Is Matter Around us Pure

"Most of the matter around us exist as a mixture of two or more pure components."

1.0Introduction

We know that all the matter around us is not pure. If we observe some soil and some sugar placed on two different sheets of paper with a magnifying glass, we find that soil contains clay particles, some grass particles and even some dead insects, etc. That is, soil contains particles of different kinds, thus it is called an impure substance (or mixture). Now observe sugar, it contains only one kind of particles, thus it is called a pure substance.

A substance which has only one kind of component and nothing else in it is called a pure substance. But it is quite difficult to get pure substance. Substances are mostly mixed with one another and their combination is known as mixture.

2.0Types of matter

On the basis of chemical nature, matter can be classified into two types: (i) Pure substance (ii) Impure substance (mixture)

Pure substance

A homogeneous material which contains particles of only one kind and has a definite set of properties, is called a pure

Salt in water is an example of homogeneous mixture substance. For example, $O_{2}$ , iron, sulphur contains only kind of particles, whereas sodium chloride is a pure substance, because it has a fixed number of sodium and chloride ions, combined together in fixed proportion by weight. Similarly, magnesium oxide ( MgO ), carbon dioxide $(CO_{2})$ , copper sulphate $(CuSO_{4})$ , etc. are pure substances which have definite set of properties.

Characteristics of pure substances

(1) A pure substance is homogeneous in nature. (2) A pure substance has a definite set of properties. (3) The composition of a pure substance cannot be altered by any physical means. (4) A pure substance has a definite melting point, density, boiling point, etc.

Mixture

When two or more substances (elements, compounds or both) are physically mixed together in any proportion, such that they do not undergo any chemical change, but retain their individual characteristics, the resulting product is called a mixture.

For example, Brass is a mixture of copper and zinc. Crude oil is a mixture of large number of different hydrocarbons. If we dissolve sugar in water both of which are pure compounds, the solution of sugar in water is a mixture.

Characteristics of mixtures

(1) A mixture may be homogeneous or heterogeneous. (2) The constituents of a mixture can be separated by physical means like filtration, evaporation, sublimation and magnetic separation. (3) In the preparation of a mixture, energy is neither evolved nor absorbed. (4) A mixture has no definite melting point and boiling point. (5) The constituents of a mixture retain their original set of properties. For example, magnet attracts iron filings in a mixture of sand and iron filings.

3.0Types of mixtures

Depending upon the nature of components, a mixture can be divided into two types.

(a) Homogeneous mixture

A mixture in which different constituents are mixed uniformly, is called a homogeneous mixture. This mixture has same composition throughout. For example, salt solution, sugar solution. Similarly, alloys such as brass, bronze, etc. are homogeneous solid solutions of metals.

(b) Heterogeneous mixture

A mixture in which different constituents are not mixed uniformly, is called a heterogeneous mixture. For example, Sand and iron filings, sand and water, etc.

4.0Solution

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

For example, Air is a mixture of gas in gas. Air is a homogeneous mixture of a number of gases. Its two main constituents are oxygen (21%) and nitrogen (78%). It may be noted that all mixtures are not solutions. If a mixture is to be called a solution, it must satisfy the following two conditions.

Solution of potassium iodide and iodine in water is known as lugol.

Components should be non-reacting.
Should be homogeneous.

Components of a solution

The substances present in a homogeneous solution, are called components of the solution. A solution basically has two components i.e. a solvent and a solute and such a solution is called a binary solution.

(a) Solute:

The component of the solution which dissolves in the solvent, is called solute. Usually, solute is the smaller component of the solution, for example, solution of iodine in alcohol, known as 'tincture of iodine', iodine is the solute in this solution. Similarly, in carbonated drinks (soda water), carbon dioxide gas is the solute.

(b) Solvent

The component of a solution which dissolves the other component in itself, is called solvent. Usually, a solvent is the larger component of the solution. For example, a solution of sugar in water is a solid in liquid solution. In this solution, sugar is the solute and water is the solvent.

The common examples of aqueous solutions are: (i) common salt dissolved in water. (ii) sugar dissolved in water. (iii) acetic acid dissolved in water (called vinegar).

