Changes Around Us: Class 6 Science Q&A
30 free answers on Changes Around Us (Science) for Class 6 students, across CBSE, ICSE and State boards. Includes questions such as “How is the iron blade in tools fixed to the wooden handle?”, “How Blacksmiths Shape Iron”, “Examples of Reversible and Irreversible Changes”.
Question & Answer
Questions
- ScienceClass 6CBSE
How is the iron blade in tools fixed to the wooden handle?
Many tools such as hammers and axes have iron blades attached to wooden handles. The iron blade usually has a ring that is slightly smaller than the wooden handle. To fix the handle, the iron ring is heated. When heated, iron expands and the ring becomes larger. The wooden handle is then inserted into the ring. When the iron cools down, it contracts and fits tightly around the handle. This method ensures that the blade remains firmly attached to the handle.
- ScienceClass 6CBSE
How Blacksmiths Shape Iron
A blacksmith changes a piece of iron into different tools by heating it until it becomes red hot. When iron is heated, it becomes soft and can easily be beaten into different shapes using a hammer. This method allows blacksmiths to make tools such as knives, axes, and agricultural equipment.
- ScienceClass 6CBSE
Examples of Reversible and Irreversible Changes
Let us identify some changes: Cooking of food – Irreversible changeMelting of wax – Reversible changeSouring of milk – Irreversible changeDissolving salt in water – Reversible change (salt can be obtained again by evaporation)
- ScienceClass 6CBSE
Name two changes which can be controlled.
Some changes can be controlled to prevent damage or loss. Two examples of such changes are: Rusting of ironRusting can be controlled by painting, oiling, or galvanizing iron objects.Spoiling of foodFood spoilage can be controlled by refrigeration, drying, or adding preservatives. These methods help in increasing the life of materials and food.
- ScienceClass 6CBSE
Define pasteurization.
Pasteurization is the process of heating milk at a specific temperature for a certain period of time to kill harmful microorganisms. This method helps to prevent spoilage and keeps milk safe for drinking for several days. Pasteurization was developed by the scientist Louis Pasteur. Today it is widely used in dairy industries to preserve milk and other beverages.
- ScienceClass 6CBSE
What is solution?
A solution is a mixture formed when a substance dissolves in a liquid. The substance that dissolves is called the solute, and the liquid in which it dissolves is called the solvent. For example, when salt is dissolved in water, a salt solution is formed. In this mixture, salt is the solute and water is the solvent. Solutions are usually clear and uniform throughout.
- ScienceClass 6CBSE
What are reversible changes? Give two examples of changes, which can be reversed.
Reversible Changes Reversible changes are those changes that can be undone or reversed to get back the original substance. In such changes, the substance can return to its previous state by changing the conditions. ExamplesIce changing into water and water freezing into iceWhen ice is heated, it melts into water. When the water is cooled, it turns back into ice.Stretching a rubber bandWhen we stretch a rubber band and release it, it returns to i
- ScienceClass 6CBSE
Define periodic change.Write 2 examples of periodic change.
A periodic change is a change that occurs at regular intervals of time. These changes repeat themselves after a definite period. Examples of Periodic Changes Phases of the moon – The shape of the moon changes regularly over a month. Heartbeat – The heart beats continuously at regular intervals to pump blood throughout the body. Periodic changes are important
- ScienceClass 6CBSE
Give an example of natural change.
A natural change is a change that occurs naturally without human involvement. These changes occur due to natural processes. Example Germination of seeds is a natural change. When a seed gets proper water, air, and sunlight, it grows into a plant. This process happens naturally in nature. Other examples include rainfall, growth of plants, and changes in seasons.
- ScienceClass 6CBSE
What do you mean Chemical Changes
A chemical change is a change in which one or more new substances are formed with different properties from the original substances. In chemical changes, the composition of the substance changes permanently. Chemical changes are usually permanent and irreversible. Once the change takes place, it is very difficult or impossible to bring the substance back to its original form. Examples of Chemical Changes Burning
- ScienceClass 6CBSE
What do you mean by a physical change?
A physical change is a change in which only the physical properties of a substance change. These properties include shape, size, state, or appearance. In a physical change, no new substance is formed, and the original substance remains the same. Physical changes are often temporary and can usually be reversed. For example, when ice melts into water, the substance remains water in both cases; only the state changes from solid to liquid. <strong
- ScienceClass 6CBSE
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 colorful 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.
Activities which are reversible: Simba blew balloons and put them on the She also made some flowers by origami (paper folding) to decorate the Her father made dough Mother rolled the dough balls to make Father fried the puries in hot Activities which are irreversible: Some of the balloons got Paheli cut colorful strips of paper and put them on the wall with the help of Fathe
- ScienceClass 6CBSE
Paheli mixed flour and water and (i) made dough, (ii) rolled the dough to make a 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.
Making of dough from flour and water is an irreversible Rolling the dough to make a chapati is reversible Baking the rolled chapati on a pan is an irreversible Grinding of dried chapati in a grinder is an irreversible
- ScienceClass 6CBSE
Change of a bud into a flower is a change which cannot be reversed. Give four more such example. Solution:
Examples of changes which cannot be reversed: Digestion of food Ripening of fruits Burning of wood Milk into curd
- ScienceClass 6CBSE
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.
Examples of changes which can be reversed: Folding of a paper Melting of wax Knitting of a sweater Inflating a tyre or balloon
- ScienceClass 6CBSE
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.
The two acts by the potter leads to the different kind of changes. Shaping of pot on a wheel is a physical and reversible change. While baking the pot in an oven is an irreversible change.
- ScienceClass 6CBSE
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. Change which occurs on mixing two substances, but cannot be reversed.
Here are the examples for above statements: Heating of an iron rod Baking of chapati Formation of ice from water Formation of salt solution Mixing of cement with water
- ScienceClass 6CBSE
Tearing of paper is said to be a change that cannot be reversed. What about paper recycling?
Solution: Recycling of paper is also classified as an irreversible change because the quality, colour and texture of the paper changes on recycling and we get a different type of paper not the original one.
- ScienceClass 6CBSE
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.
Solution: No, Boojho will not be successful because making of toy from broken pieces of Plaster of Paris (POP) is an irreversible change. Once the Plaster of Paris is mixed with water and dried it cannot regain its original properties.
- ScienceClass 6CBSE
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 Burning of a candle
Solution: The following changes cannot be reversed: (d) Baking of a cake is irreversible. (f) Making biogas from cow dung is irreversible. (g) Burning of a candle is irreversible.