Important Points and Formulas of class 7 Science Chapter-Metal and Non-Metals
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Important Points and Formulas of class 7 Science Chapter-Metal and Non-Metals
May 16, 2022, 16:45 IST
Class 7 Science Chapter-Metal and Non-Metals
CLASSIFICATION OF ELEMENTS
It was found that there was a wide variation in the properties of elements. Hence these were further classified into three categories, i.e. metals, non-metals, metalloids based on the properties they exhibit.
OCCURRENCE OF METALS AND NON-METALS
| Non-Metal | Free State | Combined State |
| Nitrogen | 78% of air by volume is nitrogen |
In living organisms as proteins and in
soil as nitrogen compounds |
| Carbon | As graphite, and Diamond |
Metal carbonates, natural gas, petroleum,
proteins, carbohydrates, fats and in air as carbon dioxide |
| Sulphur | Present inside the Earth’s crust | Metal sulphides and metal sulphates |
PHYSICAL PROPERTIES OF METALS AND NON-METALS
| PROPERTY | METALS | NON-METALS |
| State: |
Solids at room temperature.
Exceptions: Hg and Ga are liquids |
Mostly gases.
Exception: Some of the solid non-metals are C, S, P, I2 and bromine is a liquid non-metal. |
| Melting point |
Very high melting point and boiling point.
Exceptions: Na, K, Hg have low melting points and boiling points. Ga has low melting point but high boiling point. |
Low melting points and boiling points.
Exceptions: C, Si and B have high melting points and boiling points. |
| Hardness: |
Generally hard.
Exceptions: Na and K are soft. |
Solid non-metals are brittle. Exception:
Dimond is the hardest naturally occurring substance. |
| Density: |
Have high density.
Exception: Li, Na and K have density lower than water (1 gm/cm3) |
Have low density.
Exception: Diamond |
| Conductivity: |
Good conductors of heat and electricity.
Exceptions: Bi and W are poor conductors of electricity. |
Bad Conductors of heat and electricity.
Exception: Graphite and gas carbon are good conductors of electricity. |
| Lustre: | Have lustre |
No lustre.
Exceptions: I2 and graphite. |
| Tensile strength; |
High tensile strength
Exception: Zn has very less tensile strength. |
Do not have tensile strength.
Exception:Carbon fibre, a recently developed allotrope of carbon. |
| Malleability and ductility: |
Generally malleable and ductile.
Exception: Zinc is not malleable and ductile. |
Non-malleable and non-ductile.
Exception: Carbon fibres are ductile |
| Sonority | Sonorous | Non-sonorous |
Do solve questions given in the NCERT text book with the help of NCERT solutions for class 7 Science .
Find Below Short Notes of chapter- Metal and Non-Metals
