Class-7 Dalal Simplified Elements Compound and Mixtures ICSE Chemistry Solutions
Class-7 Dalal Simplified Elements Compound and Mixtures ICSE Chemistry Solutions Dr Viraf J Dalal Middle School Allied Publishers Solutions. Chapter-3. We Provide Step by Step Solutions of Exercise/Lesson -3 Elements Compound and Mixtures with Objective Type Questions, Fill in the blanks and Give reason , Match the following of Dr Viraf J Dalal Middle School Chemistry Allied Publishers. Visit official Website CISCE for detail information about ICSE Board Class-7.
Class-7 Dalal Simplified Elements Compound and Mixtures ICSE Chemistry Solutions Chapter-3
Differentiate between the terms elements, compounds and mixtures with suitable examples.
It is the basic unit of matter, which cannot be broken down into substances by any way but can be combined to form new substances.It is a pure substance.It classifies into metals, non-metals, metalloids and noble gases.
Example -Chlorine, Nickle, Gold
It is a combination of two or more elements.It is a pure substance.Through chemical reactions, they can be broken down into metals.
Example – Sugar, petrolium
It is a combination of two or more elements or compounds or both.The substances combined in a mixture are in a particular ratio.
Example – Milk, Alloy
State which element exists in the highest percentage in –
(a) earth’s crust
(c) human body.
(a) Oxygen (O) — 46.1%
(b) Nitrogen (N) — 78%
(c) Oxygen (O) — 65%
Elements are mainly classified into metals and non-metals. State six properties of metals which differ from non-metals.
Properties of Metals:
- They are lustrous, i.e. they shine.
- They are ductile, i.e. they can be drawn into wires.
- They are good conductors of heat and electricity.
- They have high density.
- They have high melting and boiling points.
- They are malleable, i.e. they can be drawn into sheets.
Properties of Non-Metals:
- They are non-lustrous, hence they do not shine.
- They are non-ductile, cannot be drawn into wires.
- They are bad conductors of heat and electricity.
- They have low density.
- They have low melting and boiling points.
- They are non-malleable, therefore they cannot be beaten into sheets.
Give the symbols of the following elements – and state in each case whether they are metals, non-metals, metalloids or noble gases.
|(f) Neon||Ne||Noble Gas|
|(l) Xenon||Xe||Noble Gas|
|(q) Neon||Ne||Noble Gas|
|(w) Radon||Rn||Noble Gas|
State what is meant by the term ‘activity series of metals’. State the most reactive and the least reactive metal from the following – Zn, Ag, Na, Fe, Cu, Pb.
Activity series of metals:-Activity series is a series of arrangement of metals in decreasing order of their reactivity
The most reactive metal is Na. while The least reactive metals from above option is Ag,
Give three reasons why – carbon dioxide is considered a compound, while carbon – an element.
Carbon (C) is an element and Carbon dioxide C02 constitutes of carbon and oxygen which are both independent elements combined together in a fixed ratio to form carbon dioxide C02. Carbon (C) is combustible and oxygen (O) supports combustion, but carbon dioxide C02 extinguishes fire.
State what information is provided by the formula of calcium hydroxide – Ca(OH)2
Four atoms of hydrogen combine with one atom of carbon to give methane [CH4]. State the valency of carbon.
Methane is formed by the combination of four hydrogen atoms and one carbon atom where valency of hydrogen is 1 and valency of carbon is 4.
Write the symbols of the following elements and radicals along with their valencies.
(c) Chlorine [Chloride]
(h) Sulphur [Sulphide]
(i) Bromine [Bromide]
(p) Iodine [Iodide]
Valency list: (i) 1+ (ii) +2, (iii) +3, (iv) -1, (v) -2-(vi) -3
Write the chemical formula
(a) magnesium oxide
(b) Sodium bromide
(c) calcium sulphide
(d) magnesium sulphate
(e) aluminium chloride
(f) zinc oxide
(g) calcium carbonate.
(d) Mg SO4
Give the formulas of the following acids:
(d) carbonic — acid.
