Get the simplified Class 7 Science Extra Questions and Class 7th Curiosity Chapter 4 The World of Metals and Non metals Important Extra Question Answer with complete explanation.
Class 7 Science Chapter 4 The World of Metals and Non metals Extra Questions
Class 7 Science Chapter 4 Extra Questions on The World of Metals and Non metals
The World of Metals and Non metals Class 7 Very Short Question Answer
Question 1.
What are some common objects around us that are made of metals and non-metals, and how do their properties suit their uses?
Answer:
Objects like utensils and wires are made of metals due to their strength and conductivity, while matchsticks and plastic items use non-metals for their lightness and non-conductivity.
Question 2.
What physical property of metals makes them appear shiny, and how does this differ from non-metals?
Answer:
Metals have a lustrous or shiny surface especially when freshly cut or polished, while non-metals like coal and sulphur usually appear dull.
Question 3.
What conclusion can be drawn from the fact that mercury remains in liquid form at room temperature unlike other metals?
Answer:
Mercury is an exception among metals as it is liquid at room temperature, while most other metals are solid and hard.
Question 4.
Which physical property helps us understand why iron sheets can be made into various shapes and used in construction?
Answer:
Metals like iron are malleable so they can be hammered into thin sheets without breaking. This characteristic makes them highly suitable for use in construction work.
Question 5.
Why do we use aluminium foil for wrapping food items and not use substances like sulphur or wood?
Answer:
Aluminium is malleable and non-reactive which makes it safe for food wrapping, unlike non-metals which are brittle and may react or break.
Question 6.
What property of metals causes a ringing sound when they are struck, and how is this different from non-metals?
Answer:
Metals are sonorous thus they produce a ringing sound when struck, whereas non-metals do not produce such a sound.
Question 7.
How does an activity with metal and wooden spoons placed in hot water help in comparing their heat conduction abilities?
Answer:
The metal spoon becomes hot while the wooden spoon remains cool, showing that metals are good conductors of heat while non-metals are poor conductors of heat.
Question 8.
Why do metals like copper and aluminium have wide usage in household electrical appliances and circuits?
Answer:
Copper and aluminium are good conductors of electricity, ductile, and do not corrode easily, making them ideal for wires and electrical components.
Question 9.
What conditions are necessary for the rusting of iron, and how is this demonstrated through an experiment?
Answer:
Rusting requires both air and water. An activity with iron nails in different bottles shows rusting only in the bottle with both air and water.
Question 10.
How does the corrosion of metals like copper affect their appearance and what causes this change?
Answer:
Copper reacts with moisture and gases in the air to form a green layer of basic copper carbonate, indicating corrosion.
Question 11.
Why is sodium metal stored in kerosene oil instead of being left in the open air?
Answer:
Sodium is highly reactive and can catches fire when it comes in contact with moisture or oxygen, so it is stored in kerosene to prevent accidents.
Question 12.
How do different metals behave when reacting with oxygen, and what does this tell us about their chemical nature?
Answer:
Most metals react with oxygen to form metal oxides, which are basic in nature, e.g., magnesium forms magnesium oxide when burned.
Question 13.
What are some common characteristics of metal oxides, and how can we test their nature?
Answer:
Most metal oxides are basic and can be tested using indicators like litmus paper. They often turn red litmus to blue.
Question 14.
Why is phosphorus stored in water, while iron gets rusted when exposed to water and air?
Answer:
Phosphorus reacts quickly with oxygen, so it is stored in water to prevent burning. Iron rusts due to reaction with both air and water.
The World of Metals and Non metals Class 7 Short Question Answer
Question 1.
Look at the picture showing an ironsmith working with metal to make different items like pans, tongs, and tools. What material is commonly used by the ironsmith to make these items and why is this material suitable for such items?
Answer:
Ironsmiths commonly uses iron to make these items because it is strong, hard, and malleable, which allows it to be heated, shaped, and used for making durable tools and utensils.
Question 2.
Ravi wants to make a handle for a cooking pan. He is choosing between wood and iron. Based on their properties, which material should he choose for the handle and why?
Answer:
Ravi should choose wood for making the handle of the cooking pan. This is because wood is a poor conductor of heat, so it does not get hot quickly and helps prevent burns when holding the pan. On the other hand, iron is a good conductor of heat and would become very hot during cooking, making it unsafe to touch. Therefore, for safety and comfort, wood is the better choice for a handle.
Question 3.
Compare the properties of copper and coal in terms of conductivity, appearance, and malleability. Which one is more suitable for making wires, and why?
