Important Keywords On Class 6 Science Chapter 4
| Fibre: | The hair-like materials found in stems and flowers. |
| Yarn: | The thin thread used for knitting or weaving. |
| Combing: | The process of making the cotton fully. |
| Fabric: | The clothes we wear. |
| Retting: | A process by which the jute stems soaked in water for 20 days get softened. |
| Ginning: | A process by which seeds are separated from the fibres. |
| Cotton boll: | The fruits of the cotton plant. |
| Spinning: | The process of drawing out, twisting and winding of fibres into a continuous yarn. |
The Quick Revision Points Of 6th Science Chapter 4
- There are two types of fibresтАФnatural and synthetic.
- Clothes protect us from extreme heat and cold.
- Jute is obtained from the bark of the jute plant.
- Fibres like cotton and jute are obtained from plants.
- Cotton is the most important of all natural fibres.
- Fabric from yarns is made by weaving and knitting.
- Cotton clothing is soft and comfortable to wear.
- We wear different types of clothes at different times and places.
Main Tips To Study Class 6 Science Chapter 4
1. Object Around Us
In this part of the content focuses on the importance of keeping different materials as a group and their uses in our daily life. We can see many objects around us, such as books, lunch box, table, chair, matchbox, toys and buckets. Now if we wish to make a group of objects that are made of plastic. We find buckets, lunch box, toys in this group. Similarly, make another group of objects that are made from wood. We may find a table, chair, matchbox. In everyday life, we often group materials for our convenience. At home, we usually store things in such a manner that similar objects are placed together. Such an arrangement helps us to locate them easily. Whenever we need┬аclothes to wear, we find in almirah, not in the kitchen. When we get sick, we use the doctorтАЩs thermometer, not a pen or pencil. Remember, every material has its significance. Materials are grouped for our convenience and study to their properties.
2. Properties Of Materials
Section 4.2 of class 6 Science chapter 2, provides a clear idea about the different properties of materials which we see in around us. Its different properties are appearance, hardness, transparency, solubility, floatation and┬аconduction of heat and electricity. We learnt before each material has its characteristics or properties that may differ from others.
3. Appearance Of Materials
Every material usually looks different from each other. Wood looks very different from iron. Iron gives shine and sound. It conducts heat and electricity, whereas wood has not this type of properties. Remember, materials that have certain properties like lustre, sonorous, good conductors of heat and electricity are called metals. Iron, copper, aluminium and gold are an example of metals.
4. Hardness Of Materials
When we touched any material which is made from cotton or sponge, it feels soft while stone, wood, bricks feel hard. As we know that materials which can be compressed, cut, bent or scratch easily are called soft materials. Rubber band, leaf, eraser,┬аcooked rice and chapati┬аare examples of soft materials. In the other hand, some of the materials which cannot be compressed, cut, bent or scratched easily are called hard materials, such as metals, wood, stone etc.
5. Soluble Or Insoluble
Materials can be grouped based on their solubility in water. As you know, substances that completely┬аdissolve in water┬аare called soluble substances. These are sugar, salt, lemon juice, etc. Substances that do not dissolve in water are called insoluble substances. Like sand, chalk powder, dust, kerosene etc. Remember, those liquids which do not mix well with water called immiscible. Such as oil. Oil does not mix with water in any circumstances.
6. Objects May Float Or Sink In Water
You might have noticed that some materials float in water while other sinks. Materials like sand, sugar, salt, stone sink in water. Materials like dry leaves, wax, oil and wood float on water. Generally, substances have less density than oil and water can float. But, about cotton balls, it initially floats on water, but after a few minutes, it sinks because it absorbs water.