The common non-aqueous solvents are; alcohol, carbon disulphide, carbon tetrachloride, acetone, benzene, etc.

Examples of non-aqueous solutions are: (i) Iodine dissolved in carbon tetrachloride. (ii) Sulphur dissolved in carbon disulphide. (iii) Bromine dissolved in chloroform. (iv) Sugar dissolved in alcohol, etc.

Characteristics of a solution

(1) A solution is a homogeneous mixture. (2) The size of solute particles in a solution is extremely small. It is less than $1 nm (1 0^{- 9} m)$ in diameter. (3) The particles of a solution cannot be seen even with a microscope. (4) The particles of a solution pass through the filter paper. So, a solution cannot be separated by filtration. (5) The solutions are very stable. The particles of solute present in a solution do not separate out on keeping it undisturbed. (6) A true solution does not scatter light passing through the solution (because its particles are very small). (7) The components of a solution do not chemically react with one another. (8) A solution is always transparent in nature. (9) From a true solution, the solute can be easily recovered by evaporation or crystallisation.

Methods to express concentration of solution

The concentration of a solution is the amount of solute present in a given quantity of the solution or solvent.

In a solution the relative proportion of the solute and solvent can be varied. Depending upon the amount of solute present in a solution, it can be called a dilute, concentrated or a saturated solution.

There are many ways to express the concentration of a solution. But the most common method for expressing the concentration of a solution, is called percentage method.

(i) Mass by mass percentage(w/w) The mass of the solute in grams dissolved in 100 g of the solution. Mass by mass percentage of a solution $= \frac{Mass of solute ( in g )}{Mass of solution ( in g )} \times 100$

(ii) Mass by volume percentage (w/v) The mass of the solute in grams dissolved in 100 mL of the solution Mass by volume percentage $= \frac{Mass of solute ( g )}{Volume of solution ( ml )} \times 100$

(iii) Volume by volume percentage or simply volume percentage( $v / v$ ). The volume of the solute in millilitres dissolved in 100 mL of the solution. Volume by volume percentage $= \frac{Volume of solute ( ml )}{Volume of solution ( ml )} \times 100$

Mass of solution $=$ Mass of solute + Mass of solvent

Q. A solution contains 40 g of common salt in 320 g of water. Calculate the concentration in terms of mass by mass percentage of the solution. Solution: Mass of solute (salt) $= 40 g$ Mass of solvent (water) $= 320 g$ We know, Mass of solution $=$ Mass of solute + Mass of solvent $= 40 g + 320 g = 360 g$ Mass percentage of solution $= \frac{40}{360} \times 100% = 11.1%$
Q. How much water should be added to 50 g of glucose, so as to obtain $12%$ glucose solution? Solution: Percentage concentration of glucose solution $= 12%$ Mass of solute $= 50 g$ Mass of solution $=$ ? Concentration of solution $= \frac{Mass of solute ( g )}{Mass of solution} \times 100$ $∴$ Mass of solution $= \frac{Mass of solute ( g )}{Concentration of solution} \times 100 = 416.67 g$ $∴$ Mass of water which should be added to glucose $=$ Mass of solution - Mass of solute $= (416.67 - 50) g = 366.67 g$
Q. A 250 mL of acetic acid solution in water contains 20 g of acetic acid. What is the concentration of acetic acid solution? Solution: Mass of solute $= 20 g$ Volume of solution $= 250 mL$ Mass by volume percentage $= \frac{Mass of solute}{Volume of solution} \times 100 = \frac{20 g}{250 mL} \times 100 = 8%$

Saturated solution

A solution which at a given temperature dissolves as much solute as it is capable of dissolving is said to be a saturated solution.

Example:

(a) When we add sugar to water, the crystals of sugar keep on going into the solution in the beginning. But after some time, no mass of sugar dissolves, provided temperature is kept constant. (b) At $3 0^{\circ} C, 55 g$ of common salt dissolves in 100 g of water. However, if more of common salt is added to the above solution, it does not dissolve. In such a situation, the solution of common salt containing 55 g of salt in 100 g of water is a saturated solution at $3 0^{\circ} C$ .

