JKBOSE 9th Class Science Solutions Chapter 8 Is Matter Around Us Pure ?

◆  Pure Substance. It consists particles of only one kind and has a definite set of properties. Pure substances include elements and compounds.

◆ An Element is a pure substance which is made up of only one kind of particles (atoms). It can neither be built up nor broken down into two or more simpler substances by any known physical or chemical methods, e.g., copper, silver etc.

◆ A compound is a pure substance which is obtained by the chemical combination of two or more elements in a fixed ratio by mass, e.g., water, ammonia etc.

◆ Mixture. It is a material obtained by mixing two or more substances in any proportion without any chemical change taking place.

◆ Mixtures can be homogeneous or heterogeneous.

◆ The properties of a mixture lie between those of its components whereas properties of a compound are different from those of its constituents.

◆ Mixtures can be separated into pure substances by using suitable separation techniques.

◆ Solution is a homogeneous mixture of two or more substances whose composition can be changed within certain fixed limits.

◆ Binary solution is a solution having two components.

◆ Components of a binary solution Solute are called solute and solvent.

◆ Solute is the minor component of solution whereas solvent is the major component of a solution.

◆ Concentration of a solution is the amount of solute present per unit volume or per unit mass of solvent or solution.

◆ A saturated solution is one which does not dissolve any more of the solute at a given temperature and pressure.

◆ Colloids are heterogeneous mixtures in which the particles have size more than 100 nm. These particles are called colloidal particles and constitute the dispersed phase whereas the medium in which colloidal particles are dispersed constitute dispersion (Le) stufoc to smulo medium.

◆ Suspensions. Materials which are insoluble in a solvent and have particles that are visible to naked eyes form suspensions.

◆ In suspensions, the particle size is more than 100 nm and are heterogeneous.

◆ Physical Change. It is a temporary change in which only the physical properties of substances change and it can be reversed.

◆ Chemical Change. It is a permanent change in which the chemical properties of substances change and there is change in composition and cannot be reversed.

◆ Filtration. The process of separation of an insoluble solid component of a mixture from a liquid component is called filtration.

◆ Evaporation. It is the slow process of conversion of liquid into gaseous state (vapour) at a temperature below its boiling point.

◆ Distillation. It is the process of conversion of liquid into gaseous state by heating it to the boiling point and condensing the vapour to get pure liquid.

◆ Fractional distillation. It is the process of separating two miscible liquids having different boiling points by distillation using a fractionating column.

◆ Chromatography. It is the process of separation of dissolved components of a mixture by adsorbing on a suitable substance (called adsorbent).

Ans.— It is a material containing particles of only one kind having a definite set of properties. Pure substances include elements and compounds.

Homogeneous mixture	Heterogeneous mixture
It consists of a single phase.	It consists of two or more phases.
It has a uniform composition in the throughout.	It does not have a uniform composition thoughout.
It has the same properties throughout the bulk.	It does not have same properties throughout the bulk.
There are no visible boundaries between its components.	There are visible separation between its components.
Examples : Sodium chloride dissolved in O water, ethyl alcohol dissolved in water.	Examples : Air, gun powder, iron filings, sand and sulphur.

Ans.—  Same as Q. No. 2 on TBQ Page 120.

Property	True Solution	Colloidal solution	Suspension
Nature	Homogeneous	Heterogeneous	Heterogeneous
Particle size	Less than 1 nm	1 to 100 nm	More than 100 nm
Diffusion	Diffusion rapidly	Diffusion slowly	Don’t Diffusion
Filtrability	Paritcles can pass through ordinary filter paper as well as semi – permeable membrane	Paritcles can pass through ordinary filter paper but not through demi – per – meable membrane	Particles can ‘ t through filter paper as well as semi – permeable mem – brane
Appearance	Clear and transparent	Generally clear and transparent	Opaque
Tyndall	Dont’ show	Show	May or may not shoe
Visibility	Particles are not visible	Particles can be seen only with ultra – microscope	Particles can be seen with naked eye or microscope.

Ans.— Mass of sodium chloride (solution) = 36 g

Mass of water (solvent) = 100 g

Total mass of solution = 100 + 36 = 136 g

Mass percentage of solution =  Mass of solute /  Mass of solution × 100

= 36 / 136 × 100

= 26.47

Ans.— By Distillation.

Ans.— (i) By centrifugation.

(ii) By evaporation.

(iii) By sublimation.

