
- To separate a mixture of ammonium chloride and salt.
- To separate camphor and iron filings.
5. Chromatography method: This method is used to separate those solutes which remain dissolved in only one type of solvent. The method of separation of components from a mixture is called chromatography.
- Application :separation of colors in a dye.
- Separation of pigments from natural colours.
- Separation of drugs from the blood.
6. Fractional Distillation Method:- Distillation method is used to separate such mixtures which boil without dissociation and whose components have a large gap between their boiling points.This method is used to separate a mixture of two or more miscible liquids whose boiling point difference is less than 25 K.
Application :
- Separation of various gases from air.
- Separation of petroleum products into their various components.
Crystallisation :- Crystallisation method is used to purify solid substances. By this method of crystallization, the pure solid in the form of crystals is separated from the solution.
Application :
- In purifying the salt obtained from sea water.
- To separate alum from an impure sample.
Physical And Chemical Changes
Physical Change: – These are those changes in which the physical properties and state of matter change, but there is no change in its chemical properties. At the same time, after removing the cause of change, the original substance is obtained again, such as water (H2O) is in liquid state, on heating it forms gaseous state vapor (H2O) and on cooling it forms solid state ice (H2O).
Chemical Change:- These are those changes in which the chemical properties and composition of matter change and a new substance is formed. In case of a chemical change, it is not necessary to get the initial substance after removing the cause of the change. For example, carbon dioxide gas is formed when coal is burnt.