1214 + Interview Questions in Chemistry in Class 8 Page 4 InterviewSolution

151.	Water freezing into into ice is a physical change.
Answer» ANSWER :T

Discussion

152.	What is polyester?
Answer» Answer :POLYESTER is synthetic FIBRE made from wrickles. That is why, it is widely USED for dress MATERIAL.

Discussion

153.	Write short note on gas carbon.
Answer» SOLUTION :(i) Destructive distillation of COAL. (ii) Electrodes (iii) CONDUCTION

Discussion

154.	What is the difference between synthesis and analysis?
Answer» SOLUTION :Synthesis-Combination of SUBSTANCES forminga SINGLE SUBSTANCE. Analysis-Decomposition of a single substance to formor more substances.

Discussion

155.	Which of the following allotropes of carbon is used for the manufacture of fullerenes ?
Answer» GRAPHITE DIAMOND COKE CHARCOAL. ANSWER :A

Discussion

156.	What do you mean by hydrated salt ? Give an example.
Answer» Solution :The salts which CONTAIN water of crystallizatione.g., `CuSO_(4), 5H_(2)O`

Discussion

157.	What is rayon?
Answer» Answer :A fibre obtained by chemical TREATMENT of WOODPULP is KNOWN as rayon or articial silk.

Discussion

158.	Tick true/false against the following statements. Fossil fuels can be made in the laboratory.
Answer» ANSWER :F

Discussion

159.	What is rayon or artificial silk? Silk its main characteristics?
Answer» ANSWER :rayon or ARTIFICIAL silk is a man-made firbe obtained artificially by CHEMICAL treatment of a natural SOURCE- wood PULP.

Discussion

160.	Which of the following plastics can be recycled?
Answer» Melamine POLYETHYLENE BAKELITE Both (1) and (2) Solution :Since polyethylene is_ thermoplastic it can be recycled

Discussion

161.	The reverse reaction of neutralization is ___________ .
Answer» ANSWER :HYDROLYSIS

Discussion

162.	What is a decomposition reaction? Explain different decomposition reactions with equations.
Answer» Solution :(i) SPLITTING of COMPOUND (ii) TWO or more PRODUCTS

Discussion

163.	What is a fuel?
Answer» Answer :Substances which burns to produce considerable AMOUNT of heat without LEAVING behind undesirable products is known as fuel. It exists in THREE FORMS solid (coal, wood), LIQUID (diesel, petrol) and gas (LPG, biogas).

Discussion

164.	What happens when iron is subjected to strong heating with oxygen?
Answer» SOLUTION :Ferrosferric OXIDE is FORMED.

Discussion

165.	You might know of some other examples from your area regarding reduction of air pollution. Share these with your friends.
Answer» ANSWER :STUDENTS SHALL do themselves.

Discussion

166.	Which of the following metals does not react with O2 even at high temperauter?
Answer» Magnesium Iron Aluminium GOLD Solution :Gold and platinum are the two METALS which do not react with oxygen even at a HIGHER TEMPERATURE.

Discussion

167.	""_(x)^(y)A, _(x)^(y+1)A are two isotopes of element A. Difference between number of neutrons in the isotopes is
Answer» 1-2y 1-x 1 2x-1 Answer :C

Discussion

168.	Which among the following set of elements contain same number of valence electrons?
Answer» `""_(11)^(23)X,""_(20)^(40)Y` `""_(10)^(20)X,""_(19)^(39)Y` `""_(11)^(23)X,""_(19)^(39)Y` `""_(18)^(40)X,""_(26)^(40)Y` Solution :`""_(11)^(23)X,""_(19)^(39)Y` have ONE valence electron as they are sodium and potassium with electronic arrangements2,8,1 and 2,8,8,1 RESPECTIVELY.

Discussion

169.	What are solubility curves ? Explain different areas of applications ofsolubility curves.
Answer» SOLUTION :(i) Graph (ii) SOLUBILITY (iii) Temperature (iv) State of SOLUTE (V) Comparison

Discussion

170.	What happens when steam is passed over hot magnesium metal /
Answer» SOLUTION :`MG + H_(2)O to MGO + H_(2)`

Discussion

171.	Why are tin coated iron cans used for cool drinks but not cans. Explain.
Answer» SOLUTION :(i) Comparison of reactiveties of iron, tin with the component (metal) used for galvanization. (II) Changes that take place in the food KEPT in the galvanized container. (iii) EFFECT of the REACTIVITY of tin on the food content.

