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Paheli asked for a glass of water from Boojho. He gave her a glass of ice-cold water. Paheli observed some water droplets on the outer surface of the glass and asked Boojho how these droplets of water were formed. Which of the following should be Boojho’s answer? (a) Evaporation of water from the glass. (b) Water that seeped out from the glass. (c) Evaporation of atmospheric water vapour. (d) Condensation of atmospheric water vapour.

Answer: (d) Condensation of atmospheric water vapour. The droplets of water were formed when the air reaches the surface of the ice-cold glass,... View Article

During summer, Boojho carries water in a transparent plastic bottle to his school. One day he left his bottle in the school. The bottle still had some water left in it. The following day, he observed some water droplets on the inner surface of the empty portion of the bottle. These droplets of water were formed due to (a) boiling and condensation (b) evaporation and saturation (c) evaporation and condensation (d) condensation and saturation.

Answer: (c) evaporation and condensation The water droplets were formed due to high temperature in summers; the water gets heated in a plastic... View Article

In the activity, a teacher dissolved a small amount of solid copper sulphate in a tumbler half-filled with water. Which method would you use to get back solid copper sulphate from the solution? (a) Decantation (b) Evaporation (c) Sedimentation (d) Condensation

Answer: (b) Evaporation To get back solid copper sulphate from the solution we can use the method evaporation. When the solution of copper... View Article

You might have observed the preparation of ghee from butter and cream at home. Which method(s) can be used to separate ghee from the residue? (i) Evaporation (ii) Decantation (iii) Filtration (iv) Churning Which of the following combination is the correct answer? (a) (i) and (ii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (iv) only

Answer: (b) (ii) and (iii) Because the mixture is made up of two distinct materials in different states which is ghee is liquid and the residue... View Article

While preparing chapatis, Paheli found that the flour to be used was mixed with wheat grains. Which out of the following is the most suitable method to separate the grains from the flour? (a) Threshing (b) Sieving (c) Winnowing (d) Filtration

Answer: (b) Sieving By the method of sieving, flour can be separated from wheat grains due to the difference in the size of flour and grain. The... View Article

Four mixtures are given below. (i) Kidney beans and chickpeas (ii) Pulses and rice (iii) Rice flakes and corn (iv) Potato wafers and biscuits Which of these can be separated by the method of winnowing? (a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iii) (d) (iii) and (iv)

Answer: (d) (iii) and (iv) By using the method of winnowing, mixtures of rice flakes and corn, potato wafers and biscuits can be separated since... View Article

Which amongst the following methods would be most appropriate to separate grains from bundles of stalks? (a) Hand-picking (b) Winnowing (c) Sieving (d) Threshing

Answer: (d) Threshing To separate grains from bundles of stalks threshing is the best method. Threshing is the process of separation of grain... View Article

Which of the following mixtures would you be able to separate using the method of filtration? (a) Oil in water (b) Cornflakes in milk (c) Salt in water (d) Sugar in milk

Answer: (b) Cornflakes in milk Since cornflakes are insoluble in milk it can be separated by the method of filtration. The majority of times, the... View Article

Boojho’s grandmother is suffering from diabetes. Her doctor advised her to take ‘Lassi’ with less fat content. Which of the following methods would be most appropriate for Boojho to prepare it? (a) Filtration (b) Decantation (c) Churning (d) Winnowing

Answer: (c) Churning Butter (fat) is separated by churning the curd and the remaining lassi contains less fat content. The majority of times, the... View Article

Paheli bought some vegetables such as French beans, lady’s finger, green chillies, brinjals and potatoes all mixed in a bag. Which of the following methods of separation would be most appropriate for her to separate them? (a) Winnowing (b) Sieving (c) Threshing (d) Hand-picking

Answer: (d) Hand-picking Since the vegetables are big in size handpicking is the best method for separating the vegetables. The majority of... View Article

lt was Paheli’s birthday, her brother Simba was helping her to decorate the house for the birthday party and their parents were also busy making other arrangements. Following were the activities going on at Paheli’s home: (i) Simba blew balloons and put them on the wall. (ii) Some of the balloons got burst. (iii) Paheli cut colourful strips of paper and put them on the wall with the help of tape. (iv) She also made some flowers by origami (paper folding) to decorate the house. (v) Her father made dough balls. (vi) Mother rolled the dough balls to make puries. (vii) Mother heated oil in a pan. (viii) Father fried the puries in hot oil. Identify the activities at Paheli’s home as those that can be reversed and those which cannot be reversed.

Answer: Activities which are reversible: (i) Simba blew balloons and put them on the wall. (iv) She also made some flowers by origami (paper... View Article

Paheli mixed flour and water and (i) made dough, (ii) rolled the dough to make chapati, (iii) baked the chapati on a pan, (iv) dried the chapati and ground it in a grinder to make powder. Identify the changes (i) to (iv) as the changes that can be reversed or that cannot be reversed.

Answer: (i) Making of dough from flour and water is an irreversible change. (ii) Rolling the dough to make a chapati is a reversible change.... View Article

Change of a bud into a flower is a change which cannot be reversed. Give four more such examples.

Answer: Examples of changes which cannot be reversed are listed below. Digestion of food Ripening of fruits Burning of wood Milk into curd... View Article

Conversion of ice into water and water into ice is an example of change which can be reversed. Give four more examples where you can say that the changes can be reversed.

Answer: Examples of changes which can be reversed are listed below. (i) Folding of a paper (ii) Melting of wax (iii) Knitting of a sweater (iv)... View Article

A potter working on his wheel-shaped a lump of clay into a pot. He then baked the pot in an oven. Do these two acts lead to the same kind of changes or different? Give your opinion and justify your answer.

Answer: (a) The shaping of clay into a pot is just a physical change in the clay's shape. This change is reversible.(b) The chemical... View Article

Give one example in each case: (a) Change which occurs on heating but can be reversed. (b) Change which occurs on heating but cannot be reversed. (c) Change which occurs on cooling but can be reversed. (d) Change which occurs on mixing two substances, but can be reversed. (e) Change which occurs on mixing two substances, but cannot be reversed.

Answer: Here are examples for the above statements: (a) Heating of an iron rod (b) Baking of chapati (f) Formation of ice from water (d)... View Article

Tearing of paper is said to be a change that cannot be reversed. What about paper recycling?

Answer: Recycling of paper is also classified as an irreversible change because the quality, colour and texture of the paper change on recycling... View Article

Boojho’s sister broke a white dove, a symbol of peace, made of Plaster of Paris (POP). Boojho tried to reconstruct the toy by making a powder of the broken pieces and then making a paste by mixing water. Will he be successful in his effort? Justify your answer.

Answer: No, he will not achieve in his effort. When a toy is produced with plaster of Paris(POP), the POP hardens due to the development of new... View Article

Which of the following changes cannot be reversed? (a) Blowing of a balloon (b) Folding a paper to make a toy aeroplane (c) Rolling a ball of dough to make roti (d) Baking cake in an oven (e) Drying a wet cloth (f) Making biogas from cow dung (g) Burning of a candle

Answer: The following changes cannot be reversed: (d) Baking a cake is irreversible. (f) Making biogas from cow dung is irreversible. (g) Burning... View Article

Can we reverse the following changes? If yes, suggest the name of the method. (a) Water into water vapour (b) Water vapour into water (c) Ice into water (d) Curd into milk.

Answer: (a) Water into water vapour – Yes, by using the method of condensation, water vapour can be converted to water. (b) Water vapour... View Article

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