Answer:
Copper is a good conductor of electricity, has a shiny appearance, and is malleable, meaning it can be drawn into thin wires. On the other hand, coal is a poor conductor, has a dull appearance, and is brittle, so it cannot be shaped easily. Therefore, copper is more suitable for making wires because it allows electricity to pass through it easily and can be shaped without breaking.
Question 4.
In an electric circuit, five different materials were tested one by one to see whether they allow electricity to pass through and make the bulb glow. The table below shows the materials used. Complete the table by identifying whether the bulb glows or not.
| Material used | Bulb glows (Yes/No) |
| A. Copper wire | |
| B. Plastic ruler | |
| C. Iron nail | |
| D. Coal piece | |
| E. Aluminium foil |
Answer:
| Material used | Bulb glows (Yes/No) |
| A. Copper wire | Yes |
| B. Plastic ruler | No |
| C. Iron nail | Yes |
| D. Coal piece | No |
| E. Aluminium foil | Yes |
Question 5.
Iron objects are often seen getting rusted when exposed to air and moisture. Suggest any three methods that can be used to prevent the rusting of iron.
Answer:
Rusting of iron can be prevented by following methods:
(i) Painting
(ii) Applying oil or grease
(iii) Covering the surface with another metal like zinc (This method is called galvanisation.)
Question 6.
During an activity, a teacher burned a strip of magnesium ribbon. Students noticed a white powder forming. What is this powder, and what does its reaction with water show about the nature of metal oxides?
Answer:
The white powder formed is magnesium oxide. When it is mixed with water, it forms a solution that turns red litmus paper blue, showing that it is basic in nature. This experiment proves that metal oxides are generally basic in nature.
Question 7.
What happens when sulphur is burned in the presence of oxygen, and what is formed when the resulting gas is dissolved in water?
Answer:
On burning sulphur in air (oxygen), sulphur dioxide gas is formed and when the sulphur dioxide gas is dissolved in water, sulphurous acid is formed.
Question 8.
What are some special uses of metals like zirconium and titanium?
Answer:
Zirconium is used in atomic energy applications due to its resistance to corrosion and heat, while titanium is used in the aerospace industry because it is lightweight and strong, making it ideal for aircraft and spacecraft construction.
Question 9. Why are metals and their alloys important for daily use and modern technologies?
Answer:
Metals and their alloys are important for daily use as utensils and tools due to their durability and strength. They are also essential in modern technologies and industries because of their specific properties, such as conductivity, malleability, and resistance to corrosion.
Question 10.
How is chlorine used in everyday life, and what role does it play in water purification?
Answer:
Chlorine is commonly used in water purification to kill harmful bacteria and pathogens. It helps in disinfecting water to make it safe for consumption.
The World of Metals and Non metals Class 7 Long Question Answer
Question 1.
What is the difference between metals and non-metals in terms of their physical properties?
Answer:
Metals and non-metals have distinct physical properties
- Appearance Metals are usually shiny (lustrous), while non-metals are dull.
- State Metals are solid at room temperature (except mercury), whereas non-metals can exist as solids, liquids, or gases.
- Malleability Metals are malleable which means they can be hammered into thin sheets, whereas non-metals are brittle and break easily when subjected to stress or hammered.
- Ductility Metals are ductile which means they can be drawn into wires, whereas non-metals are brittle and break easily when hammered.
- Conductivity Metals are good conductors of heat and electricity, whereas non-metals are poor conductors (insulators).
Question 2.
What is the role of metals like aluminum and copper in electrical wiring and why are they preferred over other materials?
Answer: Metals like copper and aluminum are used in electrical wiring because they allow electricity to pass through easily. Copper is the best conductor and is used in home wiring. Aluminum is also a good conductor, lighter, and cheaper, so it is used for long wires like in power lines. These metals are safe, strong, and help electricity flow without much loss.
Question 3.
Discuss the process of rusting of iron and the methods used to prevent it.
Answer:
Rusting of iron is a chemical process in which iron reacts with oxygen from the air and water to form iron oxide (rust). Rusting weakens iron, making it brittle and reducing its lifespan. These are several methods to prevent rusting of iron.
- Painting A layer of paint on the iron surface prevents moisture and oxygen from reaching the metal, thus inhibiting rust formation.
- Applying oil or grease These substances coat the iron surface and prevent contact with air and water.
- Galvanisation Iron is coated with a thin layer of zinc. Zinc acts as a sacrificial metal, protecting iron from rusting by corroding first.
Question 4.
Magnesium and sulphur are burned in air to form their respective oxides. When these oxides are dissolved in water, litmus paper shows different colour changes (Image A testing the nature oxide of magnesium, Image A testing the nature of oxide of sulphur). Based on these observations, answer the- following questions:
(i) What can you say about the nature (acidic or basic) of their oxides on the litmus test?