If a saturated solution at some particular temperature is heated, the solution becomes unsaturated, because of the increase in solubility.
If a saturated solution at some higher temperature is cooled, it remains saturated. The excess solute comes out of the solution and deposits itself in the form of crystals.

Solubility

The maximum amount of solute in grams which can be dissolved in 100 g of the solvent at a given temperature to form a saturated solution is called solubility of the solute in that solvent at that particular temperature.

Unsaturated solution

When the amount of solute contained in a solution is less than the saturation level, the solution is said to be an unsaturated solution.

For example, At $3 0^{\circ} C$ , if 45 g of common salt is dissolved in 100 g of water, such solution so formed is capable of dissolving more of the common salt, then such a solution is called an unsaturated solution.

Super saturated solution

A solution which contains more of the solute than required to make a saturated solution, is called a super saturated solution.

Solubility of some substances at $2 0^{\circ} C$

	Substance (or Solute)	Solubility in water (at 20°C )
1.	Copper sulphate	21 g
2.	Potassium nitrate	32 g
3.	Potassium chloride	34 g
4.	Sodium chloride	36 g
5.	Ammonium chloride	37 g
6.	Sugar	204 g

5.0Suspension

A suspension is a heterogeneous mixture in which the solid particles are spread throughout the liquid without dissolving in it. The particles have a tendency to settle down at the bottom of the container and can be filtered out.

For example, (1) Chalk-water mixture is a suspension of fine chalk particles in water. (2) Muddy water is a suspension of soil particles in water.

Properties of a suspension

(1) A suspension is a heterogeneous mixture. (2) The size of solute particles in a suspension is quite large. It is larger than 1000 nm or $1 0^{- 6} m$ in diameter. (3) The particles of a suspension can be seen easily with naked eyes and under microscope. (4) A suspension scatters a beam of light passing through it (because it's particles are quite large, thus makes its path

Pearls are solid sol visible). (5) The particles of suspension settle down when the suspension is kept undisturbed. (6) The process of settling down of suspended particles under the action of gravity is called sedimentation. So, suspensions are unstable. After sedimentation, it does not scatter light any more. (7) The solid particles present in the suspension can be easily separated by ordinary filter papers. No special filter paper is needed for the purpose. (8) Suspensions are either opaque or translucent.

6.0Colloidal solution or colloids

A heterogeneous solution in which the particle size is in between $1 0^{- 7} cm$ to $1 0^{- 4} cm$ such that the solute particles neither dissolve nor settle down in a solvent, is called colloidal solution. Blood is an example of colloid. Its components can be separated using centrifugation.

Smoke is an example of solid aerosol

The components of a colloidal solutions are the dispersed phase and the dispersion medium.

Dispersed phase

It is the component which is present in small proportion and consists of particles of colloidal dimensions (

1 0^{- 9} m

1 0^{- 6} m

Dispersion medium

It is the component in which dispersed phase is suspended and acts as a medium. Colloids are classified according to the state of the dispersing medium.

Dispersed Phase	Dispersion Medium	Type of Colloid	Examples
Liquid	Gas	Liquid Aerosol	Mist, Fog, Clouds, Insecticide sprays
Solid	Gas	Solid Aerosol	Smoke, Dust in air, Smog, Automobile exhaust
Gas	Liquid	Foam, Froth	Whipped cream, Froth, Shaving cream
Liquid	Liquid	Emulsion	Milk, Hair cream, Emulsified oils, Medicines, Cold cream
Solid	Liquid	Sol	Paints, Starch, Proteins, Milk of magnesia, Mud, Blood
Gas	Solid	Solid Foam	Foam, Pumice stone, Ice-cream, Rubber, Sponge
Liquid	Solid	Gel	Jellies, Cheese, Butter, Boot polish
Solid	Solid	Solid Sol	Coloured glass, Gemstones, Pearls, Milky glass

Properties of colloids

(1) A colloid is a heterogeneous mixture but it appears homogeneous. (2) The size of particles of a colloid is too small to be individually seen by naked eyes. (3) The colloidal particle do not settle down when left undisturbed i.e. colloid is quite stable. (4) The colloid particles cannot be separated from the dispersion medium by the process of filtration. A special technique of separation known as centrifugation can be used to separate the colloidal particles.