Ans.— The mixtures in which the substance is soluble in a suitable hot solvent whereas 1 the impurities are insoluble.

Ans.—(a) Chemical change, (b) Physical change, (c) Chemical change, (d) Physical change, (e) Chemical change, (f) Physical change, (g) Physical change, (h) Chemical change.

Ans.— Some examples are

Ans.— (a) Evaporation, (b) Sublimation, (c) Filtration, (d) Chromatography, (e) Centrifugation, (f) Separating funnel, (g) Filtration, (h) Magnetic separation, (i) Gravity separation, (j) Centrifugation

Ans.— Step 1. Boil some solvent (water) in a pan.

Step 2. Put some solute (tea leaves) in a t in a tea pot.

Step 3. Pour the boiling water into the tea pot and let it soak for a few minutes to form a solution.

Step 4. Stir the solution in the tea pot.

Step 5. Take some solute (sugar) into a cup.

Step 6. Filter the above solution obtained in step 4 using strainer and take this solution (filtrate) in the cup. Pour two tea-spoons of milk into the cup and stir it with a spoon. This gives us tea which is ready for drinking. The is left on the strainer because these are insoluble whereas sugar and milk are soluble solutes.

Ans.—(a) Saturated Solution. A solution in which no more of the solute can be dissolved at the given temperature is said to be saturated at that temperature. For example, 50 g of NaCl added to 100 ml of water.

(b) Pure substance. A pure substance is made of only one type of atoms or molecules. Pure substances have the same colour, taste, texture at the given temperature and pressure. Pure substance has a fixed melting or boiling point at the constant pressure. Pure substance includes elements and compounds. For example, hydrogen gas, sodium chloride, water etc.

(c) Colloid. A substance is said to be in the colloidal state if its particle size lies between win muretu 1 to 100 nm. The colloidal solution is heterogeneous and consist of two phases i.e. dispersed phase or colloidal particles and dispersion medium in which colloidal particles are suspended e.g. colloidal solution of starch in water.

(d) Suspension. It is a heterogeneous mixture in which the particles of the solute don’t dissolve but remain suspended throughout the bulk of the material and the size of particles is more than 10^-7m. The particles can be seen with naked eye.

Ans.— Soda Water — Homogeneous mixture

Wood — Homogeneous mixture

Air — Homogeneous mixture

Soil — Homogeneous mixture

Vineger — Homogeneous mixture

Filtered tea — Homogeneous mixture.

Ans.— Determine the boiling point of the given liquid. If its boiling point is 100°C at 1 atmosphere pressure it is pure water and if boiling point is above 100°C, it is impure water.

(a) Ice

(b) Milk

(c) Iron

(d) Hydrochloric acid

(e) Calcium oxid

(f) Mercury

(g) Brick

(h) Wood

(i) Air

Ans.— (a) Ice

(b) Iron

(c) Hydrochloric acid

(d) Calcium oxide

(f) Mercury

(a) soil

(b) sea water

(c) air

(d) coal

(e) soda water

Ans.— The important characteristics of a mixure are :

1. In a mixture, the components, elements or compounds are present in no fixed ratio.

2. A mixture is formed from its components as a result of physical change.

3. The properties of a mixture lie between those of its constituents.

4. A mixture may be homogeneous or heterogeneous.

5. The constituents of a mixture can be separated by physical methods only.

6. The formation of a mixture from its constituents does not involve any energy change.

Compound	Mixture
A compound is formed from its constituent elements as a result of chemical reaction.	A mixture is obtained from its (elements, compounds) components as a result of physical change.
A compound is always homogeneous in nature.	The mixtures can be homogeneous or heterogeneous.
In a compound the elements are present in a fixed ratio by weight.	In a mixture the components can be present in any ratio.
The components of a compound can’t be separated by physical methods but can be separated by chemical methods only.	The components of a mixture can be separated by physical methods only.
The formation properties of a compound are different from that of its elements.	The properties of a mixture lie between those of its components.
The formation of a compound from its elements is accompanied by energy changes.	The formation of a mixture from its constituents is not accompanied by energy changes.

Ans.— (i) The solution containing common salt in water is concentrated and is then cooled. The crystals of common salt are formed which can be separated by filtration.

(ii) Alcohol can be separated from water by fractional distillation as the two liquids differ in their boiling points.

(iii) The mixture is treated with carbon disulphide which dissolves powdered sulphur in it. It is filtered to separate carbon particles. The filtrate upon concentration and cooling gives crystals of sulphur which can be separated by the process of filtration.

