Class 7 Science - WEST-BENGAL
The World of Metals and Non-metals
The chapter 'The World of Metals and Non-metals' in Class 7 West Bengal Board (WBBSE) science introduces students to the fascinating classification of elements based on their physical and chemical properties. Students learn about the distinct characteristics of metals, such as malleability, ductility, conductivity, and sonority, contrasted with brittle and non-lustrous non-metals. The chapter explores reactions with oxygen, water, and acids, displacement reactions, and the practical uses of various elements in daily life. Understanding these concepts is vital for board exams as it forms the foundational building block for advanced chemistry in higher classes.
Start Learning FreeKey Concepts
Physical Properties of Metals
Metals are generally hard, lustrous, malleable (can be beaten into sheets), ductile (can be drawn into wires), and are good conductors of heat and electricity.
Physical Properties of Non-metals
Non-metals are mostly soft, non-lustrous, brittle, poor conductors of heat and electricity, and cannot be hammered into sheets or drawn into wires.
Reaction with Oxygen
Metals react with oxygen to form basic oxides, while non-metals react with oxygen to form acidic or neutral oxides.
Reactivity with Acids and Water
Many metals react with water and dilute acids to release hydrogen gas, whereas non-metals generally do not react with dilute acids.
Displacement Reaction
A more reactive metal can displace a less reactive metal from its salt solution in water.
Important Formulas
Board Exam Info
In the West Bengal Board (WBBSE) Class 7 Science examinations, this chapter typically carries around 6 to 8 marks. Questions usually include short-answer questions, differentiating between metals and non-metals, giving scientific reasons (e.g., why copper is used for making electrical wires), and predicting products of simple chemical reactions.
Frequently Asked Questions
Why are electrical wires made of copper or aluminium?
Copper and aluminium are metals that are excellent conductors of electricity and are ductile, meaning they can easily be drawn into thin wires.
Which non-metal is liquid at room temperature?
Bromine is the only non-metal that exists in a liquid state at room temperature.
Why is sodium stored in kerosene?
Sodium is a very reactive metal that reacts vigorously with oxygen and moisture in the air, catching fire easily. Kerosene prevents its contact with air and moisture.
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