1214 + Interview Questions in Chemistry in Class 8 Page 10 InterviewSolution

451.	Solids can change into liquids on increasing the temperature.
Answer» ANSWER :T

Discussion

452.	Soil is a ................. mixture, while ice cream is a .................. mixture. (homogeneous/heterogeneous)
Answer» SOLUTION :HETEROGENEOUS, HOMOGENEOUS

Discussion

453.	Hard water is not good for washing and industrial purposes.
Answer» ANSWER :F

Discussion

454.	Sodium is a very reactive metal.
Answer» ANSWER :1

Discussion

455.	Sodium catches fire and burns with a
Answer» lilac flame GOLDEN yellow flame blue flame green flame Solution :Sodium CATCHES FIRE and BURS with a golden yellow flame.

Discussion

456.	Slaked hme 0n reaction with ammonium chloride gives
Answer» calcmrn HYDROXIDE and AMMONIA CALCIUM hydroxide and nitrogen calcmm chlonde and nitrogen DIOXIDE calcium chloride and ammonia Solution :`Ca(OH)_2+2NH_4ClrarrCaCl_2+2NH_3+2H_2O`

Discussion

457.	Skating on ice is almost impossible at very low temperatures say at arround -30^(@)C. Why?
Answer» Solution :SKATING on ice is possible because as ice contracts on melting. So on APPLYING pressure the melting point of ice decreases and the ice below the seates starts to MELT and because of the FORMATION of thin water film skating is possible on theice But when temperature is arround `-30^(@)C` , the pressure exerted by body mass is not SUFFICIENT to melt the ice below the skates. Hence skating on ice is not possible at around `-30^(@)C`.

Discussion

458.	Single displacement reaction is also known as a ……………… reaction.
Answer» SOLUTION :SUBSTITUTION

Discussion

459.	Since we do not ass any change in be sike2- C, we can infer that copper is not able to replace wine from zinc sulphate. But why? When zinc can replace copper in beaker 'A' why cannot copper replace zinc in beaker'C'?
Answer» Answer :Copper cannot REPLACE zinc in BEAKER'C' because according to the rules of SCIENCE, a more reactive METAL can replace a less reactive metal, but a less reactive metal cannot replace a more reactive metal.

Discussion

460.	Silver tarnishes due to the formation of __________
Answer» oxide layer. sulphide layer. NITRIDE layer. HYDRIDE layer. Answer :B::C

Discussion

461.	Silver, gold and platinum are called noble metals because __________.
Answer» these are costly these are PRECIOUS these have very LESS REACTIVITY All the above Answer :C

Discussion

462.	Silk fibre obtained from silkworm was first discovered in _______
Answer» ANSWER :D

Discussion

463.	Silica gel is a hygroscopic substance.
Answer» ANSWER :F

Discussion

464.	Show the reaction of sulphur dioxide with water.
Answer» Answer :SULPHUR dioxide reacts with WATER producing SULPHUROUS ACID. `SO_2+H_2O->H_2SO_3`

Discussion

465.	Should the handle and bristles of a toothbrush be made of the same mateerial? Explain your answer.
Answer» Answer :Yes, the HANDLE and bristles of a TOOTHBRUSH should be made of the same MATERIAL, i.e. plastic. HOWEVER, the nature and type of plastic material used in the handle and bristles shoud be different.

Discussion

466.	Shell closest to the nucleus carries the Lowest amount of energy.
Answer» ANSWER :F

Discussion

467.	Scientist who proposed that atoms can neither be created nor destroyed.
Answer» SOLUTION :JOHN DALTON

Discussion

468.	Sam and his family went to watch a Hollywood movie in which the hero along with his friends rescues 76 people trappped in mines were poisonous gas was being released. During the process, gas masks containing wood carcoal were given to the people. In the movie the , hero adn his friends were research students in the nearby university. Sam asked his scientist father the role of wood charcoal in gas masks. Write the scientis explanation on the above.
Answer» Solution :WOOD charcoal has good adsorbing CAPACITY. Inareas where the inhaled air contains harmful gases, gas MASKS CONTAINING wood charcoal are used to adsorb these gases. The charcoal in the gas masks adsorbs these gases and the pure air enters the respiratory track.

Discussion

469.	Salts with water of crystallization are called _____ salts.
Answer» ANSWER :HYDRATED

Discussion

470.	S. I. unit of atmospheric pressure is _______
Answer» ANSWER :PASCAL

Discussion

471.	Rutherford's theory assumed which of the following paths for the electron ?
Answer» Spherical Circular Spiral Not defined Solution :According to RUTHERFORD electrons REVOLVE in CERTAIN paths AROUND the nucleus.