(iv) The coloured dyes in black ink can be separated by the process of paper chromatography.

Ans.— (a) Fractional Crystallisation. The process of separation of components of a mixture having different solubilities in the same solvent by crystallisation is called fractional crystallisation. This method is used for the separation of components of a mixture which are soluble in the same solvent on heating but have different solubilities. For example, a mixture of potassium nitrate and sodium chloride can be separated by this method. This can be explained as follows :

The mixture is dissolved in water. The solid is concentrated to the crystallisation point. On cooling the crystals of less soluble component i.e., sodium chloride appear first. These are separated. On further cooling the crystals of more soluble component i.e., of potassium nitrate will appear. The pure crystals can be obtained by recrystallisation from the same solvent i.e. water.

(b) Sublimation. This method is used for the separation of the components of a mixture in which one component undergoes sublimation whereas other does not. For example, a mixture of ammonium chloride and common salt can be separated by this method. For this purpose take the mixture of ammonium chloride and common salt in a china dish. Cover it with an inverted funnel and its open end is closed with cotton wool. The walls of china dish are kept cooled. On heating, ammonium chloride sublimes and condenses on the cooler parts whereas common Salt is left behind. The fine powder of ammonium chloride deposited on the funnel is scrapped with the help of a knife. Similarly, the mixture of iodine and sand can be separated by this method in which iodine sublimes whereas sand does not.

(c) Filtration. In this method, the mixutre is dissolved in a suitable solvent in which one component dissolves whereas other does not.

For example, a mixture of charcoal and sulphur can be separated by this method. The mixture is treated with carbon disulphide which dissloves sulphur whereas charcoal is left behind. The insoluble charcoal is separated by filtration and is dried. From the filtrate, sulphur can be obtained by evaporating carbon disulphide.

Ans.—(i) Distillation. The process of converting a liquid into gaseous state by heating to boiling point and condensing the vapour to get the pure liquid is called distillation.

This method is used when the solid is non-volatile and liquid does not have a high boiling point.

For example, salt can be separated from sea water by this method. For this purpose the apparatus is fitted as shown below :

The mixture of solid and liquid is taken in a distillation flask. On heating vapour of liquid (water) are produced. These are condensed in water condenser and collected in a receiver. The non-volatile sodium chloride is left behind.

Similarly, a mixture of methyl alcohol and iodine can be separated by this method.

(ii) Evaporation. Evaporation is a process of changing a liquid into its gaseous state by heating it at a temperature below its boiling point. For example, common salt can be obtained from a mixture of common salt and water by evaporation.

The mixture is heated in a china dish using sand bath when water vaporises whereas common salt is left behind.

Ans.— The gas – gas mixtures can be separated by the following method :

Fractional evaporation of mixture of liquefied gases. The mixture of two gases is liquefied by applying high pressure and then allowing it to expand. For example, when air is liquefied example, a under high pressure and allowing it stand, both oxygen and nitrogen get liquefied. The above liquid mixture is maintained at a temperature of -196°C (b.pt of liquid N₂), nitrogen boils off. For mixture of carbon

dioxide and hydrogen can be separated by passing through porous partitions as shown below.

In this case, H₂ being lighter diffuses at a faster rate as compared to CO₂.

Ans.— Chromatography. The process of separation of different components of a mixture by adsorbing them over a suitable material (called adsorbent) is called chromatography. Originally, this technique was used to separate coloured mixtures but now-a-days this method can be used for colourless as well as coloured substances.

(i) It can be applied to separate the mixture even if very small amount of mixture of the substances is available.

(ii) The components of a mixture don’t get wasted during separation.

(iii) It also helps in estimating the constituents of a mixture apart from separation.

Ans.— Chromatography is based upon the distribution of the mixture of the components between the two phases i.e. a stationary phase and a moving phase. The moving phase consists of mixture of the substances to be separated. The moving phase is applied over a solid or liquid i.e., a stationary phase. The stationary phase separates the components of the mixture by the phenomenon of either partition, adsorption or ion exchange. The different chromatographic techniques are :

(a) Column chromatography

(b) Thin layer chromatography

(c) Ion exchange chromatography

(d) Paper chromatography.