(a) Hydrochloric — HCI
(b) Nitric —HNO3
(c) Sulphuric —H2SO4
(d) Carbonic acid —H2CO3
Give the formulas of the following gases:
(a) hydrogen chloride
(c) carbon monoxide
(d) nitric oxide
(e) nitrous oxide
(f) nitrogen dioxide
(h) sulphur dioxide
(a) hydrogen chloride — HCI
(b) ammonia — NH3
(c) carbon monoxide— CO
(d) nitric oxide— NO
(e) nitrous oxide — ..N2O…
(f) nitrogen dioxide — NO2
(g) nitrogen – N2
(h) sulphur dioxide— SO2
Explain the term mixture. Differentiate between a homogenous and a heterogeneous mixture with one example of each in the
(c) liquid-liquid state of the mixture.
Substances made up of two or more elements / compounds or both, mixed together in any proportion are called mixtures.
Examples – Air, Smoke, milk and sugar
|Homogeneous Mixture||Heterogeneous mixture|
|The constituents are uniformly mixed in a homogeneous mixture.||The constituents are not mixed uniformly in a heterogeneous mixture.|
|The properties and composition are uniform throughout the mixture.||The properties and composition vary throughout the mixture.|
|Example – (i) Solid-solid – Alloys (ii) Solid-liquid – Sugar solution, (iii) Liquid-liquid – Alcohol & Water||Examples – (i) Solid-solid – Iron & Sulphur (ii) Solid-liquid – Sand & Water (iii) Liquid-liquid – Oil & Water|
State four differences between – elements, compounds and mixtures with suitable examples.
|They are pure substances which have only one kind of atom, like Na, H, O, Cl||They are pure substances that may or may not have one kind of atom. Example – H2O||They are impure substances made up of two or more elements or compounds. Example – Iron & Sulphur mixture.|
|They have properties different from compounds they make. Example – Hydrogen & oxygen are combustible, but water is not.||They have properties different from elements that they are made of. Example – Hydrogen and Oxygen are gases, but they make up water which is liquid.||They do not have definite properties, they retain properties of their components.|
|They cannot be broken down further, they are the basic unit.||They can be broken down, but only chemically.||They can be separated physically.|
|The atoms of elements exist independently.||The components when combined chemically in a definite proportion can exist independently.||The components exist independently.|
State the correct technique for separation of the following mixtures.
(a) a sublimable solid and a non-sublimable solid.
(b) a liquid component from soluble impurities in the liquid component.
(c) a lighter liquid from a heavier liquid.
(d) a low boiling point liquid from a high boiling point liquid.
(e) solid constituents in a liquid constituent by adsorption.
(c) Separating funnel
(d) Fractional distillation
(a) The principle involved in separation of the mixture
(b) The technique of separation for each of the following mixtures.
(1) Naphthalene and sodium chloride
(2) Common salt from a solution of common salt in water
(3) Pure water from impure water
(4) Kerosene and water
(5) Methyl alcohol and water
(6)Dyes of an ink
(1) By Sublimation
Principle – The process of conversion of solid directly into gaseous state and back to solid without passing through the liquid state.
Sublimable solid changes into vapour on heating and the non-sublimable solid is left behind, and they are separated.
Technique – Naphthalene and sodium chloride are heated in a dish and a funnel is kept over it, after some time naphthalene evaporates and turns into vapour which is seen on the walls of the funnel. Sodium chloride is left behind, and the mixture is separated.
(2) By Evaporation
Principle – Evaporation is the process of conversion of liquid component to its gaseous state by heating.
Technique – In a salt solution, water evaporates on heating and salt crystals are left behind in the dish.
(3) By Distillation
Principle – The process of separating two liquids by heating and converting into vapour in a distillation flask and its condensation of the vapour back into the liquid.
Technique – the mixture is kept in a distillation flask and the flask is heated. The liquid or the pure water vaporises and the impurities are left behind in the flask.
(4) By Separating funnel
Principle – The method used to separate two immiscible liquids, out of which one is heavy and the other is light.