Discussion

472.	Rutherford's alpha-ray scattering experiment was conducted in order to test the validity of Thomsom's model. What results were expected from this experiment ?
Answer» SOLUTION :(i) Basic CONCEPT of AOTM in THOMSON's model (ii) Nature of `alpha` particles (iii) Effect of bombardment of `alpha` particles with atom (according to Thomson)

Discussion

473.	Rutherford's alpha-ray scattering experiment led to the discovery of the nucleus and to the conclusion that an atom consists of large empty space. Arrange the following steps in sequence which explains the experiment and also the above mentioned conclusions. (a) To make out the observations a spherical ZnS screen was placed surrounding the gold foil. (b) The substance which acts as a source of alpha-particles is taken in a lead container and made to pass through a slit between like charged positive plates. (c)It was observed that most of the particles passed straight through the gold foil, few were deflected through small angles and very few through large angles. Very very few completely rebounded . (d) A narrow, condensed beam consisting of alpha-particles is made ot bombard on a thin a gold foil.
Answer» a c b d b c a d d b a c b d a c Solution :(i) Radioactive substance which acts as a source of `alpha`-particle is taken in a lead container and MADE to pass through a slit between like charged POSITIVE plates. (ii) A NARROW, condensed BEAM consisting of `alpha`-particle are made to collide a thin gold foil. (iii) To make out observation a spherical ZnS Screen was PLACED surrounding the gold foil. (iv) It was observed that most of the particles passed straight through the gold foil, few were deflected through small angles and very few through large angles .Very few were completely rebounded.

Discussion

474.	Rusting of iron is a……………. Change while freezing of water is a ……….. Change.
Answer» SOLUTION :CHEMICAL, PHYSICAL

Discussion

475.	Ripening of fruits is a chemical change
Answer» ANSWER :T

Discussion

476.	Rimijhim was dreaming in the morning that she went to a planet Pandora and in the atomosphere of Pandora there is no water vapour. Suddenly she woke up and started thinking what would happen if earth's atmosphere loses water vapour completely. Rimjhim was really worried. Can you find out the reason for Rimijhim's worry?
Answer» Solution :Water vapour present in the atmosphere FORMS clouds that results in rains. Rain water is the MAIN source of drinking water and is used for irrigation. If there are no rains, DROUGHT prevails. Life in the desert regions is very difficult as water vapour in the atmosphere here is very LOW. Water vapour also controls the EXCESSIVE evaporation of water from living cells.

Discussion

477.	Removing the top layer of water in an insoluble solid-liquid mixture is called
Answer» filtration decantation sedimentation sieving ANSWER :B

Discussion

478.	Removal of CO_2andH_2O from atmospheric air using KOH and anhydrous CaCl_2 is an example of _______ and _______ changes repectively.
Answer» CHEMICAL, chemical physical, physical chemical, physical physical, chemical Answer :C

Discussion

479.	Rekha and Lekha took two fresh red roses and kept them in two containers A and B into which anhydride of sulphurous acid and a greenish yellow coloured gas are passed respectively. After a few minutes these two roses lose their colour but on being exposed to the atmosphere, it was observed that Rekha' s rose regained its colour but Lekha' s rose did not. How do you account for the above changes?
Answer» SOLUTION :ANHYDRIDE of sulphrous ACID is `SO_2` When the TWO fresh red roses are exposed to , `SO_2` and `Cl_2` the roses fade away as both `CO_2`and `Cl_2` act as bleaching agents. Once thesetwo roses are exposed again to air, one of the roses Which is bleached by `SO_2` in jar A regainsits colour.This is due to the reason that `SO_2` bleaches by reduction and once the rose is exposed to air oxidation takes place. However, `Cl_2` bleaches by oxidation

Discussion

480.	Redistillation of nitric acid is carried out in a ferrosilicon vessel but not in an iron vessel. Explain.
Answer» Solution :Nitric acid is a STRONG oxidizing agent. It reacts with IRON to form ferric OXIDE. Ferrosilicon, an alloy of iron is less reactive when compared to iron and does not react with nitric acid. THUS the REDISTILLATION is carried out in a ferrosilicon vessel.

Discussion

481.	Reaction: Non-metal +H_(2) A A+PbO to Pb- Non-metal If 'A' formed in the above reaction has rotten egg smell, identity the non-metal
Answer» N P S O Answer :C

Discussion

482.	Reaction in which one of the products is water.
Answer» PRECIPITATION reaction decomposition reaction neutralizaion reaction SINGLE DISPLACEMENT reaction Answer :C

Discussion

483.	Reaction in which a great amount of energy is released to form new bonds.
Answer» SOLUTION :EXOTHERMIC REACTION

Discussion

484.	Reaction between two compounds to form a new compound.
Answer» combination decomposition single displacement double displacement Answer :A

Discussion

485.	Reaction between barium chloride and aluminium sulphate is an example of
Answer» NEUTRALISATION REACTION displacement reaction precipitation reaction. combination reaction. Solution :`3BaCl_2+Al_2(SO_4)_3to3BaSO_4+2AlCl_3` The above reaction is an example of percipitation reaction beacause in this CASE we will GET `BaSO_4` as PRECIPITATE.