Ans.— These are of eight types :

Dispersed Phase	Dispersion Medium	Type or name of colloidal solution	Examples
Solid	Solid	Solid  sol	some coloured glasses
Liquid	Solid	Gel	Cheese, butter
Gas	Solid	Solid foam	Sponge, rubber foam
Solid	Liquid	Sol	Mud, milk of magnesia
Liquid	Liquid	Emulsion	Milk, hair cream
Gas	Liquid	Foam	Froth, whipped cream
Solid	Gas	Solid aerosol	Smoke
Liquid	Gas	Liquid aerosol	Fog, mist

Ans.— Concentration of a solution. It indicates the amount of solute dissolved per unit mass or volume of solvent or solution.

The concentration of a solution can be expressed as

(i) Mass percentage of a solution = Mass of Solute / Mass of Solution × 100(ii) Mass of volume percentage of a solution = Mass Solute / Volume of solution × 100

Ans.— The process of separation of different dissolved components of a mixture by adsorbing them on a suitable material (called adsorbent) is called chromatography. The adsorbent can be solid or liquid. For example, alumina, magnesium oxide, special filter que most rotalli yd betonqos el sidstoes paper.

The components of a mixture are generally dissolved in a solvent like water, alcohol etc.

If a filter paper is used as an adsorbent for the separation of a components of a mixture, this technique is called paper chromatography.

The process of separation of coloured constituents present in a mixture of ink and water is described ahead :

(i) Take a special filter paper about 25 cm long and 4 cm broad and stick it to a glass nerod at its one end with the help of gum as shown given ahead. Mark a line at a distance of 3 cm from the lower end with the help of pencil. Put a drop of ink at the centre of this line with the help of a fine capillary.

(ii) Dip this end in water taken in a beaker upto 2 cm.

(iii) Suspend this filter paper in a tall cylinder and allow it to stand undisturbed for one hour. The water rises up the filter paper and reaches the ink drop, dissolves its components and rise upwards along with water. The different components of ink are adsorbed upto different extents on the filter paper, therefore, they travel different distances on the filter paper.

(iv) After one hour, the filter paper is taken out and dried. Different bands of colours corresponding to the components of ink are produced on the filter paper. This filter paper is called chromatograph.

Ans.— (a) Powdered chalk and sugar can be separated by using water which dissolves sugar and chalk is insoluble. It is separated by filtration. From sugar solution, sugar is obtained by evaporating water.bedoel vierne

(b) Nitre and common salt. The mixture can be separated by fractional crystallisation from the solutions in water because they have different solubilities in water.

(c) Iron and copper filings can be separated by using a magnet when iron filings cling to magnet whereas copper filings don’t.

(d) Ammonium chloride, sand and common salt. Ammonium chloride is separated by sublimation. Sand and common salt are separated by using water when sand remains insoluble and is separated by filtration. From aqueous solution, sodium chloride can be separated by evaporation.

(e) Ammonia and hydrogen can be separated by diffusion through porous pot. Ammonia and hydrogen have different rates of diffusion due to different densities.

Ans.— The liquid-liquid mixtures can be  separated by using :

1. Separating funnel

2. Fractional distillation.

1. Separation of liquid-liquid mixture by using separating funnel. This method is used when the two liquids are immiscible. For example, a mixture of carbon disulphide and water can be separated by this method.

The mixture is taken in a separating funnel. The funnel is allowed to stand for sometime. On standing, the liquid having higher density forms the lower layer whereas the liquid having lower density forms the upper layer. The two liquids are taken out from the separating funnel in separate conical flask.

2. Separation of liquid-liquid mixture using fractional distillation. The process of separating the mixture of two immiscible liquids by using distillation carried out with the help of a long fractionating column is called fractional distillation. For example, a mixture of ethyl alcohol and water can be separated by this method. The apparatus is fitted as shown below :

The mixture of ethyl alcohol and water is heated in a distillation flask fitted with a fractionating column. On heating the vapour of liquid having lower boiling point are produced first and condensed in the water condenser and collected in a receiver. When the temperature of thermometer begins to rise, the vapour of other liquid are produced and these are condensed and collected in a separate receiver.

Homogeneous mixture. e.g. Brass is a homogeneous mixture of copper and zinc.

Heterogeneous mixture. e.g. common salt and sand.

Ans.— The solid-liquid mixtures can be separated by the following methods :

1. By sedimentation and decantation. In this method, the mixture is allowed to stand when the solid particles settle down as sediment whereas clear liquid is left behind which is poured out carefully. This process is called decantation e.g. mixture of sand and water can be separated by this method. By this method, the complete separation is not possible.

