The World of Metals and Non metals Class 7 Questions and Answers Science Chapter 4

Students can use Curiosity Class 7 Science Book Solutions Chapter 4 The World of Metals and Non metals Class 7 Question and Answer as a quick reference guide.

Class 7 Science Chapter 4 The World of Metals and Non metals Question Answer

Science Class 7 Chapter 4 Question Answer The World of Metals and Non metals

The World of Metals and Non metals Class 7 Question Answer (InText)

Question 1.
Which items of daily use are made by ironsmiths? Which materials are these made of? (Page 41)
Answer:
Items of daily use made by ironsmiths are buckets (baltis), flat pans (tawas), tongs (chimtas), and farming tools like axes (kulharis), spades (phawras), trowels (khurpis) and rakes (jelees). These items are made of iron metal. Wood is used to make handles of these items.

Question 2.
Why is an iron block beaten with a hammer after heating it in a furnace? (Page 42)
Answer:
Iron block is beaten with hammer after heating it red hot in the furnace so as to give it shape of axe (kulhari), trowel, etc.

Question 3.
Are metals like copper, aluminium and iron lustrous? Are they soft or hard? (Page 42)
Answer:
Yes, these metals show lustre (metallic shine) and are mostly hard, except for sodium and potassium, which are soft.

Question 4.
What happens when metals are beaten with hammer? (Page 42)
Answer:
Metals such as copper and aluminium flatten into sheets; this demonstrates malleability. Non-metals like coal and sulfur are brittle and break.

Question 5.
Which objects become flat on beating with a hammer? (Page 43)
Answer:
A piece of copper, iron or aluminium becomes flat sheet on beating with a hammer due to the property of malleability.

Question 6.
Give examples of metal sheets. (Page 43)
Answer:
Silver foil; aluminium foil.

Question 7.
Are all metals hard and solid? (Page 43)
Answer:
No. All metals are not hard and solid. Some metals, like sodium and potassium, are very soft and can be cut with a knife. Metal mercury is found in the liquid state at room temperature.

Question 8.
What could be the potential reason that it is generally considered that copper was discovered earlier than iron? (Page 44)
Answer:
Copper is more ancient (history dating back to 9000 – 8000 BCE) compared to iron (1200 BCE, Iron Age).
Potential reason for this could be that copper occurs naturally in its native form and can be easily extracted, whereas iron is usually obtained from ores.

Question 9.
Where do you find the use of metal wires in everyday life? (Page 44)
Answer:
We find the use of copper/ aluminium wires in electrical fittings. Ornaments like bangles, necklaces and earrings are made from metal wires. Stringed musical instruments (veena, violin, sitar, guitar) and tea-strainer. mesh are also made of metal wire.

Question 10.
Have you ever seen wires made of coal or sulfur? Give reason. (Page 45)
Answer:
No. Coal and sulfur are non-metals and therefore, not ductile, so wires cannot be made from them.

Question 11.
Why are ropes of steel used in suspension bridges and in cranes to lift heavy objects? (Page 45)
Answer:
Steel ropes (a mixture of the metal iron and the non-metal carbon) have very high tensile strength, so they can safely lift heavy loads.

Question 12.
How is the sound produced by a metal spoon, plate or coin different from the sound produced by dropping a piece of coal or wood on the floor? (Page 45)
Answer:
Metals produce a ringing sound because of sonority, whereas coal and wood give a dull sound.

Question 13.
Name some metals used for making cooking vessels. Give reasons. (Page 46)
Answer:
Copper, aluminium and iron are used to make cooking vessels because they are good conductors of heat and transfer heat from one point to another of the material.

Question 14.
What type of material is used for making a screwdriver used by an electrician? Why he uses rubber gloves and shoes while working? (Page 4 7)
Answer:
An electrician uses a metal screwdriver with a plastic handle. Metals are good conductors of electricity and allow the electric current to flow through them easily. Plastic handle on screwdriver, rubber gloves and shoes protect the electrician from electric shock because plastic and rubber are poor conductors of electricity.

Question 15.
Under what conditions would an iron object develop brown deposits? (Page 48)
Answer:
An iron object develops brown deposits (rust) when it comes into contact with both air and water.

