Q1: An iron nail is kept in each of the following liquids. In which case would it lose its shine and appear dull? (a) Mustard oil (b) Soft drink (c) Coconut oil (d) Kerosene
Solution:
Ans: (b)
Explanation: Soft drinks contain water, dissolved carbon dioxide and acids (for example, citric or phosphoric acid). These components can react with iron and speed up corrosion, causing the nail to lose its shine and appear dull. Oils such as mustard oil, coconut oil and kerosene do not generally cause this kind of corrosion, so the nail would remain relatively shiny in those liquids.
Corrosion of iron nail
Q2: Pick one material from the following which is completely soluble in water. (a) Chalk powder (b) Tea leaves (c) Glucose (d) Sawdust
Solution:
Ans: (c)
Explanation: Glucose is a simple sugar that dissolves completely in water to form a clear solution. Chalk powder, tea leaves and sawdust do not dissolve entirely in water; they either remain suspended, settle down, or make the water cloudy.
Q3: You are provided with the following materials (i) magnifying glass (ii) mirror (iii) stainless steel plate (iv) glass tumbler. Which of the above materials will you identify as transparent? (a) (i) and (ii) (b) (i) and (iii) (c) (i) and (iv) (d) (iii) and (iv)
Solution:
Ans: (c)
Explanation: A magnifying glass (a clear lens) and a glass tumbler allow light to pass through so that objects can be seen clearly; they are thus transparent. A mirror reflects light and a stainless steel plate reflect or block light rather than let it pass through, so they are not transparent.
Very Short Answer Questions
Q4: Boojho found a bag containing the following materials (i) Mirror (ii) Paper stained with oil (iii) Magnet (iv) Glass spectacles Help Boojho in finding out the material(s) which is/are opaque. (a) (i) only (b) (iv) only (c) (i) and (iii) (d) (ii) and (iv)
Solution:
Ans: (c)
Explanation: A mirror is opaque because it has a reflective coating on one side that does not allow light to pass through. A magnet (usually made of iron or another metal) is also opaque because it is solid metal that blocks light. Paper stained with oil may be translucent in places, and glass spectacles are generally transparent.
Q5: While doing an activity in class, the teacher asked Paheli to handover a translucent material. Which among the following materials will Paheli pick and give her teacher? (a) Glass tumbler (b) Mirror (c) Muslin cloth (d) Aluminium foil
Solution:
Ans: (c)
Explanation: Muslin cloth is translucent because it allows some light to pass through but does not let us see objects clearly. A glass tumbler is usually transparent, so objects can be seen clearly through it. Mirror and aluminium foil are opaque or reflective and do not allow seeing through them.
Q6: Which pair of substances among the following would float in a tumbler half-filled with water? (a) Cotton thread, thermocol (b) Feather, plastic ball (c) Pin, oil drops (d) Rubber band, coin
Solution:
Ans: (b)
Explanation: A feather and a plastic ball float on water because their average density is less than the density of water and they are light. A pin and a coin are dense and sink; oil drops float on water because oil is less dense than water, but a single oil drop may behave differently in a small test depending on surface tension.
Q7: Which among the following are commonly used for making a safety pin? (a) Wood and glass (b) Plastic and glass (c) Leather and plastic (d) Steel and plastic
Solution:
Ans: (d)
Explanation: Safety pins need a strong, bendable metal for the pointed part and a material to cover or hold the end. Steel provides strength and can be shaped to a sharp point, while plastic is often used for a covering or as part of packaging. Hence steel and plastic are commonly used.
Q8: Which of the following materials is not lustrous? (a) Gold (b) Silver (c) Wood (d) Diamond
Solution:
Ans: (c)
Explanation: Lustre means a shiny appearance produced by reflection of light. Metals and crystals such as gold, silver and diamond are lustrous because they reflect light well. Wood is not lustrous since it does not reflect light in the same way and is not crystalline.
Q9: 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.
Solution:
Ans: (c)
Explanation: Materials are grouped to make study easier, to understand their properties and to use them appropriately (for example, metals together, non-metals together). Grouping is a systematic activity and is not done merely for fun.
Q10: Find the odd one out from the following. (a) Tawa (b) Spade (c) Pressure cooker (d) Eraser
Solution:
Ans: (d)
Explanation: Tawa, spade and pressure cooker are usually made of metal, while an eraser is made of rubber or a rubber-like material. Thus, the eraser is the odd one out by material.
Q11: Which type of the following materials is used for making the front glass (windscreen) of a car? (a) Transparent (b) Translucent (c) Opaque (d) All the above
Solution:
Ans: (a)
Explanation: The front glass (windscreen) of a car must allow the driver to see clearly through it, so transparent glass is used. This type of glass lets light pass through without much scattering, providing a clear view.
Very Short Answer Questions
Q12: lt was Paheli's 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?
Solution:
Ans: Paheli saw a difference because silver reacts with some gases present in the air (for example, hydrogen sulphide) and forms a dark layer on its surface, causing it to look dull. Gold is a noble metal and does not react easily with gases in the atmosphere, so it keeps its shine and appears lustrous.
Q13: 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?
Solution:
Ans: Raveena
Explanation: Honey dissolves completely in water to form a clear solution. Red chilli powder and butter do not form true solutions in water; petrol is immiscible with water and floats on its surface.
