1214 + Interview Questions in Chemistry in Class 8 Page 16 InterviewSolution

751.	How are elements classified based on atomicity? Explain with example.
Answer» Solution :MONO, DI, tri, POLY atomic ELEMENTS

Discussion

752.	How are CO_2 and dust particles removed from air before subjecting air to liquefaction
Answer» SOLUTION :By passing KOH or NAOH. 'electric precipitators or FILTERS

Discussion

753.	Hold a thin long copper wire just inside the flame forabout 30 seconds Does it indicate that the non-luminouszone of the flame has a high temperature?
Answer» Answer :Yes, it indicates that the non-Iuminous ZONE of the FLAME has a HIGH TEMPERATURE.

Discussion

754.	HNO_3 on reaction with phosphorus gives
Answer» PHOSPHORUS ACID PHOSPHORIC acid METAPHOSPHORIC acid HYPOPHOSPHORIC acid Solution :`P+5HNO_3rarrH_3PO_4+5NO_2+H_2O`

Discussion

755.	Heating of methane in the absence of air is called.
Answer» combustion decarbonxylation PYROLYSIS PHOTOLYSIS Solution :Heating of methane in the ABSENCE of air is called pyrolysis.

Discussion

756.	Heating and subsequent cooling of certain substances are given below. Classify them into either physical or che1nical change. (a) Lead nitrate. (b) Uluish green copper carbonate (c) Yellow coloured Jead oxide (d) White powdered zinc oxide
Answer» Solution :Physical changes are heating of YELLOW coloured lead oxide and WHITE powdered ZINC oxide. Chemical changes are heating of lead nitrate and BLUISH green copper carbonate.

Discussion

757.	Have you heard of the campaign : "Say No To plastica". Coin a few more slogans of this kind. There are certain governmental and non-governmemtal organisations who educate the general public on how to make wise use of plastics and develop environment friendly habits. Find out organisations in your area which are carrying out awarness programmes. Of there is none, form one.
Answer» ANSWER :Some SLOGANS for conservation of environment are :(i) "ACT like you live here."(ii) "Air is nothing but LIFE, if polluted how can we survive."

Discussion

758.	Have you seen wooden bells in the temples? Can you give a reason?
Answer» ANSWER :No, we do not FIND wooden BELLS in the TEMPLES as wooden bells do not produce a metallic (SONOROUS) sound as they are non-metallic.

Discussion

759.	Have you ever noticed tea difference in sound on dropping an iron sheet // plate, a metal coin, and a piece of coal on the floor? ?If not, you can try it now. Do you note any difference in the sound produced?
Answer» ANSWER :Iron sheet /plate and a METAL COIN when DROPPED on the floor will produce a METALLIC sound,whereas a coal piece does not produce a metallic sound when dropped on the floor.

Discussion

760.	Have you noticed how rapidly the number of vehicles is increasing in our cities?
Answer» ANSWER :Yes, the NUMBER of vehicles is increasing very RAPIDLY in our cities. This is a noticeable phenomenon and the MAIN CAUSE for growing air pollution.

Discussion

761.	Hard water forms lather with soap easily.
Answer» ANSWER :F

Discussion

762.	Hard water contains compounds of.....................and ..................
Answer» ANSWER :CALCIUM, MAGNESIUM

Discussion

763.	Growth of a plant is a slow process
Answer» ANSWER :T

Discussion

764.	Growth of a seeding into a plant is a physical change.
Answer» ANSWER :F

Discussion

765.	Graphite is used in the manufacture of crucibles as it possesses high electrical resistance.
Answer» ANSWER :FALSE

Discussion

766.	Graphite is used as a solid lubricant. Give reasons.
Answer» Solution :(i) PROPERTIES of lubricants. (ii) STRUCTURE of GRAPHITE. (iii) Bonding in graphite. (IV) Melting POINT of graphite .

Discussion

767.	Graphite is used in nuclear reactor as
Answer» MODERATOR FUEL electrode lubricant. SOLUTION :Graphite is USED in NUCLEAR reactor as moderator.