Question 16.
Why is rusting of iron a serious problem in India? (Page 50)
Answer:
Brown deposits called rust result in corrosion when iron comes in contact with air and water. Rusting or rust formation on iron cause considerable damage to iron structures. A lot of money is spent to replace or repair the rusted iron structures in India.

Question 17.
What do you observe when magnesium ribbon is burnt on a spirit lamp or a candle? (Page 51)
Answer:
It burns with a dazzling white flame and changes into ash, a white powder.

Question 18.
What effect does an aqueous solution of magnesium oxide have on blue and red litmus papers? (Page 51)
Answer:
Aqueous solution of magnesium oxide turns red litmus paper blue, indicating that it is a basic solution.

Question 19.
What is the nature of the oxide of sodium? (Page 52)
Answer:
Sodium oxide dissolves in water to give sodium hydroxide, a strong alkali that turns red litmus blue; hence it is basic in nature.

Question 20.
Does sulfur behave in water the same way metals do? (Page 53)
Answer:
No. When sulfur is placed in water no reaction occurs. Substances like sulfur and phosphorous are non metals and behave differently with air and water compared to metals. When sulfur is heated, it burns with a blue flame and forms sulfur-dioxide gas.

When water is added to this gas collected in ajar and shaken, it dissolves in water to produce sulfurous acid. Using acid-base indicator (litmus paper) the solution turns blue litmus red, showing that the oxide of sulfur is acidic in nature.

NCERT Class 7 Science Chapter 4 Question Answer The World of Metals and Non metals (Exercise)

Question 1.
Which metal is commonly used to make food packaging materials as it is cheaper, and its thin sheets can be folded easily into any shape?
(i) Aluminium
(ii) Copper
(iii) Iron
(iv) Gold
Answer:
(i) Aluminium

Question 2.
Which of the following metal catches fire when it comes in contact with water?
(i) Copper
(ii) Aluminium
(iii) Zinc
(iv) Sodium
Answer:
(iv) Sodium

Question 3.
State with reason(s) whether the following statements are True (T) or False (F).
(i) Aluminium and copper are examples of non-metals used for making utensils and statues.
(ii) Metals form oxides when combined with oxygen, the solution of which turns blue litmus paper to red.
(iii) Oxygen is a non-metal essential for respiration.
(iv) Copper vessels are used for boiling water because they are good conductors of electricity.
Answer:
(i) False: They are metals; the property is malleability.
(ii) False: They turn red litmus blue because of their basic nature.
(iii) True: Oxygen (we breathe in).
(iv) True: Copper is a metal and a good conductor of heat; hence copper vessels are used for boiling water.

Question 4.
Why are only a few metals suitable for making jewellery?
Answer:
Only a few metals like silver and gold are suitable for jewellery because they are highly malleable, ductile and possess good tensile strength.

Question 5.
Match the uses of metals and non-metals given in Column I with the jumbled names of metals and non-metals given in Column II.

Column I	Column II
(i) Used in electrical wiring	(a) ENXYGO
(ii) Most malleable and ductile	(b) NECOHIRL
(iii) Living organisms cannot survive without it.	(c) PEPORC
(iv) Plants grow healthy when fertilisers containing it are added to the soil.	(d) TENGOINR
(v) Used in water purification	(e) OGDL

Answer:

Column I	Column II
(i) Used in electrical wiring	(c) PEPORC
(ii) Most malleable and ductile	(e) OGDL
(iii) Living organisms cannot survive without it.	(a) ENXYGO
(iv) Plants grow healthy when fertilisers containing it are added to the soil.	(d) TENGOINR
(v) Used in water purification	(b) NECOHIRL

Question 6.
What happens when oxygen reacts with magnesium and sulfur. What are the main differences in the nature of products formed?
Answer:
On heating pxygen reacts with magnesium, a dazzling white light is produced and magnesium oxide (powdery white ash) is formed. On heating oxygen reacts with sulfur a blue flame appears and fumes of gas are collected in a gas-jar.