7. Transparency Of Materials
Materials can be grouped on the basis of transparency. If you are playing hide and seek with your friends. And they keep themselves behind a glass door. Can you locate them? Your answer will be тАШyesтАЩ. Remember, materials through which things can be seen are called тАШTransparentтАЩ. Such as glass, water, air, etc. The transparent materials allow almost all the┬аlight to pass through┬аthem due to which the object or person behind them can be seen clearly. Materials through which we are not able to see anything are called тАШOpaqueтАЩ, such as wood, iron, wall etc. The materials through which an object can be seen but not clearly is called тАШTranslucentтАЩ. Muslin cloth is a translucent material. Similarly, paper stained with oil is also an example of translucent material.
Important Questions For Practice
1. Which of the following statements is not true?
(a) Materials are grouped for convenience.
(b) Materials are grouped to study their properties.
(c) Materials are grouped for fun.
(d) Materials are grouped according to their uses.
2. Which type of the following materials is used for making the front glass (wind screen) of a car?
(a) Transparent (b) Translucent (c) Opaque (d) All the above
3. Mixtures of red chilli powder in water, butter in water, petrol in water, and honey in water were given to Radha, Sudha, Sofia and Raveena, respectively. Whose mixture is in solution form?
4. On a bright sunny day, Shikha was playing hide and seek with her brother. She hid herself behind a glass door. Do you think her brother will be able to locate her. If yes, why? If no, why not?
5. It was PaheliтАЩs birthday. Her grandmother gave her two gifts made of metals, one old dull silver spoon and a pair of lustrous gold earrings. She was surprised to see the difference in the appearance of the two metals. Can you explain the reason for this difference?
6. Take a small cotton ball and place it in a tumbler/bowl filled with water. Observe it for at least 10 minutes. Will it float or sink in water and why?
7. You are provided with the following materialsтАФ turmeric, honey, mustard oil, water, glucose, rice flour, groundnut oil. Make any three pairs of substances where one substance is soluble in the other and any three pairs of substances where one substance remains insoluble in the other substances.
8. Chalk, iron nail, wood, aluminium, candle, cotton usually look different from each other. Give some properties by which we can prove that these materials are different.
9. Sugar, salt, mustard oil, sand, sawdust, honey, chalk powder, petals of flower, soil, copper sulphate crystals, glucose, wheat flour are some substances given to Paheli. She wants to know whether these substances are soluble in water or not. Help her in identifying soluble and insoluble substances in water.
10. Why do you think oxygen dissolved in water is important for the survival of aquatic animals and plants?
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Answers Of Important Questions
Answer 1: (c) Materials are grouped for fun.
Answer 2: (a) Transparent
Answer 3: Raveena has got a solution because honey will dissolve in water.
Answer 4: Yes, Ground glass is translucent, so Shikha can be located.
Answer 5: The silver spoon on long exposure to moist air has lost its shine and appears dull whereas gold does not tarnish.
Answer 6: Cotton ball initially floats and then sinks as it absorbs water.
Answer 7: Soluble: (i) honey in water (ii) glucose in water (iii) groundnut oil in mustard oil
Insoluble: (i) turmeric in water (ii) rice flour in water (iii) mustard oil in water
Answer 8: Write on the basis of lustre, hardness, softness, roughness or smoothness.
Answer 9: Soluble in water тАУ Sugar, Salt, Honey, Copper sulphate crystals, Glucose
Insoluble in water тАУ Mustard oil, Sand, Sawdust, Chalk powder, Soil, Petals of flower, Wheat flour.
Answer 10: Dissolved oxygen is available for animal and plants for respiration and survival.
Important Questions On Class 6 Science Chapter 4
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For example, few types of wood have densities higher than oil but less than water, so it floats on water but not on kerosene.
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How Does Sorting Of Materials Help Us? Discuss.
It helps to collecting information and gaining systematic knowledge of things as possible. It helps in dividing materials in groups makes it convenient to study their properties. It is convenient to work with all materials or members of a group after knowing their properties.
Name Some Objects Which We See Around Us.
We see around us, chair, bullock cart, cycle, cooking utensils, books, clothes, toys, water, stones and many other objects.
Can You Write The Name Of Some Plastic And Wooden Objects?
