Selina Concise Class 7 Chemistry Solution Chapter No. 3- ‘Elements Compound and Mixture’ For ICSE Board Students.
1)
Answer :
Elements | Symbol |
Helium | He |
Silver | Ag |
Krypton | Kr |
Antimony | Sb |
Barium | Ba |
2)
Answer :
Symbol | Elements Name |
Na | Sodium |
C | Carbon |
Kr | Krypton |
U | Uranium |
Ra | Radium |
Fe | Iron |
Co | Cobalt |
3)
a)
Answer : Elements :
The substance which is made up of same kind of atom and it can not broken down into simpler one known as Element.
b)
Answer : When two or more elements chemically combine together and formed a substance or molecules , which can be broken down into simpler substance are known as compound.
4)
a)
Answer : Haemoglobin :
Haemoglobin present iron metal.
b)
Answer : Chalk :
Chalk present Calcium metal .
c)
Answer : Chlorophyll :
Chlorophyll present Magnesium metal.
d)
Answer : Chocolate wrapper :
Chocolate wrapper is made up of aluminium metal .
5)
Answer : Examples of Non- metallic elements are following .
- Oxygen.
- Nitrogen.
- Hydrogen.
- Carbon.
- Chlorine.
- Phosphorus .
- Sulphur.
6)
a)
Answer : Metalloid :
Those elements have intermediate properties between metal and non metal , they show some properties of metal and some properties of non metal , these kinds of elements known as Metalloid.
Example : Silicon , boron , arsenic , antimony , germanium , polonium ,etc.
b)
Answer : Noble gases :
Those elements or gases which do not react with other chemicals , elements or compound , these kinds of elements or gases known as inert gases or noble gases .
Example : Helium , Neon , Argon , Krypton etc.
7)
Answer :
Symbol | Elements Name |
Iron | Plaster of paris |
Copper | Chalk |
Aluminium | Common Salt |
Silver | Calcium oxide |
Carbon | Cane sugar |
Uranium | Silica |
Sodium sulphate | |
Potassium carbonate | |
Carbon dioxide |
Exercise: II Solution
1) .
Answer :
Sr .No | Compound | Mixture |
1 | Compound are made up of fixed ratio or proportion. | Mixture has not any fixed ratio or proportion |
2 | Compound is present in pure form. | Mixture is present in impure . |
3 | In a Compound two or more constituents are chemically bonded together | In a Mixture substance or constitutes are not chemically bonded with each other. |
4 | The whole compound have same properties. | The whole mixture has not same properties. |
5 | Boiling and melting point are same. | Boiling and melting point are variable. |
6 | It can not be separate from simple physical method. | It can be separate from simple physical method. |
2)
Answer : Characteristics Properties of pure substance :
- Pure substance have fixed composition or proportions of substance or constitutes.
- Pure substance have same boiling and melting point .
- Pure substances are homogeneous and they have uniform composition of whole substance .
- Pure substance are compound and elements .
Need of pure substance :
- For manufacture of medicine .
- For knowing fixed melting and boiling point of substance
- Pure substance is healthy for human being .
3).
a) .
Answer : 1) sand and sugar .
2) Sand and Stone.
3) all alloys
b) .
Answer : 1) sand and water
2) sugar in Water
3) iodine in alcohol
c) .
Answer : 1) oil in water
2) alcohol in water
3) acetone in water .
4).
a) .
Answer : Evaporation :
The process of liquid change into gas or vapour when increase the temperature known as Evaporation.
b).
Answer : Filtration :
The process of removal of solid from liquid by the use of filter medium or filter paper known as filtration.
c) .
Answer : Sublimation :
The process of solid convert into vapour or gas without changing into liquid through heating known as sublimation .
d) .
Answer : Distillation :
A liquid convert into vapour and these vapour condensed back to pure form of liquid , this process known as distillation.
e) .
Answer : Miscible liquid:
When two liquid completely mix with each other and form homogeneous liquid mixture known as miscible liquid.
f) .
Answer : Immiscible liquid :
When two liquid are not mix with each other and formed heterogeneous liquid mixture known as Immiscible liquid.
5) .
a) .
Answer : Magnetic separation
b) .
Answer : Sublimation
c).
Answer : Evaporation
d).
Answer : Winnowing
e).
Answer : Separating funnel
f).
Answer : Crystallization
g).
Answer : Centrifugation
6).
Answer : We can separate the mixture of common salt , chalk powder and camphor by following way b.
- This mixture contain camphor which is sublime substance , when we provide the heat to this mixture camphor directly converted into vapour and then get cool environment to change back solid .
- After this remaining common salt and chalk powder mixture , this mixture add in a water , common salt completely dissolved in water and chalk powder undissolved in it , So we can separate the Chalk powder from this mixture by filtration .
- After this process remaining salt solution can be separate by evaporation method, in this method when we provide temperature to the to this solution water will be evaporate and salt left behind as a residue .
7).
