Latest Posts

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... 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... 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... 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... 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 technique Threshing is the... 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.... 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... 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... 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... 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... 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... 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... 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... 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... 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... 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... 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... 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... View Article

Paheli had bought a new bottle of pickle from the market. She tried to open the metal cap to taste it but could not do so. She then took a bowl of hot water and immersed the upper end of the bottle in it for five minutes. She could easily open the bottle now. Can you give the reason for this?

Answer: When exposed to heat, almost all metals expand. As a result, when the jar is immersed in hot water,... View Article

A piece of iron is heated until it becomes red-hot. It then becomes soft and is beaten to the desired shape. What kinds of changes are observed in this process-reversible or irreversible?

Answer: It is a reversible change when a piece of iron on heating can be beaten into the desired shape.... View Article

«
1
…
1,103
1,104
1,105
1,106
1,107
…
5,472
»