Discussion

768.	Graphite is greasy, soft lubricant because it
Answer» has LOW density has weak FORCES of ATTRACTION between layers is greyish-black in colour has three dimensional structure. Solution :Graphite is greasy, SOFT lubricant BECAUE it has weakforces of attraction between layers.

Discussion

769.	Graphite fibres are used to reinforce plastic as they
Answer» have weak carbon bonds have high TENSILE strength are BRITTLE have weak forces of ATTRACTION between LAYERS. Solution :Graphite fibres are used to REINFORCE plastic as they have high tensile strength.

Discussion

770.	Graphite cannot be used as a lubricant in space because
Answer» absence of external pressure tranforms crystalline graphite to amorphousform . there is no atmosphere in sapce and HENCE graphite SUBLIMES in space. there is no atmosphere in space and hence there is no adsorbed air and WATER between layers of graphite. None of the above. Answer :C

Discussion

771.	Goldsmiths blow the outermost zone of a flame with a metallic blow-pipe for melting gold and silver . Why do they use the outermost zone of the flame?
Answer» ANSWER :The OUTERMOST zone of the flame is the hottest part, so GOLDSMITHS uses it for melting gold and SILVER.

Discussion

772.	Gold and platinum do not react with oxygen even at high temperature.
Answer» ANSWER :1

Discussion

773.	Golbal warming is mainly due to
Answer» reradiation of U.V. RAYS by `CO_(2)andH_(2)O`. reradiation of I.R. rays by `CO_(2)andH_(2)O`. reradiation of I.R. rays by`O_(2)andN_(2)`. reradiation of U.V. rays by `O_(2)andN_(2)` Answer :B

Discussion

774.	Glucose-water mixture can be separated by the method of evaporation.
Answer» ANSWER :1

Discussion

775.	Given below are three chemical equations. Study the equations and identufy the elements that show variable valency? Given reasons in support of your answer. ('M' and 'N' stand for different metals.) (i) Ms+ZnSO_4toMSO_4+ZnS (ii) 3MCl_2+N_2(SO_4)_3to3MSO_4+2NCl_3 (iii) NS+H_2SO_4toNDO_4+H_2S
Answer» Solution :(i)Calculate valency of M ANDN (metals) PRESENT in the REACTANTS and products. (ii)Valecies of M,N in their RESPECTIVE equations. (iii)Identification of the ELEMENTWITH variable valency.

Discussion

776.	Give two use of fibres.
Answer» Answer :Two use of FIBRES are :(i) These are used for MAKING fabrics from which CLOTHES are made.(ii) Fibres are also used for making a LARGE variety of husehold ARTICLES.

Discussion

777.	Give two properties and two uses of lamp black.
Answer» Solution :Light, powdery BLACK, having a relvet TOUCH. Manufacture of black CARBON PAPERS, carbon ribbons, black shoe polish.

Discussion

778.	Give two examples of substances which can be separated by the methods. (i) Fractional crystallization (ii) Sublimation (iii) Magnetic separation (iv) Gravity method (v) Filtration (vi) Distillation (vii) Diffusion (viii) Solvent extraction (ix) Dissolution in suitable solvent
Answer» Solution :(i) POTASSIUM nitrate and sodium chloride (II) Iodine and sand (iii) Nickel and lead (iv) Saw dust and sand (v) Chalk and water (vi) Salt and water (VII) Sulphur and sand (viii) CARBON dioxide and hydrogen

Discussion

779.	Give two examples for the following mixtures. (i) Solid : solid homogeneous(ii) Solid : liquid homogeneous (iii) Liquid : liquid homogeneous (v) Gas : gas homogeneous (vi) Solid : solid heterogeneous (vii) Solid : liquid heterogeneous (viii) Liquid : liquid heterogeneous
Answer» Solution :(i) Brass (II) SALT solution (iii) Soda water (iv) Water- ethylalchol (v) AIR (VI) GUN powder (vii) Sand in water (viii) Kerosene and water

Discussion

780.	Give three uses of diamond.
Answer» SOLUTION :Jewellery , delicate, operations, DEEP BORING drills.

Discussion

781.	Give the working principle involved in chromatography.
Answer» Solution :The particles of a mixture of a dye LIKE ink are soluble in water. As the water RISES on the FILTER paper, it takes ALONG with it the dye particles. Usually, a dye is a mixture of two or more colours . The coloured components that are more soluble in water, REACH to a greater height and in this way the colours get separated.

