Is Matter Around Us Pure (I)

Class - IX

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. Mixture

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. Elements are further classified into three types on the basis of their characteristics. These are metals, non – metals and metalloid. Example Fe, O, Cl, Mg

1. 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. Example – H₂O, CO₂

Elements	Compounds
An element is made up of one type of atoms.	A compound may be made of same or different atoms.
An element cannot be broken into anything simpler than it by either physical or chemical method.	The constituting elements in a compound can be separated by suitable chemical reactions.
Elements have certain characteristic properties of their own.	Constituting elements in a compound lose their own characteristics.

 

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.

Homogeneous mixture	Heterogeneous mixture
It has no visible boundary of separation between its constituents.	It has visible boundary of separation between its constituents.
It has a uniform composition throughout the mixture.	The composition of the mixture varies throughout the mixture.
It does not show Tyndall effect	It shows Tyndall effect

 

Tyndall Effect

If a light is passed through a medium and its path can be seen, then the substance is said to show Tyndall effect.

Example: - When a beam of sunlight enters a dark room through some hole in the window, path of light becomes visible due to scattering of light by the colloidal dust particles present in the air of cinema hall. This shows Tyndall effect.

Solutions, Suspensions and Colloids

Solution -

A solution is defined as a homogeneous mixture of two or more chemically non-reacting substances whose composition can be varied within limits.

A solution as 2 components: -

1. Solute : The component which is dissolved or which is present in small amount is called solute.

2. Solvent : The component which is present in larger amount is called solvent.

Types of solutions -

1. Solid in Liquid : -  sugar in water, tincture of iodine (in it iodine (solute) is dissolved in alcohol(solvent) etc.

2. Liquid in Liquid : -  alcohol in water etc.

3. Gas in Liquid : -  CO₂ dissolved in water in cold-drinks (aerated drinks)

4. Solid in Solid : -  Alloys such as Brass (copper + zinc), Bronze (copper + tin) etc.

5. Gas in Gas : - Like in air, various gases are mixed such as O₂, N₂ etc.

6. Liquid in Solid : - Like copper sulphate in dental amalgam.

7. Gas in Solid : - Gas is adsorbed over the surface of metal.

8. Solid in Gas : - camphor in air.

9. Liquid in Gas : - clouds and fog.

Properties of Solutions -

1. A solution is a homogeneous mixture.

2. Size of particles is smaller than 1 nm (10^–9 m).

3. The particles cannot be seen by microscope.

4. It is a stable mixture, solute does not settle down over a period of time.

5. If solution is passed through filter paper, solute and solvent do not separate.

6. It does not scatter light i.e. it do not show Tyndall effect.

Terms related to Solution

1. Dilute and concentrated solution -

A solution having a small amount of solute in a given solvent is dilute whereas a large amount of solute in that given solvent is concentrated when compared with one another.

2. Unsaturated and saturated solution -

- A solution that can dissolve more solute in it at a given temperature is called unsaturated solution.

- A solution which contains maximum amount of solute dissolved in a given quantity of solvent at the given temperature and which cannot dissolve any more solute at that temperature is called saturated solution.

3. Solubility -

The maximum amount of solute that can be dissolved in a given amount of solvent is called solubility of that solute in that solvent at a particular temperature.

Also, we can say that

The amount of solute needed to make saturated solution of 100 gm of solvent is called solubility of that solute in that solvent at a particular temperature.

4. Effect of Temperature on Solubility -

(a) Solubility of Solid solute in Liquid:

- As temperature increases, solubility also increases.

- Saturated solution becomes unsaturated.

- If saturated solution is cooled down, some dissolved solute separates.

(b) Solubility of Gas in Liquid:

- As temperature increases, solubility decreases.

5. Effect of Pressure on Solubility -

(a) Solid solute in Liquid:

- As temperature increases, solubility increases.

- Pressure has no effect on solubility in case of solid solute in liquid.

(b) Gas in Liquid:

- As temperature increases, solubility decreases.

- As pressure increases, solubility increases.

This is the reason that cold drinks are packaged at high pressure.

6. Concentration of Solution –

The concentration of a solution is the amount of solute present in a given amount (mass or volume) of solution.

Concentration of Solution = Amount of solute/ Amount of solution

                                     Or

Concentration of Solution = Amount of solute/ Amount of solvent

Concentration is the measure of amount. It is the amount of solute present in the amount of solution.

Suspensions -

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

Properties of Suspension -

1. It is a heterogeneous mixture.

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

3. Particles can be seen by naked eyes.

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.

 

Colloids -

Solutions in which the size of particles lies in between those of true solutions and suspensions are called colloidal solutions or simply colloids. There are two phases in a colloidal solution. These are known as dispersed phase and dispersion.

The component present in smaller proportion is the dispersed phase while the one present in greater proportion is the dispersion medium.

Types of colloids -

Dispersed Phase	Dispersion Medium	Type	Examples
1. Solid	Solid	Solid Sol	Milky glass
2. Solid	Liquid	Sol	Muddy water
3. Solid	Gas	Solid aerosol.	Smoke
4. Liquid	Solid	Gel	Jelly
5. Liquid	Liquid	Emulsion	Milk
6. Liquid	Gas	Aerosol	Fog
7. Gas	Solid	Solid foam	Pumice stone
8. Gas	Liquid	Foam	Shaving cream

Properties of Colloids -

1. It is a heterogeneous mixture

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

3. Particles can be seen by microscope.

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

5. When the solution passes through the filter paper, the solute and solvent do not separate.

6.Tyndall effect is observed.