Types Of Pure Substances
On the basis of their chemical composition substances can be classified either as elements or compound.
Elements: An element is a basic form of matter that can not be broken down into simpler substances by chemical reaction.
- It is divided into metals, non-metals and metalloids.
Properties of metals
- They have a lusture.
- They have silvery-grey or golden- yellow color.
- They conduct heat and electricity.
- They are ductile.
- They are malleable.
- They are sonorous.
Ex- Gold, Silver, Copper, Iron, Sodium, Potassium etc. Mercury is the only metal that is found liquid at room temperature.
Properties of non-metal
- They display a variety of colors.
- They are poor conductors of heat and electricity.
- They are not lustrous, sonorous, or malleable.
Ex- hydrogen, oxygen, iodine, Carbon(coal and coke) ,Bromine and Chlorine etc.
Metalloids
Some elements have intermediate properties between those of metals and non-metals, they are called metalloids.
Ex- Boron, Silicon and Germanium etc.
Some characteristics of elements:
- Majority of the elements are solid.
- Eleven elements are in a gaseous state at room temperature.
- Two elements are liquid at room temperature that is Mercury and Bromine.
- Elements like Gallium and Cesium become liquid at temperature slightly above room temperature(303K).
Compound
A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.
Difference between mixture and Compound:-
| Mixture | Compounds |
| Elements or compounds just mix together to form a mixture and no new compound is formed. | Elements react to form new compounds. |
| A mixture has a variable composition. | The composition of each new substance is always fixed. |
| A mixture shows the properties of the constituent substances. | The new substance has totally different properties. |
| The constituents can be separated fairly easily by physical methods. | The constituents can be separated only by chemical or electrochemical reactions. |