Differences in the nature of products formed

Oxide of Magnesium	Oxide of Sulfur
Magnesium burns in oxygen with a white dazzling flame.	Sulfur burns in oxygen with a blue flame.
Magnesium oxide formed is a white powdery ash.	Sulfur oxide formed is in the form of fumes of gas which is collected in a jar.
Ash so obtained is dissolved in water, the solution formed changes the red litmus paper blue.	When water is added in the gas jar and shaken, solution formed is sulfurous acid that changes blue litmus paper red.
This indicates that oxide of magnesium is basic in nature.	This indicates that oxide of sulfur is acidic in nature.

Question 7.
Complete the following flow chart:

Answer:
Magnesium, magnesium hydroxide. No change.

Question 8.
You are provided with the following materials. Discuss which material would be your choice to make a pan that is most suitable for boiling water and why?
Iron, copper, sulfur, coal, plastic, wood, cardboard
Answer:
Out of iron, copper, sulfur, coal, plastic, wood and cardboard, copper is the best for making a pan for boiling water because it is a good conductor of heat.

Question 9.
You are provided with three iron nails, each dipped in oil, water and wnegar. Which iron nail will not rust, and why?
Answer:

1. An iron nail rusts faster in vinegar (acetic acid) because the corrosive action of the acid accelerates oxidation.
2. Rusting occurs in moist air; rusting in water alone is slower because less oxygen is dissolved in water.
3. No rusting occurs in oil because oil prevents air from reaching the iron.

Question 10.
How do the different properties of metals and non-metals determine their uses in everyday life?
Answer:
Uses of metals and non-metals depend on their properties. Important uses of some metals are given below:

1. Iron is used to make pipes, storage tanks, railings, cylinders, nails, nut and bolts, agricultural tools, ships, bridges, railway lines, etc. Stainless steel, which is an alloy of iron, is used to make cooking utensils, cutlery, knives, blades, etc.
2. Aluminium is used to make overhead electric cables, electric wires, cooking utensils etc. Aluminium foil is used for packaging food items, medicines, etc. Aluminium metal in the form of alloys is used to make aero¬planes. Aluminium powder is used in antirust paints.
3. Copper is widely used to make electric wires, electric motors and many other electric appliances. It is also used to make household cooking utensils and water boilers for factories. It forms many alloys such as brass, bronze, etc.
4. Zinc metal is used for galvanization of iron to prevent its rusting. It is also used in dry cells.
5. Gold and silver are used to make jewellery.
6. Mercury is used in making thermometers.
7. Lead is used for making lead storage batteries.

Important uses of some common non-metals are given below:

1. Oxygen is essential for maintaining life processes. It is used in the process of respiration in living beings. Oxygen is also used during combustion of fuels.
2. Nitrogen is used in making fertilizers to enhance the growth of plants.
3. Phosphorus is used to make fertilizers.
4. Sulfur is used in the vulcanisation of rubber.
5. Carbon is used as a fuel in the form of charcoal, coke and coal. Graphite electrodes are used in dry cells. It is also used to make the ‘lead’ of pencils. Carbon as diamond is used in jewellery.

Question 11.
One of the methods of protecting iron from getting rusted is to put a thin coating of zinc metal over it. Since sulfur does not react with water, can it be used for this purpose? Justify your answer.
Answer:
Iron gets rusted in moist air. The rusting of iron can be prevented by applying a protective layer of zinc metal on iron – the process is called galvanisation. Sulfur does not react with water but it being a non-metal, cannot be used for this purpose.

Question 12.
An ironsmith heats iron before making tools. Why is heating necessary in this process?
Answer:
An ironsmith beats iron with a hammer after heating it in a furnace. When iron becomes red-hot, it can be easily beaten to give shape to make tools and other items.

Class 7 The World of Metals and Non metals Question Answer (Activities)

Activity 4.1: Let Us Explore (Pages 42)

Materials required: Copper, aluminium, iron nail, a piece of coal, a small lump of sulfur (powder), and a block of wood.

Procedure and Observation:

1. Obseve the appearance of above items.
2. Check whether they are hard or soft and lustrous or dull.
3. To check hardness of these materials, beat them one by one with a hammer by placing on any hard surface.
4. Observe whether they become flattened or break into pieces.
5. Record your observations in Table 4.1.

