A sample of pure matter is called a substance or anything whose composition is uniform throughout and has well-defined physical and chemical properties is called a substance.
E.g. Silver, Gold, Water, NaCl, etc.
Types of Substances:
They are of two types:
That pure substance that can’t be broken down into simple substances is called an Element or that pure substance which is made of atoms having the same Atomic number and having similar Chemical Properties.
e.g. Copper, Gold, Silver, Sodium, Hydrogen, Oxygen, etc.
All about its elements have been discovered out of which -92 are Natural while – 24 are artificial
Physical States of Elements:
These Elements exist in different physical states in:
- Gases: H2, O2, N2, He, Ne
- Liquid: Hg, Br2
- Solid: Cu, Ag, Au, etc.
Types of Elements:
Based on their nature Elements are divided into:
- Metals: Electropositive elements are called metals
e.g. Na, K, Ca, Mg, Cu, etc.
- Non Metals: Electronegative Elements are called nonmetals, e.g. Oxygen, Chlorine, Nitrogen, Sulphur, etc.
Metalloids: Elements having the properties of both metal and non-metal are called Metalloids e.g. Silicon, Ge, etc.
That pure Substance which can be further broken down into two or more than two elements is called Compound or That pure substance which is form by the chemical combination of two or more elements in fixed maceration.
That pure Substance which can be further broken down into two or more than two elements is called Compound or That pure substance which is form by the chemical combination of two or more elements in a fixed mass ratio
e.g. H20, NaCl, Glucose, CO2, NH3
Characteristics of a compounds:
(i) In a compound, elements are combined in a fixed mass ratio
(ii) Properties of a compound are completely different from its element
(iii) Components (Elements) of a compound cannot be easily separated from each other.
Types of Compounds:
They are of two types
- Molecular compounds:
Those compound which exits in spate molecular form e.g. H2O, CO2, NH3, SO2, etc.
Those compounds which do not exist in separate molecular form e.g. NaCl, KBr, NaNO3
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