(ii) Name the oxides formed after burning magnesium and sulphur in air.
(iii) Why do magnesium and sulphur form different types of oxides even though both are burned in air?
Answer:
(i) Magnesium oxide turns red litmus blue, showing it is basic in nature. Sulphur dioxide turns blue litmus red, showing it is acidic in nature.
(ii) Magnesium forms magnesium oxide, and sulphur forms sulphur dioxide gas.
(iii) Magnesium is a metal, so it forms a basic oxide. Sulphur is a non-metal, so it forms an acidic oxide. Metals and non-metals react differently with oxygen, leading to different types of oxides.
Question 5.
Write any five uses of non- metals?
Answer:
- Oxygen is essential for life as we breathe it in to survive.
- Carbon forms the foundation of all living organisms and is a key component of proteins, fats, and carbohydrates, which are vital for growth and energy.
- Nitrogen is used in the production of fertilisers and other chemicals, and is an essential nutrient for plant growth.
- Chlorine is commonly used in water purification.
- Iodine, in its solution form, is applied to wounds as an antiseptic.
The World of Metals and Non metals Class 7 Case Based Questions
Question 1.
Manik is studying the properties of metals and non-metals for his science project. He conducts an experiment with different metals and observes their properties like conductivity, malleability, and luster.
• Metal A is shiny, can be hammered into thin sheets, and conducts electricity.
• Metal B is dull, brittle, and does not conduct electricity well.
• Metal Cis shiny, conducts electricity, and is used to make wires.
Based on the properties described answer the following questions.
(i) Which metal would you expect to be used in making electrical wires? Why?
(ii) Which metal would you expect to be brittle and unsuitable for making tools or utensils?
(iii) Why is Metal A likely to be used in construction and manufacturing?
Answer:
(i) Metal C is used for making electrical wires because it is shiny, conducts electricity well, and is a good conductor of heat.
(ii) Metal B is brittle and unsuitable for making tools or utensils because it lacks malleability.
(iii) Metal A is shiny, malleable, and conducts electricity, making it suitable for construction and manufacturing, where both appearance and ability to form different shapes are important.
Question 2.
Yashwant and Anandi conducted an experiment to observe the rusting of iron nails under different conditions. They,used three glass bottles (A, B, and C) with different environments to place iron nails as shown in figures.
(i) What is the purpose of using silica gel in bottle A?
(ii) What do you think will happen to the iron nail in bottle C, which is exposed to both air and water?
(iii) What will be the expected condition of the iron nail in bottle Bafter 8-10 days?
Answer:
(i) Silica gel keeps the air dry by absorbing moisture and preventing the nail from coming into contact with water.
(ii) The iron nail in bottle C will rust because both air and water are required for rusting to occur.
(iii) The iron nail in bottle B may show little or no rusting because the oil prevents the nail from coming into contact with air, which is necessary for rusting.
The World of Metals and Non metals Class 7 Skill Based Questions
Question 1.
Riya was asked to identify metals in the school science lab. She tapped on a spoon and a piece of coal. The spoon made a ringing sound, but the coal didn’t. Based on this observation, which is likely to be a metal and Why?
Question 2.
Magnesium and sulphur burned in oxygen to give A and B and then A and B are separately dissolved in water to give C and D respectively. Observe the flowchart and complete the word equation.
(i) Magnesium + Oxygen → A
(ii) Sulphur + Oxygen → B
(iii) B + Water → D
Question 3.
Complete the crossword with the help of the clues given below:
Across
3. A soft metal that is stored in kerosene.
4. The only metal in liquid state at room temperature.
6. A metal used to protect iron from rusting in galvanisation.
7. Process that damages iron in moist air.
Down
1. This non-metal catches fire in air and is stored in water.
2. Black coating forms on this metal when exposed to air.
4. Property that allows metals to be beaten into sheets.
5. A good conductor of electricity used in wiring.
Answer:
Across
3. Sodium
4. Mercury
6. Zinc
7. Rusting
Down
1. Phosphorus
2. Silver
4. Malleability
5. Copper
The World of Metals and Non metals Extra Questions for Practice
Question 1.
Name a non-metal used in fertilisers.
Question 2.
Give one use of copper.
Question 3.
What physical property of metals makes then appear shiny, and now does this is different from non-metals.
Question 4.
Name a metal which is liquid at room temeprature.
Question 5.
Why is aluminium used for making electric cables?
Question 6.
Define ductility and give two examples of ductile metals.
Question 7.
What is corrosion? How does rusting affect iron, and how can it be prevented?
Question 8.
List some important uses of metals in our daily life.