Discussion

486.	Reaction between a base and a acid to form salt and water is known as a ………………
Answer» SOLUTION :NEUTRALIZATION REACTION or DOUBLE DISPLACEMENT reaction

Discussion

487.	Reaction : 2CaO+C to CaC_(2)+2CO 2CaC_(2)+ 2H_(2)O to A+B If A is involved in the neutralisation reaction with acid, then B may be
Answer» `CH_(4)` `C_(2)H_(2)` `Ca(OH)_(2)` `CaH_(2)` Answer :B

Discussion

488.	Rcinoval of CO_2 and H_2O from atmospheric air by using KOH and anhydrous CaCl_2 is an example _________ and __________ changes respectively.
Answer» chcmical, CHEMICAL PHYSICAL, physical chemical, physical physical, chemical Solution :By passing atmospheric AIR through KOH it will reacts with `CO_2` and forms `K_2CO_3` and `H_2O` which is an ACID base or neutralidation reaction. It is an example of chemical change. `CaCl_2` will ABSORB the water vapour from the atmospheric air. So it is an example of physical change.

Discussion

489.	Rate of evaporation is increased by increasing ________ and _________.
Answer» ANSWER :TEMPERATURE and SURFACE AREA

Discussion

490.	Ranchu' s father is working in a fertilizer industry. One day at home he heard his father making suggestion to his colleague thatbetween nitrate salts and ammonium salts, nitrate salts are preferable for use as a fertilizer .The next day Ranchu asked his brother the reason for their father' s suggestion. What answer did his brother give
Answer» Solution :oth nitrate salts and ammonium SALTSA re HIGHLY SOLUBLE in water and provide nitrogen to the soils. However, plants can take in and use nitrogen only in the form of NITRATES. Nitrate salts when added to soils can be immediately made available for the plants.Ammonium saltsc annot be directly taken in by the plants.Ammonium IONS have to be first converted to nitrate ions and only then they are made available to the plants.Therefore, ammonium salts supply nitmgen after a long time whereas nitrate salts serve the immediate requirement of the plants

Discussion

491.	Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic maerial? Advise Rana, giving your reason.
Answer» Answer :Rana should BUY COTTON shirts for summer instead of shirts MADE from synthetic MATERIAL.

Discussion

492.	Rain water does not leave any scales on boiling. Give reason.
Answer» SOLUTION :SINCE the rain water is pure it does not have any dissolved salts PRESENT in it . So it does not leave any scales on boiling.

Discussion

493.	Rain water and tap water are boiled in metallic containers A and B . The containers are emptied and then rain water samples are subjected to boilingin the same containers. In which case boiling gets delayed ? Give reason in support of your answer.
Answer» SOLUTION :(i) Components present in RAIN WATER and tap water (ii) EFFECT of constituents on metallic containers due to boiling. (iii)CHANGES that takes place in metallic containers due to boiling. (iv) Changes that are observed with respect to boiling when rain water is again taken in containers.

Discussion

494.	Rain water is found to contain more percentage of oxygen than ordinary water. Explain.
Answer» Solution :RAIN is due to condensation of WATER droplets in the atmosphere. It does not contain any dissolved salts like ordinary water. Therefore rain water can DISSOLVE more amount of oxygen than ordinary water. Moreover rain water is in contact with atmospheric AIR. HENCE, it contains more percentae of oxygen.

Discussion

495.	Protons are .................. charged particles.
Answer» SOLUTION :POSITIVELY

Discussion

496.	Protons and neutrons are collectively known as ........
Answer» SOLUTION :NUCLEONS

Discussion

497.	Prepare- a fresh solution of sodium hydroxide in a test tube by dissolving 3-4 pellets of it in 5 mL, of water. Drop a piece of aluminium foil into it. Bring a burnish matchstick near the mouth of the test tube. Observe carefully. What does the 'pop' sound indicate?
Answer» ANSWER :We will observe that metal reacts with sodium HYDROXIDE producing HYDROGEN GAS with a 'pop' sound. The 'pop' sound indicates that hydrogen gas is PRESENT.