Object/Material	Appearance (lustrous/non-lustrous)	Hard/Soft	Effect of hammering (fattens/ breaks into pieces)
Piece of copper	Lustrous	Hard	Flattens
Piece of aluminium	Lustrous	Hard	Flattens
Iron nail	Lustrous	Hard	Flattens
Piece of coal	Non-lustrous	Soft	breaks into pieces
Lump of sulphur (pea-sized)	Non-lustrous	Soft	breaks into pieces
Block of wood	Non-lustrous	Hard but not hard as metal	Neither flattens nor breaks into pieces

Activity 4.2: To Investigate Sonority (Pages 45—46)

Materials required: Metal spoon, a coin, a piece of coal, and a block of wood.

Procedure and Observation:

1. Drop the given materials one by one from a certain height.
2. Observe the sound produced by these objects.
3. It is observed that the metal spoon and the metal coin produce a ringing sound. This property of metals is called sonority and the metals are sonorous in nature.
4. Coal and wood produce dull sounds. Coal is carbon — a non-metal which is non-sonorous; wood is neither metal nor non-metal.

Activity 4.3: To Investigate Conduction of Heat (Pages 46-47)

(The activity should be demonstrated by the teacher.)
Materials required: Glass tumbler, hot water, wooden spoon, metal spoon.

Procedure and Observation:

1. Place a glass tumbler on a table.
2. Fill it with hot water.
3. Take a metal spoon and a wooden spoon of the same size and thickness.
4. Place both these spoons simultaneously into the hot water and leave them undisturbed for a few minutes.
5. Now touch the upper end of each spoon carefully.
6. It is observed that metal spoon will be hotter compared to wooden spoon.
7. There is transfer of heat from water to the metal spoon making it hotter because metals are good conductors of heat. Wooden spoon is a poor conductor of heat.

Activity 4.4: To Design and Create Conduction of Electricity (Pages 47-48)

(The activity should be demonstrated by the teacher.)
Materials required: A piece of aluminium foil, an iron nail, a lump of sulfur, a copper wire, a piece of coal, a piece of dry wood, a stone, an eraser made of rubber and a piece of nylon rope.

Procedure and Observation:

1. Design an electric circuit, like the tester circuit (given in Chapter 3). Repeat the activity using materials listed in this activity.
2. Observe which of the listed items make the bulb of the tester glow.
3. A lump of sulfur, a copper wire, a piece of coal, a piece of dry wood, a stone, an eraser made of rubber and a piece of nylon rope fail to do so.

Object/ Material	Observation (bulb glows/ does not glow)	Good conductor of electricity or poor conductor of electricity
Piece of aluminium foil	Bulb slows	Good conductor of electricitv
Iron nail	Bulb glows	Good conductor of electricitv
Lump of sulphur (peasized)	Bulb does not glow	Poor conductor of electricity
CooDer wire	Bulb glows	Good conductor of electricity
Piece of coal	Bulb does not glow	Poor conductor of electricity
Piece of dry wood	Bulb does not glow	Poor conductor of electricity
Stone	Bulb does not glow	Poor conductor of electricity

Conclusion: It is observed that all the materials that make the bulb glow are metals and materials that allow electricity to flow through them easily are called good conductors of electricity. Materials that prevent the bulb from glowing by not allowing electricity to pass through them are called poor conductors of electricity.

Activity 4.5: To Study the Effect of Air and Water on Metals (Iron) (Page 49)

Materials required: Three clean dry glass bottles (or test-tubes) with tight-fitting, caps or stoppers, silica gel, 3 iron nails tied with thread, water, oil.

Procedure & Observations:

1. Take three clean dry glass bottles (A, B, C) with tight-fitting caps.
2. Take three iron nails and tie each nail with a thread.
3. In bottle A, place an iron nail with silica gel; tighten the cap (dry air).
4. In bottle B, place an iron nail in boiled, cooled water and pour a layer of oil on top; tighten the cap (water without air).
5. In bottle C, place an iron nail so that it is partially dipped in water; keep the bottle uncapped (water + air).
6. Leave the bottles undisturbed for 8-10 days at room temperature.
7. Record your observations.