Objects that are made of plastics such as buckets, lunch boxes, toys, water containers, pipes and many objects. Objects that are made of wood such as chair, table, plough, bullock cart and its wheels, matchbox, and many objects.
Write Down The Different Types Of Objects That Are Made From The Same Material.
All objects around us are made of one or more materials. These materials may be chair, table, plough, bullock cart and its wheels. All objects are made up of wood. And books, notebooks, newspaper, toys, calendars are made up of paper.
Appearance Of An Objects
Generally, appearance deals with lustre, looks, colour, shape, state of the objects. Materials usually look different from each other. Wood looks very different from iron. Iron appears different from copper or aluminium. At the same time, there may be some similarities between iron, copper and aluminium that are not there in wood.
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How Would You Separate Some Materials? Write The Ways You Know.
First, we grouped objects in many different ways. We then found that objects around us are made of different materials. At times, an object is made of a single material. An object could also be made of many materials. And then again, one material could be used for making many different objects.
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Why Does A Tumbler Not Make With A Piece Of Cloth?
We should keep in mind that we generally use a tumbler to keep a liquid. Therefore, it would be silly, if we were to make a tumbler out of cloth. We need for a tumbler is glass, plastics, metal or other such material that will hold water.
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How Does Appearance Of Objects Help Us To Make Sort Out Of Different Materials? Show With An Activity.
Collect small pieces of different materials тАУ paper, cardboard, wood, copper wire, aluminium sheet, chalk. Separate the shiny materials into a group. Now, cuts each material into two pieces and look at the freshly cut surface. Some of these materials are appear shiny. Include these objects also in the group of shiny materials. Instead of cutting, you can rub the surface of material with sand paper to see if it has lustre. Materials that have such lustre are usually metals. Iron, copper, aluminium and gold are examples of metals. Therefore, we can differentiate the materials, according to the lustre.
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According To The Property Of Hardness, How Would You Differentiate Whether The Object Is Soft Or Hard? Justify Your Answer.
When you press different materials with your hands, some of them may be hard to compress while others can be easily compressed. Take a metal key and try to scratch with it, the surface of a piece of wood, aluminium, a piece of stone, a nail, candle, chalk, any other material or object. You can easily scratch some materials, while some cannot be scratched so easily. Materials which can be compressed or scratched easily are called тАЬsoftтАЭ while some other materials which are difficult to compress are called тАЬhardтАЭ. For example, cotton or sponge is soft while iron is hard.
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Soluble And Insoluble
Soluble: Some substances have completely disappeared or dissolved in water. These substances are termed as Soluble.
Insoluble: Substances do not mix with water and do not disappear even after we stir for a long time. These substances are termed as Insoluble.
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Name The Component Which Is Known As Universal Solvent?
Water which is known as тАЬuniversal solventтАЭ as it can dissolve maximum materials.
тАЬA Gas Dissolved In Water Is Very Important For The Survival Of Animals And Plants That Live In WaterтАЭ. Write The Name Of The Gas.
The name of the gas is oxygen which dissolved in water and very important for the survival of animals and plants that live in water.
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Write Down The Five Examples Of Each Objects That Float And Sink In Water.
Objects that float in water: plastic, wood, oil, sponge, petrol, kerosene, wax, ships etc.
Objects that sink in water: rock, marble, steel, iron, copper, nickel, sand, mercury etc.
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What Is тАЬTransparentтАЭ? Give One Example Where Transparent Materials Of Containers Are Used.
Transparent: Those substances or materials, through which things can be seen, are called transparent. Glass, water, air and some plastics are examples of transparent materials.
Shopkeepers usually prefer to keep biscuits, sweets and other eatables in transparent containers of glass or plastic, so that buyers can easily see these items.
Uses Of Oxygen Gas
Oxygen gas constitutes 20.8% of the EarthтАЩs atmosphere. Oxygen is used by animals and plants in the respiration (breathing) process. Tanks of oxygen are used in medicine to treat people with breathing problems. They are also used as life support for astronauts and scuba divers. The majority of the oxygen used in industry is used in the manufacturing of steel.