Answer : Distillation is more advantageous than evaporation because If mixture can separate by evaporation method , we can collect only residue left behind , but one constituent from the mixture is evaporate in the air , When we separate a mixture by distillation process we can collect both the components of mixture ( solid and liquid ) separately .
8).
a) .
Answer : A physical method of separation of the mixture of constituents separately distributed by two phase or transported by a mobile phase over stationary phase , this method known as chromatography .
b) .
Answer : Chromatography name come from Greek word Chroma which means colour and Graphy means writing or recording, it is said that colour writing , during ancient days by this method only separate the mixture of colour constituents , but now a days we can separate colour and colourless components also from latest chromatography technique .
c).
Answer : Advantages of Chromatography :
- Very small sample can be separate from this technique.
- This method has high accuracy and precision.
- From this technique separate the mixture of biological origin , plants extract etc.
- More than one components in a mixture can be separate from this method .
- Qualitative and quantitative analysis can be done by this technique.
d).
Answer : Paper Chromatography is the simplest type of chromatography.
e).
Answer : The principal of chromatography method based on two phase , one is stationary phase and mobile phase.
f).
Answer : Stationary phase :
Stationary phase does not move , it remains fixed it adsorb the solute on it from the mixture. Example : silica gel , filter paper , etc.
Mobile phase :
Mobile phase run or move over the stationary phase or moving substance ( solvent ) to be separate at different rates over the stationary phase .
Example : water , ethanol , Acetic acid , Acetone , etc.
9).
a) .
Answer : Sublimation :
The process of solid convert into vapour or gas without changing into liquid through heating known as sublimation .
Example : Dry ice (carbon dioxide) , salt from Ammonium etc.
b).
Answer : Filtration :
The process of removal of solid from liquid by the use of filter medium or filter paper known as filtration , the solute ( solid ) remain in a filter known as filtration .
Example : Clay and water , Chalk and water , etc.
c).
Answer : Sedimentation :
The process of setting down of solid heavier insoluble particles from mixture ( solid- liquid) , known as sedimentation . This insoluble solid particles settle down in a mixture known as sediment .
Example : Sand and water mixture , soil and water , tea leaves in water etc.
Decantation :
The separate out or transfer a Immiscible liquid from heterogeneous mixture without disturbing the sediment which is at the bottom of this mixture known as decantation.
Example : Oil and water , sand and water , rice and water mixture etc.
d).
Answer : Solvent extraction method :
Answer : The process of separation of relatives solubility of constituent in a liquid known as solvent extraction method .
Example : Salt , Sand and water mixture
e) .
Answer : Magnetic separation :
The process of Separation of constituents by using magnetic attraction known as Magnetic separation .
Example : iron and Sulphur mixture , nails and wood powder mixture etc
f) .
Answer : Separating funnel :
Two Immiscible liquid mixture can be separate from the separating funnel .
Example : By the use of separating funnel oil and water mixture can be separate .
g).
Answer : Fractional distillation :
The process of separation of miscible liquid mixture which have variable or individual boiling point known as fractional distillation.
Example : ethanol and water mixture , , crude oil , etc.
Objective type questions
1) .
a) . ………….. is made up of same kind of atom.
Answer : Elements
b) .…………..and…………are pure substance .
Answer : Elements and compound
c) In a …………….the substance can not combine chemical .
Answer : Heterogeneous mixture
d) Clay is separate from water by a method of……………..
Answer : decantation .
e) ………………..is a process to obtain very pure from of solid dissolved in a liquid.
Answer : Crystallization
(When we give heat to the solid liquid mixture here slow evaporation occur and after some liquid evaporate , solid left behind with minimum liquid , then it get cool so liquid evaporate and pure solid crystal obtain.
f) Camphor and Ammonium chloride can be ………….
Answer : Sublimate
(Camphor and Ammonium chloride mixture can be separate from the sublimation method , when the mixture of camphor and Ammonium chloride give heat camphor is a sublime substance so camphor directly convert solid into gas or vapour , this vapour get cool environment so it again Change back to original position (solid) So in this way camphor and Ammonium chloride mixture separate by Sublimation method .)
2) .
a)
Answer : residue
b)
Answer : distillate
c)
Answer : decantation
d)
Answer : fractional distillation
Multiple choice questions
1)
Answer : b) distillation .
(A liquid convert into vapour and these vapour condensed back to pure form of liquid , this process known as distillation.)
2)
Answer : d) fractional distillation .
(Crude petroleum is a miscible , components present in it , petrol, diesel , kerosene, diesel oil, lubricating oil, fuel oil, grease wax etc can be separate by fractional distillation.)
3)
Answer : a) Tap water .
(Tap water is a homogeneous mixture because several components are present in it which is not visible or completely soluble in it .)
4)
Answer : a) stationary phase.
(Stationary phase does not move , it remains fixed it adsorb the solute on it from the mixture. So filter paper act as stationary phase because it stay fixed and adsorb the solute run on it , from the solvent.)
5)
Answer : a) ink , honey , ice cream , milk
(Ink , honey , ice cream , milk , is a set of mixture several components present in this mixture ) .