Q14: 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?
Solution:
Ans: Yes. The glass door is transparent and allows light to pass through, so her brother will be able to see her behind the door.
Q15: 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?
Solution:
Ans: Initially the cotton ball will float because it is light and traps air, making its overall density less than water. Over time it absorbs water, becomes heavier and its density increases, so it will sink.
Q16: Which among the following materials would you identify as soft materials and why? Ice, rubber band, leaf, eraser, pencil, pearl, a piece of a wooden board, cooked rice, pulses and fresh chapati.
Solution:
Ans: The soft materials are leaf, rubber band, cooked rice, eraser and fresh chapati. These can be pressed, scratched or deformed easily compared with hard items like pencil, pearl or wooden board.
Q17: You are provided with the following materials - 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.
Solution:
Ans:
Soluble pairs (i) Honey - water (ii) Groundnut oil - mustard oil (oils mix with oils) (iii) Glucose - water
Insoluble pairs (i) Mustard oil - water (ii) Turmeric - water (turmeric particles do not dissolve completely; they remain suspended or settle) (iii) Rice flour - water (forms a suspension or paste, not a true solution)
Q18: During summer holidays, a group of children collected a lump of salt, green grass, broken glass piece, a small thermocol box, pen, iron nail, glass marbles, hair, naphthalene ball, a piece of sugar candy (mishri) and tried to group them on the basis of properties given in table 4.1 below. Help them in filling the table.
Solution:
Q19: Arrange the jumbled words to arrive at the appropriate names of materials and also write two uses of each. (a) milaunuim (b) tcaslpi (c) soekrnee (d) gavnier
Solution:
Ans: The arranged words are: (a) Aluminium - It can be used to wrap food in foil and in making aircraft parts. (b) Plastic - It can be used to make buckets, pencil boxes and many household items. (c) Kerosene - It can be used as fuel for lamps and as a solvent for some substances. (d) Vinegar - It can be used as a food ingredient (salad dressing) and as a preservative.
Q20: Match the objects given in column I with the materials given in column II.
Solution:
Ans: The correct match is:
Q21: Pick five objects from the word box given as Fig. 4.1 which are opaque and would sink in water.
Solution:
Ans: Objects that are opaque and would sink in water are: (i) Coin (ii) Stone (iii) Key (iv) Pencil (v) Eraser
Long Answer Questions
Q22: 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.
Solution:
Ans: We can tell these materials apart by observing properties such as hardness, surface texture, lustre and softness: Chalk - Hard, rough, non-lustrous Iron nail - Hard, smooth, lustrous (metallic) Wood - Hard, rough, non-lustrous Aluminium - Hard, smooth, lustrous (metallic) Candle - Hard (but softer than metal), smooth, non-lustrous Cotton - Soft, smooth, non-lustrous
Q23: Why do you think oxygen dissolved in water is important for the survival of aquatic animals and plants?
Solution:
Ans: Oxygen dissolved in water is used by aquatic animals for breathing and by some aquatic plants during respiration. Without sufficient dissolved oxygen, fish and many other water organisms cannot survive.
Q24: Differentiate among opaque, translucent and transparent materials, giving one example of each.
Solution:
Ans: Opaque materials: Objects cannot be seen through them (example: wood, stone). Translucent materials: Light passes through but objects are not seen clearly (example: frosted glass, oiled paper). Transparent materials: Objects can be seen clearly through them (example: clear glass, clean water).
Q25: Sugar, salt, mustard oil, sand, sawdust, honey, chalk powder, petals of a 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.
Solution:
Ans:
Soluble in water:
Sugar
Salt
Honey
Copper sulphate crystals
Glucose
Insoluble in water:
Mustard oil
Sand
Sawdust
Chalk powder
Petals of a flower
Soil
Wheat flour
The document NCERT Exemplar Solutions: Sorting Materials into Groups is a part of the Class 6 Course Science for Class 6.
FAQs on NCERT Exemplar Solutions: Sorting Materials into Groups
1. What are the different criteria for sorting materials into groups?
Ans.Materials can be sorted based on various criteria such as physical properties (color, shape, size), chemical properties (reactivity, composition), and uses (food, clothing, construction). This helps in organizing materials for easier identification and utilization.
2. Why is it important to classify materials?
Ans.Classifying materials is important because it helps in understanding their properties and uses, facilitates easier retrieval, and aids in effective waste management. It also supports scientific study and experimentation by categorizing materials based on similarities and differences.
3. Can you give examples of natural and synthetic materials?
Ans.Natural materials include wood, cotton, wool, and stone, while synthetic materials comprise plastics, nylon, and polyester. Understanding the distinction between these types helps in sorting and recycling efforts.
4. How does sorting materials contribute to environmental conservation?
Ans.Sorting materials helps in recycling and reusing resources, which reduces waste and conserves natural resources. By separating different materials, we can minimize pollution and the environmental impact of waste disposal.
5. What role do physical properties play in sorting materials?
Ans.Physical properties such as texture, density, and solubility are crucial in sorting materials. They allow us to categorize substances based on how they interact with each other and their environment, which is essential for their proper handling and use.
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