The fog you usually observe during winters is an example of liquid aerosol (5) Colloidal solutions are not transparent, but translucent in nature. (6) Particle in a colloidal solution follow zig zag path (Brownian movement).

It is normally not possible to see the colloidal particle because of their very small size. However, their path can be seen under a microscope.

Brownian movement: It is defined as continuous zig-zag movement of colloidal particles in a colloid. This Brownian movement arises due to hitting of the colloidal particles by the particles of the dispersion medium from different directions with different forces.

Brownian movement

(7) Colloidal solution scatters the beam of light passing through it. (Tyndall effect)

As a result, the path of light becomes visible. This scattering of a beam of light by colloidal particles is called the Tyndall effect. The reason for this observation is that the particles of a colloidal solution are big enough to scatter light and hence path of light becomes visible i.e. the Tyndall effect is observed.

For example, (i) Tyndall effect can also be observed when a fine beam of light enters a room through a small hole. This happens due to the scattering of light by the particles of dust and smoke in the air. (ii) Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. In the forest, mist contains tiny droplets of water, which acts as particles of colloids dispersed in air.

Tyndall effect

7.0Physical and chemical changes

There are some changes during which no new substances are formed. On the other hand, there are some other changes during which new substances are formed. So, on the basis of whether new substances are formed or not, we can classify all the changes into two groups: (i) Physical changes (ii) Chemical changes

Physical changes

Those changes in which no new substances are formed, are called physical changes. In a physical change, the substances involved do

When water boils no new substance is formed, so boiling is a physical change not change their identity. The changes in physical state, size and shape of substances are called physical changes. When ice is heated, it melts to form water. Though ice and water look different, they are both made of water molecules. Thus, no new chemical substance is formed during the melting of ice. So, the melting of ice to form water is a physical change.

When water is cooled, it solidifies to form ice. This is called freezing of water. The freezing of water to form ice is also a physical change.

Some other example of physical changes are: Boiling of water, condensation of steam, and breaking of a glass.

Chemical changes

Those changes in which new substances are formed, are called chemical changes.

In a chemical change, the substances involved change their identity. They get converted into entirely new substances.

Cutting of trees is an irreversible process but no new substance is formed during cutting of trees. Therefore, we call it a physical change

For example, When a magnesium wire is heated, it burns in air to form a white powder called 'magnesium oxide'. This magnesium oxide is an entirely new substance. Thus, a new chemical substance is formed during the burning of a magnesium wire. This is a chemical change. Some other examples of chemical changes are: Burning of candle and burning of hydrogen in oxygen to form water.

Differences between physical and chemical changes

Physical change	Chemical change
A physical change brings about changes in physical properties of the substance such as physical state, shape and size, etc. For example, ice (solid) melts to form water (liquid).	A chemical change brings about changes in the chemical properties of the substance. For example, iron undergoes rusting to form hydrated iron oxide. The chemical properties of hydrated iron oxide are different from those of iron.
There is no change in the chemical composition of the substance during the physical change. Thus, both ice and steam have the same chemical composition (made up of water molecules) as that of liquid water.	There is always a change in the chemical composition of a substance during a chemical change. For example, iron and rust have different chemical composition.
No new substance is formed in a physical change.	A new substance is always formed during a chemical change.

8.0Types of pure substances

On the basis of their chemical composition, substances can be classified either as elements or compounds.

Element: Antoine Laurent Lavoisier defined element as the simplest or basic form of matter that cannot be broken into simpler substances by chemical methods.

A pure substance which is made up of one kind of atoms only is called an element.

Majority of the elements are solid. Eleven elements are in gaseous state at room temperature. Two elements are liquid at room temperature, mercury and bromine.