Discussion

498.	Predict the possible atomic number(s) of an atom in which the third shell is incompletely filled and maximum 4 more electrons can be added to that shell of the atom.
Answer» SOLUTION :The ELECTRONIC configuration of the element could be 28142 `"or"` 284 Hence its atomic number could be 26 or 14

Discussion

499.	Potassium chloridehas solubility of 32 g at room temperature in water. However its solubility decreases to 2.4 g in alcohol at the same temperature . It becomes completely insoluble in benzene . How do you account for this variation ?
Answer» Solution :Water has high DIELECTRIC constant . KCl being IONIC compound is highly soluble in water. Alcohol has a lower dielectric constant. Hence solubility of KCl in alcohol is less. Benzene has still lower value of dielectric constant . Therefore KCl becomes COMPLETELY insoluble in benzene.

Discussion

500.	Plumboua ion is repecsented as _________ .
Answer» SOLUTION :`PB^(+2)`

Discussion

Explore topic-wise InterviewSolutions in .

Solids can change into liquids on increasing the temperature.

Soil is a ................. mixture, while ice cream is a .................. mixture. (homogeneous/heterogeneous)

Hard water is not good for washing and industrial purposes.

Sodium is a very reactive metal.

Sodium catches fire and burns with a

Slaked hme 0n reaction with ammonium chloride gives

Skating on ice is almost impossible at very low temperatures say at arround -30^(@)C. Why?

Single displacement reaction is also known as a ……………… reaction.

Since we do not ass any change in be sike2- C, we can infer that copper is not able to replace wine from zinc sulphate. But why? When zinc can replace copper in beaker 'A' why cannot copper replace zinc in beaker'C'?

Silver tarnishes due to the formation of __________

Silver, gold and platinum are called noble metals because __________.

Silk fibre obtained from silkworm was first discovered in _______

Silica gel is a hygroscopic substance.

Show the reaction of sulphur dioxide with water.

Should the handle and bristles of a toothbrush be made of the same mateerial? Explain your answer.

Shell closest to the nucleus carries the Lowest amount of energy.

Scientist who proposed that atoms can neither be created nor destroyed.

Salts with water of crystallization are called _____ salts.

S. I. unit of atmospheric pressure is _______

Rutherford's theory assumed which of the following paths for the electron ?

Rutherford's alpha-ray scattering experiment was conducted in order to test the validity of Thomsom's model. What results were expected from this experiment ?

Rusting of iron is a……………. Change while freezing of water is a ……….. Change.

Ripening of fruits is a chemical change

Removing the top layer of water in an insoluble solid-liquid mixture is called

Removal of CO_2andH_2O from atmospheric air using KOH and anhydrous CaCl_2 is an example of _______ and _______ changes repectively.

Redistillation of nitric acid is carried out in a ferrosilicon vessel but not in an iron vessel. Explain.

Reaction: Non-metal +H_(2) A A+PbO to Pb- Non-metal If 'A' formed in the above reaction has rotten egg smell, identity the non-metal

Reaction in which one of the products is water.

Reaction in which a great amount of energy is released to form new bonds.

Reaction between two compounds to form a new compound.

Reaction between barium chloride and aluminium sulphate is an example of

Reaction between a base and a acid to form salt and water is known as a ………………

Reaction : 2CaO+C to CaC_(2)+2CO 2CaC_(2)+ 2H_(2)O to A+B If A is involved in the neutralisation reaction with acid, then B may be

Rcinoval of CO_2 and H_2O from atmospheric air by using KOH and anhydrous CaCl_2 is an example _________ and __________ changes respectively.

Rate of evaporation is increased by increasing ________ and _________.

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic maerial? Advise Rana, giving your reason.

Rain water does not leave any scales on boiling. Give reason.

Rain water and tap water are boiled in metallic containers A and B . The containers are emptied and then rain water samples are subjected to boilingin the same containers. In which case boiling gets delayed ? Give reason in support of your answer.

Rain water is found to contain more percentage of oxygen than ordinary water. Explain.

Protons are .................. charged particles.

Protons and neutrons are collectively known as ........

Prepare- a fresh solution of sodium hydroxide in a test tube by dissolving 3-4 pellets of it in 5 mL, of water. Drop a piece of aluminium foil into it. Bring a burnish matchstick near the mouth of the test tube. Observe carefully. What does the 'pop' sound indicate?

Predict the possible atomic number(s) of an atom in which the third shell is incompletely filled and maximum 4 more electrons can be added to that shell of the atom.

Potassium chloridehas solubility of 32 g at room temperature in water. However its solubility decreases to 2.4 g in alcohol at the same temperature . It becomes completely insoluble in benzene . How do you account for this variation ?

Plumboua ion is repecsented as _________ .

Removal of CO_2andH_2O from atmospheric air using KOH and anhydrous CaCl_2 is an example of _ and _ changes repectively.

Rcinoval of CO_2 and H_2O from atmospheric air by using KOH and anhydrous CaCl_2 is an example _ and __ changes respectively.

Rate of evaporation is increased by increasing and _.