Discussion

782.	Give the uses of the folowing metals (a) Fe(b) Pb(c ) Cu(d) Zn
Answer» SOLUTION :(i) Electrical conductivity (II) ALLOYS (III) ARTICLES

Discussion

783.	Give the properties of cathode rays in comparison to the properties of canal rays.
Answer» SOLUTION :(i) CHARGE (ii) Mass (III) Path followed (IV) Deflection in electric and magneticfield (V) e/m ratio

Discussion

784.	Givethe postulates of Dalton's atomic theory.
Answer» SOLUTION :(i) INDIVISIBILITY (II) Atoms of same element-like (III) Atoms of different elements-unlike

Discussion

785.	Give the mass and charge of an electron , a proton and an neutron in kg and coulombs repectively .
Answer» SOLUTION :

Discussion

786.	Give the functions of nitrogen in the atmosphere.
Answer» Solution :DILUTES the ACTIVITY of oxygen, GROWTH of PLANTS

Discussion

787.	Give the existence of chlorine in the combined state in nature?
Answer» SOLUTION :NACL , KCL

Discussion

788.	Give the effect of acid rains.
Answer» SOLUTION :(i) CHEMICALS in ACID RAIN. (ii) Reaction of these chemicals with BUILDINGS.

Discussion

789.	Give the differences between oxidation and reduction in terms of oxygen, hydrogen, electropositive element and electronegative element.
Answer» Solution :(i) Addition or REMOVAL of hydrogen (or electropositive ELEMENT). (ii) Addition or removal of OXYGEN (or electronegative element).

Discussion

790.	Give the differences between isotopes and isobars.
Answer» SOLUTION :(i) ATOMIC NUMBER (II) MASS number

Discussion

791.	Give the differences between combustion and respiration.
Answer» Solution :(i) RATE of reaction (ii) Temperature (iii) CATALYST (IV) Energy

Discussion

792.	Give the clectronic configuration of xoygen. Also mention the period and the group to which the element belongs.
Answer» Solution :2, 4, VI A group, 2ND PERIOD.

Discussion

793.	Give the chemical properties of calcium carbide ?
Answer» Solution :(i) HYDROLYSIS of `CaC_(2)` `CaC_(2)+2H_(2)O to Ca(OH)_(2)+C_(2)H_(2)` `(ii) CaC_(2)+N_(2) to CaCN_(2)+C` Nitrolim `(iii) 2MgO+CaC_(2) to 3Mg+CuO+2COuarr`

Discussion

794.	Give the characteristics of _____________. (a) elements(b) compounds.(c ) mixtures
Answer» SOLUTION :(i) PURE substance (ii) Only one kind of ATOM (III) FIXED proportions by weight (iv) Any proportions by weight.

Discussion

795.	Give some uses of oxygen.
Answer» SOLUTION :(i) COMBUSTION (ii) METAL extraction (iii) Welding (IV) Rocket FUEL (v) Industry

Discussion

796.	Give reasons for the following. Sodium and potassium are stored in kerosene.
Answer» Answer :Sodium and potassium are stored in KEROSENE as they are highly reactive elements and have the CAPABILITY of catching FIRE EVEN when in CONTACT with air.

Discussion

797.	Give reasons for the following. Immersion rods for heating liquids are made up of metallic substances.
Answer» ANSWER :Metals being good conductors of HEAT and ELECTRICITY, can easily heat LIQUIDS. So , immersion RODS for heating liquids are made of metallic substances.

Discussion

798.	Give reasons for the following. Aluminium foils are used to wrap food items.
Answer» Answer :SINCE aluminium metal is malleable and can be beaten into SHEETS, THEREFORE aluminium foils are USED to wrap foods.

Discussion

799.	Give one example of a mixture which canbe separated using this method.
Answer» SOLUTION :MIXTURE of KEROSENE and WATER

Discussion

800.	Give examples which indicate that nylon fibres are very strong.
Answer» Answer :Nylon FIBRES are very STRONG and they are used in making many things which require HIGH tensile strength, such as :(i) ropes for ROCK climbing,(B) parachutes etc.