Observation: Table 4.3: Formation of brown deposit on iron nails

Glass Bottle	Conditions		Observations
	Presence of water (Yes/No)	Presence of air (Yes/No)
A	No	Yes	No brown denosit on iron nail
B	Yes	No	No brown denosit on iron nail
C	Yes	Yes	Brown deposits on iron nail

Conclusion:
• Presence of both water and air results in brown deposits or rusting of iron nails. This indicates that both water and air are essential for rusting of iron.
Precautions
• Handle iron nails carefully. You must know that black coating on silver and green coating on copper occurs due to corrosion which is caused by other substances present in air; it results in deterioration of metal surface.

Activity 4.6: To Demonstrate Effect of Air and Water on Other Metals. (Page 51)

Note: Teacher should demonstrate this activity in the class. Materials required: Magnesium ribbon, a pair of tongs, spirit lamp or a candle, watch glass, warm water, litmus paper.

Procedure and Observations:

1. Take a magnesium ribbon (3-4 cm long).
2. Hold it with a pair of tongs.
3. Ignite the other end of magnesium ribbon with a spirit lamp or a candle.
4. Magnesium ribbon burns with a dazzling white flame and changes into a white powder (ash) of magnesium oxide due to the reaction between magnesium and oxygen present in air.
5. Collect this white ash on a watch glass.
6. Add a few drops of warm water to this white powder. Stir it well.
7. Test the solution formed with litmus paper.
   
8. It is observed that the colour of the red litmus paper changes to blue in this solution. This indicates that metal oxide is basic in nature.

Conclusion:
• Generally, oxides of metals are basic in nature and change red litmus paper to blue.

Precautions:
• It is advisable to wear protective eye-glasses while doing this experiment.
• Keep a safe distance.

Activity 4-7: To Demonstrate That Non-metals Behave Differently from Metals in Air and Water (Pages 52-53)

Note: Teacher should demonstrate this activity.
Materials required: powdered sulfur, deflagrating spoon, spirit-lamp, a gas-jar with a lid, water, litmus paper.

Procedure & Observations:

1. Take a small amount of powdered sulfur in a deflagrating spoon.
2. Heat it on a flame.
3. As soon as the sulfur starts burning, introduce the deflagrating spoon into the gas-jar. Cover it with the lid.
4. Remove the lid after 3-4 minutes and take out the deflagrating spoon.
5. Quickly add a small quantity of water into the gas-jar, replace the lid and shake well so that the gas dissolves in water to form sulfurous acid.
6. Test with litmus paper – the blue litmus paper turns red, indicating the acidic nature of the solution formed.

Conclusion:
• On burning sulfur in air (oxygen) blue-coloured sulfur dioxide gas is formed. On dissolving sulfur dioxide gas in water, sulfurous acid is formed which is acidic in nature (it turns red litmus paper blue). This shows that sulfur is a non-metal.

Precautions:
•  Perform this activity in fume-hood or a well-ventilated area. Burning sulfur produces gases which can be harmful if inhaled.
•  Use a long-handled deflagrating spoon to safely heat substances.
•  Cover the gas-jar immediately so that sulfur-dioxide gas does not escape; it is harmful for humans.

Activity 4-8 (Page 53)

Aim: To explore substances like sulfur and phosphorus.
Note: Teacher should demonstrate this activity.
Materials required: Small amounts of sulfur powder and phosphorous in separate glass tumblers, small amount of water.

Procedure & Observations:

1. Take some sulfur powder and phosphorus in separate glass tumblers.
2. Add a small amount of water to these.
3. It is observed that sulfur and phosphorus behave differently with air and water.
4. There is no reaction when sulfur is placed in water.
5. Phosphorus is stored in water as it catches fire when exposed to atmospheric air.
6. Both these substances are sofj and dull in appearance.
7. Both sulfur and phosphorus are neither malleable nor ductile.

Conclusion:
• Both sulfur and phosphorus are non-metals and their oxides are acidic in nature.

Precautions:
• Handle sulfur and phosphorus carefully.