Technique – The mixture of kerosene and water is kept in a funnel. The heavier liquid that is water settles down in the funnel and removed by opening the tap at the bottom. The lighter liquid, i.e. kerosene remains in the funnel.
(5) By Fractional Distillation
Principle – The process of separating two miscible liquids with different boiling points.
Technique – The mixture of alcohol and water is kept in a distillation flask and heated slowly, the liquid which has a lower boiling point evaporates and collects in the receiver after condensation in the Leibigs condenser,
The fractionating column separates the vapours of other liquid to condense, keeping the two separated.
(6) By Chromatography
Principle – It is a method of separating the various components of a mixture by their difference in rate of flow over an absorbent medium.
Technique – Ink spots contain different solid constituents. It is kept on the filter paper. The lower end of filter paper is dipped in the solvent and hung. The solvent flows over the ink spot and the dyes separate out.
Objective Type Questions
Elements Compound and Mixtures Class-7 Dalal ICSE New Simplified Dr Viraf J Dalal Middle School Allied Publishers Solutions. Chapter-3
- An element present in the earth’s crust, atmosphere and human body.
- The chemical name for dinitrogen oxide (N2O).
- A compound containing carbon, oxygen and calcium.
- A metalloid
- A non-metal which exists in the liquid state.
- B: Oxygen
- E: Nitrous oxide
- A: Chalk
- C: Silicon
- D: Bromine
Select the correct answer from the choice in bracket.
- The least reactive metal, [magnesium/silver/copper]
- The positively charged particle of an atom, [electron/proton/neutron]
- The formula of caustic soda. [KOH/Ca(OH)/NaOH]
- The ideal method to separate iodine and KCl. [sublimation/evaporation/distillation]
- A homogeneous mixture, [brass/dust in air/ chalk and water]
Match the ideal method of separation of components in a mixture in List I with the – appropriate process in List II.
|List I||List II|
|1. Sand from a mixture of sand and water||A: Separating funnel|
|2. Kerosene from a mixture of kerosene and water||B: Sublimation|
|3. Alcohol from a mixture of methyl alcohol and water||C: Filtration|
|4. Naphthalene from a mixture of naphthalene and lead chloride||D: Distillation|
|5. Pure water from impure water||E: Fractional distillation|
|List I||List II|
|1. Sand from a mixture of sand and water||C: Filtration|
|2. Kerosene from a mixture of kerosene and water||A: Separating funnel|
|3. Alcohol from a mixture of methyl alcohol and water||E: Fractional distillation|
|4. Naphthalene from a mixture of naphthalene and lead chloride||B: Sublimation|
|5. Pure water from impure water||D: Distillation|
Give reasons for the following statements :
- If fractional distillation is carried out using a liquid-liquid mixture, one liquid will remain in the flask and the other will be collected in the receiver.
- Evaporation of a common salt solution or sea water, leaves behind common salt inside the evaporating dish after heating.
- Components in a mixture are present in varying proportions and not in a fixed proportion.
- Gunpowder is an example of a heterogeneous mixture.
- In chromatography, the absorbent medium e.g. what man filter is known as the stationary phase.
- The liquid with low boiling point vaporises first and is collected in the receiver and the higher boiling point component is left behind.
- The pure water from the solution evaporates and the vapours are lost on heating, hence the salt is left behind in the dish.
- Mixtures are impure substances made up of two or more elements or compounds or both, mixed together in any proportion.
- The components of gunpowder are mixed in any proportion by weight and are not uniform.
- Chromatography is the method of separating the various components of a mixture by their difference in rate of flow over an absorbent medium where what man filter is known as the stationary phase because it stays fixed inside the column.
Name the following:
- The non-sublimable solid from a mixture of iodine and potassium nitrate.
- The heavier liquid component from mercury and water.
- The lower boiling point component from methyl alcohol and water.
- The compound containing one atom of sulphur and two atoms of oxygen.
- An acid whose formula is ‘H2C03’.
- Potassium nitrate
- Methyl alcohol
- Sulphur dioxide
- Carbonic acid
– : End of Elements Compound and Mixtures Class-7 Dalal Simplified Solutions :–
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