Class 7 Science - KERALA
The World of Metals and Non-metals
The chapter 'The World of Metals and Non-metals' in Class 7 Science explores the fascinating physical and chemical properties that divide all elements into two major groups. Students learn how to identify metals by their luster, malleability, ductility, conductivity, and sonority, while contrasting these with non-metals which are generally brittle and poor conductors. The chapter also covers how metals and non-metals react with oxygen, water, and acids, introducing basic chemical reactions and word equations. Understanding these concepts is essential for Kerala SCERT examinations, 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 (shiny), 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, and poor conductors of heat and electricity. They can exist in solid, liquid, or gaseous states at room temperature.
Sonority
Sonority is the unique property of metals to produce a ringing sound when struck hard, which is why metal bells are used in schools and temples.
Reaction with Oxygen
When metals react with oxygen, they form basic oxides that turn red litmus blue. When non-metals react with oxygen, they form acidic oxides that turn blue litmus red.
Reactivity with Acids
Most metals react with dilute acids to release hydrogen gas, which burns with a pop sound, whereas non-metals generally do not react with acids.
Important Formulas
Board Exam Info
In Kerala SCERT Class 7 Science examinations, this chapter typically carries around 6 to 8 marks. Questions frequently include identifying properties, differentiating between metals and non-metals, explaining experimental observations like the pop sound of hydrogen gas, and completing word equations.
Frequently Asked Questions
Which metal is liquid at room temperature?
Mercury is the only metal that exists in a liquid state at room temperature.
Why are electrical wires made of copper or aluminium?
Copper and aluminium are chosen because they are excellent conductors of electricity and are ductile enough to be drawn into thin wires.
Can non-metals conduct electricity?
Most non-metals are poor conductors of electricity, but graphite (a form of carbon) is an exception and can conduct electricity.
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