IS MATTER AROUND US PURE

 IS MATTER AROUND US PURE

MATTER: Anything which occupies space and has mass is called matter. Matter can be divided in two categories.

(i) Pure Substance: It consists of single types of particles which are same in their chemical nature.

(ii) Mixtures: Mixture consists of two or more particles.

 

 

Mixture: Mixture consists of more than one kind of pure substances which can be separated by physical method.

Mixtures are of two types

(i) Homogeneous mixture

(ii) Heterogeneous mixture

(i) Homogeneous mixture: 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.

Ex: Sugar in water, etc.

Solution: A solution is a homogeneous mixture of two or more substances. Ex: Lemonade, soda water etc.

A solution has two components:

       I.          Solvent: The component of the solution that dissolves the other component in it (usually the component present in larger amount) is called the solvent.

     II.        Solute: The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.

Properties of Solution:

1. A solution is a homogeneous mixture.

2. The particles of a solution are smaller than 1 nm (10^-9) in diameter which cannot be seen by naked eyes.

3. They do not scatter a beam of light passing through the solution that is they don’t show Tyndall effect. So, the path of light is not visible in a solution.

4. The solute particles cannot be separated from the mixture by the process of filtration.

5. The solution is stable and solute particles do not settle down when left undisturbed.

Concentration of a solution

       I.          Saturated solution: When no more amount of solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

     II.          Unsaturated solution: When more amount of solute can be dissolved in a solution at a given temperature, it is called a saturated solution.

Solubility: The amount of the solute present in the saturated solution at the given temperature is
called its solubility.

The concentration of a solution is the amount of solute present in a given amount (mass or volume) of solution. Also, the amount of solute dissolved in a given mass or volume of solvent is called concentration of solution.

Concentration of solution = Amount of solute/Amount of solvent or Amount of solute/Amount of solution (Here, amount means mass or volume).

Two methods of finding concentration of solution:

(i) Mass by mass percentage of a solution = (Mass of solute/Mass of solution) ×100
(ii) Mass by volume percentage of a solution = (Mass of solute/Volume of solution) ×100

(ii) Heterogeneous mixtures: A mixture is said to be heterogeneous if all the components of the mixture are not uniformly mixed and there are visible boundaries of separation between them.

Ex: Water and sand, Air etc.

Suspension

A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Ex: Chalk in water, smoke in the air

Properties of Suspension:

1. It is a heterogeneous mixture.

2. Particles of a suspension are visible to the naked eye.

3. Size of the particles is greater than 100 nm.

4. It is unstable mixture. Solute settles down at the bottom over period of time.

5. If the solution is passed through filter paper, solute and solvent gets separated.

6. It scatters light when light is passed through the solution i.e. it shows Tyndall effect.

Colloidal solution: Colloid solution is heterogeneous mixture in which the size of particles lies between the true solutions and suspensions.

• Colloidal particles can easily scatter a beam of visible light. This phenomenon is called Tyndall effect.

Properties of colloidal solution:

1. The particles of colloid can’t be seen by naked eyes individually.

2. It is a heterogeneous mixture and thus solute and solvent can’t be separated by filter paper.

3. Size of particles is smaller than suspensions but greater than solutions (1 nm to 100 nm).

4. It is a stable mixture. Particles do not settle down at the bottom over a period of time.

5. They do not settle down when left undisturbed which means colloid is quite stable.

Separation of the components of mixtures

1. Physical methods of separating Heterogenous Mixture: Handpicking, sieving, filtration

2. Evaporation: The process of evaporation is used to separate a substance which is dissolved in water.
• It is based on the fact that liquid vaporises easily than the solid.

• Helps in separating volatile substances from non-volatile substances.

3. Centrifugation: The process of centrifugation is used to separate the cream from milk. It is a method of separating the suspended particles of substance from a liquid.

• This process is carried out by the machine called centrifuge.

• Sometimes, the solid particles in a liquid are very small and pass through a filter paper. For such particles the filtration technique cannot be used.

• The mixture is rotated rapidly so that the heavier particles in the mixtures settle down to the bottom. 

• The basic principle of centrifugation is that the denser particles are forced to the bottom and the liquid being lighter remains at the top.

4. Sublimation

• This process is used to separate mixtures that contain a sublimable volatile component from a non-sublimable impurity.

• Sublimation is process where a substance directly changes from solid to gaseous state on heating.

• Ammonium chloride, camphor, naphthalene and anthracene are some examples which can sublime.

5. Chromatography

• Used to separate those solutes which dissolve in the same solvent.

• Used for separation of colours.

• The colours which are more soluble in water rises faster and get colours get separated into layers.

 6. Crystallization

§  Used to remove impurities from solid and purify it.

§  It separates a pure solid from mixture in the form of crystals.

§  This process is used in purification of salt from sea water, separation of crystals of alum from impure samples.

§  It is better method than evaporation because:

(i) Solids decompose or some, like sugar, may get charred on heating to dryness.

(ii) Some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.

Types of pure substances

Elements: Elements can be classified into metals, non-metals and metalloids.

a) Metals: Examples of metals are gold, silver, copper, iron, sodium, potassium etc.

(i) They have a lustre (shine).

(ii) They have silvery-grey or golden-yellow colour.

(iii) They conduct heat and electricity.

(iv) They are ductile (can be drawn into wires).

(v) They are malleable (can be hammered into thin sheets).

(vi) They are sonorous (make a ringing sound when hit).

Note: Mercury is the only metal that is liquid at room temperature.

b) Non-metals: Examples of non-metals are hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine etc.

(i) They display a variety of colours.

(ii) They are poor conductors of heat and electricity.

(iii) They are not lustrous, sonorous or malleable.

c) Metalloids: Elements having intermediate properties between those of metals and non-metals are called metalloids.  Examples are boron, silicon, germanium etc.

Compounds: A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

Difference between mixtures and compounds