2. By filtration. In this method, the mixture can be separated by using filter paper when the insoluble solid is left on the filter paper whereas the clear liquid passes out from the filter paper and is collected. For example, a mixture of chalk and water can be separated by this method.

Ans.—  (a) Sublimation (b) Filtration (c) Immiscible, separating funnel (d) Sublimation (e) Petrol.

Ans.— 1. It is homogeneous.

2. It has a definite set of properties.

3. A pure substance cannot be separated into other kinds of matter by any known physical method.

Ans.— 1. The components of a mixture are present in any ratio.

2. It can be homogeneous or heterogeneous.

3. The mixture can be separated with its constituents by physical or mechanical methods only.

Ans.— (i) The properties of ammonia are different from those of its components i.e. nitrogen and hydrogen.

(ii) When ammonia is formed from nitrogen and hydrogen, energy is given out.

(iii) In ammonia, N and H are present in fixed ratio of 14: 3 by mass.

Ans.— Sodium chloride is a compound because :

(i) in sodium chloride, sodium and chlorine are combined chemically in a fixed ratio by mass.

(ii) the formation of sodium chloride from sodium and chlorine is accompanied loss of energy.

Ans.— In air :

(i) the components are not present in any fixed ratio.

(i) the properties of air are average of the properties of its components.

(ii) the components can be separated by physical methods.

Ans.— (i) Iodine crystals can be separated from sand by sublimation.

(ii) Petrol can be separated from crude oil by fractional distillation.

Ans.— (i) It can be obtained by the process of distillation. When sea water is distilled, water distils, and vapour are condensed in a receiver whereas common salt is left behind in the retort.

(ii) Kerosene oil can be separated from a mixture of kerosene oil and petrol by fractional distillation when petrol distils off first and then kerosene oil distils off.

Ans.— (i) Sublimation (ii) Ammonium chloride (iii) Water.

Ans.— Electrophoresis is the process of migration of colloidal particles towards oppositely charged electrode under the influence of an electric field. The electrophoresis is due to the charge present on the colloidal particles.

Ans.— Brownian movement. When colloidal solutions are viewed with the help of ultra-microscope, it is observed that colloidal particles follow zig-zig path. This is called Brownian movement. This effect is due to the unequal impacts of the particles of dispersion medium with colloidal particles.

Ans.—Tyndall effect. If a bright, narrow and convergent beam of light is passed through a colloidal solution and is viewed at right angles with the help of a microscope, the path of light becomes, visible and a bright cone of light called Tyndall cone is produced. This luminosity of path of a beam of light in a colloidal solution is called Tyndall effect.

Ans.— It is a solution in which water acts as a solvent.

Ans.— It indicates the exact amount of solute dissolved in an exact amount of solvent or solution.

Ans.—  A pure substance has a fixed melting and boiling points at a given pressure.

Ans.— It is the component of a solution which is present in large amount and in which solute is dissolved and has the same physical state as solution.

Ans.— A solution having three components is called a ternary solution.

Ans.— A solution in which alcohol is the solvent is called alcoholic solution.

Ans.—A solution in which more of solute can be dissolved at the given temperature and pressure is said to be unsaturated solution.

Ans.— It is a solution in which solvent is other than water.

Ans.— Emulsion. It is a colloidal solution of two immiscible liquids e.g. milk, face cream etc.

Ans.— Carbon disulphide is suitable for removing sulphur from crucible because sulphur is soluble in it.

Ans.— Fractional distillation.

(A) Element

(B) Compound

(C) Mixture

(D) both (A) and (B).

Ans.— (D) both (A) and (B).

(A) True solution

(B) Pure liquids

(C) Suspension

(D) Colloidal solution.

Ans.— (D) Colloidal solution.

(A) Air

(B) Water

(C) Ice

(D) Ice cream.

Ans.— (A) Air

(A) Diffusion through a porous pot

(B) Evaporation

(C) Centrifugation

(D) None.

Ans.— (A) Diffusion through a porous pot

(B) One type

(C) Pure substance

(D) None.

Ans.— (A) Two types of

(A) Freezing of water

(B) Digestion of food

(C) Mixing of iron fillings and sand

(D) None of these.

Ans.— (B) Digestion of food

(A) Air

(B) Milk

(C) Brick

(A) Ice

(B) Ice cream

(C) Diamond

(D) Graphite.

Ans.— (B) Ice cream

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