Discussion

172.	What happens when coal is heated in air ?
Answer» ANSWER :when COAL is heated in AIR, it BURNS and produces carbon di oxide gas

Discussion

173.	What are the products of combustion of carbon compounds?
Answer» ANSWER :`CO_(2),H_(2)O`

Discussion

174.	When magnesium ribbon burns in air to form magnesium oxide, it is a ………………… reaction.
Answer» SOLUTION :COMBINATION

Discussion

175.	What is the formula of hydrated blue copper sulphate crystal?
Answer» `CuSO_(4).5H_(2)O` `CuSO_(4).6H_(2)O` `CuSO_(4).7H_(2)O` `CusO_(4).8H_(2)O` ANSWER :A

Discussion

176.	What percentage of the world's population is without safe drinking water?
Answer» Answer :25 PER CENT of the world's POPULATION is without SAFE DRINKING water.

Discussion

177.	When electric field is applied, the cathod rays bend towards _____ .
Answer» SOLUTION :ANODE (POSITIVE TERMINAL)

Discussion

178.	Tropospheric atmosphere is turbulent. Which of the following reasons can be attributed to this?
Answer» Convectional CURRENT of air RISES up due to HIGH temperature in lower layers of the earth. Temperature changes result in change in air pressure. More effect of centrifugal force is more in this layer. None of these Answer :A::C

Discussion

179.	Which of the following can be considered as spontaneous combustion?
Answer» BURNING of LPG Burning of MAGNESIUM ribbon Burning of camphor Burning of WHITE phosphorus Solution :Spontaneous combustion is the burning of a substance at ROOM TEMPERATURE. White phosphorus burns at room temperature.

Discussion

180.	Which of the following metals liberates hydrogen when it is treated with Very dilute HNO_3 ?
Answer» Cu Zn Mg Fe Solution :`Mg+2HNO_3rarrMg(NO_3)+H_2uarr`

Discussion

181.	Tick true/false against the following statements. CNG is more polluting fuel than petrol
Answer» ANSWER :F

Discussion

182.	Which atomic particle has negligible mass?
Answer» PROTON electron NEUTRON both proton and neutron ANSWER :B

Discussion

183.	Write the main postulates of the kinetic molecular theory ?
Answer» Solution :(i) Constituents of MATTER. (ii) INTERMOLECULAR spaces (III) Intermolecular force of attractions. (iv) KINETIC ENERGY and temperature.

Discussion

184.	What is an alpha-particle ?
Answer» SOLUTION :DOUBLY ionised He ATOM

Discussion

185.	What is hot water?
Answer» ANSWER :HOT water refers to the water COMING from power plants and industries. These are released into the rivers and act as pollutants. It adversely affects the acquatic ANIMALS and plants by raising the TEMPERATURE of the water bodies.

Discussion

186.	Under what conditions, oxygen and hydrogen react with each other?
Answer» ANSWER :ELECTRIC SPARK

Discussion

187.	Two students A and B were asked to carry out one experiment. The smoke released due to the burning of candle should be passed through lime water and anhydrous copper sulphate to prove the release of CO_(2)andH_(2)O respectively due to the burning of the candle. 'A' first passed the gases through lime water and then through copper sulphate whereas 'B' did it the other way round. The Teacher commented that the set up used by 'A' was wrong. What could be the reason for it?
Answer» Solution :The PRODUCTS of the combusiton of a candle (MIXTURE of hydrocarbons) are `CO_(2)` and water vapoure. `CO_(2)` can be detected by passing it through lime water which TURNS milky. `H_(2)O` can be detected by passing it through anhydrous `CuSO_(4)` which turns blue. After passing it through anhydrous `CuSO_(4)` first, `H_(2)O` is removed and only `CO_(2)` will be passed through lime water. If the process is reversed, then `CO_(2)` will be absorbed in lime water and water vapour gets condensed. Hence colour of anhydrous `CuSO_(4)` remains unchanged.

Discussion

188.	Thomoson could successfully explain the electrical neutrality of an atom.
Answer» ANSWER :1

Discussion

189.	What are the conditions maintained in a discharge tube for the generation of cathode ray ?
Answer» SOLUTION :HIGH VOLTAGE and LOW PRESSURE

Discussion

190.	Under high pressure , gas changes to liquid state.
Answer» ANSWER :T

Discussion

191.	Under which condition does Bunsen burner produce a luminous flame and a non-luminous Harne? Give reasons in support of your answer.
Answer» SOLUTION :(i) Difference between luminous and nonluminous FLAME. (II) REACTIONS taking place in luminous and non luminous flame. (iii)Conditions REQUIRED for these reactions.

