Is Matter Around Us Pure | Class 9

 

Matter

Anything that occupy space (i.e have volume) and have mass is called matter.

Classification of Matter

Matter is classified into groups according to their physical and chemical properties.

e.g. based on physical properties as solid, liquid and gas.

       based on chemical properties as elements, compounds and mixtures.

Pure Substance

A substance that consists of only a single type of constituents particles is called Pure Substance, e.g. gold, water, etc. Based upon the nature of the constituents particles, a pure substance is of two type , i.e. elements and compounds.

Elements

An element is a basic form of matter that cannot be broken down into simpler substances by chemical reactions. An element is a pure substance. There are 118 elements found in nature till today. Based on the properties elements are further classified as Metals, Non-Metals and Metalloids.

    Metals

     A metal is an element that is :-

1. Malleable i.e. can be hammered into thin sheet.
2. Ductile i.e. can be drawn into wires.
3. Sonorous i.e. make a ringing sound when hit.
4. Conduct heat and electricity.
5. Lustrous i.e. shining in nature.

* Mercury is the only metal that exist in liquid state at room temperature.

    Non-Metals

    A non-metal is an element that is :-

        1. Non malleable.
        2. Non ductile.
        3. Not conduct heat and electricity.
* Bromine is the only non-metal that exist in liquid state at room temperature.

    Metalloids

    Elements having intermediate properties between metals and non-metals are called metalloids.

Compounds

A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion. e.g. water (H₂O), methane (CH₄), carbon dioxide (CO₂), etc.

Mixtures

Mixtures are constituted by more than one kind of pure substance. e.g. air, water, soil, minerals, etc.

Type of Mixtures

Depending upon the nature of the components, mixtures are of two types:

Homogeneous Mixture

A mixture in which the constituents are uniformly mixed throughout without any clear boundary of separation is called Homogeneous Mixture.

e.g. salt solution, sugar solution, air, etc.

Heterogeneous Mixture

A mixture that does not uniformly mix with each other i.e. has clear visible boundaries of separation between its constituents is called Heterogeneous Mixture.

e.g. oil and water mixture, sand and sugar mixture, sand and salt mixture, etc.

Difference between compounds and mixtures

Compound	Mixture
A compound is always homogeneous in nature.	A mixture may be homogeneous or heterogeneous in nature.
Definite elements are present in definite ratio.	Substances mix in any ratio.
Elements combine chemically to form compounds.	Chemical reaction does not take place in formation.
Constituents lose their properties	Constituents retain their properties.
Their constituent particles cannot be separated by physical methods.	Their constituent particles can be separated by simple physical methods.

Solution (True Solutions)

A homogeneous mixture of two or more substance is called solution. e.g. salt solution, sugar solution, lemonade, etc. There are two main components of a solution:

   Solvent

    The component of the solution that dissolves the other component in it or usually present in a large amount is called solvent.

    Solute

    The component of the solution that is dissolved in the solvent or usually present in lesser amount is called the solute.

e.g. In Sugar solution sugar is solute and water is solvent, similarly in sugar solution sugar is solute and water is solvent.

* Alloys are the mixture of two or more metals, or a metals and a non-metal and cannot be separated into their components by physical methods. But an alloy is considered as a mixture because its shows the properties of its constituents and can have variable compositions.

Properties of Solution

    1. A solution is a homogeneous mixture.
    2. The particle size are smaller than 1 nm in diameter. Therefore, they cannot be seen be naked eyes.
    3. Due to smaller size, particle do not scatter a beam of light passing through the solution.
    4. A solution is stable i.e the solute particle do not settle down when left undisturbed. 
    5. The solute particle cannot be separated from the mixture by the process of filtration.

Concentration of Solution

The concentration of a solution is the amount of solute dissolved in given amount of solution or solvent. Depending upon the amount of solute present in a given amount of solvent, it can be classified as:

Saturated solution

A solution in which no more amount of solute can be dissolved at given temperature is called as saturated solution.

Unsaturated solution

A solution in which more amount of solute can be dissolved at given temperature is called as unsaturated solution.

Suspension

A suspension is a heterogeneous mixture in which the solute particles do not dissolve, but remain suspended in the bulk of the medium.

e.g. mixture of sand in water, etc

Properties of Solution

    1. Suspension is a heterogeneous mixture.
    2. Particles can be seen by naked eyes.
    3. Particles scatters a beam of light passing through it and make the path visible (Tyndall Effect)
    4. It is unstable i.e the solute particle settle down when left undisturbed. 
    5. They can be separated by filtration.

Colloidal Solution

A colloidal solution is actually a heterogeneous mixture but appears to be a homogeneous as the particles are uniformly spread throughout the solution.

e.g. milk, blood, etc

Properties of Colloid

    1. A colloid is a heterogeneous.

    2. The particle size of a colloids is too small to be seen by naked eyes.

    3. Colloids particle scatters a beam of light passing through it and make its path visible.

    4. Colloids are stable as particles do not settle down when left undisturbed.

  5. Its particle can pass through filter paper, therefore a colloid cannot be separated by filtration. However, they get separated by a special technique called centrifugation.

Tyndall Effect

The scattering of light of colloidal particle is known as Tyndall effect. In true solution, the solute particles are so small that they cannot scatter light falling on them. In a colloidal solution the particles are big enough to scatter light.

Tyndall effect can also be observed in the following situations:

    1. When a fine beam of light enters a room through a small hole.

    2. When sunlight passes through the canopy of a dense forest.

Difference between True Solution, Colloids and Suspension

True Solution	Colloids	Suspension
Homogeneous	Appears to be homogeneous but it is heterogeneous	Heterogeneous
Particle size of solute is less than 1 nm	The particle size ranges from 1 to 100 nm	Particle size is greater than 100 nm
Does not show Tyndall effect	Show Tyndall effect	Show Tyndall effect
Particle cannot be separated by filtration	Particle cannot be separated by ordinary filter paper but can be separated by ultrafiltration	Particle can be separated by filtration.
Transparent	Transparent or translucent	Opaque
Particle don’t settle down	Particle settle down under specific condition	Particle settle down when left undisturbed
e.g. sea water, alloys, alcohol in water, etc	e.g. milk of magnesia, cough syrup, etc	e.g. mixture of sand in water, mixture of chalk powder in water, etc

Physical and Chemical Change

The properties that can be observed and specified like colour, hardness, rigidity, fluidity, density, melting point, boiling point, etc are Physical Properties.

The changes which occur without a change in composition and in chemical nature of the substance are called Physical changes.

In chemical changes, one substance reacts with another substance to undergo a change in chemical composition. Chemical change bring a change in the chemical properties of matter and a new substance is obtained. A chemical change is also called a chemical reaction.

Physical Change	Chemical Change
Only physical properties of the substance change.	Chemical properties also changes.
No new substance is formed.	One or more new substance are formed.
These changes are generally reversible.	These changes are not easily reversible, only some of them are reversible.
e.g. melting of ice, cutting of paper, melting of wax, etc	e.g. burning of coal, formation curd from milk, etc

Separating the Components of a Mixture

    1. Evaporation (Separation of Volatile Component from Non-Volatile Component)

    2. Centrifugation (Separation of Colloidal Particles from Solution)

    3. Separation by using Separating Funnel (Separation of Mixture of Two Immiscible Liquids)

    4. Sublimation (Separation of a Solid Volatile Component from Mixture) 

    5. Chromatography (Separation of Components with the Help of Same Solvent)

    6. Distillation (Separation of Two Miscible Liquids)

    7. Crystallisation (Separation of Pure Substance from its Impure Form)