Class 7 Science - CBSE
The World of Metals and Non-metals
The chapter 'The World of Metals and Non-metals' introduces Class 7 students to the fascinating classification of elements based on their physical and chemical properties. Students learn how to distinguish between shiny, malleable metals like iron and copper, and brittle, dull non-metals like sulphur and oxygen. We explore essential properties such as conductivity, ductility, and sonority, alongside chemical behaviors like reactions with oxygen, water, and acids. Understanding this chapter is crucial for CBSE exams as it builds the foundational chemical concepts needed for higher classes, frequently appearing in both objective and short-answer questions.
Start Learning FreeKey Concepts
Physical Properties of Metals
Metals are generally solid, shiny (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 either solids or gases (except bromine, which is liquid), dull in appearance, brittle, and poor conductors of heat and electricity.
Reaction with Oxygen
Metals react with oxygen to form basic oxides that turn red litmus blue, whereas non-metals react with oxygen to form acidic oxides that turn blue litmus red.
Reaction with Water and Acids
Many metals react with water and acids to produce hydrogen gas, which burns with a pop sound, while non-metals generally do not react with water or dilute acids.
Displacement Reactions
A more reactive metal can displace a less reactive metal from its salt solution in water, demonstrating the varying reactivity of different metals.
Important Formulas
Board Exam Info
This chapter typically carries around 5 to 8 marks in the CBSE Class 7 Science examination. Common question types include differentiating between metals and non-metals based on physical properties, explaining displacement reactions, writing word equations for chemical reactions, and reasoning questions such as why electrical wires are made of copper.
Frequently Asked Questions
Why is sodium stored in kerosene?
Sodium is an extremely reactive metal that catches fire spontaneously when it comes in contact with moisture and oxygen in the air. Therefore, it is stored in kerosene to prevent accidental exposure.
Which non-metal is a good conductor of electricity?
Graphite, a form of carbon, is a non-metal that is a good conductor of electricity.
Can a less reactive metal displace a more reactive metal?
No, only a more reactive metal can displace a less reactive metal from its salt solution during a displacement reaction.
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