Nature of matter.

Anything which has mass & occupies space is called matter.

Everything around us , for example book, pen , pencil, water, paper,air,all living beings etc. are composed of matters.

Matter exist in three physical State.

1.solid: have definite volume & shape

2.liquid : have definite volume but not definite shape

3.gas : have neither definite volume nor shape.

These three physical State are interchangeable..

 Soliid~ liquid ~ gas  by  heating or cooling.

At microscopic level , matter can be classified as.

Mixture or pure substance.

1. Types of mixture.                     2. Pure substance 

                                                         a) elements  

                                                           b) compounds

a)  homogeneous mixture. 

b) heterogeneous mixture.

Properties of matter

1. Physical properties : colour, odour, M.P. , B.P, Density.

2. Chemical properties : acidity or basicity, combustibility. 

Measurements :

1. SI     2. C.G.S.

1. The international system of units was established by the 11th General conference on weight & measurements in Paris in 1875.

1 unit of mass: kilograms
2. Unit of Time: second.
3. Unit of electric current : ampere
4.unit of temperature: Kelvin
5.unit of amount of substance : mole 
6. Unit of luminous intensity: candela.

Laws of chemical combinations : 

1. Law of conservation of mass :

It was proposed by Antoine lavoisier in 1789.It states that matter can neither be created nor be destroyed.

2. Law of definite proportions.
It was given by french scientists , Joseph Proust.

He stated that a givan compound always contains exactly the same proportions of elements by weight.

3.Avogadro law.

In 1811, he prosped that equal volume of gases at the same temperature & pressure should contain equal number of molecules.