Types of elements

Metals Nearly 70 elements belong to a particular class known as metals. In the metals, the atoms are very closely packed together and have special types of bonds known as metallic bond. Because of very tight packing, the metals are quite hard. Cesium and gallium are two elements which liquify slightly above room temperature.
Robert Boyle was the first scientist to use the term "Element" in 1661
Non-metals Nonmetals as the name suggests are opposite to metals which means that their properties are quite different from the metals. Only about 22 elements are nonmetals.

Properties of metals

(1) They have generally silver-grey colour. However, some metal or their alloys have golden yellow colour. (2) Metals have a lustre, the freshly cut surface has a shine on it. (3) They easily conduct heat and electricity. (4) They are malleable i.e. they can be beaten into sheets. (5) They are sonorous.

For example, Gold, silver, copper, iron, sodium, potassium, etc. Mercury is the only metal that is liquid at room temperature.

Properties of non-metals

(1) They exist in solid, liquid and gaseous state. (2) They display variety of colour. (3) They are generally neither malleable nor ductile. (4) They are poor conductors of heat and electricity. (5) They are not sonorous. For example, Hydrogen, oxygen, iodine, carbon, etc.

Metalloids

Some element have intermediate properties of the metals and nonmetals. The elements which exhibit the properties of metals as well as nonmetals are called metalloids. For example, Boron, Silicon, Germanium, etc.

Compounds

A pure substance, which is composed by two or more elements, combined chemically in a definite ratio by mass, such that it can be broken into elements only by chemical means, is called compound. The two or more elements present in a compound, are called constituents or components of the compound. For example, water is a compound of hydrogen and oxygen, combined together in the ratio of $1 : 8$ by weight. The water can be broken into its constituents only by electrochemical method i.e. by passing electric current through it. The compounds can be further classified as acids, bases and salts.

Mixtures	Compounds
Elements or compounds just mix together to form a mixture, and no new compound is formed.	Elements react to form new compounds.
A mixture has variable composition.	The composition of each new substance is always fixed.
A mixture shows the properties of the constituent substances.	The new substance has totally different properties.
The constituents can be separated easily by physical methods.	The constituents can be separated only by chemical or electrochemical methods.

9.0Basic terminology

Transparent - You can see through it clearly.
Translucent - You can see through it partially.
Opaque - You cannot see through it.
Volatile - Substance that forms vapours on heating.
Non-volatile - Substance that does not form vapours on heating.
Condenser - The part of apparatus where condensation takes place.
Charring - Process of heating of sugar to form carbon black.
Alum - Fitkari.
Hydrocarbon - A compound of hydrogen and carbon.
Constituent - A component part of something.
Uniformly - In a way that is the same in all cases.
Homogeneous - Of the same kind; Alike
Heterogeneous - Diverse in character or content.
Composition - Arrangement, ratio, and type of atoms in molecules.
Scatter - Throw in various random directions.
Pore - A minute opening in a surface.
Tendency - Typical or repeated habit, action or belief.
Canopy - A projection or shelter that resembles a roof.
Smoke - A visible suspension of carbon or other particles in air.
Smog - A mixture of smoke, gases and chemicals.
Mist - Thin layer produced by very small droplets of water collecting in the air.
Fog - A thick cloud of tiny droplets suspended in air.
Inflammability - Capable of being set on fire
Extinguish - Put an end to
Rotten - Very bad

Algebraic Expressions

An expression, its terms and factors of the terms can be represented by a tree diagram to make it easily comprehensible to you......

Data Handling

The word data means information in the form of numerical figures or a set of given facts. E.g. The percentage of marks scored by 10 students.......

The Triangles and its Properties

A closed figure formed by joining three non-collinear points is called a triangle. The three sides and three angles of a triangle are collectively known as elements of the triangle......

Visualising Solid Shapes

A solid is any enclosed three-dimensional shape, i.e., it has 3 dimensions- length, width and height, whereas there are some common (flat) shapes which can be easily drawn on paper. They have only.....

Fractions

Fractions having the same denominator are called like fractions, whereas fractions having different denominator are called unlike fractions......

Perimeter and Area

Mensuration : The process, art or the act of measuring is called mensuration. Anything that can be measured is said to be mensurable.......

Join ALLEN!

(Session 2025 - 26)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.