Discussion

192.	Thermosphere is associated with high temperature due to the absorption of ______.
Answer» SOLUTION :Internse SOLAR RADIATION

Discussion

193.	What are the major and minor plant nutrients? Give three examples for each
Answer» SOLUTION :The NUTRIENTS which are required in large and SMALL QUANTITIES respectively

Discussion

194.	To a small quantity of X, few drops of HCl are added. A colourless, odourless gas is produced. This gas on passing through lime water turns it milky proving the presence of _______ in X.
Answer» carbonate bicarbonate carbide Either (1) or (2) Solution :To a SMALL quantity of X few drops of HCl are added, a colouless, odourless gas is produced. This gas on PASSING through lime WATER TURNS it milky providing the presence of carbonate and bicarbonate is X.

Discussion

195.	The use of diamond as a gem is due to its
Answer» extreme hardness poor conductance low density high refractive INDEX. SOLUTION :The USE of diamond as a gem is due to its high refractive index.

Discussion

196.	Total number of electrons present in the penultimate shell of an element with atomic number 36 is
Answer» 18 10 8 16 Answer :A::C

Discussion

197.	The surface of the electric bulb with a tungsten filament becomes greyish black after being used for a long period of time. Explain the reason.
Answer» SOLUTION :CHANGE in STATE.

Discussion

198.	Write the electronic arrangment for the following elements. Also give the geometrical representations. (a) Oxgyen(b) Argon(c) Calcium(d) Potassium
Answer» SOLUTION :Conclusions : (i) ATOM to be empty (ii) NUCLEUS

Discussion

199.	Which zone of a flame does a goldsmith use for melting gold and silver and why?
Answer» Answer :The OUTERMOST PART/zone of the flame is used by the GOLDSMITH to MELT gold and silver as this is the hottest part of the flame and it undergoes COMPLETE combustion.

Discussion

200.	Which among the following is not a suspension ?
Answer» IODINE in POTASSIUM iodide Fog Paints Aerosol sprays Answer :A::C

Discussion

Explore topic-wise InterviewSolutions in .

Water freezing into into ice is a physical change.

What is polyester?

Write short note on gas carbon.

What is the difference between synthesis and analysis?

Which of the following allotropes of carbon is used for the manufacture of fullerenes ?

What do you mean by hydrated salt ? Give an example.

What is rayon?

Tick true/false against the following statements. Fossil fuels can be made in the laboratory.

What is rayon or artificial silk? Silk its main characteristics?

Which of the following plastics can be recycled?

The reverse reaction of neutralization is ___________ .

What is a decomposition reaction? Explain different decomposition reactions with equations.

What is a fuel?

What happens when iron is subjected to strong heating with oxygen?

You might know of some other examples from your area regarding reduction of air pollution. Share these with your friends.

Which of the following metals does not react with O2 even at high temperauter?

""_(x)^(y)A, _(x)^(y+1)A are two isotopes of element A. Difference between number of neutrons in the isotopes is

Which among the following set of elements contain same number of valence electrons?

What are solubility curves ? Explain different areas of applications ofsolubility curves.

What happens when steam is passed over hot magnesium metal /

Why are tin coated iron cans used for cool drinks but not cans. Explain.

What happens when coal is heated in air ?

What are the products of combustion of carbon compounds?

When magnesium ribbon burns in air to form magnesium oxide, it is a ………………… reaction.

What is the formula of hydrated blue copper sulphate crystal?

What percentage of the world's population is without safe drinking water?

When electric field is applied, the cathod rays bend towards _____ .

Tropospheric atmosphere is turbulent. Which of the following reasons can be attributed to this?

Which of the following can be considered as spontaneous combustion?

Which of the following metals liberates hydrogen when it is treated with Very dilute HNO_3 ?

Tick true/false against the following statements. CNG is more polluting fuel than petrol

Which atomic particle has negligible mass?

Write the main postulates of the kinetic molecular theory ?

What is an alpha-particle ?

What is hot water?

Under what conditions, oxygen and hydrogen react with each other?

Thomoson could successfully explain the electrical neutrality of an atom.

What are the conditions maintained in a discharge tube for the generation of cathode ray ?

Under high pressure , gas changes to liquid state.

Under which condition does Bunsen burner produce a luminous flame and a non-luminous Harne? Give reasons in support of your answer.

Thermosphere is associated with high temperature due to the absorption of ______.

What are the major and minor plant nutrients? Give three examples for each

To a small quantity of X, few drops of HCl are added. A colourless, odourless gas is produced. This gas on passing through lime water turns it milky proving the presence of _______ in X.

The use of diamond as a gem is due to its

Total number of electrons present in the penultimate shell of an element with atomic number 36 is

The surface of the electric bulb with a tungsten filament becomes greyish black after being used for a long period of time. Explain the reason.

Write the electronic arrangment for the following elements. Also give the geometrical representations. (a) Oxgyen(b) Argon(c) Calcium(d) Potassium

Which zone of a flame does a goldsmith use for melting gold and silver and why?

Which among the following is not a suspension ?