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With The Help Of An Activity, Boojho Wants To Know About Translucent Material. Can You Help Him?
Take a sheet of paper and look through it towards a lighted bulb. Now, put 2-3 drops of some oil and spread it on the sheet of paper. Look again towards the lighted bulb through that portion of the paper on which the oil has been spread. You will be find that the bulb is more clearly visible than before. But, not clearly through the oiled paper.
Generally, the materials through which objects can be seen, but not clearly, are known as translucent material.
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There Are Some Materials Given Below. Paheli Wants To Make A Group Material As Opaque, Transparent And Translucent. Card-Board, Air, Bricks, Water, Frosted Glass, Plywood, Oily Paper, Mirror, Polyethene, Stone, Glass.
Opaque: Card-board, Bricks, Plywood, Mirror, Stone.
Transparent: Air, Water, Glass
Translucent: Oily paper, Polyethene, Frosted glass.
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In Everyday Life, We Often Group Materials For Our ConvenienceтАЭ. Justify The Statement.
As we know that in everyday life, we often group materials for our convenience. At home, we usually store things in such a manner that similar objects are placed together. Such an arrangement helps us to locate them easily.
Similarly, a grocer usually keeps all type of biscuits at one corner of his shop, all soaps at another while grains and pulses are stored at some other place. Materials differ in their appearance and the way they mix in water or other liquids. They may float or sink in water or may be transparent, opaque or translucent. Materials can be grouped on the basis of similarities or differences in their properties.
There is another reason why we find such grouping useful as dividing materials in groups makes it convenient to study their properties and also observe any patterns in these properties.
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Paheli Wants To Know, Why Some Metals Lost Their Shine And Appear Dull?
Some metals often lose their shine and appear dull, because of the action of air and moisture on them.
Some metals as a result of oxidation with the atmospheric oxygen form oxides and by which their appearance becomes dull.
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Opaque Materials
Opaque: There are some materials through which you are not able to see. These materials are called opaque.
Wood, cardboard and metals, are examples of opaque materials.
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Given Below Are The Names Of Some Objects And Materials: Water, Basket-Ball, Orange, Sugar, Globe, Apple And Earthen Pitcher. Group Them As: A)Round Shaped And Other Shapes. B)Eatable And Non-Eatables.
(a)
Round shape: basketball, orange, globe, apple, earthen pitcher
Other shape: Water, sugar
(b)
Eatable: Water, orange, sugar, apple
Non-eatable: Basket-ball, globe and earthen pitcher
Why Do You Think Oxygen Dissolve In Water Is Important For The Survival Of Aquatic Animals And Plants?
Oxygen gas dissolves in water i.e. oxygen gas is soluble in water. The plants and animals which live in water use the oxygen dissolved in water for respiration. Thus, oxygen gas dissolved in water is very important for the survival of animals and plants that live in water.
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Take A Small Cotton Ball And Place It In A Tumbler Bowl Filled With Water. Observe It For At Least 10 Minutes. Will It Float Or Sink In Water And Why?
Cotton ball initially floats on water but after few minutes (i.e. 10 min. to 15 min.), its sinks because it absorbs water.
тАЬIf You Are Playing Hide And Seek, You Will Choose An Opaque Place To HideтАЭ. Justify Your Answer.
Generally, when we are playing hide and seek, we choose an opaque place to hide because an opaque material does not allow light to pass through them due to which the object or person behind them cannot be seen.
If we choose transparent materials to hide, person can be seen easily because transparent materials, allow almost all the light to pass through them. Therefore, in the hide and seek game we would always prefer to choose an opaque place to hide.
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Items that Float on Water
Wooden block, paper, balloon, hair, plastic bottle, wooden logs, boat etc. will float on water. A few of these like hair, balloon, can float on kerosene oil. Generally, substance have less density than oil and water can float.
For example, few types of wood have density higher than oil but less than water so it floats on water but not in kerosene.
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