Discussion

Explore topic-wise InterviewSolutions in .

How are elements classified based on atomicity? Explain with example.

How are CO_2 and dust particles removed from air before subjecting air to liquefaction

Hold a thin long copper wire just inside the flame forabout 30 seconds Does it indicate that the non-luminouszone of the flame has a high temperature?

HNO_3 on reaction with phosphorus gives

Heating of methane in the absence of air is called.

Heating and subsequent cooling of certain substances are given below. Classify them into either physical or che1nical change. (a) Lead nitrate. (b) Uluish green copper carbonate (c) Yellow coloured Jead oxide (d) White powdered zinc oxide

Have you seen wooden bells in the temples? Can you give a reason?

Have you ever noticed tea difference in sound on dropping an iron sheet // plate, a metal coin, and a piece of coal on the floor? ?If not, you can try it now. Do you note any difference in the sound produced?

Have you noticed how rapidly the number of vehicles is increasing in our cities?

Hard water forms lather with soap easily.

Hard water contains compounds of.....................and ..................

Growth of a plant is a slow process

Growth of a seeding into a plant is a physical change.

Graphite is used in the manufacture of crucibles as it possesses high electrical resistance.

Graphite is used as a solid lubricant. Give reasons.

Graphite is used in nuclear reactor as

Graphite is greasy, soft lubricant because it

Graphite fibres are used to reinforce plastic as they

Graphite cannot be used as a lubricant in space because

Goldsmiths blow the outermost zone of a flame with a metallic blow-pipe for melting gold and silver . Why do they use the outermost zone of the flame?

Gold and platinum do not react with oxygen even at high temperature.

Golbal warming is mainly due to

Glucose-water mixture can be separated by the method of evaporation.

Given below are three chemical equations. Study the equations and identufy the elements that show variable valency? Given reasons in support of your answer. ('M' and 'N' stand for different metals.) (i) Ms+ZnSO_4toMSO_4+ZnS (ii) 3MCl_2+N_2(SO_4)_3to3MSO_4+2NCl_3 (iii) NS+H_2SO_4toNDO_4+H_2S

Give two use of fibres.

Give two properties and two uses of lamp black.

Give two examples of substances which can be separated by the methods. (i) Fractional crystallization (ii) Sublimation (iii) Magnetic separation (iv) Gravity method (v) Filtration (vi) Distillation (vii) Diffusion (viii) Solvent extraction (ix) Dissolution in suitable solvent

Give two examples for the following mixtures. (i) Solid : solid homogeneous(ii) Solid : liquid homogeneous (iii) Liquid : liquid homogeneous (v) Gas : gas homogeneous (vi) Solid : solid heterogeneous (vii) Solid : liquid heterogeneous (viii) Liquid : liquid heterogeneous

Give three uses of diamond.

Give the working principle involved in chromatography.

Give the uses of the folowing metals (a) Fe(b) Pb(c ) Cu(d) Zn

Give the properties of cathode rays in comparison to the properties of canal rays.

Givethe postulates of Dalton's atomic theory.

Give the mass and charge of an electron , a proton and an neutron in kg and coulombs repectively .

Give the functions of nitrogen in the atmosphere.

Give the existence of chlorine in the combined state in nature?

Give the effect of acid rains.

Give the differences between oxidation and reduction in terms of oxygen, hydrogen, electropositive element and electronegative element.

Give the differences between isotopes and isobars.

Give the differences between combustion and respiration.

Give the clectronic configuration of xoygen. Also mention the period and the group to which the element belongs.

Give the chemical properties of calcium carbide ?

Give the characteristics of _____________. (a) elements(b) compounds.(c ) mixtures

Give some uses of oxygen.

Give reasons for the following. Sodium and potassium are stored in kerosene.

Give reasons for the following. Immersion rods for heating liquids are made up of metallic substances.

Give reasons for the following. Aluminium foils are used to wrap food items.

Give one example of a mixture which canbe separated using this method.

Give examples which indicate that nylon fibres are very strong.